Manufacturing method and manufacturing device for electrode assembly

Abstract

The present invention provides a method and apparatus for manufacturing an electrode assembly in which unit cells are wound around a separator film, the method including: (a) mounting the unit cells on the upper surface of the separator film so that electrode tabs of the same polarity are positioned vertically at the same positions after winding to form an array; (b) heat-treating one end and the other end of the unit cells where the tabs are formed, and the corresponding separator film, at the top and bottom in the longitudinal direction of the separator film, which is parallel to the winding direction of the array; and (c) winding the heat-treated unit cells around the separator film.

Description

[Technical field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0128689 filed on September 29, 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 and an apparatus for manufacturing an electrode assembly. [Background technology]

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

[0004] At present, a representative example of an electrochemical element that uses such electrochemical energy is a secondary battery, and the range of its use is tending to expand day by day.

[0005] Recently, the demand for secondary batteries as an energy source has been increasing rapidly due to technological developments and increasing demand for portable devices such as portable computers, mobile phones, and cameras. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and working potential, long cycle life, and low self-discharge rate, have been much researched and are now commercially available and in wide use.

[0006] In addition, as interest in environmental issues grows, much research is being conducted on electric vehicles and hybrid electric vehicles as alternatives to vehicles that use fossil fuels such as gasoline and diesel vehicles, 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 with high energy density and discharge voltage is actively underway, and some of them are already at the commercialization stage.

[0007] Such lithium secondary batteries have a structure in which an electrode assembly is built into a secondary battery case, and the electrode assemblies are structurally classified into a jelly roll type electrode assembly manufactured by winding up a positive electrode sheet, a negative electrode sheet, and a separator film, a stacked type electrode assembly in which unit positive electrodes, unit negative electrodes, and a separator film are stacked, a stack / folded type electrode assembly in which unit cells such as a bi-cell, full cell, or mono-cell are wound up with a separator film, and a stack / lamination type electrode assembly in which the unit cells are stacked and laminated.

[0008] In this case, in the folding process of winding unit cells with a separator film, the unit cells are placed on the separator film and then simply wound, which generates unbonded areas between the folding surface and the unit cells. This increases the interfacial resistance in the unbonded areas, which can cause lithium precipitation.

[0009] In particular, such an unbonded region is more noticeable in the inclined portions where the electrode included in the unit cell has a flat portion where the thickness of the active material layer is constant and inclined portions where the thickness gradually decreases at both ends.

[0010] Therefore, lithium precipitated from this poses a threat to the safety of the secondary battery, and there is a problem in that the cycle characteristics are significantly reduced.

[0011] Therefore, there is a pressing need to develop a manufacturing technique for an electrode assembly for a secondary battery that can solve these problems. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method and apparatus for manufacturing an electrode assembly that can suppress lithium deposition at both ends where electrode assembly tabs are formed, thereby improving the safety and cycle characteristics of a secondary battery. [Means for solving the problem]

[0013] The terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that is appropriate to the technical idea of ​​the present invention, based on the principle that the inventor himself can appropriately define the concept of the term in order to explain the invention in the best possible way.

[0014] Hereinafter, according to an embodiment of the present invention, there is provided a method for manufacturing an electrode assembly in which a unit cell is wound with a separator film, comprising the steps of: (a) mounting the unit cells on an upper surface of the release film to produce an array; (b) heat-treating one end and the other end of the separator film where the tabs of the unit cells are formed at the upper and lower parts in the longitudinal direction of the separator film parallel to the winding direction of the array, and the separator film corresponding thereto; and (c) winding the heat-treated unit cell with the separator film.

[0015] In step (a), the unit cells may be mounted on the upper surface of the separator film such that electrode tabs of the same polarity are at the same vertical positions after winding.

[0016] Also, the heat treatment in step (b) may be performed by heating or hot air, and the heat treatment in step (b) may be performed at 50°C to 200°C.

[0017] Specifically, when the heat treatment is performed on the region, the electrode included in the unit cell has a flat portion where the thickness of the active material layer is constant and an inclined portion where the thickness of the active material layer decreases at both ends of the flat portion, The one end and the other end of the unit cell where the tabs are formed may include regions corresponding to the inclined portions.

[0018] In one specific example, the winding speed in step (c) is 5 rpm ~30 rpm It could be.

