Manufacturing method of electrode assembly

Abstract

A method for manufacturing an electrode assembly according to one embodiment of the present invention is a method for manufacturing an electrode assembly by stacking two or more unit cells, each having an anode, a first separator, and a cathode sequentially stacked, with a second separator in between, and, prior to stacking the unit cells, a step of inspecting the alignment state of the anode and the cathode contained in a lower unit cell disposed below the unit cell, and a step of correcting the stacking position of the unit cells to be stacked if there is a defect in the alignment state as a result of the inspection.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an electrode assembly, specifically a method for manufacturing an electrode assembly that can minimize the impact even if an alignment error of the electrode occurs. Background Technology

[0002] Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative and clean energy. As part of this effort, the fields of power generation and energy storage utilizing electrochemistry are the most actively researched.

[0003] Currently, a representative example of an electrochemical device utilizing such electrochemical energy is the secondary battery, and its scope of application is steadily expanding.

[0004] Recently, as technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has been rapidly increasing. Among these, a lot of research has been done on lithium secondary batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, and they have also been commercialized and are widely used.

[0005] Furthermore, as interest in environmental issues grows, extensive research is being conducted on electric vehicles and hybrid electric vehicles to replace fossil fuel-powered vehicles, such as gasoline and diesel cars, which are major causes of air pollution. While nickel-metal hydride batteries are primarily used as power sources for these electric and hybrid vehicles, research utilizing lithium-ion batteries, which offer high energy density and discharge voltage, is actively underway and is already in the commercialization stage.

[0006] Such a lithium secondary battery is manufactured by forming an electrode composite layer by coating a positive or negative active material, a binder, and a conductive material in the form of a slurry onto a current collector and drying it to produce a positive and negative electrode, interposing a separator between the positive and negative electrodes, and embedding the laminated electrode assembly together with an electrolyte in a battery case.

[0007] In addition, the electrode assembly may be manufactured in a stacked or folded form of each component, but a unit cell may be manufactured as an electrode assembly including an electrode and a separator, and manufactured in a stacked or folded form.

[0008] That is, generally, a laminate (unit cell) consisting of a stacked structure of an anode, a separator, and a cathode is manufactured, and an electrode assembly can be manufactured by stacking multiple of these unit cells with a separator in between. In the method of manufacturing such an electrode assembly, the electrode assembly is formed by repeating the process of arranging unit cells, placing a separator sheet on top of them, and then stacking additional unit cells, or by configuring the top or bottom layer of the unit cells as a separator and stacking them in sequence.

[0009] In this process, unit cells are stacked based on the position of the center of the unit cell to align the unit cells. At this time, if there are defective unit cells with errors in the position of the electrodes (negative or positive electrodes) contained within the unit cells, even if the unit cells are arranged in correct alignment based on the center, there is a problem that the alignment error of the electrodes within the defective unit cells causes an alignment error between the positive and negative electrodes, which increases the defect rate of the electrode assembly. The problem to be solved

[0010] The problem that the present invention aims to solve is to provide a method for manufacturing an electrode assembly that can minimize alignment errors in the entire electrode assembly even if electrode alignment errors exist within the unit cells, in a process of manufacturing an electrode assembly by stacking unit cells.

[0011] However, the problems that the embodiments of the present invention aim to solve are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention. means of solving the problem

[0012] A method for manufacturing an electrode assembly according to one embodiment of the present invention is a method for manufacturing an electrode assembly by stacking two or more unit cells, each having an anode, a first separator, and a cathode sequentially stacked, with a second separator in between, and, prior to stacking the unit cells, a step of inspecting the alignment state of the anode and the cathode contained in a lower unit cell disposed below the unit cell, and a step of correcting the stacking position of the unit cells to be stacked if there is a defect in the alignment state as a result of the inspection.

[0013] The step of correcting the stacking position of the unit cell may include detecting a first gap between one edge portion of the cathode included in the lower unit cell and one edge portion of the anode of the lower unit cell, and a second gap between the other edge portion of the cathode included in the lower unit cell and the other edge portion of the anode of the lower unit cell, and moving the stacking position of the unit cell to be stacked toward the smaller of the first gap and the second gap.

[0014] After the step of moving the stacking position of the unit cell is completed, the one-sided edge portion and the other-sided edge portion of the cathode of the unit cell may each coincide with the one-sided edge portion and the other-sided edge portion of the first separator of the lower unit cell, or be positioned inside them.

