Electrode, Manufacturing method for electrode, and Secondary cell having the same

Abstract

The present invention relates to an electrode, a method for manufacturing an electrode, and a secondary battery including the same, wherein the thickness of the current collector in the non-welded portion corresponding to the welded portion of the electrode is configured to be greater than the thickness of the current collector in the retaining portion to secure excellent mechanical properties and further reduce electrode resistance.

Description

Technology Field

[0001] The present invention relates to a secondary battery electrode, and more specifically, to an electrode having a structure in which the thickness of the current collector in the uncurrent portion is greater than the thickness of the current collector in the retaining portion. Background Technology

[0002] Recently, rechargeable secondary batteries are being widely used as an energy source for mobile devices and are also attracting attention as a power source for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] One form of secondary battery is a pouch-type secondary battery in which an electrode assembly is embedded in a pouch-type case made of a laminate sheet. FIG. 1 shows a cross-section of an electrode assembly of a conventional pouch-type secondary battery. The electrode assembly of the pouch-type secondary battery generally has a structure in which a positive electrode (80-p), a separator (not shown), and a negative electrode (80-n) are alternately stacked. Each electrode (80) is composed of a current collector (81) and an active material (82), and is composed of a retaining part (A) on which the active material (82) is coated on the surface of the current collector (81) and a non-coated part (B) on which the active material is not coated. The structure is formed by welding bundles of non-coated parts (B) of each electrode (80), connecting one side of an electrode tab (not shown) to the welded bundle of non-coated parts (B), and discharging the other side of the electrode tab to the outside of the pouch-type case.

[0004] Meanwhile, when manufacturing a secondary battery, a first process is carried out to bundle each unbonded part together in order to electrically connect each electrode, and a second process is carried out to electrically connect electrode tabs to the welded unbonded part bundles. At this time, generally, the unbonded parts are bundled together through first welding, and electrode tabs are connected to the unbonded part bundles through second welding.

[0005] However, conventionally, as shown in FIG. 1, the thickness of the unwelded portion (B) is thin, so the mechanical strength of the unwelded portion (B) bundle weld is weak, and there are problems such as the current collector tearing when overwelded, the unwelded portion bundle separating when underwelded, and the electrode tab easily short-circuiting due to physical impact after assembly of the secondary battery. Prior art literature

[0006] Korean Registered Patent Publication No. 1784743 (September 28, 2017) The problem to be solved

[0007] The present invention has been devised to solve the above-mentioned problems. The present invention aims to provide an electrode, a method for manufacturing an electrode, and a secondary battery including the same, which can secure excellent mechanical properties and further reduce electrode resistance by configuring the thickness of the current collector in the non-welded portion corresponding to the welded portion of the electrode current collector to be greater than the thickness of the current collector in the retaining portion. means of solving the problem

[0008] An electrode according to an example of the present invention comprises a retaining portion formed by coating an active material on one or both sides of a current collector, and a non-retaining portion on the current collector in which the active material is not coated. In this electrode, the thickness of the current collector located in the non-retaining portion may be greater than the thickness of the current collector located in the retaining portion. In this case, the electrode may have a shape having a single non-retaining portion and a single retaining portion, wherein the area of ​​the non-retaining portion is smaller than the area of ​​the retaining portion, and the non-retaining portion is arranged to exist at one end of the retaining portion.

[0009] The above active material is applied continuously, the thickness of the current collector located in the retaining portion is constant, and the thickness of the current collector located in the non-retaining portion may be constant.

[0010] The above-mentioned collector includes a connecting portion formed between the collector located in the retaining portion and the collector located in the non-retaining portion, and the connecting portion may become thicker as it extends from the retaining portion toward the non-retaining portion.

[0011] The thickness of the current collector located in the above-mentioned non-current portion may be equal to or smaller than the combined thickness of the current collector located in the above-mentioned retaining portion and the above-mentioned active material.

[0012] The above-mentioned non-electrical portion can be electrically connected to the electrode tab.