[0019] The heat treatment in step (b) and the winding in step (c) are carried out successively, and therefore the heat treatment time is affected by the winding speed.

[0020] Meanwhile, the electrode assembly may be a single-sided electrode in which an active material layer is formed only on the inner side, in which the electrode located at the outermost position when the electrode assembly is wound.

[0021] Moreover, each of the unit cells may be a bicell, a full cell, or a monocell.

[0022] According to another embodiment of the present invention, there is provided an apparatus for manufacturing an electrode assembly in which a unit cell is wound with a separator film, comprising: a winder for winding up the array in which the unit cells are mounted on the upper surface of the separation film; and An electrode assembly manufacturing apparatus is provided, the apparatus including: one end and the other end where the tabs of the unit cells are formed, which are located at upper and lower portions of the separator film in a longitudinal direction parallel to a winding direction of the array; and a heater for heat-treating the separator film corresponding to the one end and the other end.

[0023] Here, the heater may be of a heating type or a hot air type.

[0024] The heater may be formed over the entire area where the unit cell is mounted on the upper surface of the separation film.

[0025] The winder may be located to one side of the heater. [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic diagram of an electrode assembly manufacturing apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a side schematic view of a unit cell of the present invention. [Diagram 3] 1 is a schematic cross-sectional view of an electrode assembly according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments thereof with reference to the accompanying drawings.

[0028] In addition, the terms and words used in the present specification and claims should not be interpreted in their ordinary and dictionary sense, but should be interpreted in the sense and concept that is appropriate to the technical idea of ​​the present invention, in accordance with the principle that the inventors can appropriately define the concept of terms in order to best describe the invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, so that at the time of filing this application, there may be various equivalents and modifications that can replace these, and the scope of the present invention is not limited to the embodiments described below.

[0029] According to one embodiment of the present invention, there is provided a method for manufacturing an electrode assembly in which a unit cell is wrapped with a separator film, comprising the steps of: (a) mounting the unit cells on an upper surface of the release film to produce an array; (b) heat-treating one end and the other end of the separator film where the tabs of the unit cells are formed at the upper and lower parts in the longitudinal direction of the separator film parallel to the winding direction of the array, and the separator film corresponding thereto; and (c) winding the heat-treated unit cell with the separator film.

[0030] According to another embodiment of the present invention, An apparatus for manufacturing an electrode assembly in which a unit cell is wound with a separation film, comprising: a winder for winding up the array in which the unit cells are mounted on the upper surface of the separator film such that electrode tabs of the same polarity are at the same vertical positions as each other after winding; and An electrode assembly manufacturing apparatus is provided, the apparatus including heaters positioned at upper and lower portions in a longitudinal direction of the separator film parallel to a winding direction of the array, and configured to heat-treat one end and the other end where the tabs of the unit cells are formed, together with the separator film corresponding thereto.

[0031] Hereinafter, a method and an apparatus for manufacturing an electrode assembly according to the present invention will be described with reference to a schematic diagram of an apparatus for manufacturing an electrode assembly.

[0032] Specifically, FIG. 1 shows a schematic diagram of an apparatus for manufacturing an electrode for a secondary battery according to one embodiment of the present invention.

[0033] Referring to FIG. 1, an apparatus 100 for manufacturing an electrode assembly for a secondary battery according to the present invention includes a winder 130 for winding up an array 120 in which unit cells (108: 101, 102, 103, 104, 105, 106, 107) are mounted on the upper surface of a separator film 110, and heaters 140 located at the top and bottom in the longitudinal direction of the separator film 110 parallel to the winding direction of the array 120, for heat-treating one end and the other end of the unit cells 108 where tabs are formed, together with the corresponding separator film 110.

[0034] First, according to one embodiment of the present invention, the electrode assembly of the present invention is fabricated by arranging a number of unit cells 108 on a separation film 110 to manufacture an array 120 .

[0035] At this time, the unit cells 108 are arranged such that the electrode tabs of the same polarity are at the same positions in the vertical direction after being wound.

[0036] Each of the unit cells 108 may be a bicell having electrodes of the same polarity at both ends, a full cell having electrodes of opposite polarity at both ends, or a monocell including one electrode.