[0015] The above alignment defect may occur when the gap between the edge of the positive electrode and the edge of the negative electrode included in the lower unit cell is different from one side and the other side of the lower unit cell.

[0016] The stacking position prior to the step of correcting the stacking position of the unit cell is a position where the center of the lower unit cell and the unit cell coincide, and the unit cell newly placed after the step of correcting the stacking position of the unit cell can be placed at the stacking position prior to the correction step.

[0017] The center of the lower unit cell can be indicated by a laser irradiated from the lower unit cell and a laser irradiation unit positioned above the unit cell.

[0018] The step of inspecting the alignment state of the anode and the cathode included in the lower unit cell may include the step of irradiating light from a light source disposed at the bottom of the lower unit cell, and the step of detecting the shadows of the anode and the cathode generated by the light using a detector disposed at the top of the lower unit cell to derive the gap between the edge of the anode and the edge of the cathode.

[0019] The step of inspecting the alignment state of the anode and the cathode included in the lower unit cell may include detecting the position of the anode from a detector positioned at the top of the lower unit cell, detecting the position of the cathode by irradiating light from a light source positioned at the bottom of the lower unit cell, and deriving the distance between the edge of the anode and the edge of the cathode by combining the position of the anode and the position of the cathode.

[0020] The second separator may be formed integrally with the unit cell or the lower unit cell at the bottom of the unit cell or at the top of the lower unit cell.

[0021] The lower unit cell and the unit cell form a set, and the second separator disposed between the lower unit cell and the unit cell in the set can be folded at the edge of the unit cell and formed continuously with the second separator disposed between the lower unit cell and the unit cell in an adjacent set. Effects of the invention

[0022] According to embodiments of the present invention, in a process of manufacturing an electrode assembly by stacking unit cells, even if an electrode alignment error exists within the unit cell, the alignment error in the entire electrode assembly can be minimized to prevent the occurrence of defects.

[0023] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0024] FIGS. 1 to 4 are drawings illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. FIG. 5 is a drawing illustrating a first variation of a method for measuring the spacing between electrodes of a lower unit cell in one embodiment of the present invention. FIGS. 6a and 6b are drawings illustrating a second variation of a method for measuring the spacing between electrodes of a lower unit cell in one embodiment of the present invention. FIG. 7 is a drawing illustrating an electrode assembly obtained by a method for manufacturing an electrode assembly according to another embodiment of the present invention. Specific details for implementing the invention

[0025] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0026] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0027] Furthermore, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and thus the present invention is not necessarily limited to what is illustrated. Thicknesses have been enlarged in the drawings to clearly represent various layers and regions. Additionally, for convenience of explanation, the thickness of some layers and regions has been exaggerated in the drawings.

[0028] Furthermore, when a part such as a layer, membrane, region, or plate is said to be "on" or "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Also, saying that a part is "on" or "on" a reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "on" or "on" facing the opposite direction of gravity.

[0029] Furthermore, throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] Additionally, throughout the specification, "planar" means when the subject part is viewed from above, and "cross-sectional" means when the cross-section obtained by vertically cutting the subject part is viewed from the side.

[0031] Hereinafter, a method for manufacturing an electrode assembly according to one embodiment of the present invention will be described with reference to FIGS. 1 to 6.

[0032] FIGS. 1 to 4 are drawings illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention, FIG. 5 is a drawing illustrating a first variation of a method for measuring the distance between electrodes of a lower unit cell in an embodiment of the present invention, and FIGS. 6a and 6b are drawings illustrating a second variation of a method for measuring the distance between electrodes of a lower unit cell in an embodiment of the present invention.

[0033] Referring to FIGS. 1 to 4, a method for manufacturing an electrode assembly according to one embodiment of the present invention is for manufacturing an electrode assembly in which an anode and a cathode are alternately stacked and a separator is located between the anode and the cathode, and in particular, a method for manufacturing an electrode assembly obtained by manufacturing a stack (unit cell) having a stacked structure of an anode / separator / cathode and stacking a plurality of these unit cells with a separator in between.

[0034] First, as illustrated in FIG. 1, a separator and a unit cell are stacked on a stack table (100). In this embodiment, the second stacked unit cell is specifically exemplified as a lower unit cell, and the case of additionally stacking unit cells after inspecting the lower unit cell is described as an example, but it is not limited thereto, and each step described can be applied to every stacking step of a unit cell.

