CN116724431A - Electrode assembly - Google Patents

Abstract

An electrode assembly includes a plurality of electrodes arranged in a stack along a stacking axis, and respective membrane portions of an elongated membrane sheet are positioned between and wound around each electrode in the stack along a serpentine path. The middle one of the separator parts may be bonded to the middle one of the electrodes such that in order to peel the middle separator part from the middle electrode at a speed of 100mm/min along the stacking axis, a peeling force in the range of from 5gf to 35gf per 20mm width applied to the edge of the middle separator part will be spent. Further, the top and bottom ones of the membrane portions may each have a gas permeability value of from 70sec/100ml to 85sec/100ml at a pressure of 0.05MPa and a room temperature per square inch.

Description

Electrode assembly

Technical Field

The present application claims priority from korean patent application No.10-2021-0090600 filed on 7.9 of 2021, korean patent application No.10-2021-0090592 filed on 7.9, and korean patent application No.10-2021-0090601 filed on 7.9 of 2021, the entire contents of which are incorporated herein by reference.

The present application relates to an electrode assembly.

Background

Unlike primary batteries, secondary batteries are rechargeable, and have been widely studied and developed in recent years due to their small size and large capacity. As the technological development and demand for mobile devices have increased, the demand for secondary batteries as an energy source has also been rapidly increasing.

Secondary batteries may be classified into button-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries according to the shape of a battery case. In the secondary battery, an electrode assembly mounted inside a battery case is a chargeable/dischargeable power generating element having a stacked structure including electrodes and separators.

The electrode assembly may be generally classified into a jelly-roll type (jelly-roll type), a stack type, and a stack and fold type. In the jelly-roll type, a separator is interposed between a sheet-type positive electrode and a sheet-type negative electrode, each of the sheet-type positive electrode and the sheet-type negative electrode is coated with an active material, and the entire arrangement is wound. In the stack type, a plurality of positive electrodes and negative electrodes are sequentially stacked with a separator interposed therebetween. In the stack and fold type, the stacked unit cells are wound with long length separation films.

[ Prior Art literature ]

[ patent literature ]

Korean patent application laid-open No. 10-2013-01332230

Disclosure of Invention

Technical problem

The present application provides, inter alia, an electrode assembly having reduced deviations in adhesion and gas permeability on each layer while still maintaining adequate adhesion and gas permeability.

Solution to the problem

An exemplary aspect of the present application provides an electrode assembly. The electrode assembly according to this aspect of the application includes: a plurality of electrodes arranged in a stack along a stacking axis with respective separator portions between each electrode in the stack. The plurality of electrodes includes a top electrode positioned at a top of the stack along the stacking axis, a bottom electrode positioned at a bottom of the stack along the stacking axis, and an intermediate electrode disposed between the top electrode and the bottom electrode along the stacking axis. The membrane portion includes a top membrane portion contiguous with the top electrode, a bottom membrane portion contiguous with the bottom electrode, and an intermediate membrane portion contiguous with the intermediate electrode. The intermediate separator portion may be bonded to the intermediate electrode to the extent that: in order to peel the intermediate separator portion from the intermediate electrode at a speed of 100mm/min along the stacking axis, a peeling force in the range of from 5gf to 35gf per 20mm width of the intermediate separator portion applied to the edge of the intermediate separator portion would be spent. Further, the top membrane portion and the bottom membrane portion each have a gas permeability value of 70sec/100ml to 85sec/100ml per square inch of the corresponding membrane portion at a pressure of 0.05MPa and room temperature.

According to some aspects of the application, the membrane portion may be part of an elongated membrane sheet. Such an elongated diaphragm sheet may be folded between each diaphragm portion such that the elongated diaphragm sheet follows a serpentine path traversing back and forth along an orthogonal dimension (orthogonal dimension) orthogonal to the stacking axis to extend between each of the successive electrodes in the stack.

Advantageous effects of the application

The electrode assembly according to the exemplary aspects of the present application desirably can prevent side effects such as precipitation of lithium (Li) in the electrode assembly and non-charging of the electrode assembly. The electrode assembly according to the exemplary embodiment of the present application may also have uniform performance.

Drawings

Fig. 1 is a cross-sectional view illustrating an example of an electrode assembly according to an exemplary embodiment of the present application.

Fig. 2 is a sectional view of the electrode assembly of fig. 1, showing the positions of the upper surface, the lower surface, and the middle portion of the electrode assembly.

