Manufacturing method of electrode assembly

Abstract

The present invention provides a method for manufacturing an electrode assembly, the method including: (S10) forming a stack in which positive electrodes, separators, and negative electrodes are alternately arranged by arranging positive electrodes and negative electrodes on a separator having a bent portion formed by folding the separator in a zigzag pattern; (S20) applying pressure to the stack to fix the positions of the positive electrodes and the negative electrodes relative to the separator; (S30) applying heat and pressure to the stack to bond the positive electrodes, the separator, and the negative electrodes; and (S40) cutting a side of the stack to form an electrode assembly, the side including the bent portion.

Description

[Technical Field]

[0001] The present invention claims the benefit of the filing date of Korean Patent Application No. 10-2022-0098947, filed with the Korean Intellectual Property Office on August 9, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing an electrode assembly including a zigzag separator, and to a method for improving the electrolyte wetting of the electrode assembly. [Background technology]

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions, and in recent years, lithium secondary batteries have become widely used due to their high energy density, high voltage, and long cycle life, making them suitable for use in a variety of fields. With the increasing demand for electric vehicles and energy storage devices in recent years, developments are underway in materials and structures to maximize capacity and energy density.

[0004] The secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and may be manufactured by housing the electrode assembly in a case together with an electrolyte. Secondary batteries may be classified into pouch-type, cylindrical-type, prismatic-type, coin-type, etc. depending on the shape of the case housing the electrode assembly, and may be classified into jelly roll-type, stack-type, etc. depending on the manufacturing method and shape of the electrode assembly.

[0005] Stack-type electrode assemblies are manufactured by stacking multiple positive electrodes, separators, and negative electrodes prepared to a predetermined size. However, transporting the individual electrodes and separators is cumbersome, and maintaining a consistent arrangement during stacking is difficult, resulting in low productivity. To address this issue, a zigzag stacking electrode assembly has been developed, in which a long sheet-like separator is folded in a zigzag pattern and positive and negative electrodes are alternately positioned between adjacent folds. For example, a zigzag electrode assembly can be manufactured by tilting or swinging a table on which the electrode assemblies are stacked when a long sheet-like separator wound into a cylinder is supplied, or by reciprocating a supply roll that transports the separator to fold the separator in a zigzag pattern and position each electrode between the folded electrodes. Zigzag stacking simplifies the stacking process, resulting in high productivity, and is capable of maintaining a stable stacked structure even when the separator has relatively low adhesive strength.

[0006] Typically, during zigzag stacking, the separator is bent at regular intervals to form bends. These intervals are larger than the width of the positive and negative electrodes to ensure sufficient clearance. Therefore, zigzag electrode assemblies include regions where separator-only bends are stacked on both sides. These regions have empty spaces compared to the regions where the electrodes and separators are stacked together, and because they are not fixed, they tend to fold or collapse, making them difficult to insert into a case or pouch. To address this issue, heat and pressure are applied to the bends to bond the bends and / or adjacent bends. However, during the process of bonding the separators, pores formed in the separators close, resulting in reduced air permeability, increased resistance, and reduced wettability to the electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a method for manufacturing a zigzag electrode assembly having a structure in which the separator bending is not folded or dropped, the separator bending is easily inserted into a case or pouch, and the separator wettability with respect to the electrolyte is excellent. [Means for solving the problem]

[0008] One aspect of the present invention provides a method for manufacturing an electrode assembly, comprising: (S10) forming a stack in which positive electrodes, separators, and negative electrodes are alternately arranged on a separator that has been zigzag-folded to form a bent portion; (S20) applying heat and pressure to the stack to fix the positions of the positive electrodes and negative electrodes relative to the separator; (S30) applying heat and pressure to the stack to bond the positive electrodes, separators, and negative electrodes; and (S40) cutting a side of the stack to form an electrode assembly, the side including the bent portion.

[0009] In the method for manufacturing the electrode assembly, the width of the negative electrode may be 1% to 10% longer than the width of the positive electrode.

