Method for manufacturing an electrode assembly

Abstract

A method for manufacturing an electrode assembly according to an embodiment of the present invention is 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 stacked in sequence, with a second separator sandwiched therebetween, the method including the steps of: inspecting an alignment state of the positive electrode and the negative electrode included in a lower unit cell disposed below the unit cell before stacking the unit cells; and correcting a stacking position of the unit cells to be stacked if the alignment state is found to be poor as a result of the inspection.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0143905 dated October 26, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing an electrode assembly, and more particularly to a method for manufacturing an electrode assembly that can minimize the effect of electrode alignment errors even if they occur. [Background technology]

[0003] The rapid increase in the use of fossil fuels has led to an increased demand for alternative and green energy, and as part of this, the most actively researched field is the field of electrochemical power generation and storage.

[0004] Currently, a typical example of an electrochemical element that utilizes such electrochemical energy is a secondary battery, and the range of its use is expanding more and more.

[0005] In recent years, with the increasing technological development and demand for portable devices such as portable computers, portable phones, and cameras, the demand for secondary batteries as energy sources has been rapidly increasing. Of these, lithium secondary batteries, which exhibit high energy density and working potential, long cycle life, and low self-discharge rate, have been the subject of much research and are now commercially available and widely used.

[0006] Furthermore, with growing concern about environmental issues, active research is being conducted into electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline and diesel, which are one of the main causes of air pollution. Nickel-metal hydride secondary batteries are mainly used as the power source for such electric vehicles and hybrid electric vehicles, but research into the use of lithium secondary batteries, which have high energy density and discharge voltage, is also being actively conducted, and some of them are already in the commercialization stage.

[0007] Such a lithium secondary battery is manufactured by coating a current collector with a positive or negative electrode active material, a binder, and a conductive material in a slurry state, and drying the coating to form an electrode mixture layer to manufacture a positive electrode and a negative electrode, interposing a separator between the positive electrode and the negative electrode, and incorporating the laminated electrode assembly together with an electrolyte into a battery case.

[0008] In addition, the electrode assembly may be manufactured by stacking or folding each component, or may be manufactured by manufacturing a unit cell as an electrode assembly including an electrode and a separator, and then stacking or folding the unit cell.

[0009] That is, generally, a laminate (unit cell) having a stacked structure of a positive electrode / separator / negative electrode is manufactured, and a plurality of these unit cells are stacked with a separator sandwiched therebetween to manufacture an electrode assembly. In such a manufacturing method of an electrode assembly, a unit cell is arranged, a separator sheet is arranged thereon, and then additional unit cells are stacked, or the top or bottom layer of the unit cell is formed of a separator, and these steps are repeated to form an electrode assembly.

[0010] In this process, the unit cells are stacked based on the center position of the unit cells to align them. If there is a defective unit cell where the position of the electrode (negative or positive electrode) contained in the unit cell is incorrect, even if the unit cells are properly aligned based on the center, the alignment error of the electrode inside the defective unit cell will result in an alignment error between the positive and negative electrodes, resulting in a high defect rate for the electrode assembly. Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention 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 a unit cell in a process of manufacturing an electrode assembly by stacking unit cells.

[0012] However, the problems to be solved by the embodiments of the present invention are not limited to the above-mentioned problems, and can be expanded in various ways within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0013] According to one embodiment of the present invention, a method for manufacturing an electrode assembly includes stacking two or more unit cells, each having a positive electrode, a first separator, and a negative electrode stacked in sequence, with a second separator sandwiched therebetween, and includes inspecting an alignment state of the positive electrode and the negative electrode included in a lower unit cell disposed below the unit cell before stacking the unit cells, and correcting the stacking position of the unit cells to be stacked if the inspection reveals a defect in the alignment state.

[0014] The correcting the stacking position of the unit cells may include detecting a first gap between one end of the negative electrode included in the lower unit cell and one end of the positive electrode of the lower unit cell and a second gap between the other end of the negative electrode included in the lower unit cell and the other end of the positive electrode of the lower unit cell, and moving the stacking position of the unit cells to be stacked to the one having the smaller size of the first gap or the second gap.

[0015] After the step of shifting the stacking position of the unit cells is completed, the one end and the other end of the negative electrode of the unit cell may be aligned with or positioned inside the one end and the other end of the first separator of the lower unit cell, respectively.