Fig. 3 is a top view illustrating an electrode assembly manufacturing apparatus for manufacturing an electrode assembly according to the present application.

Fig. 4 is a front view conceptually illustrating the electrode assembly manufacturing apparatus of fig. 3.

Fig. 5 is a view schematically showing an electrode assembly manufacturing method for manufacturing an electrode assembly according to the present application.

Fig. 6 is a perspective view of a diaphragm heating unit of a diaphragm supply unit according to an exemplary embodiment of the present application.

< reference numerals >

10: assembled electrode assembly

11: first electrode

12: second electrode

14: diaphragm

100: apparatus for manufacturing electrode assembly

110: stacking table

111: table BODY (TABLE BODY)

112: stack table heater (STACK TABLE HEATER)

120: diaphragm supply unit

121: diaphragm heating unit

121a: main body

121b: diaphragm heater

122: diaphragm roller (SEPARATOR ROLL)

130: first electrode supply unit

131: first electrode mounting TABLE (SEATING TABLE)

133: first electrode roller

134: first cutter

135: first conveyor belt

136: first electrode supply head

140: second electrode supply unit

141: second electrode mounting table

143: second electrode roller

144: second cutter

145: second conveyor belt

146: second electrode supply head

150: first electrode stacking unit

151: first SUCTION HEAD (SUCTION HEAD)

151a: vacuum suction port

151b: bottom surface

153: first mobile unit

160: second electrode stacking unit

161: second suction head

163: second mobile unit

170: holding mechanism

171: first holder

172: second retainer

180: pressing UNIT (PRESS UNIT)

181. 182: press block

S: stack

Detailed Description

The objects, specific advantages and novel features of the application will become more apparent from the following detailed description of illustrative embodiments when considered in conjunction with the drawings. In this specification, when reference numerals are added to constituent elements of each drawing, it should be noted that the same constituent elements are given the same numerals even though they are shown in different drawings. Furthermore, the present application may be embodied in several different forms and is not limited to the exemplary embodiments described herein. Further, in describing the present application, detailed descriptions of related known techniques that may unnecessarily obscure the gist of the present application will be omitted.

Fig. 1 is a cross-sectional view illustrating an example of an electrode assembly according to an exemplary embodiment of the present application. That is, referring to fig. 1, an electrode assembly 10 according to an exemplary embodiment of the present application includes a stack of electrodes in which one or more first electrodes 11 alternate with one or more second electrodes 12. Each electrode in the stack is separated from each other by a separator 14 located therebetween, and the separator 14 may be a single elongated separator 14 that is repeatedly folded so as to follow a serpentine or zig-zag path around each successive electrode.

The electrode assembly 10 is a chargeable/dischargeable power generating element, wherein the first electrode may be a positive electrode and the second electrode may be a negative electrode. Alternatively, however, the first electrode may be a negative electrode and the second electrode may be a positive electrode. Further, the electrode assembly 10 may be provided in a form in which the outermost portion is surrounded by the separator 14 (e.g., by winding the separator around the assembled electrode assembly 10), as shown in fig. 1. As for the electrode and the separator including the electrode assembly, materials commonly used in the art may be used.

As further discussed herein, the "upper surface" of the electrode assembly 10 refers to the uppermost position of the electrode assembly 10 in the stacking direction of the electrode assembly, which is denoted by reference numeral 2 in fig. 2. Accordingly, subsequent reference to "upper surface breathability" relates to the breathability of the separator 14 adjacent to the uppermost electrode in the electrode assembly. Likewise, a subsequent reference to "upper surface adhesion" refers to the adhesion between the uppermost electrode in the electrode assembly and the adjoining portion of the separator 14.

Further, as discussed herein, the "lower surface" of the electrode assembly 10 refers to the lowermost position of the electrode assembly 10 in the stacking direction of the electrode assembly, which is denoted by reference numeral 3 in fig. 2. Accordingly, subsequent reference to "lower surface gas permeability" relates to the gas permeability of the separator 14 adjacent to the lowermost electrode in the electrode assembly. Likewise, a subsequent reference to "lower surface adhesion" refers to the adhesion between the lowermost electrode in the electrode assembly and the adjoining portion of separator 14.

