Electrode assembly, secondary battery including the same, method for manufacturing a secondary battery, and secondary battery manufacturing apparatus used therefor

Abstract

The present invention relates to an electrode assembly, a secondary battery including the electrode assembly, a method for manufacturing the electrode assembly, and an apparatus for manufacturing the electrode assembly, and more particularly, to an electrode assembly capable of improving unbonded areas of an electrode and a separator inside a unit cell and an unbonded area of ​​a unit cell and a separator sheet inside an electrode assembly, a secondary battery including the electrode assembly, a method for manufacturing the electrode assembly, and an apparatus for manufacturing the electrode assembly. The present invention provides a method for manufacturing a secondary battery, comprising: a unit cell manufacturing step of manufacturing a unit cell including an electrode and a separator; an electrode assembly manufacturing step of manufacturing an electrode assembly by folding a plurality of unit cells and separator sheets so that they are alternately stacked; a compensation step of compensating for a height difference formed on an outer surface of the electrode assembly; and a pressurizing step of pressurizing the electrode assembly, wherein the compensation step compensates for a height difference formed on the outer surface of the electrode assembly by disposing a compensation sheet in an area formed to be relatively lower than an interior of the electrode assembly.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0122787 filed on September 14, 2021, and Korean Patent Application No. 10-2022-0115146 filed on September 13, 2022, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to an electrode assembly, a secondary battery including the same, a method for manufacturing a secondary battery for manufacturing the same, and a secondary battery manufacturing apparatus used therefor. More specifically, the present invention relates to an electrode assembly capable of improving an unbonded region of an electrode and a separator inside a unit cell and an unbonded region of a unit cell and a separator sheet inside an electrode assembly, a secondary battery including the same, a method for manufacturing a secondary battery for manufacturing the same, and a secondary battery manufacturing apparatus used therefor.

Background Art

[0003] A battery (cell, battery) that generates electrical energy through a physical or chemical reaction of a substance and supplies power to the outside is used when it is not possible to obtain an alternating current power supply supplied to a building or when a direct current power supply is required due to a living environment surrounded by various electrical and electronic devices.

[0004] Among such batteries, a primary battery and a secondary battery, which are chemical batteries using a chemical reaction, are generally widely used. The primary battery is commonly referred to as a dry battery and is a consumable battery. The secondary battery is a rechargeable battery manufactured using a material capable of repeating an oxidation-reduction process between an electric current and a substance a plurality of times. When a reduction reaction of the material occurs due to an electric current, the power supply is charged, and when an oxidation reaction of the material occurs, the power supply is discharged. By repeating such charging and discharging, electricity is generated.

[0005] Here, among secondary batteries, a lithium-ion battery manufactures an electrode by coating an electrode slurry in which an active material, a conductive material, and a binder are mixed on a positive electrode conductive foil and a negative electrode conductive foil to a predetermined thickness, and can manufacture an electrode assembly by interposing a separator between both conductive foils.

[0006] In addition, secondary batteries can also be classified according to the structure of the electrode assembly having a positive electrode / separator / negative electrode structure. For example, the secondary battery manufactures an electrode assembly by winding a long sheet-like positive electrode and negative electrode multiple times in a bulk jelly roll shape with a separator interposed therebetween, and stores the manufactured electrode assembly in a cylindrical can or the like and seals it to produce a cylindrical secondary battery, or folds a bi-cell or the like in which a positive electrode and a negative electrode of a predetermined size unit are laminated with a separator interposed therebetween so that they are laminated to manufacture an electrode assembly, and stores the manufactured electrode assembly in a pouch and seals it to produce a pouch-type secondary battery, etc. can be classified.

