Drag calendering device, dry electrode manufacturing apparatus comprising calendering device, dry electrode manufactured by apparatus, and secondary battery comprising dry electrode

Abstract

The present invention relates to a technology associated to a dry electrode, which is an electrode manufactured by a drying method and, more specifically, to an electrode composition with a new constitution for manufacturing a dry electrode, a dry electrode formed using the electrode composition, a secondary battery comprising the dry electrode, and a dry electrode manufacturing method and apparatus using the electrode composition, wherein the omission of a process essential in the prior art in order to manufacture an electrode without a solvent by a dry method can not only simplify the manufacturing process but also provide a dry electrode with superior quality.

Description

Drag calendering device, dry electrode manufacturing device including said calendering device, dry electrode manufactured by said device, and secondary battery including said dry electrode

[0001] This invention was supported by the following national research and development project.

[0002] [Project ID] 1415187718

[0003] [Assignment No.] 20023145

[0004] [Ministry Name] Ministry of Trade, Industry and Energy

[0005] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0006] [Research Project Name] Development of Materials and Components Technology

[0007] [Research Project Title] Development of Binder and Manufacturing Process for Carbon Reduction Dry Process in Secondary Batteries

[0008] The present invention relates to a technology concerning a dry electrode manufactured by a dry method, and more specifically, to a dry electrode composition developed to enable the omission of a process that was essential in the prior art for manufacturing an electrode without a solvent by a dry method, a drag calendering device, a dry electrode manufacturing device including said device, a dry electrode manufactured by said device, and a secondary battery including said dry electrode.

[0009] Rechargeable batteries, typified by lithium-ion batteries, are electrical energy storage devices that operate through electrochemical reactions in an electrode layer composed of an active material, a conductive material, and a binder. The electrochemical properties of rechargeable batteries can be said to be influenced by various factors, such as the type and content of each of these components, their compositional ratios, and the method of manufacturing the electrodes.

[0010] In the case of electrode manufacturing methods, conventionally, all components are placed in a solvent and mixed and dispersed to create a uniform electrode composition slurry, which is then coated onto a metal electrode plate acting as a current collector and dried to produce an electrode of a certain thickness (wet electrode method). Since this method has been applied for a long time, the manufacturing process is already stabilized and the yield is relatively high. However, this method has many inconveniences in the manufacturing process, such as the mandatory installation of a drying chamber to remove the solvent and the need to recover all evaporated solvent to prevent air pollution; consequently, it is a method with high equipment and manufacturing costs.

[0011] Recently, there has been a movement to use the dry method to overcome the disadvantages of the wet method. The dry method is a technology that manufactures an electrode and a secondary battery containing it by creating an electrode composition by stirring and mixing active materials, conductive materials such as conductive carbon black, and binders—which are components for secondary battery electrodes—without a solvent, kneading the composition, manufacturing a dry electrode through a calender, and attaching it to a metal electrode plate which serves as a current collector. Since the dry method does not use solvents, a drying oven is not required, and consequently, a solvent recovery device is not needed. Therefore, the secondary battery electrode manufacturing process is very simple and highly environmentally friendly, and the equipment costs are significantly lower than those of the wet method, making it a very economical electrode manufacturing method.

[0012] The electrode of a secondary battery consists of three components: an active material, a conductive material (conductive additive), and a binder. The selection of the binder is crucial for manufacturing the electrode using the dry method, and the conventional dry electrode binder is polytetrafluoroethylene (PTFE), known as Teflon. It is known that when a mixing technique involving shear force, such as the kneading method, is used, the binder undergoes a phenomenon called fabrication, where it stretches into thin, long strands, thereby effectively binding the active material and the conductive material. Various methods have been disclosed for manufacturing dry electrodes using PTFE, such as a method in which the electrode composition is first kneaded through a kneading process and then the kneaded electrode composition is ground into particles of an appropriate size and calendered, or a method in which the electrode composition is mixed and then calendered at a high temperature.

[0013] PTFE is a fluorinated resin particle composed of fluorine components. It is a polymer that lacks compatibility or adhesion at the interface with active materials or conductive materials due to its poor adhesion to other substances. Furthermore, when using PTFE binders, very high pressure is required to produce thin dry electrodes. Even if thin electrodes are produced under high pressure, it has been pointed out that the interface between the binder and other components delaminates during the expansion and contraction processes that occur during repeated charge-discharge cycles, consequently degrading long-term electrochemical properties. Additionally, fluorinated resins are not environmentally friendly as they generate hydrogen fluoride (HF) gas in the event of a fire, which presents a problem that necessitates minimizing their use.

[0014] One method to compensate for these disadvantages of PTFE is to mix PTFE particles with other adhesive compounds, specifically other binders for secondary batteries, as much as possible. However, mixing other binders with PTFE drastically reduces the fiberization of the mixed binder, hindering the fiberization of the PTFE binder to the point where even kneading is not possible, making the manufacture of dry electrode sheets very difficult. This is because other binders lack fiberization capabilities and thus interfere with the fiberization of PTFE. To overcome these drawbacks, a method known as high-temperature calendering is sometimes used, in which a polymer that melts at a relatively low temperature is kneaded with PTFE by methods such as kneading at a high temperature of at least 100°C, and then calendered again at a high temperature of at least 100°C. However, there is a problem in that processing at such high temperatures ultimately makes it difficult to maximize the effects of equipment operation and energy savings.

[0015] To overcome these problems, it is necessary to develop a new technology that enables the manufacture of dry electrodes by simply mixing all components constituting the electrode without prior kneading or grinding processes, and then immediately calendering at room temperature rather than high temperature, in a dry electrode composition in which a large amount of another adhesive binder is mixed with PTFE to improve PTFE adhesion.

[0016] Accordingly, the objective of the present invention is to provide a drag calendering device of a new configuration that can easily manufacture a dry electrode sheet having a thickness of 100 microns or less by omitting the processes that were necessary in the prior art consisting of kneading, grinding, and calendering, and mixing immediately, using only room temperature calendering instead of high temperature.

[0017] Another objective of the present invention is to provide a dry electrode manufacturing apparatus of a novel configuration that enables a continuous manufacturing process in which a dry electrode can be manufactured immediately after manufacturing a dry electrode sheet using a drag calendering device, is highly economically advantageous, and allows for substantial mass production.

[0018] Another objective of the present invention is to provide a dry electrode manufactured through a dry electrode manufacturing device of a novel configuration, formed on one or both sides of a metal electrode plate serving as a current collector, and having excellent adhesion to the current collector as well as bonding strength between each component within the electrode.

[0019] Another objective of the present invention is to provide a secondary battery capable of effectively maintaining stable electrochemical characteristics by including a dry electrode manufactured through a dry electrode manufacturing apparatus of a novel configuration.

[0020] The objectives of the present invention are not limited to those mentioned above, and may naturally include objectives of the invention that a person skilled in the art can recognize from the description in the detailed description of the invention that follows, even if not explicitly mentioned.

[0021] To achieve the objectives of the present invention described above, the present invention first provides a drag calendering device comprising: two or more calender rolls arranged at regular intervals and driven individually, wherein a first calender roll arranged at the foremost of the calender rolls is installed lower than the second calender roll so as to form a certain angle with the adjacent second calender roll; and an electrode composition supply unit that supplies a dry electrode composition to the first calender roll.

[0022] In a preferred embodiment, the constant angle is 10° to 50°, which is the angle formed by a plane passing through the rotation axis of the first calendar roll and the rotation axis of the second calendar roll and a plane passing through the rotation axis of the second calendar roll parallel to the ground.

[0023] In a preferred embodiment, the calendar roll is any one of a metal roll, a ceramic roll, or a metal-ceramic roll having a coating layer made of ceramic material formed on the surface of the metal roll.

[0024] In a preferred embodiment, the ceramic material is any one selected from the group consisting of titania, silica, alumina, and zirconia.

[0025] In a preferred embodiment, the average surface roughness of the calendar roll is less than 0.5 microns.

[0026] In a preferred embodiment, the surface adhesion force of the calendar roll is 0.5 to 10 N / 18 mm.

[0027] In a preferred embodiment, the electrode composition supply unit includes a feeding member installed at its lower portion to guide the electrode composition to be supplied consistently to the first calendar roll.

[0028] In a preferred embodiment, the feeding member comprises a flat plate having circular or polygonal holes of the same size formed at regular intervals.

[0029] In a preferred embodiment, the size of the circular or polygonal hole is 0.1-10 mm.

[0030] In a preferred embodiment, the rear calendar roll in the calendar section rotates 1.05 to 4.0 times faster than the front calendar roll, and when a dry electrode composition is introduced between the first calendar roll and the second calendar roll, the dry electrode composition is dragged toward the rear calendar roll, which rotates faster than the front calendar roll, to form a dry electrode sheet.

[0031] In addition, the present invention provides a dry electrode manufacturing apparatus comprising: a progressing calendar unit in which two or more calendar rolls are sequentially arranged and individually driven to drag a dry electrode composition supplied from an electrode composition supply unit to the rear to form a dry electrode sheet; an attachment calendar unit in which two or more calendar rolls are sequentially arranged adjacent to the rearmost calendar roll of the progressing calendar unit and individually driven to attach the dry electrode sheet formed in the progressing calendar unit to a current collector to form a dry electrode; and a current collector supply and recovery unit that supplies the current collector to the calendar roll of the attachment calendar unit and recovers the dry electrode formed in the attachment calendar unit.

[0032] In a preferred embodiment, the progress calendar unit is a drag calendaring device of any one of the above claims.

[0033] In a preferred embodiment, the rear calendar roll in the attachment calendar unit rotates 1.0 to 1.5 times faster than the front calendar roll.

[0034] In a preferred embodiment, the current collector is supplied by the current collector supply and recovery unit to between the rearmost calendar roll of the advance calendar unit and the frontmost calendar roll of the attachment calendar unit, or between the frontmost calendar roll of the attachment calendar unit and the calendar roll adjacent thereto.

[0035] In a preferred embodiment, the diameter of the calendar roll of the attachment calendar unit is larger than the diameter of the calendar roll of the progress calendar unit.

[0036] In a preferred embodiment, the apparatus further includes one or more control units, wherein the control unit includes one or more control rolls installed on the upper or lower portion of a rear calendar roll that is dragged after the dry electrode sheet is formed in the advance calendar unit, or a calendar roll included in one or more units among one or more calendar rolls included in the attachment calendar unit, and controls one or more of the surface flatness, thickness, or porosity of the dry electrode sheet or dry electrode.

[0037] In a preferred embodiment, two or more calendar rolls included in the attachment calendar unit are heated to 50°C to 200°C.

[0038] In a preferred embodiment, the apparatus further includes a scrubbing unit installed between the progress calendar unit and the attachment calendar unit to trim or remove unnecessary parts from the dry electrode sheet before attaching the dry electrode sheet to the current collector.

[0039] In addition, the present invention comprises an attachment calendar unit in which a fourth calendar roll and a fifth calendar roll are sequentially arranged and individually driven, and a first dry electrode sheet and a second dry electrode sheet are respectively attached to both sides of a current collector supplied between the fourth calendar roll and the fifth calendar roll; A progression calendar unit in which a third calendar roll, a second calendar roll, and a first calendar roll are sequentially arranged adjacent to the outer side of the fourth calendar roll and driven individually to form a first dry electrode sheet by dragging a dry electrode composition supplied to the first calendar roll toward the fourth calendar roll, and a second progression calendar unit in which a sixth calendar roll, a seventh calendar roll, and an eighth calendar roll are sequentially arranged adjacent to the outer side of the fifth calendar roll and driven individually to form a second dry electrode sheet by dragging a dry electrode composition supplied to the eighth calendar roll toward the fifth calendar roll, are installed facing each other with respect to the current collector; The present invention provides a dry electrode manufacturing apparatus comprising: an electrode composition supply unit including a first supply unit installed between the second calendar roll and the first calendar roll to supply a dry electrode composition to the first calendar roll, and a second supply unit installed between the seventh calendar roll and the eighth calendar roll to supply a dry electrode composition to the eighth calendar roll; and a current collector supply and recovery unit that supplies the current collector between the fourth calendar roll and the fifth calendar roll and recovers a double-sided dry electrode formed in the attachment calendar unit.

[0040] In a preferred embodiment, the fourth and fifth calendar rolls, the third and sixth calendar rolls, the second and seventh calendar rolls, and the first and eighth calendar rolls, which face each other with respect to the current collector, each have the same speed and opposite rotational directions.

[0041] In a preferred embodiment, the first progress calendar unit rotates the second calendar roll 1.05 to 4.0 times faster than the first calendar roll, and the third calendar roll rotates 1.05 to 4.0 times faster than the second calendar roll, and the second progress calendar unit rotates the seventh calendar roll 1.05 to 4.0 times faster than the eighth calendar roll, and the sixth calendar roll rotates 1.05 to 4.0 times faster than the seventh calendar roll.

[0042] In a preferred embodiment, the calendar roll included in the progress calendar unit is any one of a metal roll, a ceramic roll, or a metal-ceramic roll having a coating layer made of ceramic material formed on the surface of the metal roll.

[0043] In a preferred embodiment, the ceramic material is any one selected from the group consisting of titania, silica, alumina, and zirconia.

[0044] In a preferred embodiment, the average surface roughness of the calendar roll included in the progress calendar unit is less than 0.5 microns.

[0045] In a preferred embodiment, the surface adhesion force of the calendar roll included in the progress calendar unit is 0.5 to 10 N / 18 mm.

[0046]

[0047] In a preferred embodiment, the diameter of the calendar roll of the attachment calendar unit is larger than the diameter of the calendar roll of the progress calendar unit.

[0048] In a preferred embodiment, the apparatus further includes a control unit comprising two control rolls installed above or below a calendar roll that is dragged after the first dry electrode sheet is formed in the first progress calendar unit and a calendar roll that is dragged after the second dry electrode sheet is formed in the second progress calendar unit, and which control one or more of the surface flattening, thickness, or porosity of the first and second dry electrode sheets.

[0049] In a preferred embodiment, the fourth and fifth calendar rolls included in the attachment calendar unit are heated to 50°C to 200°C.

[0050] In a preferred embodiment, the scrubbing unit further comprises first and second scrubbers installed respectively between the first progress calendar unit and the attachment calendar unit and between the second progress calendar unit and the attachment calendar unit, for trimming or removing unnecessary portions from the first and second dry electrode sheets before attaching the first dry electrode sheet and the second dry electrode sheet to the current collector.

[0051] In a preferred embodiment, a release coating layer is formed on the surface of the control roll.

