Electrode assembly

Abstract

The present application provides an electrode assembly.

Description

[Technical field]

[0001] This application claims priority to Korean Patent Application No. 10-2021-0090600, filed on July 9, 2021, Korean Patent Application No. 10-2021-0090592, filed on July 9, 2021, and Korean Patent Application No. 10-2021-0090601, filed on July 9, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly. [Background technology]

[0003] Unlike primary batteries, secondary batteries are rechargeable and have the potential to be small and have large capacity, so they have been the subject of much research and development in recent years. As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is growing rapidly.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, square batteries, and pouch-type batteries according to the shape of the battery case. The electrode assembly attached inside the battery case of a secondary battery is a power generating element capable of charging and discharging, which is made of a laminated structure of electrodes and a separator.

[0005] The electrode assemblies can be generally classified into a jelly-roll type, a stack type, and a stack-and-folding type. In the jelly-roll type, a separator is interposed between a sheet-like anode and cathode coated with an active material, and the entire arrangement is wound up. In the stack type, a number of anodes and cathodes are stacked in sequence with a separator interposed therebetween. In the stack-and-folding type, stacked unit cells are wound up with a long length of separator film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2013-0132230 Summary of the Invention [Problem to be solved by the invention]

[0007] First, the present invention provides an electrode assembly that reduces variations in adhesion and air permeability across layers while maintaining adequate adhesion and air permeability. [Means for solving the problem]

[0008] An exemplary embodiment of the present invention provides an electrode assembly. The electrode assembly according to this aspect of the present invention preferably includes a plurality of electrodes arranged in a laminate along a lamination axis, and each separation membrane portion is located between each electrode in the laminate. The plurality of electrodes includes an upper electrode located at the top of the laminate along the lamination axis, a lower electrode located at the bottom of the laminate along the lamination axis, and an intermediate electrode located between the upper electrode and the lower electrode along the lamination axis. The separation membrane portion includes an upper separation membrane portion in contact with the upper electrode, a lower separation membrane portion in contact with the lower electrode, and an intermediate separation membrane portion in contact with the intermediate electrode. The intermediate separation membrane portion may be bonded to the intermediate electrode to such an extent that a peeling force of 5 gf / 20 mm to 35 gf / 20 mm is required to peel the intermediate separation membrane portion from the intermediate electrode at a speed of 100 mm / min along the lamination axis. In addition, the upper separation membrane portion and the lower separation membrane portion may each have an air permeability value of 70 sec / 100 ml to 85 sec / 100 ml per square inch of each separation membrane portion at a pressure of 0.05 MPa and room temperature.

[0009] The present invention one According to an embodiment of the section, the separator section may be part of a long separator sheet, which may be folded between each separator section such that the long separator sheet extends between each successive electrode in the stack along a serpentine path that traverses back and forth along the transverse dimension perpendicular to the stack axis. Effect of the Invention

[0010] The electrode assembly according to an embodiment of the present invention can preferably prevent side effects such as lithium (Li) precipitation in the electrode assembly and non-filling of the electrode assembly. The electrode assembly according to an embodiment of the present invention can also have uniform performance. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view illustrating an example of an electrode assembly according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the electrode assembly of FIG. 1, showing the location of the upper surface, lower surface and middle portion of the electrode assembly. [Diagram 3] 1 is a top view showing an electrode assembly manufacturing apparatus for manufacturing an electrode assembly according to the present invention; [Figure 4] A front elevational view conceptually illustrating an apparatus for manufacturing the electrode assembly of FIG. 3 is shown. [Diagram 5] 1 is a schematic diagram showing a method for manufacturing an electrode assembly according to the present invention; [Figure 6] 1 is a perspective view of a separation membrane heating section of a separation membrane supply section according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The object, specific advantages, and novel features of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings and embodiments. In this specification, when adding reference numbers to components in each drawing, it should be noted that the same components are given the same numbers even if they are displayed in different drawings. Furthermore, the present invention may be embodied in several different forms and is not limited to the embodiments described in this specification. In addition, in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the gist of the present invention will be omitted.