Finally, as discussed herein, the "middle" of the electrode assembly 10 refers to a middle position between the upper and lower surfaces of the electrode assembly 10 in the stacking direction of the electrode assembly, as shown by reference numeral 1 in fig. 2. For example, when the electrode assembly 10 is formed of nine electrodes and is viewed from the side, as shown in fig. 2, the "middle" position relates to the position of the fifth electrode in the stack. Accordingly, a subsequent reference to "intermediate gas permeability" relates to the gas permeability of the separator 14 adjacent to the intermediate electrode in the electrode assembly. Likewise, subsequent reference to "intermediate adhesion" refers to adhesion between the intermediate electrode in the electrode assembly and the adjoining portion of the separator 14.

Referring to fig. 3 and 4, an apparatus 100 for manufacturing an electrode assembly according to an exemplary embodiment of the present application includes: a stacking stage 110; a diaphragm supply unit 120 for supplying the diaphragm 14; a first electrode supply unit 130 for supplying the first electrode 11; a second electrode supply unit 140 for supplying the second electrode 12; a first electrode stacking unit 150 for stacking the first electrode 11 on the stacking table 110; a second electrode stacking unit 160 for stacking the second electrode 12 on the stacking table 110; and a pressing unit 180 for bonding the first electrode 11, the separator 14, and the second electrode 12 to each other. Further, the apparatus 100 for manufacturing an electrode assembly according to an exemplary embodiment of the present application may include a holding mechanism 170 for fixing the stack (including the first electrode(s) 11, the second electrode(s) 12, and the separator 14) to the stack stage 110 when the stack is assembled.

The diaphragm supply unit 120 may have a passage through which the diaphragm 14 passes toward the stacking table 110. In particular, the diaphragm supply unit 120 may include a diaphragm heating unit 121, the diaphragm heating unit 121 defining a passage through which the diaphragm 14 passes toward the stacking table 110. As shown in fig. 6, the diaphragm heating unit 121 may include a pair of bodies 121a, each of which may be in the form of a square block, and the bodies 121a may be spaced apart by a distance defining one of the dimensions of the channel through which the diaphragm 14 passes. At least one or both of the bodies 121a may further include a diaphragm heater 121b for heating the respective body 121a, thereby transferring heat to the diaphragm 14.

The diaphragm supply unit 120 may further include a diaphragm roller 122, and the diaphragm 14 is wound on the diaphragm roller 122. Accordingly, the separator 14 wound on the separator roller 122 may be gradually unwound and passed through the formed passage to be supplied to the stacking table 110.

The first electrode supply unit 130 may include: a first electrode roller 133, on which the first electrode 11 is wound in the form of a sheet; a first cutter 134 for cutting the first electrode 11 at regular intervals while the first electrode 11 is unwound and supplied from the first electrode roll 133, thereby forming the first electrode 11 having a predetermined size; a first conveyor belt 135 for moving the first electrode 11 cut by the first cutter 134; and a first electrode supply head 136 for picking up (e.g., via vacuum suction) the first electrode 11 conveyed by the first conveyor belt 135 and setting the first electrode 11 on the first electrode setting table 131.

The second electrode supply unit 140 may include: the second electrode setting table 141, the second electrode 12 is set on the second electrode setting table 141 before being stacked on the stacking table 110 by the second electrode stacking unit 160. The second electrode supply unit 140 may further include: a second electrode roll 143 on which the second electrode 12 is wound in the form of a sheet; a second cutter 144 for cutting the second electrode 12 at regular intervals while the second electrode 12 is unwound and supplied from the second electrode roll 143, thereby forming a second electrode 12 of a predetermined size; a second conveyor 145 for moving the second electrode 121 cut by the second cutter 144; and a second electrode supply head 146 for picking up (e.g., via vacuum suction) the second electrode 12 conveyed by the second conveyor 145 and seating the second electrode on the second electrode seating table 141.

The first electrode stacking unit 150 may be configured to stack the first electrode 11 on the stacking table 110. The first electrode stacking unit 150 may include a first pumping head 151 and a first moving unit 153. The first suction head 151 may pick up the first electrode 11 seated on the first electrode seating table 131 through one or more vacuum suction ports (not shown) formed on a bottom surface of the first suction head 151 via vacuum suction, and then the first moving unit 153 may move the first suction head 151 to the stacking table 110 to allow the first suction head 151 to stack the first electrode 11 on the stacking table 110.