[0052] In a preferred embodiment, the dry electrode composition comprises 80-98% by weight of an active material, 1.0-10% by weight of a binder, and 1-10% by weight of a cotton-forming agent.

[0053] In a preferred embodiment, the surface-forming agent is one or more carbon-based nanomaterials selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes (few-wall CNTs), branched carbon nanotubes, carbon nanoribbons, and carbon nanofibers, or one or more non-carbon-based nanomaterials selected from the group consisting of boron nitride nanotubes, boron nitride nanoribbons, and aramid nanofibers.

[0054] In a preferred embodiment, the binder comprises polytetrafluoroethylene and an acrylonitrile-ethylene glycol-maleic acid copolymer.

[0055] In a preferred embodiment, the polytetrafluoroethylene is included in an amount of 10 to 50 weight percent.

[0056] In addition, the present invention provides a dry electrode manufactured by any one of the dry electrode manufacturing devices described above.

[0057] In addition, the present invention provides a secondary battery comprising the dry electrode described above.

[0058] The drag calendering device of the present invention described above has a new configuration that allows for the convenient production of a dry electrode sheet with a thickness of 100 microns or less by mixing using only room temperature calendering rather than high temperature, by omitting the processes that were necessary in the prior art consisting of kneading, mixing, grinding, and calendering.

[0059] In addition, the dry electrode manufacturing apparatus of the present invention enables a continuous manufacturing process in which a dry electrode can be manufactured immediately after manufacturing a dry electrode sheet using a drag calendering device. Furthermore, since a dry electrode can be easily manufactured even with a minimized PTFE content by mixing a significant amount of a conventional secondary battery binder into the dry electrode composition used, it is highly economically advantageous and practically enables mass production.

[0060] In addition, the dry electrode of the present invention is manufactured using a dry electrode manufacturing device of a novel configuration and is formed on one or both sides of a metal electrode plate serving as a current collector, and exhibits excellent adhesion to the current collector as well as bonding strength between each component within the electrode.

[0061] In addition, the secondary battery of the present invention can effectively maintain stable electrochemical characteristics by including a dry electrode manufactured through a dry electrode manufacturing device of a novel configuration.

[0062] These technical effects of the present invention are not limited to the scope mentioned above, and naturally include effects of the invention that a person skilled in the art can recognize from the description of specific details for implementing the invention that follows, even if not explicitly mentioned.

[0063] FIGS. 1a and FIGS. 1b are schematic diagrams of a drag calendaring device according to various embodiments of the present invention.

[0064] FIG. 2 is a schematic diagram of a dry electrode manufacturing apparatus according to another embodiment of the present invention.

[0065] FIG. 3 is a schematic diagram of a dry electrode manufacturing apparatus having a double-sided electrode according to another embodiment of the present invention.

[0066] FIG. 4 is a schematic diagram of an interval feeding plate forming a feeding member of an electrode composition supply unit included in the drag calendering device of the present invention or an electrode composition supply unit included in the dry electrode manufacturing device.

[0067] FIG. 5 is the infrared spectral spectrum (FTIR spectrum) of a binder used in an electrode composition supply unit included in the drag calendering device of the present invention or in an electrode composition supply unit included in the dry electrode manufacturing device.

[0068] Figure 6 shows the appearance of a dry electrode sheet manufactured in Example 3 of the present invention.

[0069] FIG. 7 shows a dry electrode sheet prepared using boron nitride nanotubes as a plane-forming agent in Example 8 of the present invention.

[0070] Figure 8 is the impedance spectrum of a coin cell obtained in Example 19 of the present invention.

[0071] Figure 9 is the charge / discharge cycle test result of a coin cell obtained in Example 19 of the present invention.

[0072] Figure 10 is the charge / discharge cycle test result of a coin cell obtained in Example 21 of the present invention.

[0073] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the description of the invention, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0074] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0075] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this invention.

[0076] The term "drag calendering" as used in this invention refers to a calendering technique in which the calendered sheet moves along the front roll by varying the rotational speeds of the rolls, rather than moving downwards with the calendered rolls rotating at the same speed.

[0077] In interpreting the components, they shall be interpreted as including a margin of error even without separate explicit notation. In particular, when terms of degree such as "approximately" or "substantially" are used, they may be interpreted as referring to or close to the numerical value where inherent manufacturing and material tolerances are presented.

[0078] In the case of an explanation of a temporal relationship, for example, when the temporal sequence is explained using 'after', 'following', 'next', 'before', etc., it includes cases where the sequence is not continuous unless 'immediately' or 'directly' is used.

[0079] Hereinafter, the technical configuration of the present invention will be described in detail with reference to the attached drawings and preferred embodiments.

[0080] However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Throughout the specification, the same reference numerals used to describe the present invention indicate the same components. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions could obscure the essence of the invention, such detailed description is omitted.

[0081] In the description of the present invention, each component of the electrode composition is placed in a dry blender, such as a powder mixer, and simply mixed under certain conditions (rpm, time) is called a "mixture," and these components are placed in a kneader, which is a type of mixing machine, and compounded under certain conditions (temperature, rpm, time) is called a "compound." The difference between mixing and compounding in the present invention is that in the case of mixing, no torque is applied to the mixer, whereas in the case of compounding, torque is applied during compounding, which is a processing method similar to the so-called general compounding technique for polymer materials.

[0082] As described above, the present invention aims to provide various dry electrode manufacturing technologies, including an apparatus suitable for manufacturing dry electrodes, an electrode composition, and a dry electrode manufacturing method. In particular, the invention aims to provide a technology capable of manufacturing a dry electrode by producing a thin dry electrode sheet through room-temperature calendering after mixing, even when using an electrode composition containing PTFE or a mixed binder made by mixing PTFE with another binder, and attaching the sheet to a current collector through a continuous process. Here, "thin thickness" refers to a thickness of 100 microns or less in the state of a dry electrode sheet, which corresponds to a loading level of 15-25 mg / cm² in the case of an electrode composition using 95 wt% NCM811. 2 It is a thickness corresponding to. In addition, in the description of the present invention, "raw material" or "composition" refers to the dry electrode composition of the present invention unless otherwise mentioned, and electrode composition particles refer to an electrode composition in the form of small lumps in which the constituent components of the electrode are mixed.

[0083] The technical features of the present invention are a drag calendering device of a new configuration that can easily manufacture a dry electrode sheet having a thickness of 100 microns or less by mixing and calendering alone, while omitting the kneading and grinding processes that were essential in the prior art for manufacturing dry electrodes; a dry electrode manufacturing device of a new configuration that enables a continuous manufacturing process in which a dry electrode can be manufactured immediately after manufacturing a dry electrode sheet using the drag calendering device, is very economically advantageous, and allows for substantial mass production; a dry electrode manufactured through the dry electrode manufacturing device and formed on one or both sides of a metal electrode plate which is a current collector, having excellent adhesion to the current collector as well as bonding strength between each component within the electrode; and a secondary battery that can effectively maintain stable electrochemical characteristics including the dry electrode.

[0084] In other words, the inventors found through their research that it is very difficult to obtain a dry electrode sheet with a smooth surface when a dry electrode composition is continuously fed between the first and second calender rolls of a calender device in accordance with the roll width, as in the known technology. Specifically, when raw materials are directly fed between the two rolls from the upper part of the gap area between the first and second calender rolls, the fed composition accumulates between the two rolls. At this time, the calender device attempts to send all the electrode composition mixtures accumulated in the gap forward, but the composition between the roll gaps is inevitably subjected to strong pressure. Consequently, not only is it difficult to produce a dry electrode sheet with a thin thickness, but in many cases, the problem of the active material breaking occurs. Through preliminary experiments, the inventors were able to produce dry electrode sheets thicker than 200 microns using known devices, but found it difficult to produce dry electrode sheets thinner than 100 microns. This was a common problem regardless of whether the binder included in the dry electrode composition was a PTFE-only binder or a mixed binder in which PTFE is mixed with other binders for secondary batteries. However, electrodes manufactured from dry electrode sheets thicker than 200 microns have an electrode layer that is too thick to exhibit proper electrochemical properties. For example, in the case of a dry electrode composition using 95 wt% of NCM811, the currently most widely used cathode active material—specifically, NCM811 in the form of secondary particles, which consists of clustered nanometer-sized small particles—if the thickness of the dry electrode sheet is 200 microns, the loading level is 35-45 mg / cm². 2This is because the loading level is too high, making it difficult for the dry electrode manufactured therefrom to exhibit stable electrochemical characteristics. As a result, dry electrodes manufactured from dry electrode sheets with a thickness of 200 microns or more can be considered unsuitable for actual use. Although it is possible to perform calendering (high-temperature calendering) by kneading at high temperatures and heating the calender rolls to high temperatures to compensate for these problems, this results in significant heat loss and makes equipment operation difficult, and is also disadvantageous in terms of improving energy efficiency in a true sense. The present invention solves these problems.

[0085] Accordingly, the drag calendering device of the present invention comprises two or more calender rolls arranged at regular intervals and driven individually, wherein the first calender roll positioned at the foremost among the calender rolls is installed lower than the second calender roll so as to form a certain angle with the adjacent second calender roll; and an electrode composition supply unit that supplies a dry electrode composition to the first calender roll.

[0086] As illustrated in FIG. 1a, the drag calendering device (100) of the present invention may include a calendering unit (110) and an electrode composition supply unit (120). If necessary, it may further include a control unit (600) as illustrated in FIG. 1b.

[0087] The calendar section (110) has a structure in which two or more individually driven calendar rolls are arranged at regular intervals, and as illustrated, the first calendar roll (111) placed at the foremost among the calendar rolls is installed lower than the second calendar roll (112) so as to form a certain angle with the adjacent second calendar roll (112).

[0088] The arrangement structure of the remaining calender rolls, including the first calender roll (111) and the second calender roll (112) of the calender section (110), is a structure devised by experimentally confirming that it is advantageous not to directly feed the electrode composition (mixture) from above between the first calender roll and the second calender roll arranged in a horizontal state in order to manufacture a dry electrode sheet of relatively thin thickness by calendering (room temperature calendering) the dry electrode composition in a mixed state at room temperature without pretreatment such as kneading. This is because it has been experimentally confirmed that, as in the present invention, in a structure where the first calendar roll (111) of the calendar section (110), particularly the electrode composition supply section (120), is not arranged horizontally with the remaining rolls (112, 113) but rather the remaining calendar rolls including the first calendar roll (111) and the second calendar roll (112) are arranged at an oblique angle forming a certain angle, when the electrode composition (mixture) is introduced from the electrode composition supply section (120) located between the first calendar roll (111) and the second calendar roll (112), the electrode composition (mixture) falls onto the first calendar roll (111), and as the first calendar roll (111) rotates, it naturally moves toward the second calendar roll (112), thereby enabling the manufacture of a dry electrode sheet with a thinner thickness. Therefore, the first calender roll (111) and the second calender roll (112) may be the most important rolls for determining the thickness of the dry electrode sheet.

[0089] Here, the fixed angle is the angle formed by the plane passing through the rotation axis of the first calendar roll (111) and the rotation axis of the second calendar roll (112) and the plane passing through the rotation axis of the second calendar roll (112) parallel to the ground, and can be 10° to 50°. The fixed angle, or alternate angle, is 10-50 degrees from the horizontal (plane parallel to the ground) in the arrangement of the calendar rolls, and it may be particularly effective to arrange them to have an alternate angle of 15-45 degrees. This is because, as illustrated, if the first calendar roll (111) is positioned below the remaining rolls to form a fixed angle, when the electrode composition is fed over the first calendar roll (111), the first calendar roll (111) rotates, allowing the electrode composition to be naturally sent to the gap area with the second calendar roll (112).

[0090] The calender rolls included in the calender unit (110) are components that form a dry electrode sheet by adjusting the thickness to a certain level. The number of calender rolls can be determined as needed as long as there are at least two, and generally, the number of calender rolls required per side can be between two and eight. The calender unit (110) of the present invention may be equipped with a device capable of heating each calender roll, or a precise spacing adjustment device, similar to a calendering device for general polymer materials. However, it has been experimentally confirmed that in order to manufacture a thin dry electrode sheet through room temperature calendering as in the present invention, the characteristics of the calender rolls included in the calender unit (110), such as the roll material, the roll surface flatness, and the roll surface adhesion, must be adjusted within a certain range as follows.

[0091] First, the calender roll used in the calender section (110) of the present invention is made of a metal material such as stainless steel (SUS), a ceramic material, or has a coating layer formed on a metal roll made of another material such as a ceramic material. At this time, the thickness of the coating layer made of another material such as a ceramic material coated on the surface of the metal roll can be formed to a thickness of 0.05 to 10 mm depending on the diameter of the calender roll. If the thickness is less than 0.05 mm, it is too thin and may wear out easily, which is disadvantageous, and if it is more than 10 mm, it is economically disadvantageous because a layer that is too thick must be formed. The ceramic material may include one or more selected from the group consisting of titania, silica, alumina, and zirconia.

[0092] Second, the surface flatness of the calender roll used in the calender section (110) of the present invention may be such that the surface irregularity is formed to be less than 0.5 microns. If the roll surface flatness deviates from this range, the roll may not be able to pull the electrode composition, pull too much of it, or not detach from the roll, which may cause problems. Meanwhile, as the larger the surface irregularity, the stronger the tendency to pull a large amount of electrode composition during calendering, making it difficult to produce a thin dry electrode sheet, the surface irregularity may be more advantageous to be less than 0.2 microns.

[0093] Third, the surface adhesion of the calendar roll used in the calendar section (110) of the present invention is also important, because the surface of the roll must have a certain range of adhesion to the electrode composition during the process in which the electrode composition between the first calendar roll (111) and the second calendar roll (112) is pressed and passed to the second calendar roll (112) and then to the third calendar roll (113). The adhesion of the calendar roll constituting the calendar section (110) can be easily measured using Scotch tape (3M Scotch Tape, width: 18mm), and the peel-off force when the Scotch tape is attached to the surface of the roll and then peeled off may be in the range of 0.5-10N / 18mm (3M Scotch tape; width: 18mm). This is because if the surface adhesion force is less than 0.5 N / 18 mm, slippage occurs on the roll, resulting in a problem where smooth calendering is not possible, and if it is higher than 10 N / 18 mm, the thickness of the dry electrode sheet becomes too thick or there are parts where the dry electrode sheet does not detach well from the roll. As one embodiment, when the surface of the calender roll has a surface adhesion force in the range of 2-8 N / 18 mm (3M, Scotch tape, width: 18 mm), it exhibited superior characteristics.