[0016] The misalignment may occur when the distance between the end of the positive electrode and the end of the negative electrode included in the lower unit cell is different between one side and the other side of the lower unit cell.

[0017] The stacking position before correcting the stacking position of the unit cell is a position where the center of the lower unit cell coincides with the center of the unit cell, and the unit cell newly arranged after correcting the stacking position of the unit cell may be arranged at the stacking position before the correcting step.

[0018] The center of the lower unit cell can be indicated by a laser irradiated from a laser irradiation unit disposed on the lower unit cell and an upper portion of the unit cell.

[0019] The step of inspecting the alignment state of the positive electrode and the negative electrode included in the lower unit cell may include the steps of irradiating light from a light source disposed at a lower part of the lower unit cell, detecting shadows of the positive electrode and the negative electrode generated by the light with a detector disposed at an upper part of the lower unit cell, and deriving a distance between an end of the positive electrode and an end of the negative electrode.

[0020] The step of inspecting the alignment state of the positive electrode and the negative electrode included in the lower unit cell may include the steps of detecting a position of the positive electrode from a detection unit disposed in an upper part of the lower unit cell, detecting a position of the negative electrode by irradiating light from a light source disposed in a lower part of the lower unit cell, and deriving a distance between an end of the positive electrode and an end of the negative electrode by combining the positions of the positive electrode and the negative electrode.

[0021] The second separator may be integrally formed 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.

[0022] The lower unit cell and the unit cell form one set, and the second separation film disposed between the lower unit cell and the unit cell in one set may be bent at an end of the unit cell and formed continuously with the second separation film disposed between the lower unit cell and the unit cell in another adjacent set. [Effects of the Invention]

[0023] According to an embodiment of the present invention, in a process of manufacturing an electrode assembly by stacking unit cells, even if there is an electrode alignment error within a unit cell, the alignment error in the entire electrode assembly can be minimized, thereby preventing the occurrence of defects.

[0024] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 3] 1 is a diagram illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 4] 1 is a diagram illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 5] 10 is a diagram illustrating a first modified example of a method for measuring a gap between electrodes of a lower unit cell in an embodiment of the present invention. [Figure 6a] 10 is a diagram illustrating a second modified example of a method for measuring the gap between electrodes of a lower unit cell in an embodiment of the present invention. [Figure 6b] 10 is a diagram illustrating a second modified example of a method for measuring the gap between electrodes of a lower unit cell in an embodiment of the present invention. [Figure 7] 10 is a view showing an electrode assembly obtained by a manufacturing method of an electrode assembly according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand the present invention. The present invention may be embodied in various forms and is not limited to the embodiments set forth herein.

[0027] In order to clearly describe the present invention, parts not necessary for the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0028] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. Thicknesses are exaggerated to clearly show various layers and regions in the drawings. In the drawings, the thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0029] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that 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. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the direction opposite to gravity.

[0030] Furthermore, throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, not excluding other elements, unless otherwise specified.

[0031] Also, throughout the specification, "in a plane" means a portion of the subject matter viewed from above, and "in cross section" means a portion of the subject matter viewed from the side along a vertical cross section.

[0032] Hereinafter, a method for manufacturing an electrode assembly according to an embodiment of the present invention will be described with reference to FIGS.

[0033] 1 to 4 are views illustrating a method for manufacturing an electrode assembly according to an embodiment of the present invention, FIG. 5 is a view illustrating a first modified example of a method for measuring the gap between electrodes of a lower unit cell in an embodiment of the present invention, and FIGS. 6a and 6b are views illustrating a second modified example of a method for measuring the gap between electrodes of a lower unit cell in an embodiment of the present invention.

[0034] Referring to FIGS. 1 to 4, a method for manufacturing an electrode assembly according to an embodiment of the present invention is for manufacturing an electrode assembly in which positive electrodes and negative electrodes are alternately stacked and a separator is disposed between the positive electrodes and negative electrodes. In particular, the method is for manufacturing an electrode assembly by manufacturing a stack (unit cell) having a stacked structure of positive electrode / separator / negative electrode and stacking a plurality of these unit cells with separators sandwiched between them.

[0035] First, as shown in Fig. 1, a separator and unit cells are stacked on a stack table 100. In this embodiment, the unit cell stacked for the second time is specifically described as a lower unit cell, and after inspecting the lower unit cell, additional unit cells are stacked. However, the present invention is not limited to this, and each of the steps described can be applied to each unit cell stacking step.