The second electrode stacking unit 160 may also be configured to stack the second electrode 12 on the stacking table 110. The second electrode stack unit 160 may have the same structure as the aforementioned first electrode stack unit 150. In this case, the second electrode stacking unit 160 may include a second pumping head 161 and a second moving unit 163. The second suction head 161 may pick up the second electrode 12 mounted on the second electrode mounting table 141 via vacuum suction. Then, the second moving unit 163 may move the second pumping head 161 to the stacking table 110 to allow the second pumping head 161 to stack the second electrode 12 on the stacking table 110.

The stacking table 110 may be rotatable so as to rotate between positions facing the first electrode stacking unit 150 and the second electrode stacking unit 160. The retaining mechanism 170 may retain the assembled stack (including the first electrode 11, the second electrode 12, and the diaphragm 14) as the stack table 110 rotates, so as to fix the position of the stack relative to the stack table 110. For example, the retaining mechanism 170 may apply downward pressure to the upper surface of the stack to press it toward the stacking table 110. The holding mechanism 170 may include, for example, a first holder 171 and a second holder 172 to fix opposite sides of the first electrode 11 or the second electrode 12. The retainers 171, 172 may each be in the form of one or more clamps or other clamping mechanisms.

Thus, in operation, 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 separator 14 stacked on the stacking table 110. Then, the holding mechanism 170 is pressed down on the upper surface of the first electrode 11 to fix the position of the first electrode 11 on the stacking table 110. Thereafter, the stacking table 110 rotates in the direction of the second electrode stacking unit 160 while continuously supplying the separator 14 so as to cover the upper surface of the first electrode 11. In addition, the second electrode 12 is supplied from the second electrode supply unit 140, and is stacked by the second electrode stacking unit 160 on a portion of the separator 14 covering the upper surface of the first electrode 11. Then, the holding mechanism 170 releases the upper surface of the first electrode 11 and then presses down on the upper surface of the second electrode 12 to secure the position of the built stack S with respect to the (vis-a-vis) stacking table 110. Thereafter, by repeating the process of stacking the first electrode 11 and the second electrode 12, a stack S in which the separator 14 is zigzag folded and positioned between each of the continuous first electrode 11 and second electrode 12 may be formed.

After stacking the components of the electrode assembly, the electrode assembly may undergo one or more hot pressing operations. Specifically, the electrode assembly may be moved to the pressing unit 180, and the pressing unit 180 applies heat and pressure to the stack by pushing the heated pressing blocks 181 and 182 toward each other with the stack between the pressing blocks 181 and 182. As a result, the components of the stack (i.e., the electrode and the separator) are thermally engaged with each other in order to desirably prevent the completed electrode assembly from falling off or the components of the electrode assembly from moving their positions within the stack.

The hot pressing operation applied to the electrode assembly may include a primary hot pressing operation, a preheating operation, and a secondary hot pressing operation. The primary hot pressing involves an operation after the first electrode and the second electrode are alternately stacked between the folded separator to define a stack, in which the stack is held by a holder, and then the stack is heated and pressed. The secondary hot pressing operation involves an operation after the primary hot pressing operation in which gripping of the stack by the gripper is stopped and the stack is heated and pressed once again. The preheating operation involves a process of heating the stack at a constant pressure for a certain time between the primary hot pressing operation and the secondary hot pressing operation.

Referring to fig. 5, the method may first include a stacking process of assembling a stack (stacked cell) on a stacking table by alternately stacking first and second electrodes on a separator, wherein the separator is continuously supplied before stacking a subsequent electrode of the first and second electrodes and sequentially folded over a previously stacked electrode of the first and second electrodes. After the stacking process, the stack may be moved away from the stacking station. During this time, the septum is pulled, and after the septum is pulled a predetermined length, the septum is cut. Thereafter, the cut ends of the separator of a predetermined length are wound around the stacked cells. The movement of the stack away from the stack table may be accomplished by a gripper, which is desirably a movable member that can grip the stack on the stack table and then move the stack to the pressing unit 180 that performs the hot pressing operation. Then, the initial hot pressing operation is performed in a state in which the wound stacked cells are held by the holder. After the primary hot pressing operation is completed, the grip of the stacked cells by the gripper is released. After removing the gripper, a preheating operation is performed. After the preheating operation, a secondary hot pressing operation is performed. When the secondary hot pressing operation is completed, the completed electrode assembly may be completed.