[0010] The method for manufacturing the electrode assembly may further include (S11) wrapping an outer periphery of the laminate formed in (S10) with an end portion of the separator.

[0011] In the method for manufacturing the electrode assembly, the step (S20) may be to apply a pressure of 1 MPa to 6 MPa to the laminate at a temperature of 50° C. to 60° C. for 1 second to 60 seconds.

[0012] In the method for manufacturing the electrode assembly, step (S20) may include partially bonding the positive electrode and the separator, and the separator and the negative electrode, respectively, to fix the positions of the positive electrode and the negative electrode relative to the separator.

[0013] In the method for manufacturing the electrode assembly, the step (S30) may be to apply a pressure of 1 MPa to 6 MPa to the laminate at a temperature of 50° C. to 60° C. for 1 second to 60 seconds.

[0014] In the method for manufacturing the electrode assembly, the step (S30) may be to completely bond the positive electrode and the separator, and the separator and the negative electrode.

[0015] In the method for manufacturing the electrode assembly, the side may be formed of a separator including the bent portion, and the electrode assembly may not include the bent portion.

[0016] In the method for manufacturing the electrode assembly, the bent portion may extend parallel to a longitudinal direction of the separator.

[0017] In the method for manufacturing the electrode assembly, the distance between the bent portion and the negative electrode may be smaller than the distance between the bent portion and the positive electrode.

[0018] In the method for manufacturing the electrode assembly, the length of the negative electrode in the width direction may be 10 to 15 times the distance between the bent portion and the negative electrode.

[0019] In the method for manufacturing the electrode assembly, step S40 may involve cutting the side surface of the electrode assembly in a direction parallel to the height direction.

[0020] In the method for manufacturing the electrode assembly, the step (S40) is to cut the cutting point between the negative electrode and the bent portion, and the ratio of the distance between the cutting point and the negative electrode to the distance between the cutting point and the bent portion may be 1:8 to 1:10.

[0021] In the method for manufacturing the electrode assembly, the electrode assembly may have a distance between the end of the separator and the positive electrode that is 1.5 to 2 times the distance between the end of the separator and the negative electrode.

[0022] Another aspect of the present invention provides an electrode assembly manufactured according to the above-described method for manufacturing an electrode assembly. [Effects of the Invention]

[0023] The manufacturing method of the present invention has excellent productivity for producing a zigzag electrode assembly, and provides an electrode assembly having a structure in which the separator is free from breakage or unevenness, thereby improving the productivity of an electrochemical device including the electrode assembly.

[0024] In addition, in the electrode assembly manufactured by the manufacturing method of the present invention, the separator is uniformly impregnated with the electrolyte, thereby preventing or minimizing dendritic deposition of lithium from the separator. [Brief explanation of the drawings]

[0025] [Figure 1] 3 is a conceptual diagram illustrating a step of applying pressure to a stack to fix the positions of a positive electrode and a negative electrode relative to a separator during a manufacturing process of an electrode assembly according to an embodiment of the present invention. [Figure 2] 3 is a conceptual diagram illustrating a step of applying heat and pressure to a laminate to bond a positive electrode, a separator, and a negative electrode together, in a process of manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 3] 1 is a conceptual diagram showing a cross section of a laminate in a manufacturing stage of a conventional electrode assembly. [Figure 4] 3 is a conceptual diagram illustrating a cross section of a laminate in a process of manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 5] 3 is a conceptual diagram illustrating a cross section of a laminate in a process of manufacturing an electrode assembly according to an embodiment of the present invention. [Figure 6] 1 is a conceptual diagram illustrating a cross section of an electrode assembly according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, each configuration of the present invention will be described in more detail so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited to the following content.

[0027] As used herein, the term "comprising" is used to list materials, compositions, devices, and methods useful in the present invention, and is not limited to the listed examples.

[0028] As used herein, "about" and "substantially" mean a numerical value or range of degree or approximation thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using disclosures in which precise or absolute numerical values ​​are provided to aid in the understanding of the invention.