[0013] 1 is a cross-sectional view of an example of an electrode assembly according to an embodiment of the present invention. That is, referring to FIG. 1, an electrode assembly 10 according to an embodiment of the present invention includes an electrode stack of one or more first electrodes 11 alternating with one or more second electrodes 12. Each electrode in the stack is separated from the others by an intervening separator membrane 14, which may be one long separator membrane 14 that is folded to repeat around each successive electrode along a serpentine or zigzag path.

[0014] The electrode assembly 10 is a chargeable and dischargeable power generating element, and the first electrode may be an anode and the second electrode may be a cathode. Alternatively, however, the first electrode may be a cathode and the second electrode may be an anode. The electrode assembly 10 may be provided in a form in which the outermost periphery is surrounded by a separator 14, for example, as shown in FIG. 1, in which the separator is surrounded by the assembled electrode assembly 10. For the electrode assembly and separator including the electrode assembly, commonly used materials may be used.

[0015] As discussed further herein, the "top surface" of the electrode assembly 10 refers to the topmost position in the stacking direction of the electrode assembly 10, designated by reference number 2 in Fig. 2. Thus, the "top surface air permeability" subsequently referred to relates to the air permeability of the separator 14 that contacts the topmost electrode in the electrode assembly. Similarly, the "top surface adhesive strength" subsequently referred to refers to the adhesive strength between the abutting portion of the topmost electrode and the separator 14 in the electrode assembly.

[0016] Furthermore, as discussed herein, the "lower surface" of the electrode assembly 10 refers to the lowermost position in the stacking direction of the electrode assembly 10, designated by reference number 3 in Fig. 2. Therefore, the "lower surface air permeability" subsequently referred to relates to the air permeability of the separator 14 in contact with the lowest electrode in the electrode assembly. Similarly, the "lower surface adhesive strength" subsequently referred to refers to the adhesive strength between the abutting portion of the separator 14 and the lowest electrode in the electrode assembly.

[0017] Finally, as discussed herein, the "middle" of the electrode assembly 10 refers to a middle position between the top and bottom surfaces of the electrode assembly 10 in the stacking direction of the electrode assembly 10, as designated by reference number 1 in FIG. 2. For example, when the electrode assembly 10 consisting of nine electrodes is viewed from the side as in FIG. 2, the "middle" position relates to the position of the fifth electrode in the stack. Thus, the "middle air permeability" subsequently referred to relates to the air permeability of the separator 14 that contacts the middle electrode in the electrode assembly. Similarly, the "middle adhesion" subsequently referred to refers to the adhesion between the abutting portion of the middle electrode and the separator 14 in the electrode assembly.

[0018] 3 and 4, an apparatus for manufacturing an electrode assembly according to an embodiment of the present invention (electrode assembly manufacturing apparatus 100) includes a stack table 110, a separation membrane supply unit 120 for supplying a separation membrane 14, a first electrode supply unit 130 for supplying a first electrode 11, a second electrode supply unit 140 for supplying a second electrode 12, a first electrode stack unit 150 for stacking the first electrode 11 on the stack table 110, a second electrode stack unit 160 for stacking the second electrode 12 on the stack table 110, and a press unit 180 for bonding the first electrode 11, the separation membrane 14, and the second electrode 12 to each other. In addition, the electrode assembly manufacturing apparatus 100 according to an embodiment of the present invention includes a holding mechanism 170 for fixing the stack (including the first electrode 11, the second electrode 12, and the separation membrane 14) to the stack table 110 by assembling the stack.

[0019] The separation membrane supply unit 120 may have a passage through which the separation membrane 14 passes toward the stack table 110. In particular, the separation membrane supply unit 120 may include a separation membrane heating unit 121 that defines a passage through which the separation membrane 14 passes toward the stack table 110. As shown in FIG. 6, the separation membrane heating unit 121 includes a pair of bodies 121a, each of which may be configured in a rectangular block shape, and the bodies 121a may be spaced apart by a distance that defines one of the dimensions of the passage through which the separation membrane 14 passes. At least one or both of the bodies 121a may further include a separation membrane heater (separator heater 121b) that transfers heat to the separation membrane 14 by heating the respective bodies 121a.

[0020] The separation membrane supply unit 120 may further include a separation membrane roll (separator roll 122) on which the separation membrane 14 is wound. Thus, the separation membrane 14 wound on the separation membrane roll 122 can be supplied to the stack table 110 by passing through the passage formed by gradually unwinding.