[0007] On the other hand, during the manufacture of the electrode, due to the viscosity of the electrode slurry, there has been a problem that the electrode slurry is unevenly applied to the conductive foil, resulting in a difference in the coating thickness of the electrode slurry. In particular, in a pouch-type secondary battery, such a difference in the coating thickness of the electrode slurry forms an unbonded region of the electrode and the separator inside the unit cell manufactured including the electrode after manufacturing the electrode, and an unbonded region of the unit cell and the separator sheet of the electrode assembly including the unit cell, which causes lithium precipitation due to the interfacial resistance in the negative electrode and increases the resistance of the electrode. Summary of the Invention Problems to be Solved by the Invention

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to improve an electrode assembly that improves an unbonded region of an electrode and a separation membrane inside a unit cell and an unbonded region of a unit cell and a separation membrane sheet inside an electrode assembly, a secondary battery including the same, a secondary battery manufacturing method for manufacturing the same, and a secondary battery manufacturing apparatus used therefor.

Means for Solving the Problems

[0009] The present invention includes a unit cell manufacturing step of manufacturing a unit cell including an electrode and a separation membrane; an electrode assembly manufacturing step of manufacturing an electrode assembly by folding so that a plurality of unit cells and separation membrane sheets are alternately laminated; a correction step of correcting a height difference formed on the outer surface of the electrode assembly; and a pressing step of pressing the electrode assembly. The correction step corrects a height difference formed on the outer surface of the electrode assembly by disposing a correction sheet in a region formed to be relatively low in height with respect to the inside of the electrode assembly. A secondary battery manufacturing method is provided.

[0010] The correction step may correct the outer surface of the electrode assembly so that the height is uniform.

[0011] The electrode assembly includes a first region having a first height; and a second region having a second height formed at a height lower than the first height. The correction step may dispose the correction sheet in the second region to correct a height difference between the first region and the second region.

[0012] The correction step may dispose the correction sheet in the second region by an amount equal to the difference between the second height and the first height with respect to the first height.

[0013] The second region may be located corresponding to an edge portion of the electrode assembly.

[0014] The electrode assembly includes an electrode tab connected to the electrode. The second region may be located corresponding to a region where the electrode tab of the electrode assembly is located.

[0015] The correction sheet may be made of an insulating material.

[0016] The correction sheet may contain a synthetic resin and an adhesive substance.

[0017] The correction sheet may be a CPP tape (Cast PolyPropylene tape).

[0018] Further, the present invention provides an electrode assembly in which a plurality of unit cells including an electrode and a separation membrane and a separation membrane sheet are alternately laminated, the electrode assembly including: a first region having a first height; a second region having a second height formed at a height lower than the first height; and a correction sheet disposed in the second region to correct a height difference between the first region and the second region.

[0019] The correction sheet may be disposed by an amount corresponding to the height difference between the first region and the second region.

[0020] The second region may be located corresponding to an edge of the electrode assembly.

[0021] The electrode assembly includes an electrode tab connected to the electrode; the second region may be located corresponding to a region where the electrode tab of the electrode assembly is located.

[0022] Furthermore, the present invention provides a secondary battery including an electrode assembly in which a plurality of unit cells including an electrode and a separation membrane and a separation membrane sheet are alternately laminated, the electrode assembly including: a first region having a first height; a second region having a second height formed at a height lower than the first height; and a correction sheet disposed in the second region to correct a height difference between the first region and the second region.

[0023] Furthermore, the present invention provides a secondary battery manufacturing apparatus for manufacturing a secondary battery including an electrode assembly folded such that a plurality of unit cells each including an electrode and a separation membrane and a separation membrane sheet are alternately laminated. The electrode assembly includes a first region having a first height, a second region having a second height formed at a height lower than the first height, and a correction sheet disposed in the second region for correcting a height difference between the first region and the second region. The secondary battery manufacturing apparatus includes a pressing press for pressing the electrode assembly, and the pressing press is formed such that a pressing surface for pressing the electrode assembly has a step, thereby providing a secondary battery manufacturing apparatus.

[0024] The pressing surface includes a first pressing surface for pressing the first region, a second pressing surface for pressing the second region, and a connecting surface connecting the first pressing surface and the second pressing surface. The second pressing surface may be formed to protrude from the first pressing surface toward the electrode assembly.

[0025] The connecting surface may be formed to have an inclination with respect to the first pressing surface and the second pressing surface.

