Method for manufacturing electrode and electrode

Abstract

The present invention relates to a method for manufacturing an electrode and an electrode, the method comprising: a step for attaching an adhesive tape; a coating step; a drying step; and a step for removing the adhesive tape, wherein, in the step for attaching the adhesive tape, the adhesive tape is continuously attached along the transfer direction of a current collector sheet.

Description

Method for manufacturing electrodes and electrodes

[0001] This application claims the benefit of priority from Republic of Korea Patent Application No. 10-2024-0053075, filed on April 22, 2024.

[0002] The present invention relates to a method for manufacturing an electrode using an adhesive tape, wherein the method suppresses the desorption of an electrode active material, and to an electrode manufactured thereby.

[0003]

[0004] As technological development and demand for industrial fields such as mobile devices, automobiles, and energy storage devices increase, the demand for batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries with high energy density and discharge voltage have been studied extensively and are now commercialized and widely used.

[0005] Secondary batteries are classified into cylindrical and prismatic batteries, in which the electrode assembly is built into a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is built into a pouch-type case made of aluminum laminate sheet, depending on the shape of the battery case.

[0006] The positive and negative electrodes that make up the electrode assembly are manufactured by applying the electrode slurry manufactured in the mixing process to the electrode current collector through a slot die in a set pattern and at a constant thickness, and then drying. However, since the electrode slurry is a fluid, after the electrode slurry application process, the electrode slurry flows down due to its fluidity, and this phenomenon is called sliding.

[0007] Meanwhile, the positive and negative electrodes constituting the electrode assembly face each other with a separator interposed between them, and the length of the sliding region of the positive electrode and the length of the sliding region of the negative electrode may be different, and the inclined shape of the sliding region may also appear in various forms such as an upward convex shape, a downward convex shape, a straight shape, an S shape, etc., and even if the inclined shape is the same, the inclination may appear differently. Accordingly, there is a risk that the negative electrode sliding region may have a part that locally has an imbalance in the NP Ratio depending on the facing position, and the imbalance in the NP Ratio may cause lithium to precipitate from the negative electrode, which may cause a safety accident such as a short circuit.

[0008] Since the possibility of an imbalance in the NP Ratio theoretically tends to be lower when the ratio of the anode loading to the cathode loading at the anode / cathode facing area is greater, recent technological attempts have been made to increase the anode loading in the anode sliding region. One such attempt is a technology that minimizes the sliding length of the anode active material layer by overlapping a dam coating composition on the edge where the anode slurry is applied, thereby suppressing the anode slurry from flowing down. However, this technology has limitations in reducing the length of the sliding region.

[0009] FIG. 1 illustrates a conventional technique for manufacturing an electrode using tape to reduce the length of a sliding region. Referring to FIG. 1, a conventional electrode manufacturing method includes intermittently attaching a plurality of tapes (3) at intervals from each other to a portion of an electrode current collector sheet (11) where electrode tabs are to be formed, applying and drying an electrode slurry, and then removing the tapes. At this time, since the tapes are attached to the portion where the sliding region is to be formed, a significant portion of the sliding region is removed from the electrode active material layer during the tape removal process, thereby reducing the length of the sliding region. The reason for intermittently attaching the tapes in the conventional technique was to minimize the amount of electrode active material detached during the tape removal process. However, this intermittent attachment method has the following problems: there is a risk that the tapes will be peeled off from the electrode current collector sheet during the electrode manufacturing process due to hot air from a drying furnace or physical external force; there is also a risk of tolerance occurring depending on the attachment location of the tapes, as illustrated in FIG. 2; and there is also the problem of reduced productivity due to intermittent attachment.

[0010] Therefore, there is a need to develop a technology for manufacturing an electrode that can solve these problems while suppressing the desorption of the electrode active material.

[0011] [Prior Art Literature]

[0012] (Patent Document 1) Japanese Patent Application Laid-Open No. 2005-183181

[0013]

[0014] The technical idea of ​​the present invention is to provide an electrode that reduces the length of a sliding region.

[0015] Another problem that the technical idea of ​​the present invention seeks to solve is to provide a method for manufacturing an electrode that minimizes the detachment phenomenon of the electrode while resolving the problem caused by the intermittent attachment described above when manufacturing an electrode using a tape.

[0016]

[0017] A method for manufacturing an electrode according to exemplary embodiments includes a step of attaching an adhesive tape on an edge of a portion of a holding portion where an electrode active material layer is to be formed, among an electrode current collector sheet; a coating step of applying an electrode slurry to the portion of the holding portion; a drying step of removing a solvent in the electrode slurry; and a step of peeling and removing the adhesive tape from the electrode current collector sheet, wherein in the step of attaching the adhesive tape, the adhesive tape is continuously attached along a conveying direction of the current collector sheet.

[0018] In exemplary embodiments, the thickness A of the adhesive tape, the thickness B of the electrode active material layer after the drying step, and the adhesive strength C of the adhesive tape may satisfy the following condition 1.

[0019] [Condition 1]

[0020] 0.15≤B / (A×C)

[0021] In the above condition 1, A and B are each values ​​in μm, and C is the adhesive strength measured by a 90° peel test after attaching the adhesive tape to the SUS plate, and is a value in gf / inch.

[0022] In exemplary embodiments, the adhesive strength of the adhesive tape may be less than or equal to 20 gf / inch.

[0023] In exemplary embodiments, the thickness of the adhesive tape may be 150 μm or less.

[0024] In exemplary embodiments, the electrode active material layer thickness after the drying step may be 50 μm or more.

[0025] In exemplary embodiments, the adhesive tape may be a pressure-sensitive adhesive tape.

[0026] In exemplary embodiments, the coating step may include a top coating step of applying electrode slurry to the top surface of the current collector sheet; and a bottom coating step of applying electrode slurry to the bottom surface of the current collector sheet, and the drying step may include a top drying step of drying the electrode slurry applied in the top coating step; and a bottom drying step of drying the electrode slurry applied in the bottom coating step.

[0027] In exemplary embodiments, in the step of attaching the adhesive tape, the adhesive tape may be attached to the upper and lower surfaces of the electrode current collector sheet, respectively, and may be attached so as to completely overlap with the electrode current collector sheet in between.

[0028] In exemplary embodiments, the adhesive tape may include a base portion having a predetermined width and extending along the transport direction of the current collector sheet; and a protrusion portion protruding from the base portion toward a predetermined portion of the holding portion along the transverse direction of the current collector sheet.

[0029] The method for manufacturing an electrode according to exemplary embodiments may further include, after the step of removing the adhesive tape, a rolling step of roll-pressing an electrode current collector sheet on which an electrode active material layer is formed.