[0037] For example, the bicell may have a structure such as anode / separator / cathode / separator / anode, the full cell may have a structure such as anode / separator / cathode, and the monocell may have a structure in which one of the cathode or anode and the separator are stacked.

[0038] However, it goes without saying that the unit cells 108 should be arranged in a stacked form in which the positive and negative electrodes are alternately arranged after winding.

[0039] Meanwhile, the electrodes included in the unit cell 108 have a slope at one end where a tab is formed by applying electrode active material slurry during the manufacturing process of the electrodes, and at the other end.

[0040] To specifically explain this, a side view of a unit cell of the present invention is shown in FIG.

[0041] 2, a unit cell 200 is composed of a number of electrodes 210, 220, and 230. Although a bicell composed of three electrodes 210, 220, and 230 is shown in FIG. 2, the present invention is not limited to this.

[0042] The electrodes 210, 220, and 230 are formed in a structure in which active material layers 212, 222, and 232 are formed on current collectors 211, 221, and 231, respectively, and electrode tabs 211a, 221a, and 231a are formed on one side of the current collectors 211, 221, and 231, respectively.

[0043] Considering the active material layers 212, 222, 232, the active material layers 212, 222, 232 have a flat portion P where the thickness of the active material layers 212, 222, 232 is constant, and inclined portions L1, L2 where the thickness of the active material layers 212, 222, 232 decreases on both ends of the flat portion P. Specifically, there is an inclined portion L1 on one end side in the direction in which the tab is formed, and a corresponding inclined portion L2 on the other end side.

[0044] As described above, since the active material layers of the electrodes 210, 220, and 230 constituting the unit cell 200 have the inclined portions L1 and L2, when such a unit cell 200 is wound up with a separation film, the inclined portion L1 at one end where the tab is formed and the corresponding inclined portion L2 at the other end are not adhered to each other because a space is generated between the separation film and the inclined portion L1. As a result, lithium deposition often occurs in the above-mentioned regions.

[0045] However, referring again to FIG. 1, in the present invention, for an array 120 in which such unit cells 108 are mounted on a separation film 110, a process is performed in which one end where a tab is formed in the unit cell 108 and the other end, together with the corresponding separation film 110, are heat-treated.

[0046] At this time, the end where the tabs are formed and the other end of the unit cell 108 where the heat treatment is performed may be a region including a region corresponding to the inclined portion of the electrode.

[0047] The heat treatment is performed by heaters 140 located at the upper and lower parts of the separation film 110 in the longitudinal direction. At this time, the heat treatment can be performed by heating or hot air, and therefore the heaters 140 can be a heating type or hot air type device.

[0048] The heat treatment can be carried out at a temperature of 50°C to 200°C.

[0049] If the temperature is too low and outside the above range, the adhesive effect intended by the present invention cannot be fully obtained, whereas if the temperature is too high, deformation of the active material layer and the separation film occurs, which is not preferable.

[0050] After the heat treatment, the unit cells 108 are wound up in a separation film 110 .

[0051] At this time, the heat treatment time may be affected by the winding speed performed after the heat treatment.

[0052] Specifically, the winder 130 that winds the array 120 may be located on one side of the heater 140, so that the heat treatment in step (b) and the winding in step (c) may be performed consecutively. Therefore, the heat treatment time may be affected by the winding speed.

[0053] At this time, the winding speed in the step (c) is 5 rpm ~30 rpm It could be.

[0054] If the winding speed is too fast and out of the above range, a sufficient heat treatment effect cannot be obtained, whereas if the winding speed is too slow, overheating may occur, which is undesirable.

[0055] In addition, the heater 140 for performing the heat treatment is not limited in size, but is formed over the entire portion where the unit cells 108 are mounted on the upper surface of the separation film 110 so that the unit cells 108 are sufficiently heat-treated.

[0056] Specifically, when performed in this manner, the heat treatment time for the unit cell may be 3 to 20 seconds.

[0057] If the temperature is outside the above range, a sufficient heat treatment effect may not be obtained or the material may be overheated, which is undesirable.

[0058] Meanwhile, in the electrode assembly manufactured in this manner, when the electrode is wound, the outermost electrode may be a single-sided electrode having an active material layer formed only on the inner side.

[0059] Therefore, the electrodes facing the separation film 110 in the two unit cells 106 and 107 at the winding end points in FIG. 1 may be single-sided electrodes.