[0094] The calendar roll included in the calendar section (110) is a roll for moving the electrode composition, which is formed into a sheet shape in the first calendar roll (111) and the second calendar roll (112), to the third calendar roll (113) and / or the subsequent calendar rolls, that is, to proceed in the forward direction. Therefore, the rotational speed of the calendar roll may vary depending on the position, but generally, it may be more effective to rotate the rear calendar roll faster than the front calendar roll. The rotational speed ratio of the front calendar roll to the rear calendar roll is determined experimentally and may be in the range of 1:1.05 to 1:4. This is because if the calendar roll rotational speed ratio is less than 1:1.05, there is a problem where the electrode sheet formed between the first calendar roll and the second calendar roll falls down or the dry electrode sheet becomes thick, and if it exceeds 1:4, there is a problem where the dry electrode sheet wrinkles or tears. In one embodiment, in the case of the first calendar roll (111) / second calendar roll (112), the second calendar roll (112) can be rotated 1.05 to 4 times faster than the first calendar roll (111), and in the case of the second calendar roll (112) / third calendar roll (113), the speed of the third calendar roll (113) can be implemented to be rotated 1.05 to 4 times faster than the second calendar roll (112).

[0095] The electrode composition supply unit (120) is a component that supplies a dry electrode composition (mixture) to the first calendar roll (111) of the calendar unit (110), and may have a structure including a hopper containing the dry electrode composition (mixture) as shown in FIG. 1a, and may further include a feeding member installed at the bottom of the hopper.

[0096] The feeding member is a component that guides the electrode composition to be supplied consistently to the first calendar roll (111). As shown in FIG. 4, it includes a flat plate having circular or polygonal holes of the same size formed at regular intervals, and the size of the circular or polygonal holes and the spacing between the holes can be adjusted within the range of 0.1 to 10 mm. If necessary, such as when the holes are large, a mesh may be formed inside the holes. At this time, the diameter and spacing of the holes can be selected and used by adjusting them according to variables such as the roll rotation speed and roll diameter. If the diameter of the holes is smaller than 0.1 mm, there is a problem that the particles constituting the electrode composition do not escape easily, and if it is larger than 10 mm, too much of it escapes, making it difficult to control the thickness of the dry electrode sheet to be thin, which is actually disadvantageous.

[0097] In this way, the drag calendering device (100) of the present invention can control the form in which an electrode composition is fed through a feeding member. If a feeding member is not installed, the electrode composition is fed into the front surface forming the electrode width, but if a feeding member is installed at the bottom of the hopper, the electrode composition is fed at regular intervals, making interval feeding possible. This allows for easy thickness control and enables the manufacture of a thinner dry electrode sheet.

[0098] To examine this more specifically, the electrode composition (mixture) introduced between the calender rolls exists in the form of particles. As the calender rolls, specifically the first calender roll (111) and the second calender roll (112), rotate, the particles constituting the electrode composition introduced between the first calender roll (111) and the second calender roll (112) spread out in the direction of travel and the width direction as the calender rolls rotate, and are compressed to form a sheet shape. However, if there are too many electrode composition particles in the surrounding area, there is insufficient space for them to spread sideways, and all electrode composition particles tend to be compressed in the machine direction (MD) all at once. This tendency eventually results in too much electrode composition (mixture) attempting to pass between the rolls, causing high pressure to be applied. This can lead to problems where it becomes difficult to control the thickness and very difficult to obtain a thin sheet shape.

[0099] To address these problems, the present invention utilizes a method in which a feeding member is installed to feed the electrode composition (mixture) particles at regular intervals rather than uniformly across the entire width of the calender roll, thereby reducing spatial constraints when the electrode composition (mixture) is compressed between the calender rolls and the particles spread out. The present invention refers to this as the interval feeding method. To implement this, as described above, a feeding member, specifically a flat plate with a hole, is installed at the bottom of the electrode composition supply unit (120), and the electrode composition is partially fed through this hole.

[0100] As illustrated in FIG. 1b, the drag calendering device (100) of the present invention may further include a control unit (600), and the control unit (600) may include one or more control rolls installed on the upper or lower part of the rear calender roll that is dragged after the dry electrode sheet is formed in the calender section (110) to control one or more of the surface flattening, thickness, or porosity of the dry electrode sheet.

[0101] The drag calendering device (100) of the present invention having the configuration described above is positioned at the bottom such that the first calender roll (111), where the electrode composition supply unit (120) is located, forms an oblique angle with the remaining rolls rather than being horizontally aligned, so that the electrode composition is fed from the electrode composition supply unit (120) onto the first calender roll (111), allowing the first calender roll (111) to rotate and naturally move toward the second calender roll (112). In addition, by installing a feeding member, the electrode composition is fed in an interval feeding manner, so that it is fed at regular intervals rather than being fed across the entire width of the electrode. Therefore, a dry electrode sheet of 100 microns or less can be manufactured using a room temperature calendering method in which the electrode composition is mixed and calendered at room temperature.

[0102] Next, the dry electrode manufacturing device of the present invention is a device that includes a drag calendering device (100) of the configuration described above to obtain a dry electrode sheet (free standing film) of a desired thickness from an electrode composition (mixture) and then attaches the dry electrode sheet to a current collector to manufacture a dry electrode. It can be classified into a single-sided electrode manufacturing device that forms an electrode on only one side of the current collector and a double-sided electrode manufacturing device that forms electrodes on both sides of the current collector. In addition to the characteristic components of the present invention described below, the single-sided and double-sided dry electrode manufacturing devices of the present invention may include various types of convenience and auxiliary devices necessary for mass production, such as sensors and controllers for measuring thickness or tension, a device for heating each calender roll, a spacing adjustment device for precisely adjusting the spacing of each roll, or a preheating device for preheating a primer layer formed on one or both sides of the current collector. Furthermore, various sensors and other auxiliary devices for operating each component included in these devices smoothly may be designed and installed to enable continuous operation. Since specific details regarding these auxiliary devices can be determined by a person skilled in the art through trial and error, the present invention does not specifically limit them.

[0103] First, as shown in FIG. 2, the cross-sectional electrode manufacturing device may include a progress calendar unit (100), an attachment calendar unit (400), and a current collector supply and recovery unit (500). The progress calendar unit (100) is a component that forms a dry electrode sheet by dragging a dry electrode composition supplied from an electrode composition supply unit backward while two or more calendar rolls are sequentially arranged and driven individually, and the drag calendering device (100) of the configuration described above can be used as is. As one embodiment, as shown in FIG. 2, the progress calendar rolls included in the progress calendar unit (100) correspond to a first calendar roll (111), a second calendar roll (112), and a third calendar roll (113), and these are calendar rolls that play the role of making a dry electrode sheet from the input dry electrode composition. For example, the electrode composition introduced onto the first calender roll (111) is a composition in a particulate state, and the rolls allow this composition to be converted into a sheet form as it passes between the first calender roll (111) and the second calender roll (112) and then proceed to the third calender roll (113).

[0104] The attachment calendar unit (400) is a component that forms a dry electrode plate by attaching a dry electrode sheet formed in the advance calendar unit (100) to a current collector while two or more calendar rolls are individually driven and sequentially arranged adjacent to the rearmost calendar roll of the advance calendar unit (100). It may include an attachment calendar roll section (410), and if necessary, may further include a heater section (420) as shown in FIG. 2. Here, the attachment calendar roll section (410) includes rolls for attaching the dry electrode sheet and the current collector, namely the fourth calendar roll (411), the fifth calendar roll (412), and the sixth calendar roll (413), and a heating member for controlling the temperature of the calendar rolls included in the attachment calendar roll section (410), although not shown. In one embodiment, the heating element can be installed inside each of the fourth calender roll (411) to the sixth calender roll (413) and driven individually, and the temperature of each of the fourth calender roll (411) to the sixth calender roll (413) can be adjusted to a range where it can function as a heating roll. In this way, the temperature of the calender rolls included in the attachment calender roll section (410) can be adjusted in a temperature range of 50-200°C so that the laminated dry electrode layer is well attached to the primer layer of the current collector using the heater element. However, if the temperature of the calender roll is less than 50°C, the temperature is too low and the adhesion between the electrode layer and the current collector is reduced, which is disadvantageous, and if it exceeds 200°C, the temperature is too high and there is a risk that the laminated dry electrode plate will warp, which is rather disadvantageous.

[0105] The heater unit (420) is a component for preheating the primer layer of a current collector so that the dry electrode layer adheres well to the primer layer of the current collector. It may be necessary because, in order to first make a dry electrode sheet and attach it to the current collector, it is desirable to form an adhesion-enhancing layer, i.e., a primer layer, on the surface of the current collector to enhance adhesion. As shown in FIGS. 2 and 3, one single-sided electrode manufacturing device and two double-sided electrode manufacturing devices may be installed to control the temperature of the surface of the current collector on which the primer layer is formed. Here, the heater unit (420) may be configured so that the primer layer of the current collector passes through a temperature range of 50°C to 200°C, and if the preheating temperature is outside this range, preheating may not occur or there is a risk that the primer layer may be thermally damaged. As one embodiment, the heater unit (420) may be implemented in a known configuration with various methods applied, such as installing several infrared lights to preheat the primer layer and causing the primer layer formed on the surface of the metal electrode plate, i.e., the current collector, to pass through facing the infrared lights or passing through a hot air chamber, or heating two rolls into which the current collector is introduced.

[0106] Accordingly, even if the attachment calendar unit (400) includes only the attachment calendar roll section (410), the temperature of the calendar rolls included in the attachment calendar roll section (410) is adjusted to a heating roll state having a temperature range of 50-200°C so that the dry electrode layer adheres well to the primer layer of the current collector, and then the current collector with the dry electrode sheet and primer layer formed thereon is heat-pressed while passing it between two heating rolls so that the dry electrode sheet and the primer layer of the current collector can be well bonded. However, as shown in FIGS. 2 and 3, if additional heater sections (420, 421, 422) are installed, the primer layer of the current collector is preheated, so heat-pressing occurs better when passing between two heating rolls, and the dry electrode sheet adheres better to the primer layer of the current collector, thereby further strengthening the adhesion between the dry electrode sheet and the current collector.

[0107] In addition, since the current collector is fed between the fourth calender roll (411) and the fifth calender roll (412) and the dry electrode sheet and current collector transferred from the third calender roll (113) are attached, the rotational speed of the two rolls into which the current collector is fed, namely the fourth calender roll (411) and the fifth calender roll (412), can basically be rotated at the same speed. Although the sixth calender roll (413) is not actually used to directly attach the dry electrode sheet and the current collector, it is a roll that further heat-compresses the dry electrode sheet formed by attachment between the fourth calender roll and the fifth calender roll, so it is included in the category of the attachment calender roll section.

[0108] Meanwhile, if the rear calendar roll (412) is rotated slightly faster than the front calendar roll (411), the current collector, i.e., the dry electrode plate, to which the dry electrode sheet is attached will move forward while being pulled taut, thereby obtaining a beautiful appearance. Therefore, if necessary, the rear attachment calendar roll in the attachment calendar unit (400) can be driven to have a rotational speed ratio of 1:1.0 to 1.5 times that of the front attachment calendar roll. This is because if the rotational speed of the rear attachment calendar roll is faster than 1.5 times, the dry electrode sheet attached to the current collector will wrinkle or curl severely, making it impossible to obtain a high-quality dry electrode plate. In particular, it was more desirable for the rear attachment calendar roll to have a rotational speed ratio of 1:1.0 to 1.3 times that of the front attachment calendar roll. At this time, the calendar roll included in the attachment calendar roll part (410) may include all three characteristics of the calendar roll used in the calendar part (110) described above, or at least the characteristics regarding the material of the roll may be implemented identically.

[0109] It can be seen that, excluding the current collector supply and recovery unit (500), the above-described single-sided electrode manufacturing device is configured such that both the progress calendar unit (100) and the attachment calendar unit (400) include multiple calendar rolls. The calendar rolls included in the single-sided electrode manufacturing device do not all need to have the same diameter, and as needed, it is acceptable to use some calendar rolls with a larger or smaller diameter compared to other calendar rolls. As a result of the inventors' research, it was confirmed that since the calendar roll included in the progress calendar unit (100) is an important roll for determining the thickness of the dry electrode sheet, it is advantageous for the diameter of the calendar roll to be as small as possible for smooth rotation, and that for the calendar roll included in the attachment calendar unit (400), it is effective to make the diameter of the calendar roll larger to increase the surface area for applying heat after inserting the current collector and attaching the dry electrode sheet. Therefore, although they are depicted with the same diameter for convenience, the calendar roll of the attachment calendar unit (400) may be used with a larger diameter than the calendar roll of the progress calendar unit (100). Additionally, since a dry electrode sheet is produced even by room temperature calendering, it does not matter if the calendar roll included in the progress calendar unit (100) does not use a heating part, but it may be effective to use a heating roll that includes a temperature-controllable heating part for the calendar roll included in the attachment calendar unit. In addition, as described above, it is acceptable to adjust the rotation speed of each calendar roll included in the forward calendar unit (100) and the attachment calendar unit (400) differently. In particular, in the case of the two calendar rolls at the connection point between the forward calendar unit (100) and the attachment calendar unit (400), for example, the third calendar roll (113) and the fourth calendar roll (411) of FIG. 2, the rear calendar roll (fourth calendar roll) can be rotated faster than the front calendar roll (third calendar roll) at a ratio of 1:1.05 to 1.5. This is because if the rotation ratio is less than 1.05, a problem occurs where a part of the electrode sheet is left on the front calendar roll, and if it is more than 1.5 times faster, it is pulled too much, causing the dry electrode to twist.

[0110] The current collector supply and recovery unit (500) is a component for supplying a current collector (metal electrode plate) or a support film, etc. to the calendar roll of the attachment calendar unit (400) and finally recovering and winding the dry electrode completed through the attachment calendar unit (400). It may be a known configuration including an unwinder that unwinds and supplies the film or metal electrode plate (current collector), etc., and a rewinder that winds and recovers the completed dry electrode plate. By the current collector supply and recovery unit (500), the current collector may be supplied between the rearmost calendar roll of the advance calendar unit (100) and the frontmost calendar roll of the attachment calendar unit (400), or between the frontmost calendar roll (411) of the attachment calendar unit (400) and the adjacent calendar roll (412) as shown in FIG. 2.