[0030] In exemplary embodiments, the content of the binder included in the electrode slurry may be 5 parts by weight or less with respect to 100 parts by weight of the solid content of the electrode slurry.

[0031] An electrode according to exemplary embodiments includes a holding portion in which an electrode active material layer is laminated on an electrode current collector sheet; and a non-coated portion positioned at at least one edge of the electrode current collector sheet in the transverse direction (Y direction), the non-coated portion having the electrode current collector sheet exposed, wherein an end surface of the electrode active material layer in the transverse direction of the electrode active material layer is perpendicular to a plane of the electrode current collector sheet.

[0032] In exemplary embodiments, the electrode active material layer includes a sliding region in which the thickness of the electrode active material layer gradually decreases in a direction from the holding portion toward the non-holding portion. The sliding region may have a lateral length of 1 mm or less.

[0033] In exemplary embodiments, the ratio of the minimum thickness T2 of the sliding region to the maximum thickness T1 of the sliding region is 0.8 or greater.

[0034]

[0035] According to exemplary embodiments of the present invention, the length of the sliding region of the electrode active material layer can be significantly reduced, and an electrode having a uniform loading amount can be provided.

[0036] According to exemplary embodiments of the present invention, since the adhesive tape is continuously attached rather than intermittently, the risk of the adhesive tape being detached is reduced, the productivity of electrode manufacturing is improved, and the risk of tolerance in the attachment position due to intermittent attachment can be prevented.

[0037] According to exemplary embodiments of the present invention, cracks can be suppressed from occurring in an electrode active material layer during the removal process of an adhesive tape, and an electrode with excellent capacity can be manufactured as a result of reducing the rate of detachment of the electrode active material.

[0038]

[0039] Figure 1 is a drawing for explaining a conventional technique for manufacturing an electrode using tape.

[0040] Figure 2 is a drawing to explain the problems of conventional technology.

[0041] FIG. 3 is a flowchart illustrating a method for manufacturing an electrode according to exemplary embodiments of the present invention.

[0042] FIG. 4 is a drawing showing an electrode manufacturing method according to exemplary embodiments.

[0043] Figure 5 is a drawing showing various embodiments of attaching an adhesive tape.

[0044] Figure 6 is a flowchart illustrating a method for manufacturing an electrode according to exemplary embodiments of the present invention.

[0045] Figure 7 is a drawing for explaining a problem when performing a rolling step without removing the adhesive tape.

[0046] FIG. 8 is a diagram illustrating a notching step according to exemplary embodiments.

[0047] Figure 9 is a flowchart for explaining an electrode manufacturing method according to exemplary embodiments.

[0048] Figure 10 is a flowchart illustrating an electrode manufacturing method according to exemplary embodiments.

[0049] Fig. 11 is a schematic diagram of an electrode manufacturing system according to Fig. 10.

[0050] Fig. 12 is a drawing showing an electrode current collector sheet after the adhesive tape attachment step (P110).

[0051] Fig. 13 is a schematic diagram of an electrode manufacturing system according to another embodiment.

[0052] FIG. 14 is a drawing showing an adhesive tape according to exemplary embodiments.

[0053] Fig. 15 is a drawing showing a coating step according to exemplary embodiments.

[0054] Figure 16 is a plan view and a cross-sectional view of an electrode according to exemplary embodiments.

[0055]

[0056] [Explanation of symbols]

[0057] 11: Electrode current collector sheet

[0058] 12: Electrode slurry, electrode active material layer

[0059] 3: Tape

[0060] 30: Adhesive tape

[0061] 100: Electrode

[0062] 110: Main body

[0063] 11, 111: Whole house

[0064] 112: Maintenance Department

[0065] 120: Electrode tab

[0066] 121: Ministry of Ignorance

[0067] 122: Electrode tab retainer

[0068]

[0069] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0070] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0071] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0072] In this specification, it should be understood that terms such as “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0073] In this specification, the term “combination(s) thereof” included in the surface of the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Makushi format, and means including one or more selected from the group consisting of the above components.

[0074] In this specification, the description of “A and / or B” means “A or B or both.”

[0075] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0076] In this specification, the transport direction (MD) of the electrode collector sheet is defined as the X direction, the transverse direction (TD) of the electrode collector sheet is defined as the Y direction, and the direction perpendicular to the plane obtained by the combination of the X direction and the Y direction is defined as the Z direction.

[0077] In this specification, the maintenance portion means a region among the electrode current collector sheets where electrode slurry is applied, and the non-conductive portion means a region among the electrode current collector sheets where electrode slurry is not applied and the current collector is exposed.

[0078] In this specification, the adhesive strength of the adhesive tape can be measured by the following method. An adhesive tape cut to a length of 150 mm and a width of 20 mm is prepared, and the adhesive tape is placed against a SUS (Steel Use Stainless) plate having a length of 75 mm and a width of 25 mm, and the adhesive tape is attached to the SUS plate in the longitudinal direction. That is, the SUS plate is attached to an area corresponding to half of the longitudinal direction of the adhesive tape. Thereafter, a test sample is prepared by rubbing a roller 10 times so that the adhesive tape is evenly attached. Next, the SUS plate portion of the test sample is fixed to the sample stage of a Universal Testing Machine (UTM) (LS5, AMETEK), and the half of the adhesive tape to which the SUS plate is not attached is connected to the load cell of the UTM equipment. The load cell is moved 50 mm at a speed of 100 mm / min, with a force applied at a 90° angle, and the load applied to the load cell is measured. At this time, the average value of the load measured in sections of 20 mm to 40 mm during the travel section is obtained, and this is repeated a total of 5 times, and the average value is evaluated as the adhesive strength (gf / inch) of the adhesive tape.

[0079]

[0080] Method for manufacturing electrodes

[0081] (First embodiment)

[0082] FIG. 3 is a flowchart for explaining an electrode manufacturing method according to exemplary embodiments, and FIG. 4 is a drawing showing an electrode manufacturing method according to exemplary embodiments.

[0083] Referring to these drawings, the electrode manufacturing method according to exemplary embodiments of the present invention may include an adhesive tape attachment step (P110), a coating step (P120), a drying step (P130), and an adhesive tape removal step (P140).

[0084] According to an electrode manufacturing method according to exemplary embodiments of the present invention, an adhesive tape (30) is attached to the edge of a portion intended for a maintenance portion in an electrode current collector sheet (11), and while the adhesive tape (30) is attached to the electrode current collector sheet (11), an electrode slurry (12) is applied and dried, and then the adhesive tape (30) is peeled off. When the adhesive tape (30) is peeled off, the electrode active material layer (12) formed on the adhesive tape (30) is removed together, so that the end surface of the electrode active material layer forms a perpendicular angle with respect to the current collector plane, and thus the length of the sliding region of the electrode active material layer (12) is significantly reduced, and an electrode having a uniform loading amount can be provided. In particular, the electrode manufacturing method according to the present invention is significant in that the effect of reducing the length of the sliding region is much superior compared to the conventional technology of controlling the sliding length of the electrode active material layer by forming a dam coating layer.