According to an exemplary embodiment of the present application, the primary hot pressing operation may include applying heat and pressure to the stack for a period of time from 5 seconds to 20 seconds under a pressure condition of 1MPa to 2.5MPa under a temperature condition of from 45 ℃ to 75 ℃. Preferably, the primary hot pressing operation may include applying heat and pressure to the stack for a period of time from 10 seconds to 20 seconds under a pressure condition of 1MPa to 2MPa at a temperature condition of from 45 ℃ to 65 ℃. More preferably, the primary hot pressing operation may include applying heat and pressure to the stack at a temperature condition of from 45 ℃ to 60 ℃ under a pressure condition of from 1MPa to 1.5MPa for a period of from 10 seconds to 20 seconds.

According to an exemplary embodiment of the present application, the preheating operation may include applying heat and pressure to the stack for a period of time from 10 seconds to 40 seconds under a pressure condition from 0.5MPa to 2MPa and a temperature condition from 50 ℃ to 85 ℃. Preferably, the preheating operation may include applying heat and pressure to the stack at a pressure condition of from 0.5MPa to 1.5MPa and a temperature condition of from 55 ℃ to 85 ℃ for a period of from 10 seconds to 35 seconds.

According to an exemplary embodiment of the present application, the secondary hot pressing operation may include applying heat and pressure to the stack for a period of time from 5 seconds to 10 seconds under a pressure condition from 1MPa to 2.5MPa under a temperature condition from 50 ℃ to 85 ℃. Preferably, the secondary hot pressing operation may include applying heat and pressure to the stack at a temperature condition of from 55 ℃ to 85 ℃ under a pressure condition of from 1.5MPa to 2.5MPa for a period of from 5 seconds to 10 seconds. More preferably, the secondary hot pressing operation may include applying heat and pressure to the stack for a period of time from 5 seconds to 10 seconds under a pressure condition from 1.5MPa to 2MPa at a temperature condition from 50 ℃ to 85 ℃.

When the temperature, pressure, and time conditions disclosed herein are not met, the components of the electrode assembly may not adhere properly together, which may cause the electrode assembly to fall out or the components of the electrode assembly to move their position within the assembly, especially when the electrode assembly is moved prior to insertion into the battery housing. The problem of excessively high air permeability of the separator may also occur.

On the other hand, when performing the hot pressing operations disclosed herein (including meeting the respective pressure, temperature, and time conditions), the electrode assemblies may be manufactured without separately heating and/or pressing each horizontal electrode assembly (i.e., heating and/or pressing each electrode and separator pair at each step of the process) in order to join the components together. Such individual hot pressing at each level may adversely cause the effect of heat and/or pressure build up in the lower separator in the stack, as the already stacked layers will experience heat and/or pressure for each application. This can negatively affect such portions of the separator by, for example, reducing porosity (and breathability). In contrast, the present application allows the entire electrode assembly to be simultaneously joined, which improves uniformity and the like. Accordingly, it is possible to simultaneously achieve an appropriate level of adhesion between the electrodes, and also to achieve a separator having an appropriate amount of air permeability while minimizing damage to the unit electrodes.

In the present application, "gas permeability" of the electrode assembly refers to gas permeability of the separator assembly of the electrode assembly. Further, unless specifically stated otherwise, "gas permeability" refers to gas permeability of all separators including an electrode assembly, wherein the gas permeability of each separator may be independently the same or different.

When the gas permeability range disclosed herein is satisfied, the movement speed of lithium ions in the separator in the electrode assembly can be increased while maintaining the safety of the electrode assembly. As a result, providing a separator having the gas permeability values disclosed herein greatly improves the performance, safety, and efficiency of the charge and discharge cycles of the electrode assembly.

According to the present application, the method for measuring the air permeability of the separator is not particularly limited, and the air permeability may be measured by using a method commonly used in the art. For example, a Gri (Gurley) type densitometer (No. 158) manufactured by Toyoseiki may be used according to JIS Gri (JIS Gurley) measurement method of Japanese industrial standards. That is, the breathability of a membrane may be obtained by measuring the time taken for 100ml (or 100 cc) of air to pass through a 1 square inch membrane at room temperature (i.e., 20 ℃ to 25 ℃) at a pressure of 0.05 MPa.

According to an exemplary embodiment of the present application, the middle gas permeability of the electrode assembly may be in the range of 75sec/100ml to 85sec/100 ml.

According to an exemplary embodiment of the present application, the upper surface air permeability of the electrode assembly may be in the range of 80sec/100ml to 85sec/100 ml.

