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, the method being for improving the electrolyte wetting of the electrode assembly. [Background technology]

[0003] Electrochemical elements convert chemical energy into electrical energy using electrochemical reactions, and in recent years, lithium secondary batteries, which have high energy density and voltage, long cycle life, and can be used in a variety of fields, have been widely used. In recent years, the demand for electric vehicles and energy storage devices has increased, and materials and structures have been developed 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. The secondary battery may be classified into a pouch type, a cylindrical type, a square type, a coin type, etc. depending on the shape of the case in which the electrode assembly is housed, and may be classified into a jelly roll type, a stack type, etc. depending on the manufacturing method and shape of the electrode assembly.

[0005] A stack-type electrode assembly is manufactured by stacking a plurality of positive electrodes, separators, and negative electrodes prepared in a predetermined size, but the transportation of the individual electrodes and separators is complicated, and it is difficult to maintain a constant arrangement during stacking, resulting in low productivity. For this reason, a zigzag stacking type electrode assembly has been developed in which a long sheet-like separator is folded in a zigzag shape and positive and negative electrodes are alternately arranged between adjacent folds. For example, a zigzag type 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 shape and arrange each electrode between the electrodes. Zigzag stacking is simple compared to the conventional contrast step, has excellent productivity, and can stably maintain a stacked structure even if the adhesive strength of the separator is relatively low.

[0006] In general, when zigzag stacking, the separator is bent at a certain interval to form bendings, and this interval is set larger than the width of the positive and negative electrodes to ensure a margin. Therefore, the zigzag electrode assembly includes a region where a bent portion consisting of only the separator is stacked on both sides, and since this region has an empty space compared to the region where the electrode and the separator are stacked together and is not fixed, it may be folded or sagged, making it difficult to insert the electrode assembly into a case or pouch. To solve this problem, heat and pressure are applied to the bent portion to bond the bent portion and / or the adjacent bent portion. However, during the process of bonding the separator, the pores formed in the separator are closed, resulting in low air permeability, high resistance, and low 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-type electrode assembly having a structure in which the separator bending is not folded or dropped off, the separator bending is easily inserted into a case or pouch, and the separator wettability with respect to an electrolyte is excellent. [Means for solving the problem]

[0008] One aspect of the present invention provides a method for manufacturing an electrode assembly, the method including: (S10) arranging positive and negative electrodes alternately on a separator having a bent portion formed by folding in a zigzag pattern to form a stack in which the positive electrodes, separators, and negative electrodes are arranged alternately; (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 negative electrode may have a widthwise length that is 1% to 10% longer than the widthwise length 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 a step of applying a pressure of 1 MPa to 6 MPa to the laminate at a temperature of 50° C. to 60° C. for 1 to 60 seconds.

[0012] In the method for manufacturing the electrode assembly, the 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 a step of applying 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 made 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 parallel to a height direction.

[0020] In the method for manufacturing the electrode assembly, the step (S40) is to cut a cutting point between the negative electrode and the bent portion, and a ratio of a distance between the cutting point and the negative electrode and a 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. Effect of the Invention

[0023] The manufacturing method of the present invention has excellent productivity for producing a zigzag-type electrode assembly, and provides an electrode assembly having a structure in which a separator is not broken or uneven, 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, so that dendritic precipitation of lithium from the separator can be prevented or minimized. [Brief description of the drawings]

[0025] [Figure 1] 4 is a conceptual diagram illustrating a step of applying pressure to a stack during a manufacturing process of an electrode assembly according to an embodiment of the present invention to fix the positions of a positive electrode and a negative electrode relative to a separator. [Diagram 2] 4 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 in a process for manufacturing an electrode assembly according to an embodiment of the present invention. FIG. [Diagram 3] 1 is a conceptual diagram showing a cross section of a laminate in a manufacturing stage of a conventional electrode assembly. [Figure 4] 4 is a conceptual diagram showing a cross section of a laminate in a process of manufacturing an electrode assembly according to an embodiment of the present invention. [Diagram 5] 4 is a conceptual diagram showing 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 PREFERRED EMBODIMENTS

[0026] Hereinafter, each component of the present invention will be described in more detail so that a person having ordinary knowledge in the technical field to which the present invention belongs 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" are used to mean a numerical value or degree range or approximation thereof, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly using the disclosure 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 a pouch type, a cylindrical type, a square type, or a coin type, but is not limited to these specific shapes.

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

[0031] The term "electrode" as used herein collectively refers to a "positive electrode" and a "negative electrode" and may mean that an electrode active material is applied to at least one surface of a material having electrical conductivity without inducing a chemical change in an electrochemical device, and then dried. The material and the electrode active material are not limited in type as long as they 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 schematic in order to explain or emphasize the contents of the embodiment of the present invention.

[0034] According to an embodiment of the present invention, there is provided 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 being zigzag folded, (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, the separators, and the negative electrodes, and (S40) cutting a side of the stack to form an electrode assembly, the side including 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 disposing a positive electrode and a negative electrode on the separator with the bent portion formed thereon to form a stack in which the positive electrode, the separator, and the negative electrode are alternately disposed.