[0085] The above adhesive tape attachment step (P110) may be a step of attaching an adhesive tape (30) having a predetermined width on the edge of a portion of the electrode current collector sheet (11) where the electrode active material layer is to be formed.

[0086] Referring to Fig. 4, the adhesive tape (30) can be continuously attached along the transport direction (X direction) on the continuously transported current collector sheet (11). Since the adhesive tape (30) is continuously attached rather than intermittently attached, the risk of the adhesive tape being detached from the current collector sheet (11) is reduced, the productivity of electrode manufacturing is improved, and the risk of tolerance in the attachment position due to intermittent attachment can be prevented.

[0087] FIG. 5 is a drawing illustrating various embodiments of attaching an adhesive tape. Referring to FIG. 5, an adhesive tape (30) can be attached to an appropriate position corresponding to a coating pattern of an electrode slurry. Referring to (a) of FIG. 5, when the electrode slurry is applied in one row, the adhesive tape (30) can be attached on each of the edges in the width direction (Y direction) of the intended retention portion of the first row, and referring to (b) of FIG. 5, when the electrode slurry is applied in two rows, the adhesive tape (30) can be attached on each of the edges in the width direction (Y direction) of the intended retention portion of the second row. Referring to (c) of FIG. 5, when the electrode slurry is applied in two rows, an adhesive tape (30) having a relatively wide width length may be attached between a intended retention portion and another intended retention portion. In Fig. 5, an embodiment is illustrated in which the adhesive tape is attached to each of the edges in the width direction of the intended maintenance portion, but it is not limited thereto and may be attached to one edge.

[0088] In exemplary embodiments, the adhesive tape (30) is preferably a pressure-sensitive adhesive tape (PSA) that can be easily attached to and then removed from the electrode current collector sheet (11). During the drying step (P130), a force is applied to shrink the electrode slurry as the solvent of the electrode slurry is removed. If the adhesive tape (30) is a heat-peelable tape, the heat-peelable tape experiences volume expansion due to the heat energy of the drying step. At this time, if the volume expansion occurs unevenly, cracks may occur. On the other hand, since the pressure-sensitive adhesive tape does not experience volume expansion in the drying step (P130), it does not cause such a problem, and therefore, the pressure-sensitive adhesive tape is more preferable as the adhesive tape of the present invention.

[0089] In exemplary embodiments, the thickness A of the adhesive tape, the thickness B of the electrode active material layer after the drying step, and the adhesive strength C of the adhesive tape may satisfy the following condition 1.

[0090] [Condition 1]

[0091] 0.15≤B / (A×C)

[0092] In the above condition 1, A and B are each values ​​in μm, and C is the adhesive strength measured by a 90° peel test after attaching the adhesive tape to the SUS plate, and is a value in gf / inch.

[0093] According to the present invention, if the thickness of the adhesive tape, the adhesive strength of the adhesive tape, and the thickness of the electrode active material layer after the drying step are controlled to satisfy the above condition 1, the detachment of the electrode active material can be effectively prevented.

[0094] In exemplary embodiments, the thickness of the adhesive tape may be 150 μm or less, preferably 80 μm or less, more preferably 40 μm or less, and most preferably in the range of 5 to 20 μm. A smaller thickness of the adhesive tape is preferable in terms of suppressing detachment of the electrode active material, but if the thickness is too small, the mechanical rigidity may be reduced, which may cause the adhesive tape to break during the removal process, which is not preferable.

[0095] In exemplary embodiments, the thickness of the electrode active material layer after the drying step may be 50 μm or more, preferably 70 μm or more, and more preferably in the range of 80 to 160 μm. Here, the thickness refers to the thickness of the electrode active material layer located on one side of the current collector sheet. In the case of a double-sided electrode in which electrode active material layers exist on both sides of the current collector, the total thickness of the electrode active material layer is twice the above range. In addition, the thickness may be an average value of the thickness of a portion excluding the sliding region among the electrode active material layers. The larger the value of the thickness of the electrode active material layer, the more preferable it is in terms of suppressing delamination of the electrode active material.

[0096] In exemplary embodiments, the thickness ratio (A / B) of the thickness A of the adhesive tape to the thickness B of the electrode active material layer after the drying step may be in the range of 0.05 to 0.5, preferably 0.05 to 0.25, and more preferably 0.05 to 0.1. When the thickness ratio value satisfies the above range, the mechanical strength of the adhesive tape can be secured while suppressing the delamination of the electrode active material. If the thickness ratio value is excessively large, the peeling force of the adhesive tape may decrease. Conversely, if the thickness ratio value is excessively small, it may be difficult to apply the electrode slurry onto the adhesive tape.

[0097] In exemplary embodiments, the adhesive strength of the adhesive tape may be 20 gf / inch or less, preferably 10 gf / inch or less, and more preferably 5 gf / inch or less. A lower adhesive strength of the adhesive tape is preferable in terms of suppressing delamination of the electrode active material, and if the adhesive strength of the adhesive tape exceeds the above range, wrinkles may occur in the current collector sheet after the adhesive tape is removed, which is not preferable.

[0098] The above coating step (P120) may be a step of applying electrode slurry to a portion of the current collector sheet (11) to be maintained. In one embodiment, the coating step (P120) may be performed as a continuous process of continuously applying electrode slurry onto the current collector sheet (11) being transported along the transport direction (X direction). In one embodiment, the means for applying the electrode slurry may be a slot die coater configured to be capable of discharging the electrode slurry. However, the present invention is not limited thereto.

[0099] In the above coating step (P120), the electrode slurry may be applied over the intended holding portion and a portion of the adhesive tape. In order to peel the adhesive tape from the current collector sheet during the process of removing the adhesive tape, the portion of the adhesive tape on which the electrode slurry is not applied must be pulled, so it is preferable that the electrode slurry is not applied on one portion of the adhesive tape facing the uncoated portion. Since the adhesive tape is positioned on the edge of the intended holding portion, part or all of the electrode sliding area may be formed on the adhesive tape.

[0100] The above electrode slurry may be a slurry for a positive electrode or a negative electrode. In general, secondary batteries are designed to have an NP-Ratio of 1 or higher, and the shorter the length of the sliding region of the negative electrode, the greater the risk of NP-Ratio reversal. Therefore, the manufacturing method according to the present invention may be more effective in manufacturing the negative electrode.