[0021] The first electrode supply unit 130 may further include a first electrode roll 133 on which the first electrode 11 is wound in a sheet state, a first cutter 134 which cuts the sheet-like first electrode 11 wound around the first electrode roll 133 at regular intervals to form first electrodes 11 of a predetermined size when the sheet-like first electrode 11 is unwound and supplied, a first conveyor belt 135 which moves the first electrode 11 cut by the first cutter 134, and a first electrode supply head 136 which picks up (e.g., by vacuum suction) the first electrode 11 transported by the first conveyor belt 135 and seats it on the first electrode seating table 131.

[0022] The second electrode supply unit 140 may further include a second electrode roll 143 on which the second electrode 12 is wound in sheet form, a second cutter 144 which cuts the sheet-like second electrode 12 wound around the second electrode roll 143 at regular intervals when it is unwound and supplied to form second electrodes 12 of a predetermined size, a second conveyor belt 145 which moves the second electrode 12 cut by the second cutter 144, and a second electrode supply head 146 which picks up (e.g., by vacuum suction) the second electrode 12 transported by the second conveyor belt 145 and seats it on the second electrode seating table 141.

[0023] The first electrode stacking unit 150 may be configured to stack the first electrodes 11 on the stack table 110. The first electrode stacking unit 150 may include a first suction head 151 and a first moving unit 153. The first suction head 151 picks up the first electrode 11 seated on the first electrode seating table 131 by vacuum suction via one or more vacuum suction ports (not shown) formed on the bottom surface 151b, and then the first moving unit 153 moves the first suction head 151 to the stack table 110 so that the first suction head 151 can stack the first electrode 11 on the stack table 110.

[0024] The second electrode stacking unit 160 may be configured to stack the second electrodes 12 on the stack table 110. The second electrode stacking unit 160 may have the same structure as the first electrode stacking unit 150 described above. In this case, the second electrode stacking unit 160 may include a second suction head 161 and a second moving unit 163. The second suction head 161 may pick up the second electrode 12 seated on the second electrode seating table 141 through vacuum suction. Then, the second moving unit 163 may move the second suction head 161 to the stack table 110 so that the second suction head 161 can stack the second electrode 12 on the stack table 110.

[0025] The stack table 110 may be rotatable between positions facing the first electrode stack unit 150 and the second electrode stack unit 160. By rotating the stack table 110, the holding mechanism 170 can grip the stack (including the first electrode 11, the second electrode 12, and the separation membrane 14) being assembled to fix the position of the stack relative to the stack table 110. For example, the holding mechanism 170 can apply downward pressure to the upper surface of the stack to press it toward the stack table 110. The holding mechanism 170 may include, for example, a first holder 171 and a second holder 172 that fix opposing sides of the first electrode 11 or the second electrode 12. The holders 171, 172 may each be in the form of one or more clamps or other clamping mechanisms.

[0026] As a result, the first electrode 11 is supplied from the first electrode supply unit 130 to the first electrode stacking unit 150, and the first electrode stacking unit 150 stacks the first electrode 11 on the upper surface of the separation film 14 stacked on the stacking table 110. The holding mechanism 170 then presses the upper surface of the first electrode 11 to fix the position of the first electrode 11 on the stacking table 110. Thereafter, the separation film 14 is continuously supplied, and the stack table 110 is rotated toward the second electrode stacking unit 160 to cover the upper surface of the first electrode 11. Meanwhile, the second electrode 12 is supplied from the second electrode supply unit 140, and is stacked by the second electrode stacking unit 160 on the portion where the separation film 14 covers the upper surface of the first electrode 11. Thereafter, the holding mechanism 170 releases the upper surface of the first electrode 11, and then presses the upper surface of the second electrode 12 to fix the position of the stack S to be stacked on the stacking table 110. Thereafter, the process of stacking the first electrodes 11 and the second electrodes 12 is repeated, whereby the separation membrane 14 is folded in a zigzag pattern to form a laminate S located between successive first electrodes 11 and second electrodes 12.