According to an exemplary embodiment of the present application, the lower surface gas permeability of the electrode assembly may be in the range of 80sec/100ml to 85sec/100 ml.

According to an exemplary embodiment of the present application, the lower surface air permeability may be less than or equal to the upper surface air permeability. Further, the intermediate breathability may be less than or equal to the lower surface breathability.

That is, the magnitudes of the upper surface air permeability, the lower surface air permeability, and the intermediate air permeability may satisfy the following formula 1.

[ formula 1]

The air permeability of the upper surface is more than or equal to that of the lower surface is more than or equal to that of the middle

The value of the gas permeability in formula 1 relates to the gas permeability of the separator in the electrode assembly after the completion of the heating and pressing steps.

According to an exemplary embodiment of the present application, the adhesive force between the electrode and the separator at any position in the electrode assembly (i.e., the upper surface, the middle and the lower surface) may be in the range of 5gf/20mm to 30gf/20 mm.

In the present application, there is no particular limitation on the method for measuring the adhesive force of the separator. For example, samples of the lower, middle, and upper portions of the electrode assembly may be separated from the stack. Such samples may include a positive electrode and a separator or a negative electrode and a separator. Samples, which may have a width of 55mm and a length of 20mm, are each adhered to a corresponding slide, and electrodes are positioned on the adhesive surface of the slides. The samples were then tested separately by performing a 90 peel test at a speed of 100mm/min according to the test method set forth in ASTM-D6862. That is, the edge of the membrane is pulled upward at 90 ° relative to the slide at a speed of 100mm/min in order to peel the membrane from the electrode along the width direction of the sample (i.e., from 0mm to 55 mm).

According to an exemplary embodiment of the present application, the intermediate adhesive force of the electrode assembly may be in the range of 5gf/20mm to 10gf/20 mm.

According to an exemplary embodiment of the present application, the upper surface adhesive force of the electrode assembly may be in the range of 5gf/20mm to 30gf/20 mm.

According to an exemplary embodiment of the present application, the lower surface adhesive force of the electrode assembly may be in the range of 5gf/20mm to 30gf/20 mm.

According to an exemplary embodiment of the present application, the adhesive force between the positive electrode and the separator and the adhesive force between the negative electrode and the separator may be the same as each other or may be different from each other.

According to an exemplary embodiment of the present application, a deviation between the middle adhesive force of the electrode assembly and the upper surface adhesive force or the lower surface adhesive force of the electrode assembly may be in the range of 3gf/20mm to 20gf/20mm.

According to an exemplary embodiment of the present application, the deviation between the middle gas permeability of the electrode assembly and the upper surface gas permeability or the lower surface gas permeability of the electrode assembly may be in the range of 3sec/100ml to 20sec/100ml.

When the above air permeability and adhesion conditions are satisfied, cleaning and process treatment may preferably be facilitated, and also wetting of the separator by the electrolyte may be facilitated, so that an electrode assembly having uniform properties may be manufactured. In addition, side effects such as precipitation of lithium (Li) in the electrode assembly and non-charging of the electrode assembly can be prevented.

The withstand voltage of the electrode assembly of the present application may be in the range of 1.5kV to 1.8 kV. The electrode assembly of the present application is manufactured by an electrode assembly manufacturing method including a primary hot pressing operation, a preheating operation, and a secondary hot pressing operation, which can produce both excellent adhesive force and excellent pressure resistance, compared to the case where only the primary hot pressing operation is performed.

Mode for the application

Although the present application has been described in detail by way of specific exemplary embodiments, the present application is not limited thereto. Those skilled in the art can implement various different implementations within the technical spirit of the present application.

1) Example 1

19 positive electrode sheets, 20 negative electrode sheets, and an elongated separator were supplied from respective positive electrode supply units, negative electrode supply units, and separator supply units to the stacking stage.

More specifically, the positive electrode and the negative electrode are supplied after being cut from the positive electrode sheet and the negative electrode sheet, respectively, and the separator is supplied in the form of an elongated separator sheet. Thereafter, as described above, the supplied separator is folded while rotating the stacking table and stacking the positive electrode and the negative electrode. The stack was pressed down and secured using a holding mechanism, forming a stack comprising 39 electrodes.

After assembling the stack, the primary hot pressing operation was performed by holding the stack with a holder and pressing for 15 seconds while heating the stack under a temperature condition of 50 ℃ and a pressure condition of 1.46 MPa.