[0101] In exemplary embodiments, the electrode slurry may be applied onto the electrode current collector sheet (11) at a loading amount such that the thickness of the electrode active material layer is 50 μm or more, preferably 70 μm or more, and more preferably in the range of 80 to 160 μm after the drying step (P130) described below. Here, the thickness may be an average value of the thickness of a portion of the electrode active material layer excluding the sliding region.

[0102] In exemplary embodiments, the electrode slurry can be prepared by mixing and stirring an electrode active material, a binder, a conductive agent, and other additives in a solvent.

[0103] The solvent may be a solvent generally used in the relevant technical field, and may include dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these may be used alone or a mixture of two or more thereof. It may be preferable to include the solvent in an amount that ensures an appropriate viscosity in consideration of the applicability and processability of the electrode slurry.

[0104] The solvent may be included in an amount such that it has an appropriate viscosity and solids content. For example, the solvent may be included in an amount such that the solids content in the electrode slurry is 40 wt% to 75 wt%, specifically 45 wt% to 70 wt%, and more specifically 45 wt% to 60 wt%. In addition, the electrode slurry may have a viscosity that allows for coating, and the electrode active material layer formed from the electrode slurry may have a thickness of a certain level or more, thereby ensuring excellent energy density.

[0105] In exemplary embodiments, the electrode slurry may contain a binder in an amount of 5 parts by weight or less, preferably 1 to 5 parts by weight, and more preferably 1.5 to 4 parts by weight, based on 100 parts by weight of the solid content of the electrode slurry. When the binder content is within the above numerical range, the electrode can have the adhesive strength required for the electrode, while also alleviating the phenomenon of electrode breakage or delamination of the electrode active material when the adhesive tape is peeled off.

[0106] In exemplary embodiments, the transport speed of the electrode current collector sheet may be 20 m / min or more, specifically 30 to 120 m / min, and more specifically 40 to 100 m / min. A lower transport speed of the electrode current collector sheet is preferable in terms of suppressing desorption of the electrode active material. However, if the transport speed is too low, productivity may be reduced.

[0107] The above drying step (P130) is a step for removing a solvent in the electrode slurry, and the drying step (P130) can be performed by a commonly used electrode drying device.

[0108] In exemplary embodiments, the drying temperature in the drying step (P130) may be in the range of 50°C to 200°C, but is not limited thereto. The electrode is dried through a plurality of drying zones, and the drying temperature of each drying zone can be independently set. The drying temperature of each drying zone can be appropriately set in consideration of the effect on the electrode when the adhesive tape according to the present invention is peeled, the coating form of the electrode slurry, the solid content of the electrode slurry, the loading amount of the electrode slurry, etc.

[0109] In one embodiment, the drying temperatures of the drying zones in the first half may be set to a relatively high temperature, the drying temperatures of the drying zones in the middle may be set to a relatively lower temperature than the drying temperatures of the drying zones in the first half, and the drying zone in the second half may be set to a temperature between the drying temperatures of the previous drying zones and room temperature as a cooling section. In addition, the drying temperature may be gradually decreased along the transport direction of the electrode, the drying temperature may be maintained the same in a certain drying zone, or the drying temperature may be decreased and then increased along the transport direction of the electrode.

[0110] If the drying temperature is too high during the drying stage, the difference in elongation between the uncoated and uncoated portions will become more severe, which can lead to wrinkles in the uncoated portion, reduced adhesive strength, and electrode cracks due to overdrying. Conversely, if the drying temperature is too low, the time required to dry the electrode will be excessively long, which is undesirable from a productivity perspective.

[0111] The step (P140) of peeling and removing the adhesive tape may be a step of peeling and removing the adhesive tape (30) from the current collector sheet (11), as illustrated in FIG. 4. As the adhesive tape is removed, part or all of the sliding area of ​​the electrode active material layer (12) formed on the adhesive tape (30) may be removed together.

[0112] The method for peeling off the adhesive tape is not particularly limited. The adhesive tape may be removed from the current collector sheet by lifting the portion of the adhesive tape where the electrode active material layer is not formed while pressing the adhesive tape, or the adhesive tape may be peeled off by absorbing the adhesive tape using an absorbent means.

[0113] Fig. 6 is a flowchart illustrating a method for manufacturing an electrode according to exemplary embodiments of the present invention. Referring to Fig. 6, the method for manufacturing an electrode according to exemplary embodiments of the present invention may further include a rolling step (P150) after the step of removing the adhesive tape (P140). The rolling step (P150) may be performed by roll-pressing an electrode current collector sheet on which an electrode active material layer is formed.

[0114] Fig. 7 is a drawing for explaining a problem when performing a rolling step without removing the adhesive tape. Referring to Fig. 7, when performing a rolling step with the adhesive tape attached, cracks may be induced in the electrode active material layer due to stress occurring at the edge of the adhesive tape (30) having a predetermined thickness. Therefore, it is preferable to perform the rolling step with the adhesive tape (30) removed from the electrode current collector sheet (11).

[0115] The method of the above roll-pressing is not particularly limited, and the rolling step (P150) can be performed using the rolling roller (40) illustrated in FIG. 7. Although only one rolling roller (40) is illustrated in FIG. 7, the rolling step (P150) can be performed by passing the electrode current collector sheet (11) on which the electrode active material layer (12) is formed between the pair of rolling rollers (40).

[0116] The method for manufacturing an electrode according to exemplary embodiments of the present invention may further include, after the rolling step (P150), a notching step (P160) of notching an electrode tab in a non-coated portion, and a cutting step (P170) of punching out an electrode current collector sheet on which an electrode active material layer is formed into the size of a unit electrode.

[0117] Fig. 8 is a drawing illustrating a notching step according to exemplary embodiments. Referring to Fig. 8, an electrode tab can be formed by notching along a notching line (dotted line) located on a non-conductive portion, and a unit electrode (100) can be obtained by cutting along a cutting line (dotted line) located on a retaining portion.

[0118] In one embodiment, the notching step (P150) may notch the electrode tab (Tab) so that the boundary between the holding portion where the electrode active material layer (12) is formed and the uncoated portion (11) where the electrode active material layer is not formed is located within the electrode tab (Tab) region. Referring to FIG. 8, when setting the notching and cutting line, the electrode tab notching line may be set to span the uncoated portion (11) and the holding portion (12), and the cutting line (UL) of the upper portion of the electrode and the cutting line (BL) of the lower portion may be set to be located on the inner region of the holding portion (12). In this case, since there is a high possibility that the electrode sliding region is not included or, even if included, the length of the sliding region is very small not only in the electrode tab but also in the electrode main body, the risk of NP-Ratio reversal can be effectively prevented.