[0035] The lower unit cell (10) has a form in which a cathode / first separator / anode are sequentially stacked on a second separator. Here, for convenience of explanation, the components included in the lower unit cell (10) are referred to as the lower cathode (11), the lower first separator (12), and the lower anode (13) to distinguish them from the components included in the unit cell (20) described later. However, this is not limited to these, nor are the components included in each unit cell different from one another. Additionally, although the second separator (30) has been described as a component not included in the unit cell, this is merely for convenience of explanation, and the separator / cathode / separator / anode structure can be defined as a unit cell and is not specifically limited.

[0036] The lower unit cell (10) can be stacked with its position set so that the center of the lower unit cell (10) is positioned at a predetermined location, for example, it can be positioned so that the center (C) of the lower unit cell (10) coincides with the center of the unit cells positioned prior to the lower unit cell (10). At this time, the position where the lower unit cell (10) is positioned to be aligned can be indicated by a laser, etc., irradiated from a laser irradiation unit (400) positioned on a stack table (100) for manufacturing an electrode stack.

[0037] After the lower unit cell (10) is stacked and before the unit cell (20) is additionally stacked on top of it, the alignment state of the lower anode (13) and lower cathode (11) included in the lower unit cell (10) is inspected. That is, as shown in FIG. 1, the alignment state can be confirmed by measuring the first gap (G1) between one end of the lower anode (13) and the lower cathode (11) and the second gap (G2) between the other end, and comparing the values. At this time, the gap between the lower anode (13) and the lower cathode (11) can be detected by a light source (200) that irradiates light from the bottom of the lower anode (13) and the lower cathode (11) and a detector (300) placed on top, and a specific method will be described later with reference to FIG. 5 and FIG. 6a and 6b.

[0038] If the detected first gap (G1) and second gap (G2) are the same, stacking can continue at the same location, that is, the center (C) marked by the laser aligns with the center of the unit cells that are subsequently stacked. However, as shown in FIG. 1, the first gap (G1) and second gap (G2) of the lower anode (13) and lower cathode (11) in the lower unit cell (10) are different from each other, and in particular, if the lower anode (13) is skewed to one side, a process is performed to correct this. That is, since the cathode generally has a larger area than the anode in an electrode assembly, if the arrangement is misaligned during the manufacturing process of the unit cell, as in the lower unit cell (10) of FIG. 1, the lower anode (13) is skewed to one side (overhang), and the first gap (G1) and second gap (G2) of the lower anode (13) and lower cathode (11) become different from each other. In this case, if stacking is continued without position correction of the unit cells to be subsequently stacked, defects may occur due to the misalignment of the lower anode (13). Therefore, in this embodiment, after stacking the lower unit cells (10), the alignment of the lower unit cells (10) is detected, and if there is a misalignment in the alignment, a correction step is performed.

[0039] Next, the stacking position of the unit cell (20) stacked on the lower unit cell (10) as shown in FIG. 2 is corrected.

[0040] The unit cell (20) refers to a unit cell stacked on a lower unit cell (10), and is stacked on the lower unit cell (10) with a second separator (30) in between. In addition, the unit cell (20) includes a negative electrode (21), a first separator (22), and a positive electrode (23) sequentially from the bottom.

[0041] The stacking position of the unit cell (20) is adjusted by the amount of defects that occurred in the alignment state of the lower unit cell (10) performed earlier. That is, the alignment reference is shifted toward the side having the smaller value between the first gap (G1) and the second gap (G2) between the lower anode (13) and the lower cathode (11) in the lower unit cell (10). For example, as shown in FIG. 2, since the size of the first gap (G1) on the left side is smaller in FIG. 2, the center (C) is moved to the left so that the center of the unit cell (20) coincides with the second center (C'). At this time, the amount of moving the center (C) to the second center (C') can be calculated by a control unit (not shown) by taking into account the difference between the first gap (G1) and the second gap (G2) detected earlier. In particular, since an excessive amount of movement can actually increase the degree of overhang, preferably, the amount of movement is controlled within a range where both ends (211, 212) of the negative electrode (21) included in the unit cell (20) each coincide with or are positioned further inside than the corresponding end of the first separator (12) included in the lower unit cell (10).

[0042] Next, as shown in FIG. 3, the stacking of the unit cells (20) is completed.