[0036] The lower unit cell 10 has a configuration in which an anode / first separator / cathode are stacked in this order on a second separator. For convenience of explanation, the components included in the lower unit cell 10 are referred to as a lower anode 11, a lower first separator 12, and a lower cathode 13 to distinguish them from the components included in the unit cell 20 described below. However, this is not limited thereto, and the components included in each unit cell are not necessarily different from each other. In addition, 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 a separator / anode / separator / cathode structure can be defined as a unit cell, and is not particularly limited thereto.

[0037] The lower unit cells 10 may be stacked after their positions are set so that the centers of the lower unit cells 10 are located at predetermined positions. For example, the lower unit cells 10 may be arranged so that the center (C) of the lower unit cells 10 coincides with the center of the unit cell located in front of the lower unit cell 10. In this case, the positions at which the lower unit cells 10 are arranged so that they are aligned may be indicated by a laser irradiated from a laser irradiation unit 400 arranged on a stack table 100 for manufacturing an electrode stack.

[0038] After stacking the lower unit cells 10 and before stacking additional unit cells 20 thereon, the alignment of the lower positive electrode 13 and lower negative electrode 11 included in the lower unit cells 10 is inspected. That is, as shown in FIG. 1, the first gap (G1) between one end of the lower positive electrode 13 and the lower negative electrode 11 and the second gap (G2) between the other end of the lower positive electrode 13 and the lower negative electrode 11 are measured and compared to confirm the alignment. Here, the gap between the lower positive electrode 13 and the lower negative electrode 11 can be detected using a light source 200 that irradiates light from below the lower positive electrode 13 and the lower negative electrode 11 and a detector 300 disposed above the lower positive electrode 13 and the lower negative electrode 11; a specific method for this will be described below with reference to FIGS. 5 and 6a and 6b.

[0039] If the detected first gap (G1) and second gap (G2) are the same, subsequent stacking can be performed in the same position, i.e., so that the center (C) indicated by the laser coincides with the center of the unit cell to be subsequently stacked. However, as shown in FIG. 1, if the first gap (G1) and second gap (G2) between the lower positive electrode 13 and the lower negative electrode 11 in the lower unit cell 10 are different, and in particular, if the lower positive electrode 13 is offset to one side, a correction process is performed. That is, because the negative electrode generally has a larger area than the positive electrode in an electrode assembly, if the arrangement of the unit cells is misaligned during the manufacturing process, the lower positive electrode 13 will be offset to one side (overhang), as in the lower unit cell 10 of FIG. 1, and the first gap (G1) and second gap (G2) between the lower positive electrode 13 and the lower negative electrode 11 will be different. In this case, if subsequent stacking is performed without correcting the position of the unit cells to be subsequently stacked, defects may occur due to the offset of the lower positive electrode 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 any deviation in the alignment, a correction step is performed.

[0040] Next, as shown in FIG. 2, the stacking position of the unit cell 20 stacked on the lower unit cell 10 is corrected.

[0041] The unit cell 20 refers to a unit cell stacked on the lower unit cell 10, and is stacked on the lower unit cell 10 with a second separation membrane 30 sandwiched therebetween. The unit cell 20 also includes, from the bottom up, a negative electrode 21, a first separation membrane 22, and a positive electrode 23.

[0042] The stacking position of the unit cells 20 is adjusted by the amount of misalignment of the lower unit cells 10 that occurred previously. That is, the alignment reference is shifted to the side of the lower unit cell 10 with the smaller of the first distance (G1) and second distance (G2) between the lower positive electrode 13 and the lower negative electrode 11. For example, as shown in FIG. 2, because the first distance (G1) on the left side is smaller, the center (C) is shifted to the left, and the unit cells 20 are stacked so that their centers coincide with the second centers (C'). In this case, the amount by which the center (C) is shifted to the second centers (C') can be calculated by a control unit (not shown) taking into account the difference between the first distance (G1) and the second distance (G2) that was previously detected. In particular, if the amount of movement is excessive, the degree of overhang may become even greater. Therefore, preferably, the amount of movement is controlled within a range in which both side edges 211, 212 of the anode 21 included in the unit cell 20 coincide with the corresponding edges of the first separator 12 included in the lower unit cell 10 or are positioned further inward than the corresponding edges.