[0119]

[0120] (Second embodiment)

[0121] The second embodiment differs from the first embodiment described above in that it is a method for manufacturing a double-sided electrode in which an electrode active material layer is formed on both sides of an electrode current collector sheet.

[0122] According to the second embodiment, the coating step (P120) includes a top coating step (P121) of applying electrode slurry to the top surface of the current collector sheet; and a bottom coating step (P122) of applying electrode slurry to the bottom surface of the current collector sheet, and the drying step (P130) includes a top drying step (P131) of drying the electrode slurry applied in the top coating step; and a bottom drying step (P132) of drying the electrode slurry applied in the bottom coating step.

[0123] Fig. 9 is a flowchart for explaining an electrode manufacturing method according to exemplary embodiments. Referring to Fig. 9, an upper surface attachment step (P111) of an adhesive tape, an upper surface coating step (P121), an upper surface drying step (P131), an adhesive tape removal step (P140), an adhesive tape lower surface attachment step (P112), a lower surface coating step (P132), and an adhesive tape removal step (P140) may be sequentially performed.

[0124] According to this embodiment, the upper surface drying step is performed in a state where no adhesive tape is attached to the lower surface of the electrode current collector sheet, and the drying step is performed in a state where no adhesive tape is attached to the upper surface of the electrode current collector sheet, so that the adhesive tape attached to the opposite surface of the drying surface during the drying step can be prevented from having an effect on the current collector sheet.

[0125] In the embodiment illustrated in Fig. 9, the adhesive tape removal step (P140) is performed after the upper surface drying step and the lower surface drying step, respectively. However, if done differently, the adhesive tape attached to the upper surface and the lower surface can be removed at once after the drying step.

[0126]

[0127] (Embodiment 3)

[0128] The third embodiment is similar to the second embodiment described above in that it is a method for manufacturing a double-sided electrode, but differs from the second embodiment in the step of attaching the adhesive tape.

[0129] FIG. 10 is a flowchart for explaining an electrode manufacturing method according to exemplary embodiments, and FIG. 11 is a schematic diagram of an electrode manufacturing system according to FIG. 10.

[0130] Referring to FIG. 11, in exemplary embodiments, the electrode current collector sheet (11) unwound from the unwinder (UW) may sequentially pass through an adhesive tape attachment section (210), a first coating section (221), a first drying section (231), a second coating section (222), a second drying section (232), and an adhesive tape recovery section (240). Accordingly, in the method for manufacturing an electrode according to the second embodiment, as illustrated in FIG. 10, an adhesive tape attachment step (P110), an upper surface coating step (P121), an upper surface drying step (P131), a lower surface coating step (P122), a lower surface drying step (P132), and an adhesive tape removal step (P140) may be sequentially performed.

[0131] According to the third embodiment, in the step (P110) of attaching the adhesive tape, the adhesive tape (30) may be attached to the upper and lower surfaces of the electrode current collector sheet (11), respectively, and may be attached so as to completely overlap with the electrode current collector sheet (11) interposed therebetween.

[0132] Fig. 12 is a drawing showing an electrode current collector sheet after the adhesive tape attachment step (P110). Referring to Fig. 12, in the adhesive tape attachment step (P110), the adhesive tape (30) is attached simultaneously to the upper and lower surfaces of the current collector sheet (11), so that the area where the adhesive tape is attached on the upper surface and the area where the adhesive tape is attached on the lower surface can be made to completely overlap each other. According to the third embodiment, the risk of tolerance in the attachment position of the adhesive tape can be reduced.

[0133] Fig. 13 is a schematic diagram of an electrode manufacturing system according to another embodiment. Referring to Fig. 13, an electrode current collector sheet (11) unwound from an unwinder (UW) may sequentially pass through an adhesive tape attachment section (210), a first coating section (221), a first drying section (231), a first adhesive tape recovery section (241), a second coating section (222), a second drying section (232), and a second adhesive tape recovery section (242). As described above, the adhesive tape removal step (P140) may be performed after the upper surface drying step (P131) and after the lower surface drying step (P132).

[0134]

[0135] (Embodiment 4)

[0136] The fourth embodiment differs from the first embodiment in that the adhesive tape has a protrusion that protrudes toward the intended maintenance portion along the transverse direction (TD, Y direction) of the electrode current collector sheet.

[0137] Fig. 14 is a drawing showing an adhesive tape according to exemplary embodiments. Referring to Fig. 14, the adhesive tape (30) may include a base portion (31) having a predetermined width and extending along the transport direction (X direction) of the current collector sheet; and a protrusion portion (32) protruding from the base portion (31) toward a predetermined portion of the holding portion along the transverse direction (Y direction) of the current collector sheet.

[0138] Since the adhesive tape (30) having such a shape is continuously attached along the transport direction (X direction) of the electrode current collector sheet (11), the problem of the adhesive tape being detached from the current collector sheet during the manufacturing step of the electrode can be prevented. In addition, since the drying step is performed while the base portion is attached to the non-coated portion, the phenomenon of wrinkles occurring in the non-coated portion during the drying step can be suppressed. In addition, since the occurrence of wrinkles is prevented, cracks can be prevented from occurring in the electrode active material layer. In addition, since the electrode active material layer (12a) formed between the protrusion and the adjacent protrusion is a portion that is discarded in the subsequent notching and cutting step, even if a part of the electrode active material layer is detached during the removal process of the adhesive tape, it does not affect the unit electrode and thus does not cause a decrease in the capacity of the electrode.

[0139] In exemplary embodiments, the transverse length (a) of the base portion may be 1 mm or more, more specifically in the range of 3 to 50 mm, and even more specifically in the range of 5 to 40 mm. The protruding length (b) of the protruding portion may be 1 mm or more, and even more specifically in the range of 3 to 25 mm. The sum (a+b) of the transverse length of the base portion and the protruding length of the protruding portion may be 2 mm or more, more specifically in the range of 5 to 60 mm, and even more specifically in the range of 10 to 50 mm.

[0140] Fig. 15 is a drawing showing a coating step according to exemplary embodiments.

[0141] Referring to FIGS. 14 and 15, the transverse direction (Y direction) length of the electrode slurry (12) illustrated in FIG. 15 is shorter than the transverse direction (Y direction) length of the electrode slurry (12) illustrated in FIG. 14. Coating the electrode slurry as illustrated in FIG. 15 is more preferable because it can reduce the amount of electrode active material detached during the removal process of the adhesive tape.

[0142]

[0143] electrode

[0144] Figure 16 is a top view and a cross-sectional view of an electrode according to exemplary embodiments.