[0043] In a stacked state, the difference between the first correction gap (G1') between one end of the negative electrode (21) included in the unit cell (20) and the second correction gap (G2') between the other end of the lower anode (13) included in the lower unit cell becomes smaller than the difference between the first gap (G1) and the second gap (G2). That is, the misalignment value between the negative electrode and the anode becomes smaller than before the correction is performed, thereby allowing the degree of overhang to be mitigated.

[0044] Next, additional unit cells (20') are stacked as shown in FIG. 4.

[0045] At this time, additional unit cells (20') are stacked so as to be aligned with the original stacking position of the first unit cells. In this process, since the position of the reference center (C) is marked at the same position by the laser irradiation unit (400), it is possible to continue aligning them to the correct position.

[0046] By this stacking method, even if a unit cell contains cells with poor alignment of the positive and negative electrodes, the degree of defect can be mitigated by distributing the defect to adjacent cells, thereby reducing the risk of defects caused by defective cells.

[0047] Next, with reference to FIG. 5 and FIG. 6a and 6b, a method for measuring the spacing between electrodes of a lower unit cell in one embodiment of the present invention will be described.

[0048] FIG. 5 is a drawing for explaining an example of a method for measuring the distance between electrodes of a lower unit cell in one embodiment of the present invention, and FIG. 6a and FIG. 6b are drawings for explaining variations of a method for measuring the distance between electrodes of a lower unit cell in one embodiment of the present invention.

[0049] FIG. 5 illustrates a lower unit cell (10) as viewed from a detector (300) positioned at the top while light is shone from a light source (200) in FIG. 1 to 4. When the lower unit cell (10) is detected from the top by the detector (300), such as a camera, it is difficult to accurately detect the position of the lower cathode (11) positioned at the bottom of the first separator (12) having the largest area. However, since the first separator (12) is semi-transparent to light, when light is shone from the bottom, the shadow of the lower cathode (11) is observed from the top, making it possible to detect the position of the lower cathode (11) as shown in FIG. 5. That is, the part indicated by the dotted line in FIG. 5 represents the shadow of the lower cathode (11). Therefore, when light is shone from a light source (200) from below, the shadow of the lower cathode (11) and the boundary of the lower anode (13) are both visible, so it is possible to detect the ends of the lower cathode (11) and the lower anode (13), and the gap (G1, G2) between them at once by a detector (300) positioned at the top.

[0050] FIGS. 6a and 6b respectively illustrate a lower unit cell (10) viewed from a detector (300) positioned at the top in a state where light is not shone from the light source (200) in FIGS. 1 to 4 (Fig. 6a) and a state where strong light is shone from the light source (200) in FIG. 4. In the state where light is not shone, as in FIG. 6a, the lower cathode (11) is obscured by the first separator (12), so the position of the lower cathode (11) is not detected, but the position of the lower anode (13) can be detected more accurately. In addition, as shown in FIG. 6b, when strong light is shone from the light source (200), the shadow of the lower cathode (11) becomes clearer, and the edge of the lower anode (13) is not clearly detected due to the strong light, so the position of the lower cathode (11) can be detected more accurately. Accordingly, the position of the lower anode (13) is detected when the light source (200) is turned off, and the position of the lower anode (11) is detected when the light source (200) emits a stronger light, and the distance (G1, G2) between the lower cathode (11) and the lower anode (13) can be calculated from this.

[0051] In this way, depending on the process conditions and environment, the process of the embodiment described in FIG. 5 or the modified example described in FIG. 6a and 6b can be appropriately selected to accurately detect the gap between the lower cathode (11) and the lower anode (13).

[0052] Next, a method for manufacturing an electrode assembly in another embodiment will be described with reference to FIG. 7.

[0053] FIG. 7 is a drawing illustrating an electrode assembly obtained by a method for manufacturing an electrode assembly according to another embodiment of the present invention.

[0054] The manufacturing method in another embodiment differs only in the shape of the second separator (30), and the rest of the configuration is the same as the previous embodiment, so the description of the identical configuration is omitted.