[0029] As used herein, the term "electrochemical device" may refer to a primary battery, a secondary battery, a supercapacitor, etc. The electrochemical device may be a lithium ion secondary battery and may be in the form of a pouch, cylinder, prismatic, or coin, but is not limited to these specific shapes.

[0030] The term "separator membrane" as used herein may refer to, but is not limited to, a functional separator membrane having a porous coating layer containing an inorganic material and a binder formed on at least one surface of a porous substrate such as a polyolefin substrate or nonwoven fabric. The term "separator membrane" may refer collectively to a press-standing separator membrane formed from an inorganic material and a binder without a porous substrate, or a separator membrane made of a porous substrate without a porous coating layer.

[0031] As used herein, the term "electrode" collectively refers to a "positive electrode" and a "negative electrode," and may refer to an electrode in which an electrode active material is applied to at least one surface of a material that is conductive without inducing a chemical change in an electrochemical device, and then dried. The material and the electrode active material may be of any type that can be used in an electrochemical device.

[0032] As used herein, "spacing" means the shortest distance between specified points.

[0033] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The drawings may be exaggerated, omitted, or schematically illustrated in order to explain or emphasize the contents of the embodiment of the present invention.

[0034] One embodiment of the present invention provides a method for manufacturing an electrode assembly, including: (S10) forming a stack in which positive electrodes, separators, and negative electrodes are alternately arranged on a separator that is zigzag folded to form a bent portion, (S20) applying heat and pressure to the stack to fix the positions of the positive electrodes and negative electrodes relative to the separator, (S30) applying heat and pressure to the stack to bond the positive electrodes, separators, and negative electrodes, and (S40) cutting a side of the stack to form an electrode assembly, wherein the side includes the bent portion.

[0035] The step (S10) is a step of forming a bent portion by folding the separator in a zigzag pattern, and alternately arranging positive and negative electrodes on the separator with the bent portion to form a stack in which positive electrodes, separators, and negative electrodes are alternately arranged.

[0036] In step (S10), the separator may have a length in its longitudinal direction (or MD; machine direction) longer than its length in its transverse direction (or TD; transform direction). The bent portions may be formed by bending the separator in a zigzag pattern at predetermined intervals along the MD. For example, the bent portions may extend parallel to corners of the separator in the TD. The predetermined intervals may be equal or different, but are preferably equal and longer than the width of the positive electrode or negative electrode.

[0037] The separator, positive electrode, and negative electrode may each be rectangular, but are not limited thereto. For example, the separator, positive electrode, and negative electrode may each be rectangular in shape, with the MD direction being longer than the TD direction. A plurality of positive electrodes and negative electrodes are arranged along the MD direction of the separator, with the MD of the separator and the TD direction of the positive and negative electrodes being parallel. The number of positive and negative electrodes may be determined depending on the capacity required for the final electrochemical device.

[0038] The length of the positive electrode in the MD direction may be the same as the length of the negative electrode in the MD direction. A is the TD direction length W of the positive electrodeC Based on this, the TD direction length W of the positive electrode C The negative electrode may be 1% to 10% longer than the above range. If the negative electrode is less than this range, repeated use of the electrochemical device may result in the problem of lithium dendritic deposition on the surface of the negative electrode. If the negative electrode is more than this range, the lithium deposition prevention effect may no longer be improved, and the problem of consistent electrode arrangement in the electrode assembly may occur.

[0039] The positive electrode and the negative electrode may be alternately arranged between adjacent bent portions formed in the separator. Therefore, the stack may have a structure in which the positive electrode and the negative electrode are alternately arranged with the separator sandwiched therebetween. Preferably, the positive electrode and the negative electrode may be aligned such that their respective TD centerlines coincide.

[0040] After step (S10), the method may further include a step (S11) of wrapping the outer periphery of the laminate formed in step (S10) with the end portion of the separator.