[0026] Furthermore, the present invention provides a secondary battery manufacturing method including a unit cell manufacturing step of manufacturing a unit cell including an electrode and a separation membrane, an electrode assembly manufacturing step of manufacturing an electrode assembly by folding such that a plurality of unit cells and a separation membrane sheet are alternately laminated, a correction step of correcting a height difference formed on an outer surface of the electrode assembly, and a pressing step of pressing the electrode assembly. The pressing step includes a first pressing step of pressing the electrode assembly using a first pressing press and a second pressing step of pressing the electrode assembly using a second pressing press. At least one of the first pressing press and the second pressing press is formed such that a pressing surface for pressing the electrode assembly has a step.

[0027] The first pressing press is formed such that a pressing surface for pressing the electrode assembly has a step, and the second pressing press may be formed such that the pressing surface for pressing the electrode assembly is flat at a predetermined height.

Advantages of the Invention

[0028] By including a correction step for correcting the height difference formed on the outer surface of the electrode assembly, in the pressing step, the unbonded regions of the electrodes and the separator inside the unit cell and the unbonded regions of the unit cells and the separator sheets inside the electrode assembly are pressed to bond the unbonded regions as described above, thereby having the advantage of being able to improve the performance of the secondary battery.

[0029] Also, by forming at least one of the pressing surfaces of the pressing press for pressing the electrode assembly to have a step, the unbonded regions of the electrodes and the separator inside the unit cell and the unbonded regions of the unit cells and the separator sheets inside the electrode assembly are pressed to bond the unbonded regions as described above, thereby having the advantage of being able to improve the performance of the secondary battery.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, with reference to the accompanying drawings, the preferred embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited or restricted to the following embodiments.

[0032] To clearly explain the present invention, a detailed description of parts not related to the explanation or related known technologies that may obscure the gist of the present invention is omitted. When adding reference numerals to the components of each drawing in this specification, the same or similar reference numerals are assigned to the same or similar components throughout the specification.

[0033] In addition, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way, they should be construed as meanings and concepts that conform to the technical idea of the present invention.

[0034] As shown in FIG. 1, the present invention provides a secondary battery manufacturing method including: a unit cell manufacturing step (S10) of manufacturing a unit cell including an electrode and a separator; an electrode assembly manufacturing step (S20) of manufacturing an electrode assembly by folding so that a plurality of unit cells and separator sheets are alternately laminated; a correction step (S30) of correcting the height difference formed on the outer surface of the electrode assembly; and a pressing step (S40) of pressing the electrode assembly.

[0035] First, the unit cell manufacturing step (S10) is a step of manufacturing a unit cell including an electrode and a separator, and can be performed in various ways.

[0036] For example, in the unit cell manufacturing step (S10), an electrode slurry is applied onto an electrode current collector (e.g., a conductive foil) and coated on the electrode current collector to manufacture an electrode of a positive electrode or a negative electrode. After an isolation membrane is interposed between the electrodes, the electrodes and the isolation membrane are pressed and adhered to manufacture a unit cell.

[0037] However, in the process of manufacturing the electrode, the electrode slurry may be unevenly coated on some regions on the electrode current collector, and a difference in thickness may occur between the electrode slurry coated on the some regions where the electrode slurry is unevenly coated and the electrode slurry coated on the regions where the electrode slurry is evenly coated. In particular, when the regions where the electrode slurry is unevenly coated are coated with even less electrode slurry than the surrounding regions where the coating is uniform, a space may be formed between the electrode and the isolation membrane, and an unbonded region may occur.

[0038] On the other hand, after the unit cell manufacturing step (S10), as shown in FIG. 1, an electrode assembly manufacturing step (S20) of manufacturing an electrode assembly 10 including the unit cell may be performed.

[0039] Here, the electrode assembly manufacturing step (S20) is a step of manufacturing an electrode assembly by folding such that a plurality of unit cells and separation membrane sheets are alternately laminated, and it can be performed by various methods.