[0060] To more clearly explain this, a cross-sectional view of a wound electrode assembly is shown in FIG.

[0061] 3, the electrode assembly 300 has a structure in which unit cells are wound with a separation film 310. In this case, the electrodes 320 and 330 included in the outermost unit cells 106 and 107 are single-sided electrodes in which active material layers 322 and 332 are formed only on the inside of the electrode assembly 300 on current collectors 321 and 331, respectively.

[0062] Specifically, the upper electrode 320 has an active material layer 321 formed only on the lower surface of a current collector 321, and the lower electrode 330 has an active material layer 332 formed only on the upper surface of a current collector 331.

[0063] In this manner, when the outermost electrode is a single-sided electrode, there is no waste of the active material layer and the overall thickness of the electrode assembly is reduced, which is more preferable.

[0064] Those skilled in the art will appreciate that the present invention can be applied in various ways and modified within the scope of the present invention based on the above content. [Explanation of symbols]

[0065] 100 Electrode assembly manufacturing equipment 110 Separation film 101,102,103,104,105,106,107 Unit cell 120 Array 130 Winding machine 140 Heater 200 unit cells 300 electrode assembly [Industrial Applicability]

[0066] According to the present invention, when a heat treatment is performed before winding in a state where unit cells are arranged on a separator film, for one end of an electrode assembly where a tab is formed and the corresponding other end of the electrode assembly where adhesion is poor, the non-adhered area between the separator film and the unit cells can be minimized, and thus lithium deposition can be minimized, thereby improving the safety and cycle characteristics of a secondary battery including the same.

Claims

1. A method for manufacturing an electrode assembly in which a unit cell is wound with a separator film, comprising the steps of: (a) mounting the unit cells on an upper surface of the release film to produce an array; (b) heat-treating one end and the other end of the separator film where the tabs of the unit cells are formed at the upper and lower parts in the longitudinal direction of the separator film parallel to the winding direction of the array, and the separator film corresponding thereto; and (c) winding the heat-treated unit cell with the separator film; Including, an electrode included in the unit cell has a flat portion where the thickness of the active material layer is constant and an inclined portion where the thickness of the active material layer decreases at both ends of the flat portion; The one end and the other end of the unit cell where the tabs are formed include regions corresponding to the inclined portion.

2. 2. The method of claim 1, wherein step (a) comprises mounting the unit cells on the upper surface of the separator film such that electrode tabs of the same polarity are at the same vertical positions after winding.

3. The method of claim 1 , wherein the heat treatment in step (b) is performed by heating or hot air.

4. The method of claim 1, wherein the heat treatment in step (b) is performed at 50° C. to 200° C.

5. The method of claim 1, wherein the winding speed in step (c) is 5 rpm to 30 rpm.

6. The method of claim 1 , wherein the heat treatment in step (b) and the winding in step (c) are performed continuously.

7. The method of claim 1 , wherein the electrode assembly is a single-sided electrode in which an active material layer is formed only on the inside, and the electrode located at the outermost side when the electrode assembly is wound up.

8. The method for manufacturing an electrode assembly according to claim 1 , wherein each of the unit cells is a bicell, a full cell, or a monocell.

9. An apparatus for manufacturing an electrode assembly in which a unit cell is wound with a separation film, comprising: a winder for winding up the array in which the unit cells are mounted on the upper surface of the separation film; and a heater for heat-treating one end and the other end of the separation film, the one end and the other end being located at upper and lower portions in a longitudinal direction of the separation film parallel to a winding direction of the array and at which the tabs of the unit cells are formed, and the separation film corresponding to the one end and the other end are located at upper and lower portions in a longitudinal direction of the separation film parallel to a winding direction of the array, an electrode included in the unit cell has a flat portion where the thickness of the active material layer is constant and an inclined portion where the thickness of the active material layer decreases at both ends of the flat portion; the one end and the other end of the unit cell where the tabs are formed include regions corresponding to the inclined portion.

10. The electrode assembly manufacturing apparatus according to claim 9 , wherein the heater is of a heating type or a hot air type.

11. The electrode assembly manufacturing apparatus of claim 9 , wherein the heater is formed over an entire area where the unit cell is mounted on the upper surface of the separation film.

12. The electrode assembly manufacturing apparatus according to claim 9 , wherein the winder is located on one side of the heater.

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