[0036] In the step (S10), the separator may have a length in a longitudinal direction (or MD; machine direction) longer than a length in a 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 to each other and longer than the width direction length of the positive electrode or negative electrode.

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

[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 length W of the positive electrode in the TD directionC Based on this, the TD direction length W of the positive electrode C If the length is less than this range, repeated use of the electrochemical device may cause a problem in that lithium is precipitated in a dendritic form on the surface of the negative electrode. If the length exceeds this range, the effect of preventing lithium precipitation is no longer improved, and a problem may occur in that it becomes difficult to uniformly arrange the electrodes in the electrode assembly.

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

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

[0041] The separation membrane may have a length in the MD direction longer than that in the TD direction, and is zigzag-folded at predetermined intervals along the MD direction to form a plurality of bent portions, but the end portions may extend without being bent. Referring to Figs. 3 to 5, the end portions 15 of the separation membrane may wrap the outer circumferential surface of the laminate 10 one or more times, and the interfaces between the electrodes 13 and 14 and the separation membrane 11 constituting the laminate 10 are compressed by the wrapping pressure of the end portions 15, thereby maintaining stable contact between the electrodes and the separation membrane. For example, the end portions 15 of the separation membrane may wrap the bent portions 12 located on both sides of the laminate.

[0042] In the step S20, pressure is applied to the laminate formed in the 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 part 120 that holds the laminate 10 while the pressing plate 110 presses the laminate 10.

[0044] The laminate 10 includes a structure in which a positive electrode, a separator, and a negative electrode are alternately stacked through the step (S10) or the step (S11), but the position of the positive electrode or the negative electrode relative to the separator is not completely fixed. The laminate 10 may be disposed between the upper and lower pressing plates 110 while being sandwiched between one or more clips 121 provided on the fixing part 120. The pressing plate 110 may have a groove 111 at a position corresponding to the clip 121, and the clip 121 may press only the laminate 10 fixed to the clip 121 without applying pressure. The first pressing device 100 may bond the separator and the electrode stacked in the remaining part of the laminate 10 excluding the part captured by the clip 121. The shape and number of the pressing plate 110, the clip 121, etc. are not limited to those shown in FIG. 1.

[0045] The step (S20) may be a step of 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 be a step of 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) induces 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 fix the electrode in a position where the center line of the TD length of the electrode and the center line of the space between the adjacent bent portions of the separator coincide with each other. 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 range of adhesive strength. If the pressure is less than 1 MPa, the position of the electrode is not fixed, and the electrode may come off from the fixed position during handling of the laminate 10. 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, which may cause problems with the air permeability and electrical resistance of the separator.

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

[0047] In step S30, the positive electrode, the separator, and the negative electrode are bonded to the laminate 10 compressed in step S20 by applying heat and pressure.

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

[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 thermocompression bonding both sides 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 a laminate in which the electrodes and the separator are partially bonded to each other through the step (S20) and the positions of the electrodes relative to the separator are fixed, but the separator and the electrodes are not completely bonded to each other. The laminate 10 may be disposed between upper and lower pressure plates 210, and the pressure plates 210 may thermocompress both sides of the laminate 10. The second press device 200 may thermocompress both sides of the laminate 10, including the parts that were not pressed by being held by the 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] The step (S30) may be a step of 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 (S30) may be a step of 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, the step (S30) may apply a higher temperature and pressure than the step (S20). The 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 and use of the electrochemical device, causing 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, causing problems in the air permeability and electrical resistance of the separator.

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

[0053] The step (S40) is a step of cutting the side of the laminate 10 thermocompression-bonded in the step (S30) to form an electrode assembly. Figures 3 to 5 are conceptual diagrams showing a cross section of the laminate 10 after the step (S30) in Figure 2, viewed from the direction A. The laminate 10 may have a length in the MD direction longer than its length in the TD direction, and the direction A 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 laminated 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 a positive electrode 13 and a negative electrode 14 are alternately arranged with a separator 11 sandwiched therebetween, and the separator 11 may include one or more bent portions 12 formed by folding in a zigzag pattern. For example, the TD-direction length W 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 A and the length W of the part consisting only of the separation membrane 11 S The portion consisting only of 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 electrode is not disposed and an empty space may be included. If the laminate 10 is immediately inserted into a case, the portion consisting only of the separation membrane 11 may be inserted in a folded state, or the separation membrane 11 may be torn due to its rattling. Conventionally, heat and pressure (P) are applied from above and below (in a direction parallel to the Z direction) to the portion consisting only of the separation membrane 11 to bond adjacent separation membranes 11, and the length W S The strength of the separator 11 corresponding to the above-mentioned point was improved to prevent folding and falling off. However, in the process of bonding the separators 11 together, the pore structure formed in the separator 11 collapsed, reducing the air permeability, which caused a problem that the separator 11 was difficult to impregnate with the electrolyte.

[0056] 4 and 5 are means for solving the problems of the prior art as shown in FIG. 3, and are conceptual diagrams showing the step (S40), and FIG.