[0055] As illustrated in FIG. 7, the second separator (30) placed between the unit cells (10, 20) is not separated and included as a component of each unit cell, but is formed integrally as a whole, so that the second separator (30) of each unit cell is placed by folding the second separator (30). That is, the second separator (30) is placed on the stack table (100), and after placing the unit cells thereon, the second separator (30) is folded to cover the corresponding unit cells, and the lower unit cells (10) are placed in the folded state. Afterward, before folding the second separator (30) to the opposite side, the positions of the lower positive electrode (13) and the lower negative electrode (11) within the lower unit cells (10) are detected to determine the stacking position of the unit cells (20), and then the second separator (30) is folded to cover the lower unit cells (10). Next, the electrode assembly is completed by repeating the process of placing the unit cell (20) at the determined stacking position and folding the second separator (30) so that it covers the unit cell (20).

[0056] In this way, even in a process where the second separator (30) is formed integrally and stacking and folding are repeated, by detecting the alignment between the positive and negative electrodes included in the unit cell and correcting the stacking position so that the neighboring unit cell mitigates the defect, i.e., the overhang value, when a defect exists, the risk caused by the overhang defect can be minimized and an electrode stack with suppressed defects can be obtained.

[0057] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention. Explanation of the symbols

[0058] 10: Lower unit cell 20: Unit Cell 100: Stack table 200: Light source 300: Detector 400: Laser Irradiation Unit

Claims

Claim 1 A method for manufacturing an electrode assembly by stacking two or more unit cells, each having a positive electrode, a first separator, and a negative electrode sequentially stacked, with a second separator in between, the method comprising: a step of inspecting the alignment state of the positive electrode and the negative electrode contained in a lower unit cell disposed below the unit cell before stacking the unit cells; and a step of correcting the stacking position of the unit cells to be stacked if there is a defect in the alignment state as a result of the inspection. Claim 2 A method for manufacturing an electrode assembly according to claim 1, wherein the step of correcting the stacking position of the unit cell comprises: a step of detecting a first gap between one edge portion of the negative electrode included in the lower unit cell and one edge portion of the positive electrode of the lower unit cell, and a second gap between the other edge portion of the negative electrode included in the lower unit cell and the other edge portion of the positive electrode of the lower unit cell, and a step of moving the stacking position of the unit cell to be stacked toward the smaller of the first gap and the second gap. Claim 3 A method for manufacturing an electrode assembly in which, after the step of moving the stacking position of the unit cell is completed, the one-sided edge portion and the other-sided edge portion of the cathode of the unit cell each coincide with the one-sided edge portion and the other-sided edge portion of the first separator of the lower unit cell, or are disposed inside thereof. Claim 4 A method for manufacturing an electrode assembly according to claim 2, wherein the above alignment defect is a case where the gap between the edge of the positive electrode and the edge of the negative electrode included in the lower unit cell is different from each other on one side and the other side of the lower unit cell. Claim 5 A method for manufacturing an electrode assembly according to claim 2, wherein the stacking position prior to the step of correcting the stacking position of the unit cell is a position where the center of the lower unit cell and the center of the unit cell coincide, and the additional unit cell newly placed after the step of correcting the stacking position of the unit cell is placed at the stacking position prior to the correction step. Claim 6 In claim 5, the center of the lower unit cell is a method for manufacturing an electrode assembly indicated by a laser irradiated from the lower unit cell and a laser irradiation unit disposed above the unit cell. Claim 7 A method for manufacturing an electrode assembly according to claim 1, wherein the step of inspecting the alignment state of the anode and the cathode included in the lower unit cell comprises: a step of irradiating light from a light source disposed at the bottom of the lower unit cell; and a step of detecting the shadows of the anode and the cathode generated by the light using a detector disposed at the top of the lower unit cell to derive the gap between the edge of the anode and the edge of the cathode. Claim 8 A method for manufacturing an electrode assembly according to claim 1, wherein the step of inspecting the alignment state of the anode and the cathode included in the lower unit cell comprises: detecting the position of the anode from a detector positioned at the top of the lower unit cell; detecting the position of the cathode by irradiating light from a light source positioned at the bottom of the lower unit cell; and deriving the gap between the edge of the anode and the edge of the cathode by combining the position of the anode and the position of the cathode. Claim 9 In claim 1, the second separator is formed integrally with the unit cell or the lower unit cell at the bottom of the unit cell or the top of the lower unit cell, in a method for manufacturing an electrode assembly. Claim 10 A method for manufacturing an electrode assembly according to claim 1, wherein the lower unit cell and the unit cell form a set, and the second separator disposed between the lower unit cell and the unit cell in the set is folded at the edge of the unit cell and is continuously formed with the second separator disposed between the lower unit cell and the unit cell in an adjacent set.

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