[0013] The entire current collector located in the above-mentioned non-conductive portion may be formed by stacking multiple conductor pieces.

[0014] A method for manufacturing an electrode according to an example of the present invention may include: 1) a step of preparing a current collector in the form of a flat plate; 2) a step of forming a thickness difference on the current collector such that the thickness of the current collector in the area corresponding to the non-current portion of the current collector is greater than the thickness of the current collector in the area corresponding to the retaining portion of the current collector; and 3) a step of applying an active material to the area corresponding to the retaining portion of the current collector in which the thickness difference is formed. At this time, the electrode manufactured by the electrode manufacturing method may have a shape having a single non-current portion and a single retaining portion, wherein the area of ​​the non-current portion is smaller than the area of ​​the retaining portion and the non-current portion is arranged to exist at one end of the retaining portion.

[0015] In step 2) above, the area corresponding to the retaining portion of the current collector may be rolled, the area corresponding to the retaining portion of the current collector may be stretched, or one or more conductor pieces may be stacked in the area corresponding to the non-retaining portion of the current collector, thereby forming the thickness of the current collector in the area corresponding to the non-retaining portion of the current collector to be thicker than the thickness of the current collector in the area corresponding to the retaining portion of the current collector.

[0016] A method for manufacturing an electrode according to another example of the present invention may include: 1) a step of preparing a current collector in the form of a flat plate; 2) a step of applying an active material to an area corresponding to a retaining portion of the current collector; and 3) a step of forming a thickness difference such that the thickness of a current collector not coated with the active material is greater than the thickness of the current collector coated with the active material. At this time, the electrode manufactured by the electrode manufacturing method may have a shape having a single non-existent portion and a single retaining portion, wherein the area of ​​the non-existent portion is smaller than the area of ​​the retaining portion, and the non-existent portion is arranged to exist at one end of the retaining portion.

[0017] In step 3) above, one or more conductor pieces are stacked in the area corresponding to the unoccupied portion of the current collector, so that the thickness of the current collector in the area corresponding to the unoccupied portion of the current collector can be formed to be thicker than the thickness of the current collector in the area corresponding to the retained portion of the current collector.

[0018] A secondary battery according to one example of the present invention comprises an electrode assembly in which a positive current collector, comprising a retaining portion coated with a positive active material and a non-retaining portion not coated with the positive active material, and a negative current collector, comprising a retaining portion coated with a negative active material and a non-retaining portion not coated with the negative active material, are alternately stacked. In this secondary battery, at least one of the positive current collector and the negative current collector may be formed such that the thickness of the current collector of the retaining portion coated with the positive active material or the negative active material is smaller than the thickness of the current collector of the non-retaining portion. At this time, the electrode constituting the electrode assembly may have a shape having a single non-retaining portion and a single retaining portion, wherein the area of ​​the non-retaining portion is smaller than the area of ​​the retaining portion, and the non-retaining portion is arranged to exist at one end of the retaining portion.

[0019] The non-bonded portions of the positive current collector and the negative current collector are formed in mutually opposite directions and are stacked alternately, and each non-bonded portion of the positive current collector is joined by welding at one end, and each non-bonded portion of the negative current collector can be joined by welding at the other end.

[0020] The above positive current collector or the above negative current collector further includes a connecting portion having a gradually decreasing thickness, and the connecting portion may correspond to a retaining portion of an adjacent current collector. Effects of the invention

[0021] According to the present invention, the thickness of the current collector of the non-current portion corresponding to the weld portion of the electrode is configured to be greater than the thickness of the current collector of the retaining portion, thereby increasing the mechanical properties of the weld portion. As a result, the tearing of the current collector that occurs during over-welding is suppressed, making it possible to perform strong welding on the non-current portion bundles, and also to perform strong welding between the welded non-current portion bundles and the electrode tabs.