After the primary hot pressing operation, the grippers were released from the stack and a preheating operation was performed in which the temperature of the press block was kept at 60 ℃ (temperature condition) and a pressure of 1MPa (pressure condition) was applied to the stack for 15 seconds (pressing time).

After the preheating operation, a secondary hot pressing operation in which the pressing block was held at 60 ℃ (temperature condition) and a pressure of 1.8MPa (pressure condition) was applied to the stack within 7 seconds (pressing time) was performed.

2) Examples 2 to 12 and comparative examples 1 to 6

The electrode assemblies of examples 2 to 6 were manufactured in the same manner as the manufacturing method of the electrode assembly of example 1, except that they were performed under the temperature conditions, the pressure conditions, and the pressing time shown in table 1 below.

The electrode assemblies of comparative examples 1 to 15 were manufactured by performing the primary and secondary hot-pressing operations in the same manner as the manufacturing method of the electrode assembly in example 1, except that they were performed under the temperature conditions, the pressure conditions, and the pressing times shown in the following tables 2 and 3. That is, in the case of comparative examples 1 to 12, the preheating operation was not performed.

TABLE 1

TABLE 2

TABLE 3

3) Experimental example 1 adhesive force evaluation

The electrode assemblies of examples 1 to 6 and comparative examples 4, comparative example 8 and comparative examples 11 to 17 were disassembled and analyzed to measure upper surface adhesion, lower surface adhesion and intermediate adhesion. Specifically, the adhesion between the negative electrode and the separator located at the lowermost end of the stack was measured. Further, the adhesion between the anode and the separator located at the uppermost end of the stack was measured. Finally, the adhesion force between the anode and the separator located at the intermediate position along the stacking direction of the stack was measured.

In each separate electrode assembly, the negative electrode and separator being sampled had a width of 55mm and a length of 20mm. The sampled sample is adhered to a slide and the electrodes are positioned on the adhesive surface of the slide. Thereafter, the slide with the sample was mounted on an adhesive force measuring device and tested by performing a 90 ° peel test at a speed of 100mm/min according to the test method set forth in ASTM-D6862. That is, the edge of the membrane is pulled up at 90 ° relative to the slide at a speed of 100mm/min in order to peel the membrane from the electrode along the width direction of the sample (i.e., from 0mm to 55 mm). After ignoring any initial significant fluctuations, the applied force value (in grams/mm) for each sample width was measured while the membrane was peeled off the electrode.

The results are shown in table 4 below.

TABLE 4

From the results of table 4, in comparative examples 4, 8, 11 and 12 in which the secondary hot pressing was performed under 3MPa (a pressure condition higher than 2.5 MPa) without preheating, it was confirmed that the adhesive force at least one position in the electrode assembly exceeded 35gf/20mm.

In addition, it was confirmed by comparative examples 12 to 17 that the adhesive force at least one position in the electrode assembly exceeded 35gf/20mm even when the secondary hot pressing was performed under a pressure condition of 3MPa (higher than 2.5 MPa), and even when the preheating was performed.

Specifically, 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 manufacturing method of the present application, and in the case of comparative example 17 in which preheating was performed but the preheating pressure, temperature and time conditions of the electrode assembly of the present application were not all satisfied, it was confirmed that the adhesive force at least one position in the electrode assembly exceeded 35gf/20mm greatly.

When the adhesive force of the electrode assembly exceeds 35gf/20mm, cleaning and handling may be difficult, and thus the handling cost may increase. In addition, it may be difficult to manufacture an electrode assembly having uniform performance due to poor wetting of the separator by the electrolyte.

In contrast, when using the hot pressing method of the present application (including the associated pressure, temperature and time conditions), it was confirmed that cleaning and handling operations were much easier and the performance of the electrode assembly was much more uniform.

In addition, in the case of examples 1 to 4, since the deviation between the adhesive forces at different positions within the stack was also small, it was confirmed that the electrode assembly had more uniform performance.

4) Experimental example 1 pressure resistance evaluation

The withstand voltages of the electrode assemblies of examples 1 to 5 and the electrode assemblies of comparative examples 2, 5, 6, 9 and 10 were measured (wherein the pressure conditions of the secondary hot pressing were the same as those of examples 1 to 5, and the total pressing time was the same as or similar to that of examples 1 to 5).