[0111] In cases where the progress calendar unit (100) included in the single-sided dry electrode manufacturing device (1) of the present invention is not configured to further include a control unit (600) as shown in FIG. 1b, the single-sided dry electrode manufacturing device (1) may further include a control unit (600). As shown in FIG. 2, the control unit (600) may include one or more control rolls (or flattening rolls) installed on the upper or lower part of the rear calendar roll, i.e., the third calendar roll (113), which is dragged after the dry electrode sheet is formed between the first calendar roll (111) and the second calendar roll (112) of the progress calendar unit (100) in order to control one or more of the surface flattening, thickness, or porosity of the dry electrode sheet. That is, when a dry electrode composition is fed onto the first calender roll (111) in the single-sided dry electrode manufacturing device (1) of the present invention, the first calender roll (111) rotates and naturally forms a dry electrode sheet of a certain thickness, which then moves toward the second calender roll (112). The dry electrode sheet that has moved to the second calender roll (112) then moves to the third calender roll (113), and this process is repeated until it moves to the fourth calender roll (411). At this time, if a control unit (600) including a control roll is placed on the upper part of the third calender roll (113) in the middle, for example, and pressed with a certain pressure to flatten the surface of the dry electrode sheet that has moved to the third calender roll (113), it helps to improve the surface roughness of the dry electrode sheet. At this time, it is advantageous to use a heating roll with release properties as the control roll. The release properties of the control roll can be obtained by forming a coating layer made of DLC (diamone-like carbon), graphite, or graphene. Additionally, heating the control roll can further reduce the thickness of the dry electrode while achieving flattening. However, since increasing the temperature of the control roll may cause a portion of the dry electrode sheet to fall off toward the control roll, the temperature of the control roll may be set to 200°C or lower. Furthermore, it is obvious that the control roll does not necessarily have to be installed on the upper part of the third calender roll (113), but can be installed in an appropriate location depending on the number of rolls or the desired direction.Furthermore, although not illustrated, the control unit (600) may include one or more control rolls installed on the upper or lower side of one or more calendar rolls included in the attachment calendar unit (400) to control one or more of the surface flatness, thickness, or porosity of the dry electrode.

[0112] If necessary, the single-sided dry electrode manufacturing apparatus (1) of the present invention may further include a scrubbing unit (700). The scrubbing unit (700) is installed between the progress calendar unit (100) and the attachment calendar unit (400) and is a component for removing unnecessary parts of a dry electrode sheet, such as trimming the edges of the dry electrode sheet formed in the progress calendar unit (100) and / or scrubbing the residue before attaching the dry electrode sheet to the current collector. It may include a trimming section and a scrubbing section. The trimming section removes unnecessary parts of the calendared dry electrode sheet, particularly unclean parts of the edges, and the scrubbing section removes remaining residue. Known technology may be adopted as is, as long as it can remove the edges of the electrode sheet and the residue. As shown in FIG. 2, the scrubbing unit (700) can be installed below the fourth calender roll, and it is obvious that the installation location and number of the trimming and scrubbing units can be modified as needed. However, it would be preferable to install it below the calender roll to efficiently remove the removed debris. In particular, it may be advantageous for the manufacture of a dry electrode plate by a continuous process to have the trimming of the edge portion of the dry electrode sheet and the removal of debris by the scrubbing unit (700) carried out at the calender roll, that is, the fourth calender roll (411), which performs the function of attaching the dry electrode sheet to the current collector. In other words, as shown in FIG. 2, a scrubbing unit (700) is installed at the bottom of the fourth calender roll (411) to clean the edge area, and then immediately attached to the current collector inserted between the fourth calender roll (411) and the fifth calender roll (412). Since the dry electrode sheet can be firmly attached to the current collector by heat-pressing it while passing from the fourth calender roll (411) to the sixth calender roll (413), it is effective to manufacture a dry electrode plate in a continuous process in the same device.

[0113] In addition, as shown in FIG. 3, the double-sided electrode manufacturing device (1) of the present invention has a structure in which, based on the current collector supplied between the fourth calendar roll (411) and the fifth calendar roll (412) of the attachment calendar unit (400) by the current collector supply and recovery unit (500) in the single-sided electrode manufacturing device (1) shown in FIG. 2, two progress calendar units (100) are installed facing each other adjacent to the fourth calendar roll (411) and the fifth calendar roll (412), respectively. Therefore, since the arrangement structure and the symbols on the drawings, such as the number and installation location of each component, are different, each component, namely the calendar roll, control roll, heater unit, hopper, scrubbing unit, etc., has the same characteristics as described above, we will focus on the arrangement structure that differs.

[0114] Accordingly, the double-sided electrode manufacturing device (1) of the present invention may include, as shown in FIG. 3, an attachment calendar unit (400), a progress calendar unit including a first progress unit (210) and a second progress unit (220), an electrode composition supply unit including a first supply unit (301) and a second supply unit (302), and a current collector supply and recovery unit (500). Of course, if necessary, it may include various types of convenience and auxiliary devices required for mass production, such as a control unit, a scrubbing unit, sensors and controllers for measuring thickness or tension, or a preheating device for preheating a primer layer formed on one or both sides of a current collector.

[0115] The attachment calendar unit (400) serves to attach a first dry electrode sheet and a second dry electrode sheet to each of the two sides of a current collector supplied between the fourth calendar roll (411) and the fifth calendar roll (412) as the fourth calendar roll (411) and the fifth calendar roll (412) are sequentially arranged and driven individually. Here, the first dry electrode sheet may be formed in the first progress unit (210), and the second dry electrode sheet may be formed in the second progress unit (220).

[0116] As described above, the progress calendar unit includes a first progress calendar unit (210) and a second progress calendar unit (220) installed facing each other with respect to a current collector supplied between the fourth calendar roll (411) and the fifth calendar roll (412) of the attachment calendar unit (400). The first progress calendar unit (210) is formed by sequentially arranging the third calendar roll (213), the second calendar roll (212), and the first calendar roll (211) adjacent to the outside of the fourth calendar roll (411) and driving them individually to drag the dry electrode composition supplied to the first calendar roll (211) toward the fourth calendar roll (411) to form a first dry electrode sheet. The second progress calendar unit (220) is arranged sequentially adjacent to the outer side of the fifth calendar roll (412) with the sixth calendar roll (223), the seventh calendar roll (222), and the eighth calendar roll (221) driven individually to drag the dry electrode composition supplied to the eighth calendar roll (221) toward the fifth calendar roll (412) to form a second dry electrode sheet.

[0117] In this way, the fourth calendar roll (411) and the fifth calendar roll (412), the third calendar roll (211) and the sixth calendar roll (221), the second calendar roll (212) and the seventh calendar roll (222), and the first calendar roll (213) and the eighth calendar roll (223), which are opposite to each other with the center of the entire house, each have the same speed and opposite rotation direction. At this time, each calendar roll included in the first progress calendar unit (210) and the second progress calendar unit (220) can be driven to have different rotational speeds. In the first progress calendar unit (210), the second calendar roll (212) can be implemented to rotate 1.05 to 4.0 times faster than the first calendar roll (211), and the third calendar roll (213) can be implemented to rotate 1.05 to 4.0 times faster than the second calendar roll (212). In the second progress calendar unit (220), the seventh calendar roll (222) can be implemented to rotate 1.05 to 4.0 times faster than the eighth calendar roll (221), and the sixth calendar roll (223) can be implemented to rotate 1.05 to 4.0 times faster than the seventh calendar roll (222).

[0118] The electrode composition supply unit includes a first supply unit (301) and a second supply unit (302). The first supply unit (301) is installed between the second calendar roll (212) and the first calendar roll (211) to supply the electrode composition to the first calendar roll (211), and the second supply unit (302) is installed between the seventh calendar roll (222) and the eighth calendar roll (221) to supply the dry electrode composition to the eighth calendar roll. Therefore, the first supply unit (301) and the second supply unit (302) of the electrode composition supply unit may have the same configuration as the electrode composition supply section (120) included in the drag calendering device shown in FIG. 1, differing only in the number and the installation location, while the remaining configuration may be identical.

[0119] In the single-sided and double-sided dry electrode manufacturing apparatus of the present invention having the configuration described above, once a single-sided or double-sided dry electrode is manufactured through calendering, the dry electrode can finally be manufactured by passing it through a rolling roll. This rolling roll is a component for obtaining a desired level of porosity and electrode density by readjusting the thickness of the dry electrode sheet attached to the current collector. The rolling roll is typically composed of a heating roll equipped with a heating section capable of raising the temperature, which has release properties such as a DLC coating on its surface; since this is a technology that is conventionally practiced, there is no need to limit it to a special device.

[0120] Meanwhile, although not specifically illustrated in FIGS. 2 and 3, the structure of the calendar roll may be designed to have a crown / reverse crown structure as follows, and a post-processing chamber may be installed in the latter part of the dry electrode manufacturing device to enable post-processing operations such as a hot air device, infrared heating lamp, and ultraviolet irradiation lamp, and a rolling roll may be further installed.

[0121] Specifically, regarding the crown / reverse crown structure, each calender roll included in the single-sided electrode manufacturing device and double-sided electrode manufacturing device of the present invention may be designed so that the middle portion protrudes (crown) or recedes (reverse crown) as necessary to minimize the thickness variation in the width direction of the dry electrode sheet obtained by calendering. In this case, the degree of the crown or reverse crown may vary depending on various conditions such as the type of electrode composition, calendering speed, and roll width; however, since this can be determined by a person skilled in the art through trial and error, it is not to be limited to any specific conditions.

[0122] The post-processing chamber is installed in the rear part of the dry electrode manufacturing device and may include a structure capable of post-processing operations such as a hot air device, infrared heating lamp, or ultraviolet irradiation lamp. While passing through this chamber, post-processing such as removing thermal history, final drying, or curing of the dry electrode manufactured in the preceding stage can be performed; the post-processing chamber may be installed before the rolling rolls. This is because dimensional deformation of the electrode must not occur after passing through the rolling rolls.

[0123] The dry electrode composition used in the drag calendering device of the present invention having the configuration described above and in the single-sided and double-sided dry electrode manufacturing device including the same may use any known dry electrode composition, but if a dry electrode composition containing a plane-forming agent is used, a dry electrode having superior characteristics can be obtained.

[0124] This is because the inventors have confirmed that by using a so-called sheet forming agent (dry electrode sheet forming agent) to create a dry electrode composition using nanomaterials in the shape of tubes, ribbons, or fibers, and then calendering it using the drag calendering device of the present invention and the single-sided and double-sided dry electrode manufacturing device including the same, dry electrode sheets and dry electrode plates with a thickness of less than 100 microns can be produced using only room temperature calendering.

[0125] As one embodiment, the dry electrode composition used in the present invention may comprise 80-98% by weight of an active material, 1-10% by weight of a binder, and 1-10% by weight of a plane-forming agent, and in particular, may comprise 85-97% by weight of an active material, 1.5-8% by weight of a binder, and 1.5-7% by weight of a plane-forming agent. The compositional ratio of each component included in the dry electrode composition used in the present invention is determined experimentally. Below the lower limit of each component, the effect of each component is not realized, which is disadvantageous; and above the upper limit, each component is used excessively beyond what is necessary, which reduces economic efficiency or prevents proper realization of electrochemical performance, which is disadvantageous. Specifically, if the binder content is low at less than 1.0% by weight, the electrode plane is not properly formed during electrode manufacturing, which is disadvantageous; and if the content is 10% by weight or more, although the electrode plane of the dry electrode is formed well, the relatively low active material content makes it difficult to realize electrical capacitance, which may actually be disadvantageous. In the case of a cotton-forming agent, if the content is less than 1.0 weight%, the cotton-forming power is reduced and it is disadvantageous, and if it is 10 weight% or more, there is too much tube-shaped cotton-forming agent, so the appearance is not clean and many defects occur, which may be disadvantageous.

[0126] As described above, since the present invention is intended to manufacture a dry electrode using only a room-temperature calendering technique without pretreatment, it is evident that it can be applied regardless of the type of active material and the type of secondary battery, such as a lithium-ion battery or an all-solid-state battery, and is applicable to all types of active materials capable of manufacturing electrodes by the dry method. Accordingly, the active material in the dry electrode composition of the present invention may be a positive electrode active material or a negative electrode active material, and may be any one selected from the group consisting of alkali metal elements, alkaline earth metal elements, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, graphite, silicon, silicon oxide, sulfur, and combinations thereof. Here, the alkali metal element may be any one selected from the group including lithium, sodium, potassium, rubidium, cesium, and francium, and the alkaline earth metal element may be any one selected from the group including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). If necessary, as described below, when the surface-forming agent is a carbon-based nanomaterial, the active material may have a structure further comprising a coating layer composed of a carbon-based nanomaterial formed on its surface.

[0127] In addition, in the dry electrode composition of the present invention, the plane-forming agent may be a thin, long nanomaterial with a diameter in the nanometer range and a length in the range of several to several hundred microns. In particular, since the plane-forming agent is not intended to improve surface adhesion properties but rather to be used together with each component of the electrode, namely the active material and the binder, to cause these components to intertwine with each other—that is, to form a plane or sheet—it may be a nanomaterial having one or more forms selected from the group consisting of tube, ribbon, and fiber forms.

[0128] In one embodiment, the plane-forming agent may be one or more carbon-based nanomaterials selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes (few-wall CNTs), branched carbon nanotubes, carbon nanoribbons, and carbon nanofibers, or one or more non-carbon-based nanomaterials selected from the group consisting of non-carbon-based nanomaterials such as boron nitride nanotubes and boron nitride nanoribbons, and polymer nanomaterials such as aramid nanofibers. However, since non-carbon-based nanomaterials are electrically insulating materials, a conductive additive must be added separately when using them as plane-forming agents. In contrast, when using carbon-based nanomaterials as plane-forming agents, the carbon-based nanomaterials themselves have good electrical conductivity, so a separate conductive additive does not need to be used, and various surface treatment techniques are possible, making it significantly more advantageous compared to other plane-forming agents.

[0129] As described above, since the surface-forming agent in the present invention is not intended to control surface characteristics, it may be used as is without special surface treatment. However, it is advantageous to manufacture a more uniform dry electrode sheet by surface-treating the surface of the surface-forming agent to enhance adhesion, form surface chemical bonds, or impart other functional purposes, or by using a method that pre-treats the surface of the active material to ensure uniform adhesion of the surface-forming agent. For example, when using carbon nanotubes as the surface-forming agent, using an active material surface-coated with a small amount of carbon nanotubes is advantageous as it allows the dry electrode sheet to have more uniform electrical conductivity. However, considering economic aspects, using untreated carbon nanotubes may be more effective.