[0040] Specifically, in the electrode assembly manufacturing step (S20), the unit cells manufactured in the above-described unit cell manufacturing step (S10) are arranged side by side on the separation membrane sheet, and the unit cells and the separation membrane sheet, one surface of which is formed to have the same area and shape corresponding to each other, are arranged so as to be alternately laminated. The electrode assembly 10 can be manufactured by folding the separation membrane sheet a plurality of times in a direction surrounding the unit cells located on the separation membrane sheet. The outer surface of the electrode assembly 10 manufactured in this way may be formed in a shape in which the separation membrane sheet surrounds the electrode assembly 10. That is, since the unit cells and the separation membrane sheet are formed to have the same area and shape corresponding to each other, the outer surface of the manufactured electrode assembly 10 has the electrode portions of the unit cells not exposed, is completely surrounded by the separation membrane sheet, and can protect the unit cells located inside the separation membrane sheet.

[0041] However, in some regions between the electrodes and the separation membrane, the electrode slurry may be unevenly coated on the electrodes. In such a case, a difference in the coating thickness of the electrode slurry occurs between the uniformly coated peripheral region and the unevenly coated region, and an unbonded region may occur between the electrodes and the separation membrane. In the case of a unit cell in which an unbonded region has occurred, a specific region of the unit cell is formed to be relatively lower in height by the difference in the coating thickness of the electrode slurry compared to other regions. Therefore, when manufacturing the electrode assembly 10, when the unit cells are arranged and laminated in parallel in one direction, an unbonded region is formed again between the unit cells and the separation membrane sheet due to the unbonded region formed in the unit cells. Subsequently, when the separation membrane sheet is folded a plurality of times, the unbonded regions are accumulated, and a specific region of the electrode assembly 10 is formed to be relatively lower in height compared to other regions.

[0042] Specifically, the outer surface of the electrode assembly 10 is formed to have a step difference in a stepped shape, or is formed to be inclined with a predetermined inclination, etc., so that a height difference is formed on the outer surface.

[0043] In this case, as shown in FIG. 2, the electrode assembly 10 has a first region 11 having a first height H 1 ; and the first height H1 A second height H formed lower 2 including a second region 12 having. However, in FIG. 2, the dotted line disposed between the first region 11 and the second region 12 is shown for understanding the positions of the first region 11 and the second region 12, and does not mean that the internal region of the electrode assembly 10 is divided.

[0044] Specifically, the first region 11 means a region having a first height H in the electrode assembly 10 1 having.

[0045] Here, the first height H 1 is defined as the height at which the height from one surface of the electrode assembly 10 located in the stacking direction of the unit cell to the other surface facing the one surface is formed highest. Therefore, the first region 11 is understood as the region having the thickest thickness in the electrode assembly 10.

[0046] On the other hand, the second region 12 means a region having a second height H formed lower than the first height H in the electrode assembly 10 1 A second height H formed lower 2 having. The second height H 2 and the first height H 1 The height difference is formed by the unbonded region between the electrode and the separation membrane formed by the coating thickness difference of the electrode slurry coated on the electrode in the unit cell, and the unbonded region formed by alternately stacking the unit cell and the separation membrane sheet, and is accumulated by folding the separation membrane sheet a plurality of times.

[0047] Here, the second height H 2 is defined as the height at which the height from one surface of the electrode assembly 10 located in the stacking direction of the unit cell to the other surface facing the one surface is formed lower than the first height H 1 having. Therefore, the second region 12 is understood as all regions having a thickness thinner than the first region 11 in the electrode assembly 10.

[0048] Further, the second region 12 can be located at any part of the electrode assembly 10.

[0049] For example, as the length of the current collector increases, when applying the electrode slurry, the electrode slurry reaches less to the edge of the current collector. Therefore, the second region 12 is located corresponding to the edge of the electrode assembly 10.

[0050] In particular, the second region 12 is located corresponding to the edge region of the electrode assembly 10 where the electrode tab 14 is located among the edge regions of the electrode assembly 10.

[0051] This is understood because when manufacturing the electrodes, after applying and drying the electrode slurry to the central part of one current collector and then cutting the central part to manufacture two electrodes, it is expected that the electrode slurry is sufficiently applied to the edge region of the electrode assembly 10 that was the central part of the original current collector. However, it is difficult for the electrode slurry to reach relatively the edge region of the electrode assembly 10 where the electrode tab 14 is located. That is, in the edge region, since the electrode slurry reaches less, the thickness of the electrode slurry coating becomes thinner, and the second region 12 is formed.