[0041] The separator may be longer in the MD direction than in the TD direction and bent in a zigzag pattern at predetermined intervals along the MD direction to form multiple bends, but the end portions may extend without bending. Referring to Figures 3 to 5, the end portions 15 of the separator may wrap around the outer periphery of the laminate 10 one or more times, and the wrapping pressure of the end portions 15 compresses the interfaces between the electrodes 13 and 14 and the separator 11 that constitute the laminate 10, maintaining stable contact between the electrodes and the separator. For example, the end portions 15 of the separator may wrap around the bends 12 located on both sides of the laminate.

[0042] In step S20, pressure is applied to the stack formed in step S10 to fix the positions of the positive and negative electrodes relative to the separator.

[0043] 1, step S20 can be performed using a first pressing device 100. The first pressing device 100 can partially press the laminate 10 to fix the relative positions of the electrodes aligned in the laminate 10 with respect to the separator. The first pressing device 100 can include a pressing plate 110 that presses the laminate 10 and a fixing portion 120 that holds the laminate 10 while the pressing plate 110 presses the laminate 10.

[0044] The laminate 10 has a structure in which positive electrodes, separators, and negative electrodes are alternately stacked through step (S10) or step (S11), but the position of the positive electrode or negative electrode relative to the separator is not completely fixed. The laminate 10 may be sandwiched between one or more clips 121 provided on the fixing portion 120 and disposed between upper and lower pressing plates 110. The pressing plates 110 may have grooves 111 at positions corresponding to the clips 121, so that the clips 121 do not apply pressure and may only press the laminate 10 fixed to the clips 121. The first pressing device 100 may bond the separators and electrodes stacked in the remaining portion of the laminate 10 excluding the portion captured by the clips 121. The shapes and numbers of the pressing plates 110, clips 121, etc. are not limited to those shown in FIG. 1.

[0045] The step (S20) may involve applying a pressure of 1 MPa to 6 MPa to the laminate 10 at a temperature of 50°C to 100°C for 1 second to 30 minutes. Preferably, the step (S20) may involve applying a pressure of 1 MPa to 6 MPa to the laminate 10 at a temperature of 50°C to 60°C for 1 second to 60 seconds. The step (S20) involves inducing partial adhesion between the separator and the electrode in the laminate 10, thereby fixing the position of the electrode relative to the separator. Preferably, the step (S20) may involve fixing the electrode so that the center line of the electrode's TD length coincides with the center line of the gap between adjacent bends of the separator. When the temperature and pressure are within the above ranges, the adhesive strength between the separator and the electrode after the step (S20) may be 5 gf / 20 mm or more. The position of the electrode relative to the separator may be fixed within the above adhesive strength range. If the pressure is less than 1 MPa, the electrodes may not be fixed in position, and may come off from their designated positions during handling of the laminate 10. If the pressure is more than 6 MPa, the active material layer formed on the electrodes may be destroyed, or the pore structure formed in the separator may be destroyed, which may cause problems with the air permeability and electrical resistance of the separator.

[0046] The laminate 10 pressed in step S20 can be removed from the first press device 100 by the clip 121 and transferred to the second press device 200.

[0047] In step S30, heat and pressure are applied to the laminate 10 compressed in step S20 to bond the positive electrode, the separator, and the negative electrode. This is a conceptual diagram illustrating step S30 of a method for manufacturing an electrode assembly according to an embodiment of the present invention.

[0048] Referring to FIG. 2, step S30 may be performed using a second press 200. The second press 200 may apply pressure to both sides of the laminate 10 to bond the separators and electrodes included in the laminate 10. Specifically, both sides of the laminate 10 refer to the sides that do not include separator bending and are on which the electrodes and separators are alternately stacked. Step (S30) refers to applying heat and pressure to the laminate 10 to bond the adjacently stacked positive electrode and separator, and separator and negative electrode.

[0049] 2, step S30 may be performed using a second pressing device 200. The second pressing device 200 may bond the separator and the electrodes included in the laminate 10 by thermocompressing both surfaces of the laminate 10. The second pressing device 200 may include a pressure plate 210 that thermocompresses the laminate 10.