[0022] In addition, as the thickness of the current collector in the non-conductive portion increases, the average thickness of the current collector increases, thereby reducing electrode resistance and simultaneously allowing heat generated from the electrode to be effectively discharged to the outside through the current collector. Brief explanation of the drawing

[0023] Figure 1 shows a cross-section of an electrode assembly of a conventional pouch-type secondary battery. FIG. 2 shows a cross-section of an electrode assembly according to an example of the present invention. FIG. 3 shows a cross-section of an electrode according to an example of the present invention. FIG. 4 shows a cross-section of an electrode according to another example of the present invention. FIG. 5 shows a cross- section of an electrode assembly according to another example of the present invention. FIG. 6 shows a method for manufacturing an electrode according to an example of the present invention. FIG. 7 illustrates a method for manufacturing an electrode according to another example of the present invention. Specific details for implementing the invention

[0024] The present invention will be described in detail below with reference to the attached drawings.

[0025] FIG. 2 is a cross-section of an electrode assembly according to an example of the present invention. As shown, the electrode assembly (10) has a structure in which each electrode (100) is stacked, more specifically, a structure in which a positive electrode (100-p) and a negative electrode (100-n) are repeatedly alternately stacked, and a separator (e.g., a separator film, not shown) may be further interposed between each electrode (100).

[0026] Each electrode (100) includes an active material (110) and a current collector (120), and the active material (110) may be applied to a portion of the surface of the current collector (120). The area where the active material (110) is applied to the surface of the current collector (120) corresponds to the retaining area (A), and the area where the active material is not applied corresponds to the uncoated area (B). The active material (110) and the current collector (120) are materials generally usable in a secondary battery. For example, the positive electrode active material (110-p) may include lithium oxide (Li+O) or high-nickel (High Ni), which is attracting attention as a positive electrode material recently, and the negative electrode active material (110-n) may include a silicon / carbon (Si / C) composite material. The positive electrode current collector (120-p) may be made of aluminum (Al), and the negative electrode current collector (120-n) may be made of copper (Cu).

[0027] FIG. 3 is a cross-section of an electrode according to an example of the present invention, and through FIG. 3, we will examine the electrode (100) of the present invention in more detail. However, although the positive electrode (100-p) and the negative electrode (100-n) may differ from each other in terms of the materials of the respective components constituting the positive electrode (100-p) and the negative electrode (100-n), the structural features to be explained in the present invention are identical. Therefore, below, the positive electrode (100-p) and the negative electrode (100-n) will be distinguished only when necessary for explanation, and otherwise, they will be described simply as electrode (100).

[0028] The electrode (100) includes an active material (110) and a current collector (120), and may consist of a retaining portion (A) on which the active material (110) is applied to part or both sides of the current collector (120), and a non-retaining portion (B) on which the active material is not applied. Here, as illustrated, the current collector (120) of the present invention is formed such that the thickness (W_B) of the current collector located in the non-retaining portion (B) is greater than the thickness (W_A) of the current collector located in the retaining portion (A). That is, in the case of the conventional electrode described through FIG. 1, the current collector (11) has a flat plate shape and the thickness of the current collector in the non-retaining portion (B) and the retaining portion (A) is formed to be the same. In contrast, the present invention has a thickness gradient on the current collector (120) such that the thickness of the current collector located in the non-retaining portion (B) and the current collector located in the retaining portion (A) are formed differently. More specifically, the current collector located in the non-retaining portion (B) is formed to be thicker than the current collector located in the retaining portion (A).

[0029] As the non-transferable portion of the current collector is formed thickly in this way, the average thickness of the current collector increases overall. Since the thickness of the current collector, which serves as a pathway for electron movement, increases, not only is the electrode resistance reduced, but the thickness of the current collector, which serves as a pathway for heat movement, also increases, allowing the heat generated by the battery operation to be effectively dissipated.

[0030] More importantly, as described below, when manufacturing an electrode assembly using the electrode of the present invention or further manufacturing a secondary battery cell, the thickness of the non-welded bundle corresponding to the weld area is increased, thereby increasing the mechanical properties of the weld area. Consequently, the tearing of the non-welded bundle that may occur during over-welding can be suppressed, allowing the non-welded bundle to be welded strongly. As a result, problems such as the non-welded bundle separating due to weak welding or the electrode tab short-circuiting can be resolved.