[0027] As a result, when the first electrode 11 is supplied from the first electrode supply unit 130 to the first electrode stack unit 150, the first electrode stack unit 150 stacks the first electrode 11 on the upper surface of the separation membrane 14 stacked on the stack table 110. Thereafter, the holding mechanism 170 presses the upper surface of the first electrode 11 to fix the position of the first electrode 11 on the stack table 110. Thereafter, when the stack table 110 rotates toward the second electrode stack unit 160, the separation membrane 14 is continuously supplied to cover the upper surface of the first electrode 11. Then, the second electrode 12 supplied from the second electrode stack unit 140 is stacked by the second electrode stack unit 160 in the portion covering the upper surface of the separation membrane 14. Thereafter, the holding mechanism 170 releases the grip on the upper surface of the first electrode 11, and then presses the upper surface of the second electrode 12 to fix the position of the stack S to be constructed relative to the stack table 110. Thereafter, the process of stacking the first electrode 11 and the second electrode 12 can be repeated to form a stack S in which the separator 14 is folded in a zigzag pattern and positioned between the continuous first electrode 11 and second electrode 12.

[0028] After the components of the electrode assembly are stacked, the electrode assembly may undergo one or more heat press operations. In particular, the electrode assembly may be moved to a press section 180 where heated pressure blocks 181, 182 advance toward each other across the stack to apply heat and pressure to the laminate. As a result, the components of the laminate (i.e., the electrodes and separator) are thermally bonded to each other, preferably preventing the completed electrode assembly from becoming dislodged or the components of the electrode assembly from shifting positions within the stack.

[0029] The heat pressing operation applied to the electrode assembly may include a first heat pressing operation, a preheating operation, and a second heat pressing operation. The first heat pressing operation involves first and second electrodes being alternately stacked between folded separators to form a laminate, and the laminate being gripped by a gripper, after which the laminate is heated and pressurized. The second heat pressing operation involves an operation after the first heat pressing operation, in which the laminate is heated and pressurized again after gripping of the stack by the gripper is discontinued. The preheating operation involves a process of heating the laminate while applying a constant pressure for a specific time between the first and second heat pressing operations.

[0030] As shown in FIG. 5, the method may first include a stacking process of assembling a stack (stack cell) on a stack table by alternately stacking the first and second electrodes on a separation membrane, in which the separation membrane is continuously supplied onto the previously stacked electrodes of the first and second electrodes before the subsequent electrodes of the first and second electrodes are stacked, and is sequentially folded onto the previously stacked electrodes. After the stacking process, the stack may be moved away from the stack table. During this time, the separation membrane is pulled, and after the separation membrane is pulled by a certain length, the separation membrane is cut. Then, a predetermined length of the cut end of the separation membrane is wound around the stack cell. The movement of the stack away from the stack table may be preferably performed by a gripper, which is a movable part, that can grip the stack on the stack table and then move the stack to the press unit 180 where the heat press operation is performed. Then, a first heat press operation is performed with the wound stack cell being gripped by the gripper. When the first heat press operation is completed, the grip of the stack cell by the gripper is released. After removing the gripper, a preheating operation is performed. After the preheating operation, a second heat pressing operation is performed. When the second heat pressing operation is completed, a finished electrode assembly can be completed.

[0031] In one embodiment of the present invention, the first heat pressing operation may include a step of heating and pressing the laminate for 5 to 20 seconds under temperature conditions of 45°C to 75°C and pressure conditions of 1 MPa to 2.5 MPa. Preferably, the first heat pressing operation may include a step of heating and pressing the laminate for 10 to 20 seconds under temperature conditions of 45°C to 65°C and pressure conditions of 1 MPa to 2 MPa. More preferably, the first heat pressing operation may include a step of heating and pressing the laminate for 10 to 20 seconds under temperature conditions of 45°C to 60°C and pressure conditions of 1 MPa to 1.5 MPa.

[0032] According to an exemplary embodiment of the present invention, the preheating operation may be an operation of heating and pressurizing the laminate for 10 to 40 seconds under pressure conditions of 0.5 MPa to 2 MPa and temperature conditions of 50°C to 85°C, preferably for 10 to 35 seconds under pressure conditions of 0.5 MPa to 1.5 MPa and temperature conditions of 55°C to 85°C.

[0033] In an embodiment of the present invention, the second heat pressing operation may include a step of heating and pressing the laminate for 5 to 10 seconds under temperature conditions of 50°C to 85°C and pressure conditions of 1 MPa to 2.5 MPa, preferably for 5 to 10 seconds under temperature conditions of 55°C to 85°C and pressure conditions of 1.5 MPa to 2.5 MPa. More preferably, the second heat pressing operation may include a step of heating and pressing the laminate for 5 to 10 seconds under temperature conditions of 50°C to 85°C and pressure conditions of 1.5 MPa to 2 MPa.