[0043] Subsequently, stacking of the unit cells 20 is completed as shown in FIG.

[0044] In the stacked state, the difference between the corrected first distance (G1') between one end of the negative electrode 21 included in the unit cell 20 and the lower positive electrode 13 included in the lower unit cell and the corrected second distance (G2') between the other end thereof is smaller than the difference between the first distance (G1) and the second distance (G2). That is, the deviation between the negative electrode and the positive electrode is not smaller than before the correction, and the degree of overhang can be alleviated.

[0045] Additional unit cells 20' are then stacked as shown in FIG.

[0046] At this time, the additional unit cells 20' are stacked so as to be aligned in the same stacking position as the original first unit cells. During this process, the position of the reference center (C) is displayed at the same position by the laser irradiation unit 400, so that subsequent alignment at the correct position is possible.

[0047] With this stacking method, even if a unit cell contains a cell in which the positive and negative electrodes are poorly aligned, the degree of the defect can be distributed to adjacent cells, thereby mitigating the degree of the defect, thereby reducing the risk of defects due to defective cells.

[0048] Next, a method for measuring the spacing between the electrodes of the lower unit cell in one embodiment of the present invention will be described with reference to FIGS. 5 and 6a and 6b.

[0049] FIG. 5 is a diagram illustrating an example of a method for measuring the gap between electrodes of a lower unit cell according to an embodiment of the present invention, and FIGS. 6a and 6b are diagrams illustrating modified examples of the method for measuring the gap between electrodes of a lower unit cell according to an embodiment of the present invention.

[0050] FIG. 5 shows the lower unit cell 10 in FIGS. 1 to 4 as viewed from the detector 300 disposed above, with light irradiated from the light source 200. When the detector 300, such as a camera, is used to detect the lower unit cell 10 from above, it is difficult to accurately detect the position of the lower anode 11, which is disposed below the first separator 12, which has the largest area. However, because the first separator 12 is semi-transparent to light, when light is irradiated from below, the shadow of the lower anode 11 is observed from above, making it possible to detect the position of the lower anode 11 as shown in FIG. 5. That is, the area indicated by the dotted line in FIG. 5 indicates the shadow of the lower anode 11. Therefore, when light is irradiated from the light source 200 from below, the shadow of the lower anode 11 and the boundary of the lower cathode 13 are all visible. Therefore, the detector 300 disposed above can simultaneously detect the ends of the lower anode 11 and the lower cathode 13, as well as the gap (G1, G2) between them.

[0051] 6a and 6b show the lower unit cell 10 as seen from the detector 300 disposed above in FIGS. 1 to 4, respectively, in a state where no light is irradiated from the light source 200 (FIG. 6a) and a state where strong light is irradiated from the light source 200 (FIG. 6b). In the state where no light is irradiated, as in FIG. 6a, the lower anode 11 is blocked by the first separator 12, and the position of the lower anode 11 cannot be detected. However, the position of the lower cathode 13 can be detected more accurately. Furthermore, as shown in FIG. 6b, when strong light is irradiated from the light source 200, the shadow of the lower anode 11 becomes clearer, and the edge of the lower cathode 13 is not clearly detected due to the strong light, allowing the position of the lower anode 11 to be detected more accurately. Therefore, the position of the lower cathode 13 can be detected with the light source 200 turned off, and the position of the lower anode 11 can be detected with the light source 200 irradiating stronger light, and the distances (G1, G2) between the lower anode 11 and the lower positive electrode 13 can then be calculated.

[0052] In this way, depending on the process conditions and environment, the process of the embodiment described in Figure 5 or the modified example described in Figures 6a and 6b can be appropriately selected to accurately detect the gap between the lower negative electrode 11 and the lower positive electrode 13.

[0053] Next, a method for manufacturing an electrode assembly according to another embodiment will be described with reference to FIG.

[0054] FIG. 7 is a view showing an electrode assembly obtained by a method for manufacturing an electrode assembly according to another embodiment of the present invention.

[0055] The manufacturing method of the other embodiment differs only in the shape of the second separator 30, and the remaining configuration is the same as the previous embodiment, so a description of the same configuration will be omitted.