[0031] Below, we will examine in detail the detailed structures of the electrode (100) of the present invention.

[0032] As illustrated in FIG. 3, the thickness (W_A) of the current collector located in the retaining portion (A) in the present invention may be constant. That is, the thickness of the current collector located in the retaining portion (A) may not change even as it proceeds from one end to the other, and when viewed from above, the current collector region located in the retaining portion (A) may be formed as a flat plane without curvature. When the thickness of the retaining portion is formed to be constant in this way, the active material can be evenly coated on the surface of the retaining portion, and furthermore, the electrodes can be well aligned and stacked during the process of manufacturing an electrode assembly using the electrodes.

[0033] In addition, the thickness (W_B) of the current collector located in the non-retaining portion (B) in the present invention may also be constant. That is, as shown in FIG. 3, the thickness of the current collector located in the non-retaining portion (B) may not change when moving from one end to the other. This allows the non-retaining portions to be gathered together without tilting to one side when performing the first welding of the non-retaining portion bundles during the subsequent electrode assembly manufacturing process. Here, the welding may be a welding method generally used in the manufacture of secondary batteries, such as ultrasonic welding or laser welding. Meanwhile, the fact that the thickness of the current collector located in the retaining portion and the non-retaining portion is constant does not mean physical identical, but rather means substantially identical within a range acceptable by social norms.

[0034] FIG. 4 is a cross-section of an electrode according to another example of the present invention. As illustrated, the current collector (120) further includes a connecting portion (C) formed between the current collector located in the retaining portion (A) and the current collector located in the non-retaining portion (B), and the connecting portion (C) may be formed to become thicker as it goes from the retaining portion (A) toward the non-retaining portion (B). The connecting portion (C) may be created during the process of rolling the current collector (120) using a roller or the like, as a method of forming a thickness difference on the current collector (120) as described below.

[0035] In FIG. 4, an active material (110) is shown coated on the surface of the connecting portion (C), but the active material (110) may not be coated. Furthermore, as shown in FIG. 4, the thickness of the connecting portion (C) may increase uniformly as it moves from the retaining portion (A) to the unretaining portion (B), forming a straight line shape when viewed from the side, or the degree of thickness change may differ as the connecting portion (C) moves from the retaining portion (A) to the unretaining portion (B), forming a curved shape when viewed from the side. FIG. 5 shows an electrode assembly formed by stacking the electrodes of FIG. 4.

[0036] As the connecting portion (C) is provided, only the connecting portion (C) of the current collector (120) has a thickness gradient, and the remaining portion of the current collector excluding the connecting portion (C), namely the current collector located in the retaining portion (A) and the current collector located in the non-retaining portion (B), can each be formed with a constant thickness without a thickness gradient. However, as shown in the electrode of FIG. 3, it is obvious that the thickness (W_A) of the current collector located in the retaining portion (A) and the thickness (W_B) of the current collector located in the non-retaining portion (B) can change in a stepwise manner without the connecting portion (C).

[0037] In the present invention, the thickness (W_B) of the current collector located in the non-retaining portion (B) may be equal to or smaller than the sum of the thickness (W_A) of the current collector located in the retaining portion (A) and the thickness of the active material (110). This can prevent problems that occur when the thickness of the non-retaining portion becomes excessively large when forming an electrode assembly by stacking electrodes, such as interference between the case surrounding the electrode assembly and the non-retaining portion, or difficulties when cutting the non-retaining portion.

[0038] In the present invention, the active material (110) may be applied to only one side of the assembly or to both sides. Since the thickness of the retaining portion is related to the overall size of the electrode and the thickness of the unretaining portion is related to the electrode resistance, the electrode can be appropriately designed by considering the relationship between the two. In particular, regarding the positive electrode, if the positive material is high nickel, it has a higher charge capacity compared to conventional lithium-ion positive materials, so the amount of coating can be reduced; therefore, it may be more advantageous to apply it to one side rather than both sides of the current collector. However, it is not limited to this, and the design can be modified according to the situation.