[0034] If the temperature, pressure, and time conditions described herein are not met, the components of the electrode assembly may not be firmly attached, the electrode assembly may become detached, or the components of the electrode assembly may become misaligned within the assembly, especially when the electrode assembly is moved prior to insertion into the battery case, and problems with the separator being too breathable may occur.

[0035] On the other hand, when the heat pressing operation disclosed herein is performed (including meeting each pressure, temperature and time condition), the electrode assembly may be produced without the need to separately heat and / or press each step of the electrode assembly (i.e., heat and / or press each electrode and separator pair at each step of the process) to bond the components together. Such separate heating and pressing at each step may result in detrimental effects of the heat and / or pressure building up on the lower separator of the stack as already stacked layers subsequently experience the applied heat and / or pressure, respectively. This may adversely affect such portions of the separator, for example, by reducing porosity (and breathability). In contrast, the present invention may simultaneously bond the entire electrode assembly, improving uniformity above all else. Thus, appropriate levels of adhesion between the electrodes and a separator having appropriate breathability may be simultaneously achieved while minimizing damage to the unit electrodes.

[0036] In this application, the "air permeability" of an electrode assembly refers to the air permeability of the separator component of the electrode assembly. Furthermore, unless otherwise specified, "air permeability" refers to the air permeability of all separators comprising the electrode assembly, where the air permeability of each separator may be independently the same or different.

[0037] When the air permeability range disclosed herein is satisfied, the migration rate of lithium ions in the separator of the electrode assembly can be increased while maintaining the safety of the electrode assembly. As a result, by providing a separator having the air permeability value disclosed herein, the safety, efficiency, and performance of the charge / discharge cycle of the electrode assembly can be significantly improved.

[0038] In the present invention, the method for measuring the air permeability of the separation membrane is not particularly limited. In the method further utilized and discussed in this specification, the air permeability can be measured by a method commonly used in the art. For example, the air permeability was measured by the JIS Gurley measurement method of the Japanese Industrial Standards using a Gurley type densitometer (No. 158) manufactured by Toyo Seiki. That is, the air permeability of the separation membrane can be obtained by measuring the time it takes for 100 ml (or 100 cc) of air to pass through 1 square inch of separation membrane under a pressure of 0.05 MPa at room temperature (i.e., 20°C to 25°C).

[0039] According to an embodiment of the present invention, the intermediate air permeability of the electrode assembly may be 75 sec / 100 ml to 85 sec / 100 ml.

[0040] According to one embodiment of the present invention, the upper surface air permeability of the electrode assembly may be 80 sec / 100 ml to 85 sec / 100 ml.

[0041] According to an embodiment of the present invention, the bottom air permeability of the electrode assembly may be 80 sec / 100 ml to 85 sec / 100 ml.

[0042] According to one embodiment of the present invention, the lower surface air permeability may be equal to or lower than the upper surface air permeability. Also, the intermediate air permeability may be equal to or lower than the lower surface air permeability.

[0043] That is, the magnitudes of the upper surface air permeability, the lower surface air permeability and the intermediate air permeability can satisfy the following mathematical formula 1. [Mathematical formula 1] Top air permeability ≧ Bottom air permeability ≧ Intermediate air permeability The air permeability value of Equation 1 relates to the air permeability of the separator within the electrode assembly after the heating and pressurizing steps are completed.

[0044] According to one embodiment of the present invention, the adhesive strength between the separator and the electrode at any position (ie, the upper surface, the middle surface, and the lower surface) in the electrode assembly may be in the range of 5 gf / 20 mm to 30 gf / 20 mm.

[0045] In the present invention, the method of measuring the adhesive strength of the separator is not particularly limited. For example, the lower, middle and upper samples of the electrode assembly may be separated from the laminate. Such samples may include an anode and a separator, or a cathode and a separator. The samples, which may be 55 mm wide and 20 mm long, are attached to respective glass slides with the electrodes positioned on the adhesive surfaces of the glass slides. Next, the samples were tested by carrying out a 90° peel test at a speed of 100 mm / min according to the test method specified in ASTM-D6862. That is, the edge of the separator is pulled upward at 90° to the glass slide at a speed of 100 mm / min, and the separator is peeled off from the electrodes along the width direction of the sample (i.e., peeling from 0 mm to 55 mm).