[0130] In particular, the plane-forming agent of the present invention may be a carbon nanotube in the form of a lump (particle) or bundle with a size of 0.2 to 200 microns. This is because if the size of the particle or bundle is 0.2 microns or less, the size is too small and the plane-forming ability is significantly reduced, and if it is 200 microns or more, the particle is too large and plane-forming is hindered, which is disadvantageous. Preferably, the carbon nanotube may be a carbon nanotube with a particle or bundle size of 1 to 50 microns. In this case, the carbon nanotube is a nanomaterial with an aspect ratio of 100 or more, and is one or more selected from the group consisting of carbon nanotubes such as single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes (few-wall CNTs), and branched carbon nanotubes.

[0131] In addition, in the dry electrode composition of the present invention, the binder may be PTFE or a mixed binder of PTFE and a binder for secondary batteries (hereinafter referred to as "another binder"), and the present invention is a particularly useful technology for mixed binders. In this case, when the binder is for the positive electrode, the other binder mixed with PTFE may be one or more compounds that can be used as a binder for secondary batteries among polymers having a so-called oxidation potential of at least 4.5V. Oxidation potential refers to the potential at which an oxidation reaction occurs, and if the oxidation potential is lower than 4.5V, the organic compound of the positive electrode oxidizes easily, which significantly degrades the electrochemical performance of the battery manufactured therefrom.

[0132] Furthermore, since PTFE is in particulate form, a uniformly mixed binder can be obtained by simply mixing it with a dry blender when it is a particulate compound. However, if the compound is very flexible and difficult to mix with a dry blender, or if it is dissolved in a solution, a mixed binder can be prepared using the so-called solution blending method. A mixed binder can be obtained by dispersing PTFE in a solvent, adding a solution compound to the mixture, stirring to obtain a mixture, and then filtering it. In terms of the purity of the mixed binder, the solution blending method is advantageous because organic impurities contained in PTFE can be removed during the process of dispersion in the solvent.

[0133] Other binders that can be mixed with PTFE in the mixed binder included in the dry electrode composition of the present invention are binders that can be used as binders for all secondary batteries, and are typically homopolymers or copolymers comprising one or more selected from the group consisting of fluorine-based, acrylic acid-based, acrylate-based, cellulose-based, styrene-based, butadiene-based, acrylonitrile-based, ethylene-based, and propylene-based components. In one embodiment, the fluorine-based component may be polyvinylidene fluoride (PVDF) or a copolymer containing a fluorine component. In addition, the acrylate-based copolymer is a copolymer comprising two or more components among acrylonitrile-based, carboxylic-based, butadiene, and glycol-based monomers, wherein the carboxylic monomer may be a copolymer comprising one or more selected from the group consisting of acrylic acid, acrylate, maleic acid, and maleic anhydride. These copolymers have hydroxyl groups (-OH) or carboxyl groups (-COOH or -COO). -It is a binder that meets the purpose of the present invention as it contains a component with good adhesive properties. In addition, a representative binder may be an acrylonitrile-ethylene glycol-maleic acid copolymer (PAEM). When this copolymer is used as a binder, adhesive properties such as adhesion between the electrode layer and the metal electrode plate and cohesion of each component within the electrode are improved, and thus the electrochemical properties of the dry electrode can be improved.

[0134] A method for manufacturing a mixed binder by a liquid blending method comprises: (1) a step of preparing a first binder dispersion by dispersing a first binder, which is a fluorine-based resin, in a solvent such as water; (2) a step of preparing a second binder solution by dissolving a second binder, which contains another binder for existing secondary batteries, in an organic solvent such as NMP or DMF; (3) a step of stirring while adding the second binder solution to the first binder dispersion; and (4) a post-processing step of filtering, washing, and drying the resulting product after stirring is finished. At this time, the content of the other binder mixed with PTFE can be prepared to have a weight ratio of 90 to 10:10 to 90. Through this mixing ratio, a core-shell structured composite binder can be obtained in the form of a single particle, that is, a core-shell structured composite binder in which the interior contains fluorine-based resin particles and the outer surface is covered by a layer of another binder resin with good adhesive properties. At this time, a weight ratio of 80–20:20–80 may be more advantageous. The stirring step can be performed by slowly adding the second binder solution to the first binder dispersion while stirring. The stirring conditions are also experimentally established and can be performed by vigorously stirring for 20 minutes to 5 hours at a speed of 200–10,000 rpm at a temperature of 20–70°C; increasing the stirring speed is advantageous as it allows for obtaining smaller and more uniform composite binders. The post-processing step is a process for obtaining the core-shell structured composite binder particles generated during the stirring step. This can be performed by filtering the product obtained after stirring is finished to separate the core-shell structured composite binder particles from the solvent, followed by washing, purification, and drying. Here, filtering and washing may be performed one or more times.

[0135] In addition, in the case of a mixed binder prepared by the liquid-phase mixing method, it may be a core-shell structured composite binder in which the interior is PTFE and the exterior is surrounded by a compound forming the second binder solution. The core-shell structured composite binder may be in a form where a single PTFE particle or multiple PTFE particles are surrounded by a single second binder compound.

[0136] To examine the core-shell structured composite binder in more detail, first, the fluorine resin forming the core is not limited to being a polymer that contains a fluorine component and is capable of fiberization, but in particular, it may be polytetrafluoroethylene (PTFE), and the particle diameter may be 0.05 to 5.0 microns. If the particle size of the fluorine resin is less than 0.05 microns, it is disadvantageous because the particles are too small to make fluorine resin particles or to make a fluorine resin dispersion. If it is 5 microns or more, the total surface area of ​​the fluorine resin particles decreases, and the content of other binder resins that are applied to the surface is lowered, making it difficult to impart adhesion, which is disadvantageous.

[0137] The other binder resin forming the shell can be any polymer compound that possesses adhesive properties and can be used as a binder for secondary batteries. As a polymer capable of being used as a binder for the electrodes of a secondary battery, it may be a polymer soluble in organic or aqueous solvents and may comprise one or more polymers. In one embodiment, it may be in the form of a homopolymer, such as polyvinylidene fluoride (PVDF), which is widely used as a binder for positive electrodes, or it may be a copolymerized polymer with various functions. One or more of these binders may be mixed and used; in this case, it is advantageous because the characteristics of each binder complement each other to produce a better effect.

[0138] Other binder resins that form a representative shell may be, of course, one or more selected from the group consisting of a cellulose-based polymer binder such as polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), and carboxymethylcellulose, a flexible copolymer such as styrene-butadiene rubber or acrylonitrile-butadiene rubber, or a copolymer comprising one or more selected from the group consisting of acrylonitrile-based monomers, carboxyl-based monomers, and glycol-based monomers, but are not limited thereto.

[0139] More specifically, a copolymer can be used by copolymerizing a carboxyl monomer for imparting adhesion and an acrylonitrile monomer for imparting stable electrochemical properties as a base, and a third monomer for imparting other functions thereto. For example, when an acrylate monomer neutralized by a compound consisting of 2 to 6 carbon atoms is copolymerized, these components cause geometric interference, resulting in a copolymer that is flexible and highly adhesive. This is because, by using this to manufacture a core-shell structured composite binder, a flexible and highly adhesive composite binder can be obtained. Here, the carboxyl monomer may be one or more selected from the group consisting of acrylic acid, acrylate, maleic acid, and maleic anhydride, and in particular, the other binder resin for forming the shell may be an acrylonitrile-ethylene glycol-maleic acid copolymer.

[0140] Meanwhile, the content of the fiberizable fluorine resin (fibrous fluorine resin) included in the binder of the dry electrode composition of the present invention may be 30% by weight or less of the total weight of the binder. In the present invention, if necessary, the fiberable fluorine resin constituting the binder can be replaced with other binder resins up to 80% by weight. In the prior art, the binder included in the electrode composition for manufacturing dry electrodes was composed almost entirely of PTFE and the surface-forming ability of the dry electrode was maintained only after undergoing a pretreatment process. However, the dry electrode composition of the present invention includes a surface-forming agent, so even if the content of the fiberable fluorine resin included in the binder is reduced to up to 20% by weight, an excellent dry electrode surface can be formed immediately through a calendering process without a pretreatment process.

[0141] In addition, the dry electrode composition of the present invention may further include, if necessary, one or more conductive nanomaterials selected from the group consisting of conductive carbon black, graphene, carbon nanoplates, or graphene nanoplates, in an amount of 1 to 100 parts by weight per 100 parts by weight of the planar forming agent. In particular, when a non-carbon-based nanomaterial is used as the planar forming agent, it is essential to add a conductive nanomaterial to reinforce conductivity. However, when a carbon-based nanomaterial, particularly a carbon nanotube, is used as the planar forming agent, it is not required as an essential component; but when carbon nanotubes with an aspect ratio of 100 or more are used as the planar forming agent, additionally including a conductive nanomaterial with an aspect ratio of less than 100 has the advantage of not only helping to disperse the carbon nanotubes but also imparting higher conductivity.

[0142] The dry electrode composition of the present invention having the above-described configuration can be manufactured by mixing and stirring an active material, a binder, and a fiber-forming agent without a solvent using a known mixing device. The known mixing device that can be used at this time is a mixer or a mixture manufacturing device, and one or more selected from various dry particle mixers (dry mixers or powder mixers) such as low-speed and high-speed mixers, mixers that simultaneously implement revolution and rotation, Henschel mixers having one or more blades, extrusion mixers equipped with a single-axis or multi-axis screw, mixers using a ball mill, swing-type or twist-type mixers, and mortar-and-pound type mixers.

[0143] Next, the present invention can provide a dry electrode manufactured by a dry electrode manufacturing device having the configuration described above, and a secondary battery including the dry electrode.

[0144] The present invention described above is intended for manufacturing a dry electrode using only a room-temperature calendering technique without pretreatment. In particular, when a plane-forming agent is included in the dry electrode composition of the present invention, if the types of active material and binder are appropriately selected and used together, it can be applied to the manufacture of dry electrodes for both positive and negative electrodes. Therefore, it can be applied regardless of the type of active material or the type of secondary battery, such as a lithium-ion battery or an all-solid-state battery.

[0145] Furthermore, the present invention primarily utilizes an electrode composition for the positive electrode of a lithium-ion battery. However, the technology of the present invention is applicable to all types of secondary batteries requiring a dry electrode, including metal-ion batteries using other metal ions, various liquid electrolyte batteries using liquid electrolytes, semi-solid electrolyte batteries, polymer electrolyte batteries, or solid electrolyte batteries such as sulfide-based all-solid-state batteries.

[0146] Example 1

[0147] A drag calendering device 1 was manufactured as follows in the structure shown in FIG. 1b so that the angle of the alternate angle formed by the first calendar roll (111) and the second calendar roll (122) is 40 degrees.

[0148] (1) The calender section (110) and the electrode composition supply section (120) are composed of a first calender roll (111) to a third calender roll (113). (2) The rotational speed of each calender roll is driven individually. (3) A heating roll of 100-120°C is installed on the upper part of the third calender roll (113) by a control unit (600) to flatten the surface of the electrode.

[0149] The first calender roll (111) to the third calender roll (113) used at this time had an average surface roughness of 0.1 micron and used a zirconia roll (a roll with a zirconia layer formed 5 mm thick on a metal roll) with a peel strength of 3.5 N / 18 mm against Scotch tape.

[0150] In particular, the electrode composition supply unit (120), which is installed so that a dry electrode composition in a mixed state can be fed onto the first calendar roll (111), has a thin spacer formed at 1mm intervals with holes of 1.5mm diameter formed as a feeding member at its bottom as shown in FIG. 4, and is implemented in a structure that enables partial feeding by allowing the electrode composition to fall onto the first calendar roll (111) from 10mm above the first calendar roll (111) through the holes.

[0151] In addition, unless otherwise noted, the first calender roll (111) is set to manufacture a dry electrode sheet while rotating at a speed of 1 meter per minute (1 m / min), the second calender roll (112) at 3 m / min, and the third calender roll (113) at 5 m / min.

[0152] Example 2

[0153] A drag calendering device 2 having the same configuration as Example 1 was manufactured, except that the first calendar roll (111) and the second calendar roll (122) are arranged such that the angle of the alternate angle formed by them is 15 degrees.

[0154] Example 3

[0155] Using the drag calendering device 1 obtained in Example 1, a dry electrode composition 1 was prepared as follows, and then a dry electrode sheet 1 was manufactured.

[0156] 1. Preparation of Dry Electrode Composition 1

[0157] (1) Preparation of PTFE / PAEM mixed binder by liquid blending method

[0158] ① Step of preparing the first binder dispersion

[0159] A first binder dispersion (solid content 50 wt%) was prepared in which PTFE particles with an average particle size of 250 nanometers (0.25 microns) were dispersed in water.

[0160] ② Step of preparing the second binder solution

[0161] PAEM (acrylonitrile-ethylene glycol-maleic acid copolymer), which is used as a positive electrode binder in conventional lithium-ion batteries, was dissolved in NMP to make a second binder solution (solid content 10 wt%).

[0162] ③ Stirring step

[0163] The amount of the first binder aqueous dispersion and the second binder solution was adjusted so that the weight ratio of PTFE to PAEM was 50:50, and the second binder solution was slowly added to the first binder dispersion while stirring at 70°C for 1 hour at a speed of 2,000 rpm.

[0164] ④ Post-processing stage

[0165] After filtering the product obtained from the stirring step with a pressure filter and washing it with distilled water three times, vacuum drying (50°C, 24 hours) was performed to finally produce a light beige final reaction product, a mixed binder (PTFE (50) / PAEM (50)) with a core-shell structure and a weight ratio of PTFE and PAEM of 50:50.

[0166] (2) Preparation of a dry electrode composition in a mixture state

[0167] 95 wt% of active material (NCM811), 2 wt% of a fiber-forming agent (untreated multi-walled carbon nanotube, lump particle size: 50 microns), and 3 wt% of a mixed binder (PTFE (50) / PAEM (50)) were all placed in a powder mixer and mixed at room temperature 10 times for 1 minute at 10,000 rpm to obtain a dry electrode composition 1, which is a mixture of particles with a size of 1.5 mm.

[0168] (3) Formation of a dry electrode sheet

[0169] A dry electrode sheet 1 was formed by driving the device so that the dry electrode composition 1 was dropped onto the first calendar roll (111) through the electrode composition supply unit (120) installed to feed the dry electrode composition 1 10 mm above the first calendar roll obtained in Example 1. At this time, the temperature of the first calendar roll (111) to the third calendar roll (113) was room temperature.