[0039] Furthermore, in the present invention, the unpaired portion (B) can be electrically connected to an electrode tab (not shown). That is, an electrode assembly (10) is formed by repeatedly stacking multiple electrodes (100), and a bundle of unpaired portions (B) of each electrode is welded first, and an electrode tab is welded second to the bundle of unpaired portions, thereby allowing the unpaired portion (100) to be electrically connected to the electrode tab. By connecting the unpaired portion to the electrode tab in this way, each electrode in the electrode assembly is electrically connected to each other. At this time, it is not necessary to install a separate electrical component to connect each electrode to each other, which can reduce the labor required when assembling the electrode assembly.

[0040] Hereinafter, a method for manufacturing an electrode according to an example of the present invention will be described.

[0041] A method for manufacturing an electrode according to a first embodiment of the present invention may include the steps of: preparing a current collector (120) in the form of a flat plate; forming a thickness difference in the current collector (120); and applying an active material to a portion of the surface of the current collector (120) (i.e., a portion corresponding to a retaining portion).

[0042] First, in order to form a thickness difference in the current collector (120), the thickness of the area (AA) corresponding to the retaining portion of the current collector (120) can be formed thinly by rolling it with a roller or the like, or by compressing and stretching the area (AA) corresponding to the retaining portion of the current collector (120) with a press or the like, or by pulling and stretching the area (AA) corresponding to the retaining portion on both sides, or the thickness of the area (BB) corresponding to the retaining portion can be formed thickly by stacking a piece of conductor on the area (BB) corresponding to the non-retaining portion of the current collector (120).

[0043] Specifically, it is preferable that the roller be a cylindrical shape with the same upper and lower radius, and the length of the cylindrical roller is designed to correspond to the retaining portion so that the area (AA) corresponding to the retaining portion in the current collector can be rolled thinly in a single rolling motion. Additionally, the press can be a compression press and designed so that its width corresponds to the retaining portion. When rolling using the roller or stretching using the press in this manner, the area (AA) corresponding to the retaining portion is compressed, causing the current collector to shift toward the non-retaining portion, and the non-retaining portion can naturally be formed thickly, and in this case, a connecting portion (C) can be formed in the current collector as described above. On the other hand, when multiple conductor pieces are stacked in the area (BB) corresponding to the non-retaining portion of the current collector (120), a connecting portion (C) is not formed, and a stepwise thickness difference can be formed.

[0044] FIG. 6 illustrates a method for manufacturing an electrode according to a first embodiment of the present invention, showing that the process proceeds from left to right in the drawing, FIG. 6(a) is a view of the electrode from above, and FIG. 6(b) is a view of the electrode from the side corresponding to the illustration of each step of FIG. 6(a). As illustrated, the method includes the step of first preparing a current collector (120) in the form of a flat plate; the step of forming a thickness difference on the current collector by rolling / stretching the region (AA) corresponding to the retaining portion of the current collector or by stacking a conductor piece on the region (BB) corresponding to the non-retaining portion of the current collector; and the step of applying an active material (110) to the region (AA) corresponding to the retaining portion of the current collector. Subsequently, the current collector (120) coated with the active material (110) can be cut into a desired size (slitting), and the unnecessary part of the current collector (120) can be cut off (notching), thereby manufacturing an electrode (100) having a thickness difference on the current collector of the present invention.

[0045] The electrode manufacturing method according to the second embodiment of the present invention may first be performed by applying an active material (110) to a current collector (120), and then forming a thickness difference in the current collector (120) on which the active material (110) is applied. To form a thickness difference in the current collector (120), one or more conductor pieces (B') may be stacked in the region corresponding to the uncoated portion of the current collector (BB, where, in the case where an active material is applied to the surface of a current collector in the form of a flat plate, the thickness of the current collector in the region where the active material is applied on the surface and the thickness of the current collector in the region where the active material is not applied on the surface are the same, so the current collector in the uncoated portion is referred to as the region corresponding to the uncoated portion) to form a thicker thickness in the region corresponding to the uncoated portion (BB). At this time, the stacked plurality of conductor pieces (B') and the region corresponding to the uncoated portion (BB) of the current collector (120) may be welded so that the region corresponding to the uncoated portion (BB) and the current collector piece (B') are joined together.