[0145] Referring to these drawings, an electrode (10) according to exemplary embodiments includes a holding portion (CP) on which an electrode active material layer (12) is laminated on an electrode current collector sheet (11); and a non-coated portion (NCP) positioned at at least one edge on the transverse direction (Y direction) of the electrode current collector sheet (11), the electrode exposing the electrode current collector sheet (11). The electrode according to exemplary embodiments of the present invention can be manufactured according to the manufacturing method described above. Specifically, the electrode (10) can be manufactured by attaching an adhesive tape (30) on the transverse direction (Y direction) edge of a portion of the electrode current collector sheet (11) intended for the holding portion (CP), applying electrode slurry to the portion intended for the holding portion (CP) to form an electrode active material layer (12), and removing the adhesive tape (30) from the electrode current collector sheet (11). Accordingly, since all or a significant portion of the sliding area formed at the transverse (Y-direction) edge of the electrode active material layer is removed together during the removal process of the adhesive tape (30), the transverse (Y-direction) length of the electrode sliding area can be significantly reduced.

[0146] In the electrode active material layer (12), the end face (12S) based on the transverse direction (Y direction) of the electrode active material layer (12) may be perpendicular to the plane of the electrode current collector sheet (11). Here, the meaning of "perpendicular" may be defined as an angle in which the end face (12S) of the electrode active material layer (12) forms an angle close to perpendicular to the plane of the current collector sheet, for example, an angle in the range of 80 to 100°, preferably 85 to 97°, more preferably 87 to 95°, and most preferably 89 to 91°.

[0147] In order to make the end face (12S) of the electrode active material layer and the current collector sheet (11) perpendicular, when removing the adhesive tape (30) from the current collector sheet (11), the adhesive tape (30) is lifted along the transport direction (X direction) of the current collector sheet, but the direction (Z direction) perpendicular to the plane of the current collector sheet (11) is the direction in which the adhesive tape (30) is lifted.

[0148]

[0149] In exemplary embodiments, the electrode active material layer (12) may include a sliding region (SL) in which the thickness of the electrode active material layer (12) gradually decreases in a direction from the holding portion (CP) toward the non-conducting portion (NCP). The electrode (10) may be manufactured according to the above-described electrode manufacturing method, such that the lateral (Y-direction) length of the sliding region (SL) may be 1.0 mm or less, more preferably 0.9 mm or less, and more preferably in the range of 0.1 mm to 0.8 mm. The lateral (Y-direction) length of the sliding region (SL) is a significantly reduced length compared to the lateral length of the sliding region of an electrode manufactured by a method of overlappingly applying a conventional dam coating composition. According to one embodiment, the electrode has the effect of dramatically preventing the risk of NP-Ratio reversal by controlling the lateral (Y-direction) length of the sliding region to 1.0 mm or less.

[0150] In one embodiment, the thickness of the electrode active material layer (12) may be 50 μm or more, preferably 70 μm or more, and more preferably in the range of 80 to 160 μm. Here, the thickness of the electrode active material layer is the thickness after drying of the electrode, and can be measured using a measuring device such as a Tesa height gauge.

[0151] As the thickness of the electrode active material layer (12) increases, the rate of detachment of the electrode active material when the adhesive tape (30) is peeled off may decrease. However, if the thickness of the electrode active material layer (12) is too thick, the peelability of the adhesive tape may be limited. Therefore, it is preferable to set the thickness range of the electrode active material layer (12) within the above range.

[0152] In exemplary embodiments, the ratio of the minimum thickness T2 of the sliding region (SL) to the maximum thickness T1 of the sliding region (SL) (=T2 / T1) is 0.8 or more, preferably 0.85 to 1, more preferably 0.9 to 1, and most preferably 0.95 to 1. When the value of T2 / T1 satisfies the above range, since the step of the sliding region (SL) is small, it is easy to manage the NP-Ratio of the positive and negative electrodes.

[0153] In one embodiment, the slope of the sliding region (SL) may be 0.005 or more, specifically, in the range of 0.007 to 0.1, and more specifically, in the range of 0.01 to 0.05. Here, the slope is defined as the ratio value of the difference between T1, which is the maximum thickness of the electrode active material layer of the sliding region, and T2, which is the minimum thickness of the electrode active material layer of the sliding region, with respect to the transverse (Y direction) length a of the sliding region (SL) [=(T1-T2) / a]. When the slope of the sliding region (SL) satisfies the above range, the NP-Ratio management of the positive and negative electrodes can be easily performed.

[0154] In one embodiment, the electrode may be a cathode. Since the risk of NP-Ratio reversal is high in the sliding region of the cathode, if an electrode with a significantly reduced sliding region length is used as the cathode, the risk of NP-Ratio reversal can be more effectively prevented.

[0155] In one embodiment, the negative electrode may include a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer may be manufactured by applying a negative electrode slurry containing a negative electrode active material onto the negative electrode current collector and drying the same. The negative electrode slurry may be manufactured by mixing and stirring a negative electrode active material, a binder, and a conductive agent together in a solvent, and may optionally further include additives such as a dispersant.

[0156] The negative electrode current collector is a metal having high conductivity and to which the negative electrode slurry can easily adhere, and any metal that is non-reactive within the voltage range of the battery can be used. Specifically, copper, stainless steel, aluminum, nickel, titanium, sintered carbon; stainless steel surface-treated with carbon, nickel, titanium or silver; aluminum-cadmium alloy; non-conductive polymer surface-treated with a conductive material; or conductive polymer can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and the negative electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0157] The above negative active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO x (0 < x < 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. A metallic lithium thin film may also be used as the negative electrode active material.

[0158] The above carbonaceous material may specifically be both low-crystalline carbon and high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and examples of high-crystalline carbon include calcined carbon such as natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes. Specifically, graphite-based negative electrode active materials such as natural graphite or artificial graphite are more preferable because they can reversibly insert and de-insert lithium ions while maintaining structural and electrical properties.

[0159] The above negative active material may be included in an amount of about 80 wt% to 99.5 wt% or 88 wt% to 99 wt% relative to the total weight of the negative active material layer, but the content is not limited thereto.

[0160] The above binder is not particularly limited as long as it is a component that assists in the bonding of the negative electrode active material and the conductive material and the bonding to the current collector, and examples thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0161] When the solvent of the cathode slurry is an aqueous solvent such as water, the above binder is preferably an aqueous binder. In a specific example, the aqueous binder may be at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, and diacetyl cellulose. In a specific example, the aqueous binder may be at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. For example, the aqueous binder may be styrene-butadiene rubber.

[0162] The above binder may typically be included in an amount of 1 to 30 wt% based on the total weight of the negative electrode active material layer.

[0163] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, and the like; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0164] The above-mentioned conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the negative electrode active material layer.

[0165] The above filler is optionally used as a component that suppresses expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber can be used.