[0046] According to an embodiment of the present invention, the intermediate adhesive strength of the electrode assembly may be 5gf / 20mm to 10gf / 20mm.

[0047] According to an embodiment of the present invention, the upper surface adhesive strength of the electrode assembly may be 5 gf / 20 mm to 30 gf / 20 mm.

[0048] According to an embodiment of the present invention, the lower surface adhesive strength of the electrode assembly may be 5 gf / 20 mm to 30 gf / 20 mm.

[0049] According to one embodiment of the present invention, the adhesive strength between the anode and the separator and the adhesive strength between the cathode and the separator may be the same or different.

[0050] According to an embodiment of the present invention, the deviation between the middle adhesive strength of the electrode assembly and the upper adhesive strength or the lower adhesive strength of the electrode assembly may be 3 gf / 20 mm to 20 gf / 20 mm.

[0051] According to an embodiment of the present invention, the deviation between the intermediate air permeability of the electrode assembly and the upper surface air permeability or the lower surface air permeability of the electrode assembly may be 3 sec / 100 ml to 20 sec / 100 ml.

[0052] When the above conditions of air permeability and adhesive strength are satisfied, not only cleaning and process handling are easy, but also wetting of the separator with the electrolyte is easy, so that an electrode assembly with uniform performance can be manufactured. Also, side effects such as lithium (Li) deposition in the electrode assembly and non-charging of the electrode assembly can be prevented.

[0053] The withstand voltage of the electrode assembly of the present invention may be 1.5 kV to 1.8 kV. The electrode assembly of the present invention is manufactured by a manufacturing method for an electrode assembly including a first heat pressing operation, a preheating operation, and a second heat pressing operation, and therefore, superior adhesive strength and superior withstand voltage can be obtained at the same time, compared to a case where only the first heat pressing is performed.

[0054] Although the present invention has been described in detail with reference to specific exemplary embodiments, it is to be understood that the present invention is not limited thereto, and that various implementations are possible within the technical concept of the present invention by those skilled in the art.

[0055] 1) Example 1 Nineteen anode sheets, 20 cathode sheets and a long separation membrane were supplied to the stack table from the anode supply section, cathode supply section and separation membrane supply section, respectively.

[0056] More specifically, the anode and cathode were supplied in the form of cuts from an anode sheet and a cathode sheet, respectively, and the long separator was supplied in the form of a separator sheet. Then, as described above, the stack table was rotated to stack the anode and cathode, and the supplied separator was folded. At this time, a holding mechanism was used to press and stabilize the stack on the stack table, producing a stack including 39 electrodes.

[0057] After preparing the laminate, the laminate was gripped with a gripper and pressed for 15 seconds under heating conditions of a temperature of 50° C. and a pressure of 1.46 MPa to carry out a first heat pressing step.

[0058] After the first heat pressing step, the gripper was separated from the laminate, and a preheating operation was performed in which the temperature of the pressure block of the press section was maintained at 60°C and a pressure (pressure condition) of 1 MPa was applied to the laminate by the pressure block of the press section for 15 seconds (press time).

[0059] After the preheating operation, the temperature of the pressure block was maintained at 60°C, and a second heat press operation was performed in which the pressure block of the press section applied a pressure of 1.8 MPa (pressure condition) to the laminate for 7 seconds (press time).

[0060] 2) Examples 2 to 12 and Comparative Examples 1 to 6 The electrode assemblies of Examples 2 to 5 were manufactured in the same manner as the electrode assembly of Example 1, except that the temperature conditions, pressure conditions, and pressing times were as shown in Table 1 below.