[0052] Here, the electrode tab 14 may be formed by a notching process on the current collector before the electrode slurry is coated, or may be connected to the electrode by being attached to any part of the current collector after the electrode slurry is coated.

[0053] On the other hand, after the electrode assembly manufacturing step (S20), a correction step (S30) may be further performed to correct the height difference formed on the outer surface of the electrode assembly 10 so that the outer surface of the electrode assembly 10 is uniformly pressurized in the subsequent pressurization step (S40) described later.

[0054] That is, by correcting the height difference on the outer surface of the electrode assembly 10 through the correction step (S30), in the subsequent pressing step (S40), not only the first region 11 with a relatively high height in the electrode assembly 10 but also the second region 12 formed with a relatively low height is pressed. Therefore, the unbonded regions of the electrodes and the separation membrane located in the second region 12 and the unbonded regions of the unit cells and the separation membrane sheet can be improved.

[0055] Specifically, the correction step (S30) is a step of correcting the height difference formed on the outer surface of the electrode assembly 10 by disposing the correction sheet 13 in a region formed with a relatively low height in the electrode assembly 10, and it can be performed in various ways.

[0056] For example, in the correction step (S30), as shown in FIGS. 2 and 3, by disposing the correction sheet 13 above the separation membrane sheet of the second region 12 having a relatively low height in the electrode assembly 10, the height difference (H 1 -H 2 ) between the first region 11 and the second region 12 may be corrected. The unit cells and the separation membrane sheet are provided with corresponding areas and shapes to manufacture the electrode assembly 10, and the outer surface of the manufactured electrode assembly 10 is formed in a shape surrounded by the separation membrane sheet. Therefore, the correction sheet 13 may be provided and attached above the separation membrane sheet of the second region 12. On the other hand, although reference numerals 12 and 13 are illustrated in FIG. 3 as indicating the same position, since the correction sheet 13 is configured to be additionally disposed on the second region 12, it should be noted that the second region 12 and the correction sheet 13 are distinct concepts in the present invention. Also, in FIG. 3, the solid line disposed between the first region 11 and the second region 12 is shown for distinguishing the correction sheet 13 additionally disposed on the first region 11 and the second region 12, and it does not mean that the internal region of the electrode assembly 10 is divided.

[0057] Here, the correction sheet 13 is for the height difference (H 1 -H 2In order to reduce , various numbers can be stacked and arranged.

[0058] For example, the correction sheet 13 may be stacked and arranged in at least one or more layers depending on the thickness of the correction sheet 13 and the difference in height (H 1 -H 2 ) between the first region 11 and the second region 12.

[0059] Here, the correction sheet 13 is arranged on the upper side of the separation membrane sheet of the second region 12 by the difference (H 1 with respect to the first height H 2 of the second height H 1 -H 2 ) so that the height of the outer surface of the electrode assembly 10 is uniformly formed. Needless to say, this is also possible.

[0060] On the other hand, the correction sheet 13 is made of various materials. For example, the correction sheet 13 can be made of any material as long as it does not affect the performance of the electrode assembly, and may include, for example, synthetic resin and adhesive substances.

[0061] Also, a tape made of an insulating material may be used for the correction sheet 13. For example, a CPP tape (Cast PolyPropylene tape) used for insulating a conventional electrode tab may be used.

[0062] Furthermore, the correction sheet 13 has various widths and thicknesses. For example, the correction sheet 13 may be formed to have a width of 12 mm and a thickness of 0.03t.

[0063] On the other hand, after the execution of the correction step (S30), a pressurization step (S40) is performed to pressurize the electrode assembly 10 to bond the unit cells and the separation membrane sheet of the electrode assembly 10 to each other.

[0064] Here, the pressurization step (S40) is a step of pressurizing the electrode assembly 10 and can be performed in various ways.

[0065] For example, in the pressing step (S40), as shown in FIG. 4, it may be performed using a secondary battery manufacturing apparatus including a pressing press 100 that presses the electrode assembly 10 moving on the conveyor belt. Here, the electrode assembly 10 can move in the x direction (the direction penetrating the drawing from the back to the front) perpendicular to the y-z plane of the drawing on the conveyor belt.