[0166] In one embodiment of the present invention, the electrode may be a positive electrode. The positive electrode may include a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer may be formed by applying a positive electrode slurry containing a positive electrode active material onto the positive electrode current collector and drying it. The positive electrode slurry may be prepared by mixing and stirring a positive electrode active material, a binder, and a conductive agent in a solvent, and may optionally further include additives such as a dispersant.

[0167] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0168] The positive electrode active material is not particularly limited, and compounds known in the art that are capable of reversible intercalation and deintercalation of lithium can be used without limitation. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, LiV3O4, V2O5, Cu2V2O Vanadium oxide, chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides expressed as O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x It may include, but is not limited to, lithium manganese composite oxides having a spinel structure represented by O4; LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; disulfide compounds; lithium iron phosphate represented by LiFePO4; disulfide compounds; Fe2(MoO4)3, etc.

[0169] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0170] The above-mentioned positive electrode conductive material is used to provide conductivity to the electrode, and carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, etc. can be used. Products currently sold as conductive materials include acetylene black series (products of Chevron Chemical Company or Gulf Oil Company, etc.), Ketjen Black EC series (product of Armak Company), Vulcan XC-72 (product of Cabot Company), and Super P (product of MMM). Among these, carbon nanotubes, carbon nanofibers, and carbon black are preferable as the conductive material of the present invention, and carbon nanotubes are most preferable. The conductive network of carbon nanotubes is most preferable as a conductive material included in the positive electrode of the present invention because it can alleviate the phenomenon of binder lifting during the drying process of the positive electrode slurry.

[0171] The BET specific surface area of ​​the above carbon nanotube may be 100 m2 / g to 1000 m2 / g, 150 m2 / g to 800 m2 / g, 150 m2 / g to 500 m2 / g, 150 m2 / g to 300 m2 / g, or 150 m2 / g to 200 m2 / g.

[0172] The above positive electrode conductive material may be included in the positive electrode active material layer in an amount of 0.1 to 30 wt%, specifically 0.1 to 10 wt%, and more specifically 0.5 to 5 wt%.

[0173] The above-mentioned positive electrode binder may be any binder polymer that is commonly used without limitation. For example, various types of binder polymers such as polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, styrene butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) may be used.

[0174] The above positive electrode binder may be included in the positive electrode active material layer in an amount of 0.1 to 30 wt%, specifically 0.1 to 10 wt%, and more specifically 0.5 to 5 wt%.

[0175]

[0176] According to one embodiment of the present invention, a lithium secondary battery is provided comprising the positive electrode and / or negative electrode described above. The lithium secondary battery may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0177] The lithium secondary battery of the present invention can be manufactured using conventional methods known in the art. For example, it can be manufactured by inserting a separator between the positive and negative electrodes and injecting an electrolyte.

[0178] In the above lithium secondary battery, the positive electrode and / or negative electrode may be the electrodes described above.

[0179]

[0180] The above separator can be any porous substrate typically used as a separator in lithium secondary batteries. Examples include, but are not limited to, a polyolefin-based porous membrane or non-woven fabric. In particular, one having low resistance to electrolyte ion movement and excellent electrolyte moisture retention capacity is preferred.

[0181] Examples of the above polyolefin porous membrane include a membrane formed from a single or mixed polymer of polyolefin polymers such as polyethylene, polypropylene, polybutylene, polypentene, etc., such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.

[0182] The above nonwoven fabric may include, in addition to polyolefin-based nonwoven fabrics, nonwoven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalene, either singly or in combination. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a meltblown nonwoven fabric.

[0183] The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and pore content present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

[0184] Meanwhile, in order to improve the mechanical strength of the separator composed of the porous substrate and to suppress short circuits between the anode and cathode, a porous coating layer including inorganic particles and a binder polymer may be further included on at least one side of the porous substrate.

[0185] Meanwhile, in the lithium secondary battery, the electrolyte may include an organic solvent and lithium salt commonly used in electrolytes, and is not particularly limited.

[0186] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC) can be used.

[0187] Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0188] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the lithium salt be included in the electrolyte at a concentration of approximately 0.6 mol% to 2 mol%.

[0189] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0190] The lithium secondary battery of the present invention can be manufactured by forming an electrode assembly by placing a separator between the positive and negative electrodes, placing the electrode assembly in a cylindrical or square battery case, and then injecting an electrolyte. Alternatively, the electrode assembly can be manufactured by stacking the electrode assembly, impregnating it with an electrolyte, and placing the resulting product in a battery case and sealing it.

[0191] When manufacturing the lithium secondary battery of the present invention, the electrode assembly may be dried to remove one or more organic solvents selected from the group consisting of N-methyl-2-pyrrolidone (NMP), acetone, ethanol, propylene carbonate, ethyl methyl carbonate, ethylene carbonate, and dimethyl carbonate used in manufacturing the positive electrode. If an electrolyte having the same composition as the organic solvent used in manufacturing the positive electrode is used as the electrolyte, the process of drying the electrode assembly may be omitted.

[0192] Unlike the lithium secondary battery described above, a lithium secondary battery according to another embodiment of the present invention may be an all-solid-state battery.

[0193] The above battery case can be adopted as one commonly used in the field, and there is no limitation on the external shape according to the use of the battery. For example, it can be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0194] The lithium secondary battery according to the present invention exhibits excellent capacity and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in electric vehicles such as energy storage systems (ESS) and hybrid electric vehicles (HEVs).

[0195]

[0196] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0197]

[0198] Example 1

[0199] (Manufacture of slurry for cathode)

[0200] Artificial graphite (D) with a sphericity of 0.85 as a negative active material 50 A slurry for the negative electrode was prepared by mixing and stirring styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and carbon nanotubes as a conductive agent in a weight ratio of 96:2.5:1:0.5 in deionized water (solid content: 50 wt%).

[0201] (Attaching step of adhesive tape)

[0202] An adhesive tape was supplied to a copper foil having a thickness of 10 μm while being transported at a speed of 20 m / min, and an adhesive tape having a shape as shown in Fig. 4 was continuously attached along the transport direction of the copper foil on both edges of the intended support portion of the copper foil. The adhesive strength of the adhesive tape was 10 gf / inch, and its thickness was 16 μm.

[0203] (Application step of slurry for cathode)

[0204] The above-mentioned negative electrode slurry was applied to the intended maintenance portion. At this time, a portion of the negative electrode slurry was also applied to the portion of the adhesive tape adjacent to the intended maintenance portion. In addition, the loading amount of the negative electrode slurry was set so that the thickness after drying was 120 μm.

[0205] (Drying stage)

[0206] The cathode sheet coated with cathode slurry was placed in a drying oven and dried at a drying temperature of 120°C.

[0207] (Removing adhesive tape)

[0208] After the drying step, the adhesive tape was peeled off and removed from the copper foil.