[0170] Example 4

[0171] A dry electrode sheet 2 was manufactured by performing the same method as in Example 3, except that the drag calendering device 2 obtained in Example 2 was used.

[0172] Examples 5 to 8

[0173] Dry electrode sheets 3 to 6 were obtained by performing the same method as in Example 3, except that dry electrode compositions 2 to 5 having the compositions shown in Table 1 below were used.

[0174] NCM811 surface-forming agent binder (PTFE / PAEM) Example 5 (Dry electrode composition 2) 9523 / 0 Example 6 (Dry electrode composition 3) 95.5 13.5 / 0 Example 7 (Dry electrode composition 4) 952 0.6 / 2.4 Example 8 (Dry electrode composition 5) 952 (BNNT) 1.5 / 1.5

[0175] In Table 1, the content of all components is in weight%, and the cotton-forming agent is untreated carbon nanotubes (multi-walled) in Examples 5 to 7 and boron nitride nanotubes in Example 8; as for the binder, PTFE (polytetrafluoroethylene) was used alone in Examples 5 and 6, a PTFE / PAEM mixed binder prepared in the same way as the PTFE / PAEM mixed binder disclosed in Example 3, differing only in the content ratio of the two compounds, was used in Example 7, and Example 8 is identical to the PTFE / PAEM mixed binder disclosed in Example 3.

[0176] Example 9

[0177] A dry electrode sheet 7 was obtained by performing the same method as in Example 3, except that the surface roughness (average) of the zirconia layer (~5 millimeter thickness) formed on the surface of the first calendar roll (111) to the third calendar roll (113) constituting the drag calendering device 1 was polished to 0.2 microns.

[0178] Example 10

[0179] A dry electrode sheet 8 was obtained by performing the same method as in Example 3, except that the surface adhesion force of the first calendar roll (111) to the third calendar roll (113) constituting the drag calendaring device 1 was adjusted to 6 N / 18 mm by using a coating treatment.

[0180] Comparative Example 1

[0181] A comparative example sheet manufacturing device 1 was manufactured with the same configuration as Example 1, except that the first calendar roll (111) and the second calendar roll (122) are arranged horizontally without forming an oblique angle.

[0182] Comparative Example 2

[0183] A comparative example sheet manufacturing device 2 was manufactured with the same configuration as Example 1, except that a feeding member was not installed at the bottom of the electrode composition supply unit (120) of the device of Example 1 so that the electrode composition is not partially fed but continuously fed.

[0184] Comparative Example 3

[0185] Comparative electrode sheet 1 was manufactured using the same method as in Example 3, except that the comparative example manufacturing apparatus 1 obtained in Comparative Example 1 was used.

[0186] Comparative Example 4

[0187] Comparative electrode sheet 2 was manufactured in the same manner as in Example 3, except that the comparative example manufacturing apparatus 2 obtained in Comparative Example 2 was used and the roll temperature was set to 150°C.

[0188] Comparative Examples 5 and 6

[0189] Comparative example electrode sheets 3 and 4 were obtained by performing the same method as in Example 3, except that a dry electrode composition having the composition shown in Table 2 below was used. At this time, Comparative Example 5 was calendered at room temperature, and Comparative Example 6 was calendered at high temperature with the calender temperature raised to about 150°C.

[0190] NCM811 Surface-forming agent binder (PTFE / PAEM) Comparative Example 596.50.51.5 / 1.5 Comparative Example 696.50.51.5 / 1.5

[0191] Comparative Example 7

[0192] Comparative electrode sheet 5 was manufactured by performing the same method as in Example 9, except that the surface roughness (average) of the zirconia layer formed on the surface of the first calender roll (111) to the third calender roll (113) was polished to 2.0 microns. At this time, the gap between the rolls was adjusted so that the thickness of the calendered dry electrode sheet was about 100 microns.

[0193] Comparative Example 8

[0194] Except for coating the first calender roll (111) to the third calender roll (113) so that the surface adhesion force is 0.3 N / 18 mm, the same method as in Example 10 was performed, but it was confirmed that a dry electrode sheet was not manufactured.

[0195] Experimental Example 1

[0196] Figure 5 shows the results of visual inspection and infrared spectroscopy (FTIR: Fourier Transform InfraRed spectroscopy) of the mixed binder of PTFE and acrylonitrile-ethylene glycol-maleic acid copolymer prepared in Example 3.

[0197] The mixed binder consists of light beige particles. By varying the weight ratio of the two compounds to 20:80, a mixed binder with a weight ratio of PTFE to PAEM of 20:80 (PTFE (20) / PAEM (80)) can also be produced; however, when the PAEM content is high, the resulting mixed binder has a slightly darker beige color. As shown in Fig. 5, the synthesis of these materials is 2235 cm -1 This is a characteristic peak representing the acrylonitrile group; it shows that while this peak is absent in PTFE, it is present in the mixed binder. Therefore, it was confirmed that the PTFE / PAEM mixed binder was successfully fabricated.

[0198] Experimental Example 2

[0199] Dry electrode sheets 1 to 6 obtained in Examples 3 to 8 and comparative electrode sheets 1 to 4 prepared in Comparative Examples 3 to 6 were observed. The dry electrode sheets were tested for surface forming ability (surface forming ability) and thickness, and the results were determined by collecting the dry electrode sheets that had passed to the third calender roll (113). The results are shown in Table 3. If the dry electrode sheet was formed well without crumbling, the surface forming ability was judged to be good ("Good"). If the electrode sheet was not formed in the same process and crumbled and fell off, it was judged to be defective ("Bad"). If the electrode sheet was formed but crumbled easily even with a weak impact, it was judged to be average ("Average"). In addition, actual photographs of dry electrode sheet 1 and dry electrode sheet 6 are shown in FIGS. 6 and FIGS. 7, respectively.

[0200] Dry Sheet Thickness (um) Flat Forming Strength Dry Electrode Sheet 1 (Example 3) ~ 90 Good Dry Electrode Sheet 2 (Example 4) ~ 95 Good Dry Electrode Sheet 3 (Example 5) ~ 95 Good Dry Electrode Sheet 4 (Example 6) ~ 100 Good Dry Electrode Sheet 5 (Example 7) ~ 90 Good Dry Electrode Sheet 6 (Example 8) ~ 100 Good Comparative Electrode Sheet 1 (Comparative Example 3) ~ 115 Good Comparative Electrode Sheet 2 (Comparative Example 4) ~ 125 Good Comparative Electrode Sheet 3 (Comparative Example 5) - Poor Comparative Electrode Sheet 4 (Comparative Example 6) ~ 95 Good

[0201] As shown in Table 3, the dry electrode sheets 1 to 6 prepared in Examples 3 to 8 all had a thickness of about 90-100 microns, and good dry electrode sheets were obtained such that when the dry electrode sheets were lifted, the dry electrode sheet surface was well maintained without any sheets breaking. In particular, in the case of Examples 3 to 8 using drag calendering devices 1 and 2, it was easy to feed the dry electrode compositions 1 to 5 onto the first calender roll (111) at intervals of 1.0 mm, and it was confirmed that the dry electrode compositions dropped on the first calender roll (111) moved naturally into the gap area with the second calender roll (112) without significant disturbance. At this time, when the gap between the first calender roll (111) and the second calender roll (112) was 80 microns, the dry electrode sheet produced was 90-100 microns, and it was confirmed that the thickness of the dry electrode sheet was thinner as the angle of obliqueness increased.

[0202] On the other hand, in the case of Comparative Example 3 using Comparative Example Sheet Manufacturing Device 1, dry electrode composition 1 was dropped at intervals of 1.0 mm, but the dry electrode composition 1 introduced into the gap between the first calender roll (111) and the second calender roll (112) was mixed together and did not maintain the spacing. The thickness of the comparative example electrode sheet produced at this time was 115 microns, but the thickness was non-uniform in the machine direction (MD) and transverse direction (TD), and it was confirmed that the thickness of the calendered dry electrode sheet did not become thinner even if the roll gap was further reduced. In the case of Comparative Example 4 using Comparative Example Sheet Manufacturing Device 2, dry electrode composition 1 was present across the entire width, and as the roll rotated, these compositions were compressed together, making it difficult to produce a dry electrode sheet with a uniform and thin thickness. This is thought to be because when dry electrode compositions are present in the full width of the gap between the first calender roll (111) and the second calender roll (112), there is a strong tendency for the rolls to compress all of these dry electrode compositions together as they rotate, making it difficult to control the thickness.

[0203] From these results, it was found that an obliquely arranged calendar device and a partial feeding method are suitable for manufacturing dry electrode sheets with a relatively thin and uniform thickness.

[0204] In particular, it was confirmed that a relatively thin dry electrode sheet could be manufactured through room temperature calendering without a separate pretreatment process from a dry electrode sheet 5 prepared with a dry electrode composition 4 in which an acrylonitrile copolymer (PAEM), known to inhibit fiberization in PTFE, was mixed up to 80% by weight.

[0205] FIG. 6 is a photograph of a dry electrode sheet 1 obtained using untreated carbon nanotubes (Example 3) as a plane-forming agent, the color is black and the surface resistance is several hundred (10 2 ) was the resistance / area. On the other hand, as can be seen from Fig. 7, which shows a dry electrode sheet 6 obtained using boron nitride nanotubes (Example 8) as an area-forming agent, a gray dry electrode sheet was obtained, and the surface resistance was 107 The ohm / area ratio was high. This is because boron nitride nanotubes are not electrically conductive. As in the case of comparative electrode sheet 3, if the content of carbon nanotubes, which are the plane-forming agent, is low at about 0.5 wt%, the dry electrode sheet is not formed well during room temperature calendering. However, it was confirmed that even when using the same dry electrode composition as in comparative electrode sheet 4, the dry electrode sheet is formed well when high-temperature calendering is performed with the calender roll temperature raised to about 150°C.

[0206] In addition, when comparing the results of dry electrode sheets 1 to 4, it was confirmed that as the PTFE content increased, the thickness of the dry electrode sheet became relatively thicker.

[0207] From the results in Table 3, it can be seen that by using an appropriate amount of a plane-forming agent, a thin dry electrode sheet with a thickness of about 100 microns can be produced without difficulty through a simple process of mixing the dry electrode composition and immediately calendering at room temperature without a separate pretreatment process. In addition, it was confirmed that a dry electrode sheet is produced well even when using untreated carbon nanotubes as is. Meanwhile, although the examples and comparative examples were described using multi-walled carbon nanotubes and boron nitride nanotubes, it is obvious that the scope of the present invention is not limited to these two types of nanomaterials, and that other types of nanomaterials such as tubes, fibers, and ribbons are also nanomaterials that meet the purpose of the present invention. Meanwhile, although a small amount of carbon nanotubes can be used as a conductive material when manufacturing secondary battery electrodes, this is not used as a plane-forming agent for manufacturing dry electrode sheets but is used to impart electrical conductivity to the dry electrode layer, and the content used when used as a conductive material usually does not exceed 0.5 wt% or a maximum of 1 wt%. Therefore, although the same carbon nanotubes are used, using them as a surface-forming agent for forming dry electrode sheets according to the present invention can be considered a different application from using them as general conductive materials.

[0208] Experimental Example 3

[0209] Through the results obtained in Example 9 and Comparative Example 7, the influence of surface irregularities formed on the metal roll surface of the first to third calender rolls on the formation of the dry electrode sheet can be confirmed.

[0210] That is, in Example 9, a dry electrode sheet 7 with a thickness of ~95 microns was successfully produced, obtaining a thickness similar to that of the dry electrode sheet 1 obtained in Example 3. However, the comparative electrode sheet 5 obtained in Comparative Example 7, which had a surface roughness of about 2.0 microns, was thicker, with a thickness of about 150-200 microns, and a problem was found where the calendar device stopped in some cases. Although not described in the examples, the same phenomenon was observed in a metal roll manufactured to have the same level of roughness (2.0 microns).

[0211] From the results of Example 9 and Comparative Example 7, it can be seen that in order to obtain a thin dry electrode sheet, the surface roughness of the first to third calender rolls forming the dry electrode sheet must be controlled to a certain level (0.5 microns) or less.

[0212] Experimental Example 4

[0213] In order to determine the effect of surface adhesion on the formation of a dry electrode sheet in the first calender roll (111) to the third calender roll (113), the results of Example 10 and Comparative Example 8 were observed.

[0214] In the case of Example 10, the dry electrode sheet 8 was successfully formed, and its thickness was approximately 95 microns, which was slightly thicker than in the case of Example 3. On the other hand, in the case of Comparative Example 8, where the surface adhesion strength was 0.3 N / 18 mm, the dry electrode sheet was not formed as the calender roll slipped. Additionally, through a separate experiment, it was discovered that in the case of a roll with a surface adhesion strength of 15 N / 18 mm, not only was the manufactured dry electrode sheet thick, but the sheets calendered from the first and second calender rolls did not all pass over to the third calender roll and remained on the surface of the second calender roll.

[0215] Therefore, it was found that in order to manufacture a dry electrode sheet with a relatively thin thickness, the first to third calender rolls must use rolls with appropriately controlled surface adhesion.

[0216] Example 11

[0217] A cross-sectional dry electrode manufacturing device 1 was manufactured as follows in the structure shown in FIG. 2 such that the angle of the alternate angle formed by the first calendar roll (111) and the second calendar roll (122) is 40 degrees.

[0218] (1) It is composed of six calendar rolls, including a calendar unit (100) composed of a first calendar roll (111) to a third calendar roll (113) and an electrode composition supply unit (120), and an attachment calendar unit (400) composed of a fourth calendar roll (411) to a sixth calendar roll (413). (2) The rotation speed of each calendar roll is driven individually. (3) A heating roll at 100-120°C is installed as a control unit (600) on the upper part of the third calendar roll (113) to flatten the surface of the electrode. (4) A scrubbing unit (700) for trimming and scrubbing the edge portion of the dry electrode is installed on the lower part of the fourth calendar roll (411) so that the dry electrode has a certain width. (5) The device is designed so that an aluminum electrode plate, which is a current collector, is supplied between the 4th calender roll (411) and the 5th calender roll (412) by the current collector supply and recovery unit (500) (at this time, the primer layer of the current collector is supplied in a direction that contacts the dry electrode), (6) and when a dry electrode plate is formed by heat pressing (120°C) while passing through the 4th calender roll (411) to the 6th calender roll (413), the dry electrode plate is recovered by the current collector supply and recovery unit (500).