[0050] The laminate 10 is formed by partially bonding the electrodes and the separator through step (S20), thereby fixing the positions of the electrodes relative to the separator, but the separator and the electrodes are not completely bonded to each other. The laminate 10 may be placed between upper and lower pressure plates 210, which may thermocompress both sides of the laminate 10. The second press device 200 may thermocompress both sides of the laminate 10, including the portions that were not pressed because they were gripped by clips 121 in the previous step, to bond the separator and the electrodes to each other. The shape and number of the pressure plates 210 are not limited to those shown in FIG. 2.

[0051] Step (S30) may involve applying a pressure of 1 MPa to 6 MPa to the laminate 10 at a temperature of 50°C to 100°C for 1 second to 30 minutes. Preferably, step (S30) may involve applying a pressure of 1 MPa to 6 MPa to the laminate 10 at a temperature of 50°C to 60°C for 1 second to 60 seconds. More preferably, step (S30) may involve applying a higher temperature and pressure than step (S20). Step (S30) completely bonds the positive electrode and the separator, and the separator and the negative electrode in the laminate 10. If the pressure is less than 1 MPa, the electrode and the separator may separate during the manufacturing process or use of the electrochemical device, resulting in a short circuit due to electrode contact. If the pressure exceeds 6 MPa, the active material layer formed on the electrode may be destroyed, or the pore structure formed in the separator may be destroyed, resulting in problems with the separator's air permeability and electrical resistance.

[0052] The laminate 10 thermocompressed in step S30 may be removed from the second press device 200 and processed into an electrode assembly in a subsequent step.

[0053] Step S40 is a step of cutting the side of the laminate 10 thermocompression bonded in step S30 to form an electrode assembly. Figures 3 to 5 are conceptual diagrams showing a cross section of the laminate 10 after step S30 in Figure 2, viewed from direction A. The length of the laminate 10 in the MD direction may be longer than the length in the TD direction, and the A direction may be parallel to the MD direction of the laminate 10.

[0054] FIG. 3 is a conceptual diagram showing a process of applying heat and pressure to a region where a separator is stacked in order to solve the problems of folding and falling off of a conventional separator.

[0055] 3, a stack 10 for forming a zigzag electrode assembly has a structure in which positive electrodes 13 and negative electrodes 14 are alternately arranged with a separator 11 sandwiched therebetween, and the separator 11 may include one or more bent portions 12 formed by being folded in a zigzag pattern. For example, the length W of the negative electrode 14 in the TD direction is A is the length W of the positive electrode 13 in the TD directionC The TD length of the laminate 10 may be longer than the TD length W of the negative electrode 14. A and the length W of the part consisting only of the separation membrane 11 S The portion consisting of only the separation membrane 11 may have a structure in which the separation membrane 11 including the bent portion 12 is stacked in the height direction Z of the laminate 10, and an empty space may be included without electrodes being disposed. If the laminate 10 is immediately inserted into a case, the portion consisting of only the separation membrane 11 may be inserted in a folded state, or the separation membrane 11 may be torn due to rattling. Conventionally, heat and pressure (P) are applied from above and below (in a direction parallel to the Z direction) to the portion consisting of only the separation membrane 11 to bond adjacent separation membranes 11, and the length W S This improved the strength of the separator 11, preventing it from folding or falling off. However, during the process of bonding the separators 11 together, the pore structure formed in the separator 11 collapsed, reducing the air permeability and making it difficult for the electrolyte to penetrate the separator 11.

[0056] 4 and 5 are conceptual diagrams showing the step S40 as a means for solving the problems of the prior art as shown in FIG. 3, and FIG. 6 is a conceptual diagram showing the electrode assembly 20. In FIG.

[0057] 4 to 6, step (S40) refers to cutting the separator 11 along a predetermined point C on the separator 11 in the laminate 10 to remove at least one side of the laminate 10. The side includes a bent portion 12, and preferably, step (S40) may involve cutting both sides of the laminate 10. The electrode assembly 20 formed according to step (S40) may not include the bent portion 12.