[0061] The electrode assemblies of Comparative Examples 1 to 17 were manufactured by carrying out the first and second heat pressing operations in the same manner as the manufacturing method of the electrode assembly of Example 1, except that the operations were carried out under the temperature conditions, pressure conditions, and pressing times shown in the following Tables 2 and 3. That is, in the cases of Comparative Examples 1 to 12, the preheating operation was not carried out.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] 3) Experimental Example 1 - Adhesion Strength Evaluation After disassembling (i.e., separating layers) the electrode assemblies of Examples 1 to 6 and Comparative Examples 4, 8, and 11 to 17, the separated layers were analyzed to measure the adhesive strength between the upper, lower, and middle surfaces of the laminate S. Specifically, the adhesive strength between the cathode located at the bottom of the laminate and the separator was measured. In addition, the adhesive strength between the cathode located at the top of the laminate and the separator was measured. Finally, the adhesive strength between the cathode located at the middle position along the stacking direction of the laminate and the separator was measured.

[0066] In each of the separated electrode assemblies, the collected cathode and separator had a width of 55 mm and a length of 20 mm. The sampled samples were attached to a glass slide with the electrode positioned on the adhesive side of the glass slide. The glass slide with the sample attached was then mounted on an adhesion measuring device and tested at a 90° peel test at a speed of 100 mm / min according to the test method described in ASTM-D6862 as described above. After discounting for initial significant fluctuations, the value for the force applied per sample width (g / mm) was measured while the separator was peeled off the electrode.

[0067] The results are shown in Table 4 below.

[0068] [Table 4]

[0069] From the results in Table 4, it was confirmed that in Comparative Examples 4, 8, 11, and 12, in which the second heat press operation was performed at 3 MPa (pressure condition of 2.5 MPa or more) without preheating, at least one adhesive strength value at different positions of the electrode assembly exceeded 35 gf / 20 mm.

[0070] In addition, through Comparative Examples 12 to 17, it was confirmed that the adhesive strength value of at least one of the different positions on the electrode assembly exceeded 35 gf / 20 mm when preheating was performed or when the second heat press operation was performed at 3 MPa (pressure condition of 2.5 MPa or more).

[0071] In particular, in the case of Comparative Examples 14 and 16, in which the preheating time exceeded 30 seconds while satisfying the preheating pressure and temperature conditions of the electrode assembly of the present invention, and in the case of Comparative Example 17, in which the preheating operation was performed but none of the preheating pressure, temperature and time conditions of the electrode assembly of the present invention were satisfied, it was confirmed that one of the adhesive strength values ​​at different positions on the electrode assembly greatly exceeded 35 gf / 20 mm.

[0072] If the adhesive strength of the electrode assembly exceeds 35 gf / 20 mm, there are disadvantages in that cleaning and processing are not easy (thus, processing costs may increase) and breathability is poor (thus, it is difficult to manufacture an electrode assembly with uniform electrolyte wettability).

[0073] Meanwhile, when an electrode assembly is manufactured using the manufacturing method of the electrode assembly of the present invention, cleaning and process handling are easy, and uniform performance of the electrode assembly was confirmed.

[0074] Moreover, in the cases of Examples 1 to 4, it was confirmed that the variation in adhesive strength was small, and therefore such electrode assemblies had more uniform performance.

[0075] 4) Experimental example 1 - Voltage resistance evaluation The withstand voltages of the electrode assemblies of Comparative Examples 2, 5, 6, 9 and 10 (the pressure conditions of the secondary heat press were the same as those of Examples 1 to 5, and the total pressing time was the same or similar to those of Examples 1 to 5) as well as those of Examples 1 to 5 were measured.

[0076] In particular, the voltage applied to the electrode assemblies of Examples 1 to 5 and Comparative Examples 2, 5, 6, 9, and 10 was increased from 9 V to 4000 V, and the voltage value at which the leakage current became 0.6 mA or more was measured and determined as the withstand voltage value.

[0077] The results are shown in Table 5 below.

[0078] [Table 5]

[0079] Generally, the primary factor causing damage to electrode assemblies is pressure conditions.