[0046] The conductor piece (B') may be, for example, a plate-shaped current collector piece (B') made of aluminum (Al) in the case of a positive current collector piece, and a plate-shaped current collector piece (B') made of copper (Cu) in the case of a negative current collector piece. Additionally, the area of ​​the conductor piece (B') may be formed to be equal to or smaller than the area of ​​the region (BB) corresponding to the unoccupied portion. Furthermore, while it is preferable that the shape of the current collector piece (B') be formed to be identical to the shape of the region (BB) corresponding to the unoccupied portion, it is not limited thereto and may have other shapes, for example, the shape of the region (BB) corresponding to the unoccupied portion may be rectangular and the shape of the conductor piece (B') may be circular. Additionally, when the active material (110) is applied to both sides of the current collector (120), the conductor piece (B') can be stacked on both sides of the area (BB) corresponding to the unused portion, and when the active material (110) is applied only to one side of the current collector (120), the current collector piece (B') can be stacked on one side of the area (BB) corresponding to the unused portion.

[0047] When multiple conductor pieces are stacked in this way to form a non-conducting portion, a stepped thickness variation can be created on the current collector without the aforementioned connecting portion (C) on the current collector, and furthermore, the portion of the current collector that is cut off and discarded during the electrode manufacturing process can be recycled as a conductor piece, which has economic and environmental advantages.

[0048] FIG. 7 illustrates a method for manufacturing an electrode according to a second embodiment of the present invention, showing that the process proceeds from left to right in the drawing, FIG. 7(a) is an electrode viewed from above, FIG. 7(b) is an electrode viewed from the side, and FIG. 7(c) is an enlarged view of the dotted line portion of FIG. 7(b). As illustrated, the method includes the steps of: first, preparing a current collector in the form of a flat plate; applying an active material (110) to an area (AA) corresponding to the retaining portion of the current collector; and stacking a plurality of conductor pieces (B') in an area (BB) corresponding to the uncoated portion of the current collector (120) coated with the active material (110) to form a thickness difference on the current collector (120); and subsequently, the current collector (120) coated with the active material (110) is slitted to a desired size, and the unnecessary portion of the current collector (120) is notched, thereby manufacturing an electrode having a thickness difference on the current collector of the present invention. However, FIG. 7 shows that before cutting the entire house to a desired size, a piece of the house (B') is first stacked in the area (BB) corresponding to the unoccupied part of the entire house to form a thickness difference. Alternatively, the piece of the house (B') may be stacked after cutting the entire house to a desired size, or furthermore, the piece of the house (B') may be stacked after cutting out the unnecessary part of the entire house (120).

[0049] Meanwhile, although not illustrated, each electrode (10) may be manufactured by applying an active material (110) in a patterned manner on a wide current collector (120) and then cutting it to the appropriate size. Of course, even in this case, a thickness difference may be formed on the current collector first and then the active material may be applied, and a thickness difference may be formed on the current collector after the active material has been applied.

[0050] Hereinafter, a secondary battery including an electrode assembly according to one example of the present invention will be described.

[0051] The electrode assembly according to the present invention comprises a positive electrode and a negative electrode that are repeatedly alternately stacked. In this case, at least one of the positive electrode or the negative electrode may be a positive electrode or a negative electrode having a thickness difference formed in the current collector. That is, a thickness difference may be formed in the current collector only on the positive electrode, a thickness difference may be formed in the current collector only on the negative electrode, or a thickness difference may be formed in the current collector on both the positive electrode and the negative electrode.