[0219] The first calender roll (111) to the third calender roll (113) used at this time had an average surface roughness of 0.1 micron and used a zirconia roll (a roll with a zirconia layer formed 5 mm thick on a metal roll) with a peel strength of 3.5 N / 18 mm against Scotch tape. The fourth calender roll (411) to the sixth calender roll (413) used stainless steel metal rolls with a diameter of 150 mm.

[0220] In particular, the electrode composition supply unit (120), which is installed so that the electrode composition in a mixed state can be fed onto the first calendar roll (111), has a thin spacer formed at the bottom as a feeding member with holes of 1.5 mm in diameter at 1 mm intervals as shown in FIG. 4, and is implemented in a structure that enables partial feeding by allowing the electrode composition to fall onto the first calendar roll (111) from 10 mm above the first calendar roll (111) through the holes.

[0221] In addition, unless otherwise noted, the first calender roll (111) is set to manufacture a dry electrode sheet by rotating at a speed of 1 meter per minute (1 m / min), the second calender roll (112) at 3 m / min, and the third calender roll (113) at 5 m / min, and the fourth calender roll (411) is set to manufacture a dry electrode plate by rotating at a speed of 5.5 m / min, the fifth calender roll (412) at 6 m / min, and the sixth calender roll (413) at 6 m / min.

[0222] Example 12

[0223] A cross-sectional dry electrode manufacturing apparatus 2 was manufactured having the same configuration as Example 11, except that the first calendar roll (111) and the second calendar roll (122) are arranged such that the angle of the alternate angle formed by them is 15 degrees.

[0224] Example 13

[0225] In the single-sided dry electrode manufacturing apparatus 1 prepared in Example 11, the dry electrode composition 1 prepared in Example 3 is calendered as follows to produce a dry electrode sheet having a certain width, and the dry electrode 1 can be manufactured by attaching it to a current collector in a continuous process.

[0226] 1. A first step of setting the rotational speed ratio of the first to sixth calendar rolls.

[0227] The rotational speed ratio of the 1st calendar roll:2nd calendar roll:3rd calendar roll:4th calendar roll:5th calendar roll:6th calendar roll was set to 1:3:5:5.5:6:6.

[0228] 2. A second step was performed in which dry electrode composition 1 was introduced onto the first calender roll to start calendering.

[0229] 3. As the calendered dry electrode sheet passes to the third calender roll, a third step of primary flattening is performed using a DLC-coated flattening roll (100°C).

[0230] 4. A fourth step was performed in which the dry electrode sheet was trimmed to a certain width and removed by a scrubbing unit (700) for trimming and scrubbing installed at the bottom of the fourth calendar roll (411).

[0231] 5. A fifth step was performed in which a current collector was inserted between the fourth calendar roll (411) and the fifth calendar roll (412) to attach a trimmed dry electrode sheet to the current collector.

[0232] 6. A final dry electrode plate was manufactured including the 6th step of finally rolling at a high temperature (100℃).

[0233] At this time, the current collector was an aluminum foil with a primer layer formed on one side, and in the fifth step, the 4th calender roll (411) to the 6th calender roll (413) used a heating part to heat the heating roll to 120°C to attach the dry electrode sheet to the primer layer of the current collector.

[0234] The manufactured dry electrode 1 had a very good appearance and a thickness of 100 microns (current collector / primer layer: 16 microns, dry electrode layer: 84), and it was possible to manufacture a dry electrode with good adhesion between the current collector and the dry electrode layer and good binding strength of each component within the electrode layer.

[0235] Example 14

[0236] Dry electrode 2 was obtained by performing the same method as in Example 13, except that the rotational speed ratio of the first calender roll: second calender roll: third calender roll: fourth calender roll: fifth calender roll: sixth calender roll is 1:3:5:5:5:5.5:5.5.

[0237] Experimental Example 5

[0238] In order to observe the effect of the rotational speed of the calendar roll included in the dry electrode manufacturing apparatus, particularly the calendar roll included in the attachment calendar unit, on the formation of the dry electrode, the appearance of dry electrodes 1 and 2 obtained by varying the rotational speed ratio of the first calendar roll: second calendar roll: third calendar roll: fourth calendar roll: fifth calendar roll: sixth calendar roll as in Examples 13 and 14 was observed. For comparison, the appearance of the dry electrodes obtained by setting the rotational speed ratio to 1:3:5:5:5:5, making the rotational speeds of the rolls after the fourth calendar roll the same as the third calendar roll, or by setting the rotational speed ratio to 1:3:5:8:8:8, making the rotational speed of the fourth calendar roll rotate 60% faster than that of the third calendar roll, was compared.

[0239] In Examples 13 and 14, it was confirmed that the dry electrode sheet was cleanly attached to the primer layer of the input current collector and passed to the next calendar roll, namely the sixth calendar roll. In particular, in Example 13 compared to Example 14, that is, when the rotational speed of the fifth calendar roll (412) was slightly faster than that of the fourth calendar roll (411), it was confirmed that the dry electrode plate formed by attaching the dry electrode sheet to the current collector traveled more smoothly in the forward direction. However, when the fourth calendar roll (411) had the same rotational speed as the third calendar roll (113), although the dry electrode sheet was attached to the current collector, a phenomenon occurred in which some of the dry electrode sheet from the third calendar roll (113) did not pass to the fourth calendar roll. Also, when the fourth calender roll (411) rotates about 60% faster than the third calender roll (113), the current collector with the dry electrode sheet attached, i.e., the electrode, becomes very unsightly, such as wrinkles on the surface.

[0240] Therefore, it was found that in order to manufacture a dry electrode with a dry electrode sheet firmly attached by feeding the current collector, the rotation speed of the calendar roll at the location where the current collector is fed, that is, the calendar roll at the location where the progress calendar unit and the attachment calendar unit are connected, and the calendar rolls constituting the attachment calendar unit must also be adjusted to an appropriate range.

[0241] Example 15

[0242] Dry electrode 3 (positive electrode plate 1) was obtained by performing the same method as in Example 13, except that the temperature of the flattening roll on the third calender roll was adjusted to 120°C, with a loading level of ~20 mg / cm² 2 The thickness of the manufactured dry electrode 3 was 93 microns (current collector / primer layer: 16 microns, dry electrode layer: 77 microns), and it can be seen that increasing the temperature of the flattening roll allows for flattening as well as a slight reduction in the thickness of the dry electrode sheet.

[0243] As such, the dry electrode device of the present invention can be manufactured continuously from the input of the electrode composition to the production of a dry electrode having a certain thickness, and it can be seen that a dry electrode with a better appearance can be manufactured by installing a control unit in the device, and furthermore, the thickness of the dry electrode can be further reduced by heating the control unit.

[0244] Example 16

[0245] Dry electrode 4 was prepared by performing the same method as in Example 15, except that instead of dry electrode composition 1, a dry electrode composition comprising 92 wt% active material LFP, 2 wt% untreated multi-walled carbon nanotubes, and 6 wt% mixed binder (PTFE:PAEM weight ratio = 50:50) was used. The thickness of the prepared dry electrode 4, i.e., positive electrode plate 2, was 97 microns (current collector / primer layer: 16 microns, dry electrode layer: 81 microns), and the loading level was ~18 mg / cm². 2 It was, and finally, by high-temperature (100℃) rolling, the electrode density was ~2.3 g / cm³ 3 Phosphoric positive electrode plate 2 was fabricated.

[0246] Example 17

[0247] Dry electrode 5 was prepared by performing the same method as in Example 15, except that instead of dry electrode composition 1, an electrode composition comprising 95 wt% of an active material [graphite (synthetic graphite:natural graphite weight ratio = 50:50)], 2 wt% of untreated multi-walled carbon nanotubes, and 3 wt% of a mixed binder (PTFE:PAEM weight ratio = 20:80) was used, which is a dry electrode composition for the cathode, and a copper foil with a primer layer formed thereon was used as the current collector. The thickness of the prepared dry electrode 5, i.e., cathode plate 1, was 63 microns (current collector / primer layer: 14 microns, dry electrode layer: 50 microns), and the loading level was 7-8 mg / cm². 2 It was, and after final high-temperature (100℃) rolling, the electrode density was ~1.7 g / cm³ 3 A negative electrode plate 2 was fabricated.

[0248] Example 18

[0249] A dry electrode 6 (negative electrode plate 2) was prepared by performing the same method as in Example 17, except that a PTFE-only binder was used instead of a mixed binder in the dry electrode composition for the cathode of Example 17. At this time, the loading level was 7-8 mg / cm². 2 , electrode density is ~1.7 g / cm³ 3 The thickness of the manufactured dry electrode 6, i.e., the negative electrode plate 2, was 69 microns (current collector / primer layer: 14 microns, dry electrode layer: 55 microns).

[0250] It was observed that the remaining characteristics were similar, except that dry electrode 6 (negative electrode plate 2) was slightly thicker compared to dry electrode 5 (negative electrode plate 1).

[0251] From the results of the above-described Examples 15 to 18, it can be confirmed that the dry electrode manufacturing apparatus of the present invention can produce dry electrode sheets and dry electrode plates with a thickness of less than 100 microns whether using a dry electrode composition containing LFP, which is an active material for the positive electrode, or a dry electrode composition containing graphite, which is an active material for the negative electrode. In particular, regarding the thickness of the dry electrode, an electrode in which the thickness of the dry negative electrode is significantly thinner than that of the dry positive electrode was easily produced. This is thought to be due to the type of active material.

[0252] In particular, in conventional wet electrode manufacturing, electrode slurries are prepared by dispersing all components in organic solvents such as NMP for the manufacture of positive electrodes, whereas negative electrodes using graphite require the use of water as a solvent for the electrode slurry; thus, different types of binders must be used depending on the positive and negative electrodes. However, it has been confirmed that when using the dry electrode manufacturing apparatus of the present invention, the binder used for the positive electrode can be used identically for the negative electrode. In particular, regarding the PTFE / PAEM mixed binder—that is, by replacing most of the PTFE with an acrylonitrile-ethylene glycol-maleic acid copolymer—it has been confirmed that a negative electrode exhibiting excellent electrochemical performance can be manufactured. Therefore, using the technology of the present invention offers a significant advantage in that the same binder can be used for both positive and negative electrodes without having to select different binders depending on the type of electrode. In particular, it has been confirmed that the thickness of the negative electrode produced by the dry process of the present invention can be easily made much thinner than that of the positive electrode.

[0253] Example 19

[0254] A half-cell structured coin cell (CR2032 type) 1 was manufactured as follows using the positive electrode plate 1 prepared in Example 15. Here, a lithium metal foil was used as the counter electrode, and the electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a ratio of 30 / 50 / 20, adding 5% fluoroethylene carbonate (FEC), and then dissolving 1.15 moles of LiPF6 to use as the electrolyte. The coin cell was manufactured using a conventional method for manufacturing half-cell structured coin cells in a glove box filled with argon gas.

[0255] Example 20

[0256] A coin cell 2 with a half-cell structure was prepared using the positive electrode plate 2 prepared in Example 16 by performing the same method as in Example 19.

[0257] Example 21

[0258] A coin cell 3 with a half-cell structure was prepared using the negative electrode plate 1 prepared in Example 17 by performing the same method as in Example 19.

[0259] Example 22

[0260] A coin cell 4 with a half-cell structure was prepared using the negative electrode plate 2 prepared in Example 18 by performing the same method as in Example 19.

[0261] Experimental Example 6

[0262] Surface resistance and adhesion were evaluated for the dry electrode sheet or dry electrode manufactured in the embodiments of the present invention as follows.

[0263] The electrical conductivity of the dry electrode was measured by determining the surface resistance of the upper surface of the electrode layer formed on aluminum or copper foil (measuring instrument: Mitsubishi, 4-point probe method, flat tip used).

[0264] The adhesion of the dry electrode sheet or dry electrode was verified through an adhesion test using Scotch Tape (3M Scotch Tape). The adhesion between the electrode layer and the current collector, and the cohesion between the components within the electrode, were judged as "strong," "moderate," and "weak" based on the degree to which the electrode layer peeled off from the current collector upon tape peeling, and the amount of electrode layer material adhering to the tape. Although this method is subjective and qualitative, it is sufficient for quickly evaluating the bonding strength of the electrode. Additionally, an adhesion test was performed by cutting a portion of the dry electrode, which was manufactured in a state where the dry electrode sheet was attached to the current collector by a continuous process in the dry electrode manufacturing apparatus of the present invention. To measure the peel-off force, a dry electrode of appropriate size was attached to a glass plate using double-sided tape, Scotch Tape was attached to the electrode layer, and after 30 minutes, the force at which the tape peeled off was measured while pulling the tape with a tensile testing machine.

[0265] The surface resistance of dry electrode 3 (positive electrode plate 1) (measuring instrument: Mitsubishi, 4-point probe method, measuring tip shape: flat) is tens to hundreds of ohms / area, i.e., 10 1 -10 2 Very good surface resistance characteristics were exhibited, measured in ohms / area. This is because the carbon nanotubes used as a plane-forming agent have excellent electrical conductivity, so even if only the plane-forming agent is used, the electrode layer containing them exhibits good electrical conductivity. For the same reason, the surface resistance of the dry electrode sheet or dry electrode plate of other examples also showed similar surface resistance values. However, when using boron nitride nanotubes (BNNT), which have been confirmed to be effective for dry electrode sheets, the surface resistance was 10 7 It was measured to be as high as ohms / area. This is because BNNT is a nanomaterial with no electrical conductivity. In addition, it was confirmed that other types of active materials (LFP and graphite) also exhibited similar surface resistance. Therefore, it was found that carbon nanotubes are very useful as surface-forming agents.

[0266] In addition, when the peel strength was measured by attaching a tape to the electrode layer of positive electrode plate 1 and then peeling it off, the peel strength was measured to be 5-8 times higher when using PTFE / PAEM (weight ratio: 50:50), which is mainly used in this invention, as the binder compared to the case of PTFE alone (PTFE alone binder: 0.282 N / in, PTFE / PAEM (weight ratio: 50:50): 2.02 N / in). This is thought to be because the polar component of PAEM significantly increased the bonding strength between the components of the electrode and the adhesion strength with the current collector. Furthermore, upon observing the surface of the electrode peeled off by the tape, it was confirmed that the peeling caused by the tape was not the electrode layer peeled off from the current collector, but rather the middle of the electrode layer peeled off. This corresponds to the cohesion of the components within the electrode layer, and from this, the adhesion strength of the electrode layer to the current collector is expected to be higher than this. It is self-evident that this applies equally to other types of active materials as well.

[0267] Experimental Example 7

[0268] To determine the electrochemical characteristics of coin cells 1 to 4 prepared in Examples 19 to 22, impedance and charge / discharge cycle tests were performed using electrochemical impedance spectroscopy (EIS).