[0057] 4 to 6, the 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 may include a bent portion 12, and preferably, the step (S40) may involve cutting both sides of the laminate 10. The electrode assembly 20 formed according to the step (S40) may not include the bent portion 12.

[0058] The cutting can be performed by press cutting, laser, heat rays, 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 direction may be parallel to the height direction of the electrode assembly 20. During the cutting, only the separator 11 can be cut while the part 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 the conventional zigzag type electrode assembly.

[0060] Specifically, the distance W between the bent portion 12 and the negative electrode 14 in the laminate 10 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 is left 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 may be 10 to 15 times the length W of the negative electrode 14 in the TD direction. A The distance W between the bent portion 12 and the negative electrode AS When 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 part of the separator 11 is bent toward the electrode during the cutting process. A The distance W between the bent portion 12 and the negative electrode AS If the cutting speed exceeds 15 times, the separation membrane 11 will be torn during the cutting process.

[0062] Specifically, step S40 is to cut a cutting point C between the negative electrode 14 and the bent portion 12, and a ratio of a distance W1 between the cutting point C and the negative electrode 14 and a distance W2 between the cutting point C and the bent portion 12 may be 1:8 to 1:10. If W1:W2 is less than 1:8, at least a portion of the separator 11 is bent toward the electrode during the cutting process. If W1:W2 is more than 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, and therefore has an appearance similar to a conventional stack-type electrode assembly. However, in a stack-type (Lamination and Stack) electrode assembly, the separator and the electrode are not uniformly bonded to each other in the process of quickly laminating the separator and the electrode without going through a step of fixing the electrode position relative to the separator.

[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 stack-type electrode assemblies, and can prevent folding or falling off of the separator and reduce defects when inserted into a case.

[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-type, or pouch-type lithium secondary battery. The lithium secondary battery may be packed or modularized as a unit cell and used in battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), power storage devices, and the like.

[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 an inorganic substance and a binder was prepared, and 30 positive electrodes and 31 negative electrodes with a size of 90 mm x 315 mm and 95.5 mm x 320 mm were prepared. The separator was zigzag-contacted 20 times at 98.5 mm intervals, and the positive and negative electrodes were arranged in order while folding the separator, leaving the end portion, to prepare a stack. The interval between the negative electrode and the bent portion of the separator in the stack was 30 mm, and the interval between the positive electrode and the bent portion was 32.75 mm. The stack was wound once at the end portion 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 bend (W AS ) and cut point C was set at a point where the ratio of the distance W1 from the negative electrode to the cut point C and the distance W2 from the cut point C to the bent part was 1:9. Both side surfaces 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 thermocompression-bonded in the same manner.

[0073] Referring to FIG. 3, the portions W S The top and bottom were then heat-pressed 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 bend AS Both side surfaces of the laminate were cut by press cutting at a cutting point C where the ratio of a distance W1 from the negative electrode to the cutting point C and a 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 bend (W AS ) and cut both sides of the laminate by press cutting, with the cutting point C being a point where the ratio of the distance (W1) from the negative electrode to the cutting point C and the distance (W2) from the cutting point C to the bent portion being 1:11. 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 condition 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 confirmed. Then, the electrode assembly was fully inserted into the pouch and pulled out again to visually confirm the state of the separation membrane. The results (◯: no damage, △: separation membrane folded, ×: separation membrane broken) are summarized in Table 1 below.

[0079] [Table 1]

[0080] As shown in Table 1, in Comparative Example 2, which is a stack-type electrode assembly, the separator was found to be folded at the corners in the MD direction immediately after manufacture. In Example 1 and Comparative Example 1, which are zigzag-type electrode assemblies that have an additional step to prevent separator folding, the separator was in perfect condition immediately after manufacture and after insertion into the pouch.

[0081] However, in Comparative Examples 3 to 6 in which the dimensions of the separator and the negative electrode were adjusted and cut differently from those of the embodiment of the present invention, the separator broke during the cutting step, 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 preparing 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 interfaces between the electrodes and the separator. The time (hr) until the entire separator interface was impregnated with the electrolyte was confirmed and is 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 heat-pressed, 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: Separated membrane 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 TD direction W C : Length of positive electrode in 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 cut 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 a side of the laminate to form an electrode assembly, The side surface includes the bent portion.

2. The width direction length of the negative electrode is The method for manufacturing an electrode assembly according to claim 1, wherein the length of the positive electrode is 1% to 10% longer than the width 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 for manufacturing an electrode assembly according to claim 4 , further comprising partially bonding the positive electrode and the separator, and the separator and the negative electrode, respectively, to fix 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 claim 6, wherein in step S30, the positive electrode and the separator, and the separator and the negative electrode are completely bonded to each other.

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 first and second electrodes extend 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 step (S40) cutting the cutting point between the negative electrode and the bent portion, The method of claim 12, wherein a ratio between a distance between the cut point and the negative electrode and a distance between the cut point and the bent portion is 1:8 to 1:

10.

14. The electrode assembly includes: 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.

15. An electrode assembly produced by the method according to any one of claims 1 to 14.

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