[0058] The cutting can be performed using a press cutter, a laser, a hot wire, etc. Preferably, in step (S40), a blade is used to cut in a direction parallel to the height direction (Z direction) of the laminate 10, which may be parallel to the height direction of the electrode assembly 20. During the cutting, only the separator 11 can be cut while the portion where the electrodes are stacked and the side including the bending portion 12 are fixed.

[0059] In one embodiment of the present invention, the relationship between the TD length of the separator and the TD length of the electrode and the specific position of the cutting point C are determined to provide an electrode assembly 20 having a structure that can prevent the separator 11 from folding or falling off while maintaining the advantages of manufacturing an existing zigzag-type electrode assembly.

[0060] Specifically, the distance W between the bent portion 12 and the negative electrode 14 in the laminate 10 is AS is the distance W between the bent portion 12 and the positive electrode 13 CS The cutting point C is located between the bending portion 12 and the negative electrode 14, and a predetermined length of the separator 11 remains from each of the positive electrode 13 and the negative electrode 14 upon cutting.

[0061] Specifically, the length W of the negative electrode 14 in the TD direction A is the distance W between the bent portion 12 and the negative electrode. AS The length W of the negative electrode 14 in the TD direction can be 10 to 15 times. A is the distance W between the bent portion 12 and the negative electrode. AS If the length W of the negative electrode 14 in the TD direction is less than 10 times the length W of the negative electrode 14 in the TD direction, at least a portion of the separator 11 is bent toward the electrode during the cutting process. A is the distance W between the bent portion 12 and the negative electrode. AS If the cutting force exceeds 15 times, the separation membrane 11 will be torn during the cutting process.

[0062] Specifically, step S40 involves cutting the cutting point C between the negative electrode 14 and the bent portion 12, and the ratio of the distance W1 between the cutting point C and the negative electrode 14 to the distance W2 between the cutting point C and the bent portion 12 may be 1:8 to 1:10. If the W1:W2 ratio is less than 1:8, at least a portion of the separator 11 is bent toward the electrode during the cutting process. If the W1:W2 ratio exceeds 1:10, the separator 11 is torn during the cutting process.

[0063] In the electrode assembly 20 formed by cutting in step (S40), the distance between the end (point C) of the separator 11 and the positive electrode 13 may be 1.5 to 2 times the distance between the end of the separator 11 and the negative electrode 14. It is preferable that this ratio is maintained even if the sizes of the positive electrode 13 and the negative electrode 14 are changed.

[0064] Another embodiment of the present invention provides an electrode assembly manufactured by the method according to the above embodiment, and an electrochemical device including the same.

[0065] The electrode assembly is formed by cutting the side and does not include a bent portion of the separator, so its appearance is similar to that of a conventional stack-type electrode assembly. However, in a stack-type (Lamination and Stack) electrode assembly, the separator and the electrode are quickly stacked without undergoing a step of fixing the electrode position relative to the separator, which can lead to misalignment of the electrodes and non-uniform adhesion between the separator and the electrode.

[0066] Therefore, the electrode assembly according to one embodiment of the present invention can provide aligned electrode arrangement and uniform electrode adhesion compared to conventional stacked electrode assemblies, and can prevent folding or detachment of the separator, thereby reducing defects during case insertion.

[0067] The shape of the case or pouch into which the electrode assembly is inserted is not limited. For example, the electrochemical device may be a cylindrical, prismatic, coin-shaped, or pouch-shaped lithium secondary battery. The lithium secondary battery may be packed or modularized as a unit cell and used in electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid vehicles (PHEVs), power storage devices, etc.

[0068] The present invention will be described in more detail below with reference to specific examples and experimental examples. The following examples and experimental examples are provided to illustrate the present invention, and the present invention is not limited to the following examples and experimental examples.