[0269] As shown in the impedance measurement results of Coin Cell 1 illustrated in Fig. 8, all types of resistance are 10 0 -10 1 It exhibits low resistance characteristics in the ohm range. This is thought to be because carbon nanotubes, which are the planar forming agent, have very good electrical conductivity, so even if only the planar forming agent is used without a separate conductive material, the electrode layer containing them exhibits good electrical conductivity. In addition, as a result of a charge-discharge cycle test (Fig. 9) performed to determine the capacity retention rate of the electrical capacitance, which is one of the important electrochemical characteristics, the initial capacity was 190 mAh / g, and after 50 cycles, the electrical capacitance was measured to be 181 mAh / g. The capacity retention rate calculated from this was approximately 95%, confirming that it exhibits good electrochemical characteristics.

[0270] Although not shown, the charge / discharge cycle test results for Coin Cell 2 (Example 20), manufactured using LFP as an active material, confirmed that it exhibited excellent electrical capacity and capacity retention rate, with the capacity retention rate after 100 cycles being close to 100%.

[0271] Meanwhile, as a result of the charge-discharge cycle test for the graphite of Example 21 (artificial graphite / natural graphite = 50 / 50 weight ratio), as shown in FIG. 10, the capacity retention rate when comparing the charge capacity after 50 cycles for the PTFE / PAEM (20 / 80) mixed binder was nearly 100%, maintaining the initial capacity even after 50 cycles, whereas the coin cell 4 of Example 22, which used a PTFE-only binder, showed a capacity retention rate of about 91%. Therefore, it was found that the mixed binder is more advantageous than the PTFE-only binder even in the case of the negative electrode.

[0272] From the examples, comparative examples, and experimental results described above, it was confirmed that by using a dry electrode composition containing a plane-forming agent in the drag calendering device of the present invention and the dry electrode manufacturing device including the same, a dry electrode sheet and a dry electrode with a thickness of 100 microns or less can be manufactured by a continuous process by mixing the dry electrode composition at room temperature and then calendering at room temperature without a pretreatment process such as kneading. It was confirmed that the technology is applicable to cases where the binder included in the dry composition is a PTFE single binder as well as a mixed binder of PTFE and another secondary battery binder. Furthermore, if an acrylonitrile-ethylene glycol-maleic acid copolymer is used as another secondary battery binder, PTFE can be replaced by up to 80% by weight, which can significantly reduce the generation of hydrogen fluoride in emergency situations, making it a very environmentally friendly technology. In addition, it was confirmed that the same mixed binder of the present invention can be used for both the positive and negative electrodes, unlike the wet method. Furthermore, although the present invention was described using mainly untreated multi-walled carbon nanotubes as a plane-forming agent, it will be obvious that the same effect can be obtained by using untreated multi-walled carbon nanotubes, surface-treated carbon nanotubes, or other types of carbon nanotubes.

[0273] In particular, according to the present invention, when a dry electrode sheet is manufactured by mixing a dry electrode composition to create a mixture of particles and then calendering it at room temperature, the thickness of the electrode layer of the dry electrode sheet and the dry electrode can be controlled by using a heating roll heated by a heating unit installed in various places of a continuous process device. In the case of the cross-sectional dry electrode manufacturing device shown in FIG. 2 as one embodiment, if a flattening roll installed on the third calender roll is used as a heating roll, the thickness of the dry electrode sheet can be further reduced immediately after calendering and surface flattening. Furthermore, if the temperature of the calender roll of the attachment calender unit is controlled, the thickness of the electrode layer can be further controlled while the dry electrode sheet is attached to the current collector. Although not shown, the thickness of the dry electrode can be further reduced by undergoing a rolling process after making the dry electrode. As confirmed through the examples, according to the present invention, not only NCM811 active material but also other types of active materials such as LFP and graphite can have their thickness of a dry electrode sheet or dry electrode controlled to less than 100 microns. In particular, it was confirmed that in the case of the dry equipment of the present invention, a dry negative electrode with a significantly lower thickness than a dry positive electrode can be easily produced. This is thought to be due to the type of active material, and it was confirmed that a dry electrode with a thickness of less than 50 microns can be produced in the case of a dry negative electrode.

[0274] As such, since the technology of the present invention enables a continuous process from mixing the dry electrode composition to manufacturing the dry electrode, the present invention can be considered a highly economical technology capable of manufacturing a dry electrode and a secondary battery containing the same.

[0275]

[0276] Although the present invention has been illustrated and described with reference to preferred embodiments as described above, it is not limited to the aforementioned embodiments, and various changes and modifications may be made by those skilled in the art within the scope of the invention without departing from the spirit of the invention.

Claims

1. Two or more calendar rolls are arranged at regular intervals and driven individually, wherein a first calendar roll positioned at the foremost among the calendar rolls is installed lower than the second calendar roll so as to form a certain angle with the adjacent second calendar roll; and A drag calendering device comprising: an electrode composition supply unit that supplies a dry electrode composition to the first calender roll.

2. In Paragraph 1, A drag calendering device characterized in that the above-mentioned fixed angle is an angle formed by a plane passing through the rotation axis of the first calendar roll and the rotation axis of the second calendar roll and a plane passing through the rotation axis of the second calendar roll parallel to the ground, ranging from 10° to 50°.

3. In Paragraph 1, A drag calendering device characterized in that the above-mentioned calendar roll is one of a metal roll, a ceramic roll, or a metal-ceramic roll having a coating layer made of ceramic material formed on the surface of the metal roll.

4. In Paragraph 3, A drag calendering device characterized in that the ceramic material is selected from the group consisting of titania, silica, alumina, and zirconia.

5. In Paragraph 1, A drag calendering device characterized by the average surface roughness of the calendar roll being less than 0.5 microns.

6. In Paragraph 1, A drag calendering device characterized by the surface adhesion force of the above-mentioned calendar roll being 0.5 to 10 N / 18mm.

7. In Paragraph 1, A drag calendering device characterized in that the electrode composition supply unit includes a feeding member installed at its lower portion to guide the electrode composition to be supplied consistently to the first calender roll.

8. In Paragraph 7, The above-mentioned feeding member is a drag calendering device characterized by including a flat plate having circular or polygonal holes of the same size formed at regular intervals.

9. In Paragraph 8, A drag calendering device characterized by the size of the circular or polygonal hole being 0.1-10 mm.

10. In any one of paragraphs 1 through 9, A drag calendering device characterized in that, in the above-described calendar section, the rear calendar roll rotates 1.05 to 4.0 times faster than the front calendar roll, and when a dry electrode composition is introduced between the first calendar roll and the second calendar roll, the dry electrode composition is dragged toward the rear calendar roll, which rotates faster than the front calendar roll, to form a dry electrode sheet.

11. A progress calendar unit in which two or more calendar rolls are sequentially arranged and individually driven to drag a dry electrode composition supplied from an electrode composition supply unit backward to form a dry electrode sheet; An attachment calendar unit that forms a dry electrode by attaching a dry electrode sheet formed in the advance calendar unit to a current collector while individually driving two or more calendar rolls sequentially arranged adjacent to the rearmost calendar roll of the advance calendar unit; and A dry electrode manufacturing apparatus comprising: a current collector supply and recovery unit that supplies the current collector to the calendar roll of the above-mentioned attachment calendar unit and recovers the dry electrode formed in the above-mentioned attachment calendar unit.

12. In Paragraph 11, A dry electrode manufacturing apparatus characterized in that the above-mentioned progress calendar unit is a drag calendering device according to any one of claims 1 to 9.

13. In Paragraph 11, A dry electrode manufacturing apparatus characterized in that, in the above-mentioned attachment calendar unit, the rear calendar roll rotates 1.0 to 1.5 times faster than the front calendar roll.

14. In Paragraph 11, A dry electrode manufacturing apparatus characterized by the fact that the current collector is supplied by the above-mentioned current collector supply and recovery unit to the space between the rearmost calendar roll of the above-mentioned progress calendar unit and the frontmost calendar roll of the above-mentioned attachment calendar unit, or between the frontmost calendar roll of the above-mentioned attachment calendar unit and the adjacent calendar roll.

15. In Paragraph 11, A dry electrode manufacturing apparatus characterized in that the diameter of the calendar roll of the attachment calendar unit is larger than the diameter of the calendar roll of the progress calendar unit.

16. In Paragraph 11, A dry electrode manufacturing apparatus further comprising one or more control units, wherein the control units include at least one control roll installed on the upper or lower portion of a rear calendar roll that is dragged after the dry electrode sheet is formed in the above-described progress calendar unit, or a calendar roll included in one or more units among one or more calendar rolls included in the above-described attachment calendar unit, and control one or more of the surface flattening, thickness, or porosity of the dry electrode sheet or dry electrode.

17. In Paragraph 11, A dry electrode manufacturing apparatus characterized in that two or more calendar rolls included in the above-mentioned attachment calendar unit are heated to 50°C to 200°C.

18. In Paragraph 11, A dry electrode manufacturing apparatus characterized by further including a scrubbing unit installed between the above-mentioned progress calendar unit and the above-mentioned attachment calendar unit, which trims or removes unnecessary parts from the dry electrode sheet before attaching the dry electrode sheet to the current collector.

19. An attachment calendar unit in which a fourth calendar roll and a fifth calendar roll are sequentially arranged and individually driven, and a first dry electrode sheet and a second dry electrode sheet are respectively attached to both sides of a current collector supplied between the fourth calendar roll and the fifth calendar roll; A progression calendar unit in which a third calendar roll, a second calendar roll, and a first calendar roll are sequentially arranged adjacent to the outer side of the fourth calendar roll and driven individually to form a first dry electrode sheet by dragging a dry electrode composition supplied to the first calendar roll toward the fourth calendar roll, and a second progression calendar unit in which a sixth calendar roll, a seventh calendar roll, and an eighth calendar roll are sequentially arranged adjacent to the outer side of the fifth calendar roll and driven individually to form a second dry electrode sheet by dragging a dry electrode composition supplied to the eighth calendar roll toward the fifth calendar roll, are installed facing each other with respect to the current collector; An electrode composition supply unit comprising a first supply unit installed between the second calendar roll and the first calendar roll to supply a dry electrode composition to the first calendar roll, and a second supply unit installed between the seventh calendar roll and the eighth calendar roll to supply a dry electrode composition to the eighth calendar roll; A dry electrode manufacturing apparatus comprising: a current collector supply and recovery unit that supplies the current collector between the fourth and fifth calendar rolls and recovers the double-sided dry electrode formed in the attachment calendar unit.

20. In Paragraph 19, A dry electrode manufacturing apparatus characterized in that the fourth and fifth calender rolls, the third and sixth calender rolls, the second and seventh calender rolls, and the first and eighth calender rolls, which face each other with respect to the above-mentioned current collector, each have the same speed and opposite rotation directions.

21. In Paragraph 19, The above-mentioned first progress calendar unit rotates the second calendar roll 1.05 to 4.0 times faster than the first calendar roll, and the third calendar roll rotates 1.05 to 4.0 times faster than the second calendar roll, respectively. A dry electrode manufacturing apparatus characterized in that the second progress calendar unit rotates the 7th calendar roll faster than the 8th calendar roll, and the 6th calendar roll faster than the 7th calendar roll, respectively.

22. In Paragraph 19, A dry electrode manufacturing apparatus characterized in that the calendar roll included in the above-mentioned progress calendar unit is one of a metal roll, a ceramic roll, or a metal-ceramic roll having a coating layer made of ceramic material formed on the surface of the metal roll.

23. In Paragraph 22, A dry electrode manufacturing apparatus characterized in that the ceramic material is selected from the group consisting of titania, silica, alumina, and zirconia.

24. In Paragraph 19, A dry electrode manufacturing apparatus characterized by the average surface roughness of the calendar roll included in the above-mentioned progress calendar unit being less than 0.5 microns.

25. In Paragraph 19, A dry electrode manufacturing apparatus characterized by the surface adhesion force of the calendar roll included in the above-mentioned progress calendar unit being 0.5 to 10 N / 18mm.

26. In Paragraph 19, A dry electrode manufacturing apparatus characterized in that the diameter of the calendar roll of the attachment calendar unit is larger than the diameter of the calendar roll of the progress calendar unit.

27. In Paragraph 19, A dry electrode manufacturing apparatus further comprising a control unit including two control rolls installed above or below a calendar roll that is dragged after the first dry electrode sheet is formed in the first progress calendar unit and a calendar roll that is dragged after the second dry electrode sheet is formed in the second progress calendar unit, and which controls one or more of the surface flattening, thickness, or porosity of the first and second dry electrode sheets.

28. In Paragraph 19, A dry electrode manufacturing apparatus characterized in that the fourth and fifth calendar rolls included in the above-mentioned attachment calendar unit are heated to 50°C to 200°C.

29. In Paragraph 19, A dry electrode manufacturing apparatus further comprising a scrubbing unit including first and second scrubbers, each installed between the first progress calendar unit and the attachment calendar unit and the second progress calendar unit and the attachment calendar unit, for trimming or removing unnecessary parts from the first and second dry electrode sheets before attaching the first dry electrode sheet and the second dry electrode sheet to the current collector.

30. In Paragraph 16 or Paragraph 27, A dry electrode manufacturing apparatus characterized by the surface of the above-mentioned control roller having a release coating layer formed thereon.

31. In any one of Paragraphs 11, 13 through 29, A dry electrode manufacturing apparatus characterized by the above dry electrode composition comprising 80-98% by weight of an active material, 1.0-10% by weight of a binder, and 1-10% by weight of a cotton forming agent.

32. In Paragraph 31, A dry electrode manufacturing apparatus characterized in that the above-mentioned surface-forming agent is one or more carbon-based nanomaterials selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes (few-wall CNTs), branched carbon nanotubes, carbon nanoribbons, and carbon nanofibers, or one or more non-carbon-based nanomaterials selected from the group consisting of boron nitride nanotubes, boron nitride nanoribbons, and aramid nanofibers.

33. In Paragraph 31, A dry electrode manufacturing apparatus characterized in that the binder comprises polytetrafluoroethylene and acrylonitrile-ethylene glycol-maleic acid copolymer.

34. In Paragraph 33, A dry electrode manufacturing apparatus characterized by containing 10 to 50 weight percent of the above polytetrafluoroethylene.

35. A dry electrode manufactured by a dry electrode manufacturing apparatus according to any one of claims 11, 13 to 29.

36. A secondary battery comprising the dry electrode of claim 35.

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