[0066] Here, the pressing press 100 is configured to press the electrode assembly 10, and various configurations are possible.

[0067] For example, as described above, even when a height difference is formed on the outer surface of the electrode assembly 10, the pressing press 100 may have a pressing surface 110 formed with steps corresponding to the height difference formed on the outer surface of the electrode assembly 10 so as to press the outer surface of the electrode assembly 10 as uniformly as possible.

[0068] Specifically, as shown in FIG. 5, the pressing surface 110 is formed at the lower part of the pressing press 100 and may include a first pressing surface 111 that presses the first region 11; a second pressing surface 112 that presses the second region 12; and a connecting surface 113 that connects the first pressing surface 111 and the second pressing surface 112.

[0069] The first pressing surface 111 is a pressing surface that presses the first region 11, and various configurations are possible. For example, the first pressing surface 111 can have any shape as long as it can press the first region 11.

[0070] The second pressing surface 112 is a pressing surface that presses the second region 12, and various configurations are possible. For example, the second pressing surface 112 can have any shape as long as it can press the second region 12.

[0071] Here, the second pressing surface 112 may be formed to protrude from the first pressing surface 111 toward the electrode assembly 10.

[0072] That is, the first pressing surface 111 and the second pressing surface 112 may be formed so as to have a step with each other. Here, the second pressing surface 112 is higher than the first pressing surface 111 by the height difference (H 1 -H 2 ) of the first region 11 and the second region 12 of the electrode assembly 10.

[0073] Therefore, when the pressing press 100 presses the electrode assembly 10, there is an advantage that the first region 11 and the second region 12 of the electrode assembly 10 can be uniformly pressed despite the height difference between the first region 11 and the second region 12 of the outer shape of the electrode assembly 10.

[0074] On the other hand, the connecting surface 113 is configured to connect the first pressing surface 111 and the second pressing surface 112, and various configurations are possible.

[0075] Specifically, the connecting surface 113 is disposed between the first pressing surface 111 and the second pressing surface 112 and serves to connect the first pressing surface 111 and the second pressing surface 112 having different heights.

[0076] Here, the connecting surface 113 can connect the first pressing surface 111 and the second pressing surface 112 in various ways.

[0077] For example, as shown in FIG. 5, the connecting surface 113 may connect the first pressing surface 111 and the second pressing surface 112 in an inclined manner in order to minimize damage due to linear scratches and damage to the electrode surface.

[0078] Needless to say, the pressing press 100 may include a heating member (not shown) that is heated to a temperature exceeding room temperature in order to thermocompression bond the electrode assembly 10.

[0079] On the one hand, as shown in FIG. 6, the pressing step (S40) may include a first pressing step (S41) of pressing the electrode assembly using a first pressing press; and a second pressing step (S42) of pressing the electrode assembly using a second pressing press.

[0080] That is, in the pressing step (S40), as shown in FIG. 7, by sequentially arranging the first pressing press and the second pressing press along the moving direction of the electrode assembly 10 on the conveyor belt, the above-described electrode assembly 10 can be pressed at least two or more times. Here, the first pressing press and the second pressing press can press the electrode assembly 10 by moving in the z direction (the direction penetrating the drawing from the back to the front) perpendicular to the x-y plane of the drawing.

[0081] Here, for at least one of the first pressing press and the second pressing press, as described above, a pressing press 100 formed such that the pressing surface 110 for pressing the electrode assembly 10 has a step can be applied. Here, the above-described content regarding the pressing press 100 is incorporated by reference.

[0082] For example, the first pressing press may be formed such that the pressing surface 110 for pressing the electrode assembly 10 has a step and has different heights, and the pressing surface of the second pressing press may be formed flat at a predetermined height.

[0083] Hereinafter, with reference to FIG. 8, the size of the unbonded region of the electrode-separator membrane of the unit cell depending on whether the present invention is applied will be described. FIG. 8(a) discloses a front image of a unit cell (bi-cell) manufactured by the prior art (hereinafter referred to as "comparative example"), and FIG. 8(b) discloses a front image of a unit cell (bi-cell) manufactured by the present invention (hereinafter referred to as "example of the present invention").