[0069] Example 1 A 15 μm thick separator coated with a slurry containing inorganic materials and a binder was prepared, and 30 positive electrodes measuring 90 mm x 315 mm and 31 negative electrodes measuring 95.5 mm x 320 mm were prepared. The separator was zigzag-wrapped 20 times at 98.5 mm intervals, and the positive and negative electrodes were arranged in order while folding the separator, leaving the end portions, to prepare a stack. The distance between the negative electrode and the bent portion of the separator in the stack was 30 mm, and the distance between the positive electrode and the bent portion was 32.75 mm. The stack was wound around the end of the separator.

[0070] The laminate was attached to a first press and pressed at 60° C. and a pressure of 2 MPa for 1 minute, and then attached to a second press and thermocompression bonded at 70° C. and a pressure of 3 MPa for 30 seconds.

[0071] Distance between the negative electrode and the bent part (W AS ) and set the cutting point C at a point where the ratio of the distance W1 from the negative electrode to the cutting point C to the distance W2 from the cutting point C to the bend was 1:9. Both sides of the laminate were cut by press cutting to produce an electrode assembly with a distance W1 between the negative electrode and the separator of 3 mm.

[0072] Comparative Example 1 The same types and numbers of separators, positive electrodes, and negative electrodes as those used in Example 1 were used, and the laminate was pressurized and thermocompressed in the same manner.

[0073] Referring to FIG. 3, the portions W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W23, W24, W25, W26, W27, W28, W39, W30, W31, W32 S The top and bottom were thermocompressed at 120° C. for 20 seconds to prepare an electrode assembly.

[0074] Comparative Example 2 The same types of separators, positive electrodes, and negative electrodes as those used in Example 1 were used, but 61 separators measuring 100 mm x 380 mm were prepared, and the positive electrode, separator, and negative electrode were stacked in this order to form a stack.

[0075] Both sides of the laminate were thermocompressed at 60° C. under a pressure of 18 kgf / cm at a speed of 220 cpm to prepare an electrode assembly.

[0076] Comparative Example 3 Distance W between the negative electrode and the bent part AS Both sides of the laminate were cut by press cutting at a point where the ratio of the distance W1 from the negative electrode to the distance W2 from the cutting point C to the bent portion was 1:7, and an electrode assembly was manufactured in the same manner as in Example 1, except that the distance W1 between the negative electrode and the separator was 3.75 mm.

[0077] Comparative Example 4 Distance between the negative electrode and the bent part (W AS ) and cut point C, where the ratio of the distance (W1) from the negative electrode to the cutting point C to the distance (W2) from the cutting point C to the bent portion was 1:11. Both sides of the laminate were cut by press cutting, and an electrode assembly was manufactured in the same manner as in Example 1, except that the distance W1 between the negative electrode and the separator was 2.5 mm.

[0078] Experimental example 1: Checking the state of the long side separation membrane in the electrode assembly After preparing electrode assemblies according to Example 1 and Comparative Examples 1 to 6, the state of the separation membrane included in each electrode assembly was visually inspected. Then, the electrode assembly was fully inserted into the pouch and pulled out again, and the state of the separation membrane was visually inspected. The results (◯: intact, △: folded separation membrane, ×: broken separation membrane) are summarized in Table 1 below.

[0079] [Table 1]

[0080] As shown in Table 1, in Comparative Example 2, which is a stacked electrode assembly, folding was observed at the corners of the separator in the MD direction immediately after fabrication. In Example 1 and Comparative Example 1, which are zigzag electrode assemblies that have an additional step to prevent separator folding, the separator remained in perfect condition immediately after fabrication and after insertion into the pouch.

[0081] However, in Comparative Examples 3 to 6, in which the separator and negative electrode were cut to different dimensions than those of the embodiment of the present invention, the separator broke during cutting, or the folded separator broke while being inserted into the pouch.

[0082] Experimental example 2: Confirmation of the wetting of the separator with the electrolyte After manufacturing the electrode assemblies according to Example 1 and Comparative Examples 1 to 6, each electrode assembly was completely inserted into a pouch, 156 g of electrolyte (weight ratio of EC and EMC = 3:7) was poured into the pouch, and the pouch was vacuum-sealed.