[0209] (Rolling and notching stage)

[0210] After removing the adhesive tape, the copper foil on which the negative electrode active material layer was formed was roll-pressed, and then a negative electrode tab was formed as shown in Fig. 8, and cut into the size of a unit negative electrode (10 cm in the X direction, 20 cm in the Y direction) to complete the manufacture of the negative electrode.

[0211]

[0212] Examples 2 to 9

[0213] The negative electrode was manufactured in the same manner as in Example 1, except that the thickness A of the adhesive tape, the thickness B of the electrode active material layer after the drying step, and the adhesive strength C of the adhesive tape were changed as shown in Table 1.

[0214]

[0215] Example 10

[0216] The negative electrode was manufactured in the same manner as in Example 1, except that the adhesive tape used was an adhesive tape having protrusions as shown in Fig. 15.

[0217]

[0218] Experimental Example 1: Evaluation of the Desorption Rate

[0219] Forty cathodes were prepared according to each of Examples 1 to 10, and the number of cathodes where detachment occurred was counted by visually observing the area around the boundary where the adhesive tape was peeled off from the cathodes. The detachment rate was calculated as a percentage of the number of cathodes where detachment occurred among the 40 cathodes, and the results are shown in Table 1.

[0220]

[0221] Experimental Example 2: Measurement of sliding length

[0222] In each of the negative electrodes according to Examples 1 to 10, the transverse (Y-direction) length of the negative electrode active material layer from the point where the thickness of the negative electrode active material layer begins to decrease in the support portion of the negative electrode tab to the end of the support portion was measured, and the length is shown in Table 1. The change in the thickness of the negative electrode active material layer was measured using a confocal displacement sensor (manufacturer: Keyence).

[0223] Thickness A of adhesive tape Thickness B of electrode active material layer after drying step Adhesive force C of adhesive tape (gf / inch) B / (AХC) Shape of adhesive tape Detachment rate (%) Length of sliding area (μm) Example 1 168051 Straight (Fig. 4) 7.5 0.6 Example 2 161205 1.5 5 0.5 Example 3 16120 10 0.75 10 0.4 Example 4 1680 10 0.5 12.5 0.5 Example 5 16120 23.75 0 0.5 Example 6 40120 5 0.6 7.5 0.6 Example 7 1620 26.25 0 0.6 Example 8 4060 10 0.15 17.5 0.5 5 Example 94040100.1250.6 Example 10168051 Protruding type (Fig. 15) 50.6

[0224] Referring to Table 1, the electrodes manufactured according to the embodiments of the present invention have a sliding region length of 1 mm or less. Accordingly, the risk of NP-Ratio reversal is expected to be significantly reduced. Furthermore, in the present invention, when Condition 1 below is satisfied, it can be seen that the desorption rate of the electrode active material is reduced. Therefore, it is desirable to control the manufacturing of the electrode so that Condition 1 below is satisfied.

[0225] [Condition 1]

[0226] 0.15≤B / (A×C)

[0227]

[0228] The present invention has been described in more detail through the drawings and examples. However, the configurations described in the drawings or examples described in this specification are merely embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

Claims

1. A step of attaching an adhesive tape to the edge of a portion of an electrode current collector sheet where an electrode active material layer is to be formed; A coating step of applying electrode slurry to the above maintenance portion; A drying step for removing the solvent in the electrode slurry; and A step of removing the adhesive tape by peeling it from the electrode current collector sheet is included. A method for manufacturing an electrode, characterized in that, in the step of attaching the adhesive tape, the adhesive tape is continuously attached along the transport direction of the current collector sheet.

2. In paragraph 1, A method for manufacturing an electrode, characterized in that the thickness A of the adhesive tape, the thickness B of the electrode active material layer after the drying step, and the adhesive strength C of the adhesive tape satisfy the following condition 1: [Condition 1] 0.15≤B / (A×C) In the above condition 1, A and B are each values ​​in μm, and C is the adhesive strength measured by a 90° peel test after attaching the adhesive tape to the SUS plate, and is a value in gf / inch.

3. In paragraph 2, A method for manufacturing an electrode, characterized in that the adhesive strength of the above adhesive tape is 20 gf / inch or less.

4. In paragraph 2, A method for manufacturing an electrode, characterized in that the thickness of the adhesive tape is 150㎛ or less.

5. In paragraph 2, A method for manufacturing an electrode, characterized in that the electrode active material layer thickness after the above drying step is 50㎛ or more.

6. In paragraph 1, A method for manufacturing an electrode, characterized in that the above adhesive tape is a pressure-sensitive adhesive tape.

7. In paragraph 1, The above coating step is, A top coating step of applying electrode slurry to the upper surface of the above current collector sheet; and Includes a bottom coating step of applying electrode slurry to the bottom surface of the above current collector sheet, The above drying step is, A top surface drying step for drying the electrode slurry applied in the top surface coating step; and A method for manufacturing an electrode, comprising a lower drying step of drying the electrode slurry applied in the above lower coating step.

8. In paragraph 7, A method for manufacturing an electrode, characterized in that, in the step of attaching the adhesive tape, the adhesive tape is attached to the upper and lower surfaces of the electrode current collector sheet, respectively, and is attached so as to completely overlap with the electrode current collector sheet in between.

9. In paragraph 1, The above adhesive tape, A base portion having a predetermined width and extending along the transport direction of the entire sheet; and A method for manufacturing an electrode, characterized in that it includes a protrusion protruding from the base portion toward a portion intended for a maintenance portion along the transverse direction of the current collector sheet.

10. In paragraph 1, A method for manufacturing an electrode, further comprising a rolling step of roll-pressing an electrode current collector sheet on which an electrode active material layer is formed, after the step of removing the adhesive tape.

11. In paragraph 1, A method for manufacturing an electrode, characterized in that the content of the binder included in the electrode slurry is 5 parts by weight or less with respect to 100 parts by weight of the solid content of the electrode slurry.

12. A maintenance part in which an electrode active material layer is laminated on an electrode current collector sheet; and Located at least on one side edge of the electrode current collector sheet in the transverse direction (Y direction), the electrode current collector sheet includes an exposed non-conductive portion, An electrode in which, in the electrode active material layer, an end surface based on the transverse direction of the electrode active material layer is perpendicular to the plane of the electrode current collector sheet.

13. In paragraph 12, The electrode active material layer includes a sliding region in which the thickness of the electrode active material layer gradually decreases along the direction from the maintenance portion toward the non-conductive portion, An electrode having a transverse length of the above sliding region of 1 mm or less.

14. In paragraph 12, An electrode, wherein the ratio of the minimum thickness T2 of the sliding region to the maximum thickness T1 of the sliding region is 0.8 or more.

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