Specifically, the voltages applied to the electrode assemblies of examples 1 to 5 and comparative examples 2, 5, 6, 9 and 10 were increased from 9V to 4000V, and the voltage value at the time point when the leakage current became 0.6mA or more was measured and determined as the withstand voltage value.

The results are shown in table 5 below.

TABLE 5

In general, a major factor causing damage to the electrode assembly is a pressure condition.

From the results of table 5, it was confirmed that examples 1 to 5 (electrode assemblies of the present application) had better pressure resistance than comparative examples 2, 5, 6, 9 and 10 in which the pressure conditions of the secondary hot pressing were the same and the total time of heating and pressing (total pressing time) was the same throughout the process, but the preheating operation was omitted.

Claims (9)

1. An electrode assembly, the electrode assembly comprising:

a plurality of electrodes arranged in a stack along a stacking axis with respective diaphragm portions between each of the electrodes in the stack, the plurality of electrodes including a top electrode of the plurality of electrodes positioned at a top of the stack along the stacking axis, a bottom electrode of the plurality of electrodes positioned at a bottom of the stack along the stacking axis, and an intermediate electrode of the plurality of electrodes disposed between the top electrode and the bottom electrode along the stacking axis, and the diaphragm portions including a top diaphragm portion of the diaphragm portions that adjoins the top electrode, a bottom diaphragm portion of the diaphragm portions that adjoins the bottom electrode, and an intermediate diaphragm portion of the diaphragm portions that adjoins an intermediate electrode of the plurality of electrodes,

wherein the intermediate separator portion is bonded to the intermediate electrode to the extent that: to peel the intermediate separator portion from the intermediate electrode at a speed of 100mm/min along the stacking axis, a peeling force in the range of from 5gf to 35gf per 20mm width of the intermediate separator portion applied to the edge of the intermediate separator portion will be spent, and

wherein the top membrane portion and the bottom membrane portion each have a gas permeability value of 70sec/100ml to 85sec/100ml per square inch of the corresponding membrane portion at a pressure of 0.05MPa and room temperature.

2. The electrode assembly of claim 1, wherein the membrane portions are portions of an elongated membrane sheet folded between each membrane portion such that the elongated membrane sheet follows a serpentine path traversing back and forth along an orthogonal dimension orthogonal to the stacking axis to extend between each of the successive electrodes in the stack.

3. The electrode assembly of claim 1, wherein the intermediate separator portion has a gas permeability value of 75sec/100ml to 85sec/100ml per square inch of the corresponding separator portion at a pressure of 0.05MPa and room temperature.

4. The electrode assembly of claim 1, wherein the top separator portion is bonded to the top electrode to the extent that: in order to peel the top separator portion from the top electrode at a speed of 100mm/min along the stacking axis, it takes a peeling force in the range of from 5gf to 30gf per 20mm width of the top separator portion applied to the edge of the top separator portion.

5. The electrode assembly of claim 1, wherein the top separator portion has a gas permeability value of from 80sec/100ml to 85sec/100ml per square inch of the corresponding separator portion at a pressure of 0.05MPa and room temperature.

6. The electrode assembly of claim 1, wherein the bottom separator portion is bonded to the bottom electrode to the extent that: in order to peel the bottom separator portion from the bottom electrode at a speed of 100mm/min along the stacking axis, it takes a peeling force in the range of from 5gf to 30gf per 20mm width of the bottom separator portion applied to the edge of the bottom separator portion.

7. The electrode assembly of claim 1, wherein the bottom separator portion has a gas permeability value of from 80sec/100ml to 85sec/100ml per square inch of the corresponding separator portion at a pressure of 0.05MPa and room temperature.

8. The electrode assembly of claim 1, wherein the top separator portion and the bottom separator portion are bonded to the respective top and bottom electrodes to the extent that: in order to peel the respective top and bottom separator sections from the respective top and bottom electrodes at a speed of 100mm/min along the stacking axis, it takes a second peel force per 20mm width of the respective top and bottom separator sections applied to edges of the respective top and bottom separator sections, wherein a difference between the second peel force and the peel force of the intermediate separator section is from 3gf/20mm to 20gf/20mm.

9. The electrode assembly of claim 1, wherein the middle separator portion has a second gas permeability value per square inch at a pressure of 0.05MPa and room temperature, and wherein a difference between the second gas permeability value and the gas permeability value of the top and bottom separator portions is 3sec/100ml to 20sec/100ml per square inch at a pressure of 0.05MPa and room temperature.