[0084] First, looking at the front image of the unit cell formed by the comparative example in Fig. 8(a), it can be seen that an unbonded region of the black electrode-separator film is formed at the upper part of the unit cell, that is, at the edge B corresponding to the electrode tab. Also, in the case of an electrode assembly including the unit cell as described above, since an unbonded region is expected to occur between the unit cell and the separator film sheet, lithium is deposited on the negative electrode and the resistance of the electrode increases. Therefore, there arises a problem that the performance of the secondary battery deteriorates.

[0085] On the other hand, looking at the front image of the unit cell formed by the embodiment of the present invention in Fig. 8(b), it can be seen that almost no unbonded region is formed at the upper part of the unit cell, that is, at the edge B corresponding to the electrode tab. Therefore, it is expected that the unit cell formed by the embodiment of the present invention hardly forms not only the unbonded region of the electrode-separator film inside the unit cell but also the unbonded region between the unit cell and the separator film sheet on the electrode assembly. Thus, there is an advantage that lithium precipitation due to the interfacial resistance on the negative electrode can be minimized and the performance of the secondary battery can be improved.

[0086] As described above, although the present invention has been described with reference to the limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the equivalent scope of the technical idea of the present invention and the appended claims by those having ordinary knowledge in the technical field to which the present invention pertains.

Explanation of Reference Numerals

[0087] 10 Electrode assembly 11 First region 12 Second region 13 Correction sheet 14 Electrode tab 100 Press 110 Pressing surface 111 First pressing surface 112 Second pressing surface 113 Connecting surface S10 Unit cell manufacturing step S20 Electrode assembly manufacturing step S30 Correction step S40 Pressurization Step S41 First Pressurization Step S42 Second Pressurization Step

Claims

1. A unit cell manufacturing step of manufacturing a unit cell including an electrode and a separation membrane; An electrode assembly manufacturing step of manufacturing an electrode assembly by folding so that a plurality of the unit cells and separation membrane sheets are alternately laminated; A correction step of correcting a height difference formed on the outer surface of the electrode assembly; and Including a pressurizing step of pressurizing the electrode assembly; The correction step is A secondary battery manufacturing method of correcting a height difference formed on the outer surface of the electrode assembly by disposing a correction sheet in a region formed relatively low in height with respect to the inside of the electrode assembly.

2. The correction step corrects so that the height of the outer surface of the electrode assembly becomes uniform. The secondary battery manufacturing method according to Claim 1.

3. The electrode assembly is A first region having a first height; and Including a second region having a second height formed at a height lower than the first height; The correction step is The secondary battery manufacturing method according to Claim 1, wherein the correction sheet is disposed in the second region to correct a height difference between the first region and the second region.

4. The correction step is The secondary battery manufacturing method according to Claim 3, wherein the correction sheet is disposed in the second region by an amount equal to the difference between the second height and the first height with respect to the first height.

5. The secondary battery manufacturing method according to Claim 3, wherein the second region is located corresponding to an edge portion of the electrode assembly.

6. The electrode assembly includes an electrode tab connected to the electrode; The secondary battery manufacturing method according to Claim 3, wherein the second region is located corresponding to a region where the electrode tab of the electrode assembly is located.

7. The correction sheet is made of an insulating material. The secondary battery manufacturing method according to Claim 1.

8. The correction sheet includes a synthetic resin and an adhesive substance. The secondary battery manufacturing method according to Claim 1.

9. The correction sheet is a CPP tape (Cast Polypropylene tape). The secondary battery manufacturing method according to Claim 8.

10. The electrode is coated with an electrode slurry, The secondary battery manufacturing method according to Claim 1, wherein the height difference is formed by a difference in thickness of the coated electrode slurry.

11. The unit cell and the separation membrane sheet are formed so that one surface has an area corresponding to each other. The secondary battery manufacturing method according to Claim 1.

12. The correction sheet is provided on the upper side of the separation membrane sheet, and the method for manufacturing a secondary battery according to claim 1.