[0080] From the results in Table 5, it was confirmed that Examples 1 to 5 (electrode assemblies of the present invention) have superior voltage resistance performance compared to Comparative Examples 2, 5, 6, 9 and 10 (cases in which the pressure conditions of the secondary heat press were the same, and the total time of heating and pressing (total pressing time) was the same throughout the entire process, but the preheating operation was omitted). [Explanation of symbols]

[0081] 10...electrode assembly 11...1st electrode 11a First electrode tab 12...Second electrode 12a Second electrode tab 14...Separation membrane 100...Electrode assembly manufacturing equipment 110 Stack Table 120...Separation membrane supply section 121 Separation membrane heating section 121a Body 121b Separator heater 122 Separator roll 130...1st electrode supply section 131 First electrode seating table 133 First electrode roll 134 First cutter 135 No. 1 Conveyor Belt 136 First electrode supply head 140...Second electrode supply section 141 Second electrode seating table 143 Second electrode roll 144 No. 2 cutter 145 - Second conveyor belt 146 Second electrode supply head 150 First electrode stack section 151 1st suction head 151a Vacuum inlet 151b...Bottom surface 153 First moving part 160 Second electrode stack section 161 Second suction head 163 Second moving part 170 ···Holding mechanism 171 ···First Holder 172 2nd Holder 180 ···Press Department 181, 182: Pressure block S ···Laminate

Claims

1. an electrode assembly including a plurality of electrodes arranged along a lamination axis of the laminate, with each separation membrane portion being located between each electrode in the laminate, the plurality of electrodes including an upper electrode located at an upper portion of the laminate along the lamination axis, a lower electrode located at a lower portion of the laminate along the lamination axis, and an intermediate electrode located between the upper electrode and the lower electrode along the lamination axis, the electrode assembly including an upper separation membrane portion in contact with the upper electrode, a lower separation membrane portion in contact with the lower electrode, and an intermediate separation membrane portion in contact with the intermediate electrode, the intermediate separation membrane part is adhered to the intermediate electrode to such an extent that a peeling force of 5 gf / 20 mm to 35 gf / 20 mm is required to peel the intermediate separation membrane part from the intermediate electrode at a speed of 100 mm / min along the lamination axis; The upper separation membrane portion and the lower separation membrane portion each have an air permeability value of 80 sec / 100 ml to 85 sec / 100 ml per square inch of each separation membrane portion at a pressure of 0.05 MPa and room temperature, The intermediate separation membrane portion has an air permeability value of 75 sec / 100 ml to 85 sec / 100 ml per square inch of each separation membrane portion at a pressure of 0.05 MPa and room temperature; The magnitudes of the top surface air permeability, which is the air permeability of the separator in contact with the uppermost electrode in the electrode assembly, the bottom surface air permeability, which is the air permeability of the separator in contact with the lowest electrode in the electrode assembly, and the middle air permeability, which is the air permeability of the separator in contact with the middle electrode in the electrode assembly, satisfy the following mathematical formula 1: [Mathematical formula 1] Top air permeability ≧ Bottom air permeability ≧ Intermediate air permeability Electrode assembly.

2. 2. The electrode assembly of claim 1, wherein the separator sections are portions of a long separator sheet that is folded between each separator section such that the long separator sheet extends between each successive electrode in the stack along a serpentine path that traverses back and forth along a transverse dimension perpendicular to the stacking axis.

3. 2. The electrode assembly of claim 1, wherein the upper isolation membrane portion is adhered to the upper electrode with a peeling force of 5 gf / 20 mm to 30 gf / 20 mm required to peel the upper isolation membrane portion from the upper electrode at a speed of 100 mm / min along the lamination axis.

4. 2. The electrode assembly of claim 1, wherein the lower separation membrane portion is adhered to the lower electrode with a peeling force of 5 gf / 20 mm to 30 gf / 20 mm required to peel the lower separation membrane portion from the lower electrode at a speed of 100 mm / min along the lamination axis.

5. 2. The electrode assembly of claim 1, wherein the upper isolation membrane portion and the lower isolation membrane portion are bonded to the upper electrode and the lower electrode, respectively, at a rate of 100 mm / min along their respective lamination axes, such that a second peel force per 20 mm width is required to peel the upper isolation membrane portion and the lower isolation membrane portion from the upper electrode and the lower electrode, respectively, and a deviation between the peel force of the intermediate isolation membrane portion and the second peel force is 3 gf / 20 mm to 20 gf / 20 mm.

6. 6. The electrode assembly according to claim 1, wherein the intermediate separation membrane portion has a second air permeability value per square inch of each separation membrane portion at a pressure of 0.05 MPa and room temperature, and the second air permeability value is a deviation of the air permeability value per square inch of each separation membrane portion of the upper separation membrane portion and the lower separation membrane portion at a pressure of 0.05 MPa and room temperature of 3 sec / 100 ml to 20 sec / 100 ml.

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