[0083] The pouch was left at room temperature for 72 hours, and then the electrode assembly was taken out and disassembled to check the interface between the electrode and the separator. The time (hr) until the entire separator interface was impregnated with the electrolyte was determined and summarized in Table 2 below.

[0084] [Table 2]

[0085] As shown in Table 2, in Comparative Example 1 in which both sides of the electrode assembly including the separator bending were thermocompression bonded, the entire separator interface was not uniformly impregnated even after 72 hours. [Explanation of symbols]

[0086] 10: Laminate 11: Separation membrane 12: Bend 13: Positive electrode 14: Negative electrode 15: Separation end 20: Electrode assembly 100: First press device 110: Pressure plate 111: Groove 120: Fixed part 121: Clip 200: Second press device 210: Pressure plate W A : Length of negative electrode in the transverse direction W C : Length of positive electrode in the TD direction W AS : Distance between negative electrode and bent part W CS : Distance between the positive electrode and the bent part C: Cutting point W1: Distance between the cutting point and the negative electrode W2: Distance between the cut point and the bend

Claims

1. (S10) forming a stack in which positive electrodes, separators, and negative electrodes are alternately arranged by alternately arranging positive electrodes and negative electrodes on the separator having a bent portion formed by zigzag folding; (S20) applying heat and pressure to the laminate to fix the positions of the positive electrode and the negative electrode relative to the separator; (S30) applying heat and pressure to the laminate to bond the positive electrode, the separator, and the negative electrode; (S40) cutting the side of the laminate to form an electrode assembly; the side surface includes the bent portion, The step (S40) The cutting point between the negative electrode and the bent portion is cut, A method for manufacturing an electrode assembly, wherein the ratio of the distance between the cutting point and the negative electrode to the distance between the cutting point and the bent portion is 1:8 to 1:

10.

2. The width direction length of the negative electrode is The method for manufacturing an electrode assembly according to claim 1, wherein the positive electrode has a width direction length that is 1% to 10% longer than the width direction length of the positive electrode.

3. The method of claim 1 , further comprising: (S11) wrapping an outer periphery of the laminate formed in (S10) with an end portion of the separator.

4. The step (S20) The method for manufacturing an electrode assembly according to claim 1, wherein the laminate is subjected to a pressure of 1 MPa to 6 MPa at a temperature of 50° C. to 60° C. for 1 second to 60 seconds.

5. The step (S20) The method of manufacturing an electrode assembly according to claim 4 , wherein the positive electrode and the separator, and the separator and the negative electrode are partially bonded to each other, thereby fixing the positions of the positive electrode and the negative electrode relative to the separator.

6. The step (S30) The method for manufacturing an electrode assembly according to claim 1, wherein the laminate is subjected to a pressure of 1 MPa to 6 MPa at a temperature of 50° C. to 60° C. for 1 second to 60 seconds.

7. The method of manufacturing an electrode assembly according to claim 6, wherein step (S30) completely bonds the positive electrode and the separator, and the separator and the negative electrode.

8. the side surface is made of a separation membrane including the bent portion, The method for manufacturing an electrode assembly according to claim 1 , wherein the electrode assembly does not include the bent portion.

9. The bent portion is The method for manufacturing an electrode assembly according to claim 1 , wherein the separator extends parallel to a longitudinal direction of the separator.

10. The distance between the bent portion and the negative electrode is The method for manufacturing an electrode assembly according to claim 9 , wherein the distance between the bent portion and the positive electrode is smaller than the distance between the bent portion and the positive electrode.

11. The width direction length of the negative electrode is The method for manufacturing an electrode assembly according to claim 9, wherein the distance between the bent portion and the negative electrode is 10 to 15 times the distance between the bent portion and the negative electrode.

12. The step (S40) The method for manufacturing an electrode assembly according to claim 9 , wherein the side surface is cut parallel to a height direction of the electrode assembly.

13. The electrode assembly is The distance between the end of the separation membrane and the positive electrode is The method for manufacturing an electrode assembly according to claim 12, wherein the thickness is 1.5 to 2 times the distance between the end of the separator and the negative electrode.

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