13. An electrode assembly in which a plurality of unit cells including electrodes and separation membranes and separation membrane sheets are alternately stacked, The electrode assembly is A first region having a first height; A second region having a second height formed at a height lower than the first height; and A correction sheet disposed in the second region to correct the height difference between the first region and the second region; and includes An electrode assembly, which is folded so that the plurality of unit cells and the separation membrane sheets are alternately stacked.

14. The correction sheet is disposed by the height difference between the first region and the second region, and the electrode assembly according to claim 13.

15. The second region is located corresponding to the edge of the electrode assembly, and the electrode assembly according to claim 13.

16. The electrode assembly includes an electrode tab connected to the electrode; The second region is located corresponding to the region where the electrode tab of the electrode assembly is located, and the electrode assembly according to claim 13.

17. The electrode is coated with an electrode slurry, The second height is formed at a height lower than the first height due to the difference in the thickness of the coated electrode slurry, and the electrode assembly according to claim 13.

18. One surface of the unit cell and the separation membrane sheet is formed in an area corresponding to each other, and the electrode assembly according to claim 13.

19. The correction sheet is provided on the upper side of the separation membrane sheet, and the electrode assembly according to claim 13.

20. A secondary battery including an electrode assembly in which a plurality of unit cells including electrodes and separation membranes and separation membrane sheets are alternately stacked, The electrode assembly is A first region having a first height; A second region having a second height formed at a height lower than the first height; and A correction sheet disposed in the second region to correct the height difference between the first region and the second region; and includes A secondary battery, which is folded so that the plurality of unit cells and the separation membrane sheets are alternately stacked.

21. In a secondary battery manufacturing apparatus for manufacturing a secondary battery including an electrode assembly in which a plurality of unit cells including electrodes and separation membranes and separation membrane sheets are alternately stacked and folded, The electrode assembly is A first region having a first height; A second region having a second height formed at a height lower than the first height; and including a correction sheet disposed in the second region to correct a height difference between the first region and the second region; the secondary battery manufacturing apparatus includes a pressing press for pressing the electrode assembly; the pressing press is a secondary battery manufacturing apparatus in which a pressing surface for pressing the electrode assembly is formed to have a step.

22. the pressing surface a first pressing surface for pressing the first region; a second pressing surface for pressing the second region; and includes a connecting surface connecting the first pressing surface and the second pressing surface; the second pressing surface is formed to protrude from the first pressing surface toward the electrode assembly, and the secondary battery manufacturing apparatus according to claim 21.

23. the connecting surface is formed to have an inclination with respect to the first pressing surface and the second pressing surface, and the secondary battery manufacturing apparatus according to claim 22.

24. the electrode is coated with an electrode slurry, the second height is formed to be lower than the first height due to a difference in thickness of the coated electrode slurry, and the secondary battery manufacturing apparatus according to claim 21.

25. one surface of the unit cell and the separation membrane sheet is formed to have a corresponding area, and the secondary battery manufacturing apparatus according to claim 21.

26. the correction sheet is provided above the separation membrane sheet, and the secondary battery manufacturing apparatus according to claim 21.

27. a unit cell manufacturing step of manufacturing a unit cell including an electrode and a separation membrane; an electrode assembly manufacturing step of manufacturing an electrode assembly by folding a plurality of the unit cells and separation membrane sheets so as to be alternately laminated; a correction step of correcting a height difference formed on an outer surface of the electrode assembly; and includes a pressing step of pressing the electrode assembly; the pressing step a first pressing step of pressing the electrode assembly using a first pressing press; and a second pressing step of pressing the electrode assembly using a second pressing press; at least one of the first pressing press and the second pressing press is formed such that a pressing surface for pressing the electrode assembly has a step, the correction step a secondary battery manufacturing method of correcting a height difference formed on an outer surface of the electrode assembly by disposing a correction sheet in a region formed to be relatively low in height with respect to the inside of the electrode assembly.

28. the first pressing press is formed such that a pressing surface for pressing the electrode assembly has a step, The secondary battery manufacturing method according to claim 27, wherein the pressurizing surface of the second pressurizing press for pressurizing the electrode assembly is formed flat at a predetermined height.

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