[0056] As shown in FIG. 7 , the second separator 30 disposed between the unit cells (lower unit cell 10, unit cell 20) is not separated and included as a component of each unit cell, but is instead formed as a whole. The second separator 30 is folded to be disposed between the unit cells. That is, the second separator 30 is placed on the stack table 100, the unit cells are placed on top of it, and the second separator 30 is folded to cover the unit cells. The lower unit cell 10 is then placed in the folded state. Then, before folding the second separator 30 back in the opposite direction, the positions of the lower positive electrode 13 and lower negative electrode 11 in the lower unit cell 10 are detected to determine the stacking position of the unit cell 20, and the second separator 30 is folded to cover the lower unit cell 10. The unit cell 20 is then placed in the determined stacking position, and the process of folding the second separator 30 to cover the unit cell 20 is repeated to complete the electrode assembly.

[0057] In this way, even in the process of repeating stacking and folding with the second separator 30 integrally formed, the alignment between the positive and negative electrodes included in the unit cells is detected, and if a defect is found, the stacking position of the adjacent unit cells is corrected so that the defect, i.e., the overhang value, is alleviated, thereby minimizing the risk of overhang defects and obtaining an electrode stack with reduced defects.

[0058] Although the 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 made by those skilled in the art using the basic concept of the present invention defined in the claims below also fall within the scope of the present invention. [Explanation of symbols]

[0059] 10 Lower unit cell 20 unit cells 100 Stack Table 200 light source 300 Detector 400 Laser irradiation unit

Claims

1. A method for manufacturing an electrode assembly by stacking two or more unit cells, each unit cell having a positive electrode, a first separator, and a negative electrode stacked in order, with a second separator interposed therebetween, Before stacking the unit cells, inspecting the alignment of the positive electrode and the negative electrode included in a lower unit cell disposed below the unit cell; and If the inspection reveals a defect in the alignment, correcting the stacking position of the unit cells to be stacked, The step of correcting the stacking position of the unit cells includes: detecting a first gap between one end of the negative electrode included in the lower unit cell and one end of the positive electrode of the lower unit cell, and a second gap between the other end of the negative electrode included in the lower unit cell and the other end of the positive electrode of the lower unit cell; A method for manufacturing an electrode assembly, comprising: shifting a stacking position of the unit cells to be stacked to a smaller one of the first gap and the second gap.

2. 2. The method of claim 1, wherein after the step of shifting the stacking position of the unit cells is completed, the one end and the other end of the negative electrode of the unit cell are aligned with or positioned inside one end and the other end of the first separator of the lower unit cell, respectively.

3. 2. The method of manufacturing an electrode assembly according to claim 1, wherein the misalignment occurs when a distance between an end of the positive electrode and an end of the negative electrode included in the lower unit cell is different between one side and the other side of the lower unit cell.

4. a stacking position before correcting the stacking position of the unit cell is a position where a center of the lower unit cell coincides with a center of the unit cell; The method for manufacturing an electrode assembly according to claim 1 , wherein the unit cells newly arranged after the step of correcting the stacking positions of the unit cells are arranged in the stacking positions before the step of correcting.

5. The method for manufacturing an electrode assembly according to claim 4 , wherein the center of the lower unit cell is indicated by a laser irradiated from a laser irradiation unit disposed on the lower unit cell and an upper portion of the unit cell.

6. Inspecting the alignment of the positive electrode and the negative electrode included in the lower unit cell includes: irradiating light from a light source disposed below the lower unit cell; and 2. The method for manufacturing an electrode assembly according to claim 1, further comprising detecting shadows of the positive electrode and the negative electrode generated by the light with a detection unit disposed on an upper portion of the lower unit cell, and deriving a distance between an end of the positive electrode and an end of the negative electrode.

7. Inspecting the alignment of the positive electrode and the negative electrode included in the lower unit cell includes: detecting the position of the positive electrode from a detection unit disposed on an upper portion of the lower unit cell; detecting the position of the negative electrode by irradiating light from a light source disposed below the lower unit cell; and The method for manufacturing an electrode assembly according to claim 1 , further comprising the step of combining the position of the positive electrode and the position of the negative electrode to derive a distance between an end of the positive electrode and an end of the negative electrode.

8. The method of manufacturing an electrode assembly according to claim 1 , wherein the second separator is integrally formed with the unit cell or the lower unit cell at a lower portion of the unit cell or an upper portion of the lower unit cell.

9. 9. The 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 one set is folded at an end of the unit cell to be continuous with the second separator disposed between the lower unit cell and the unit cell in another adjacent set.

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