[0052] FIG. 2 shows an electrode assembly in which a thickness difference is formed in the current collector for both the positive electrode and the negative electrode. For convenience of explanation, the present invention will be described with reference to FIG. 2. The electrode assembly (10) according to FIG. 2 comprises a positive electrode (100-p) with a thickness difference formed in a current collector and a negative electrode (100-n) with a thickness difference formed in a current collector, which are repeatedly alternately stacked. At this time, the positive electrode (100-p) with a thickness difference formed in a current collector comprises a positive current collector (120-p) and a positive active material (110-p), and includes a positive retaining portion (Ap) formed by coating the positive active material (110-p) on one or both sides of the positive current collector (120-p), and a positive non-positive portion (Bp) where the positive active material (110-p) is not coated on the positive current collector (120-p), wherein the thickness of the positive current collector (120-p) located in the positive non-positive portion (Bp) is greater than the thickness of the positive current collector (120-p) located in the positive retaining portion (Ap), and the negative electrode (100-n) with a thickness difference formed in a current collector is a negative electrode The device includes a current collector (120-n) and a negative electrode active material (110-n), a negative electrode retaining portion (An) formed by coating the negative electrode active material (110-n) on one or both sides of the negative electrode current collector (120-n), and a negative electrode uncoated portion (Bn) where the negative electrode active material (110-n) is not coated on the negative electrode current collector (120-n), wherein the thickness of the negative electrode current collector (120-n) located in the negative electrode uncoated portion (Bn) may be formed to be greater than the thickness of the negative electrode current collector (120-n) located in the negative electrode retaining portion (An).

[0053] Here, the positive electrode unoccupied portion (Bp) and the negative electrode unoccupied portion (Bn) may be located in opposite directions, or the positive electrode unoccupied portion (Bp) and the negative electrode unoccupied portion (Bn) may be located in the same direction. For example, when viewing the electrode assembly from above, the positive electrode (100-p) has the positive electrode unoccupied portion (Bp) located to the left and the negative electrode (100-n) has the negative electrode unoccupied portion (Bn) located to the right. When the positive electrode (100-p) and the negative electrode (100-n) are stacked alternately, the bundle of the positive electrode unoccupied portion (Bp) is located on the left and the bundle of the negative electrode unoccupied portion (Bn) is located on the right, so that the positive electrode unoccupied portion (Bp) and the negative electrode unoccupied portion (Bn) are located in opposite directions. Alternatively, when the electrode assembly is viewed from above, the positive electrode (100-p) and the negative electrode (100-n) may both have the positive non-positive portion (Bp) and the negative non-positive portion (Bn) positioned to the left, but the upper and lower positions of the positive non-positive portion (Bp) and the negative non-positive portion (Bn) may be different to prevent interference between the positive non-positive portion (Bp) and the negative non-positive portion (Bn), so that the positive non-positive portion (Bp) and the negative non-positive portion (Bn) may be positioned in the same direction.

[0054] Furthermore, in the electrode assembly (10) of the present invention, each positive electrode uncoupling portion (Bp) is welded together and each negative electrode uncoupling portion (Bn) is welded together and each positive electrode (100-b) is electrically connected by the connection of each positive electrode uncoupling portion (Bp), and each negative electrode (100-n) is electrically connected by the connection of each negative electrode uncoupling portion (Bn). Subsequently, a positive electrode tab is welded to a welded bundle of positive electrode uncoupling portions (Bp), and a negative electrode tab is welded to a welded bundle of negative electrode uncoupling portions (Bn) to manufacture a secondary battery cell. At this time, according to the present invention, as described above, the thickness of the positive and negative electrode uncoupling portions is increased because the mechanical strength is increased, and accordingly, each uncoupling portion can be welded strongly. Even if an electrode tab is strongly welded onto a welded bundle of uncoupling portions, the current collector does not tear, making strong welding possible. Accordingly, the tearing of the current collector can be prevented during the first welding of each uncoupling section and during the second welding of the electrode tab on the uncoupling section bundle welded by the first welding, and furthermore, the electrode tab can be reliably prevented from short-circuiting in the uncoupling section bundle due to physical impact of the completed secondary battery cell.

[0055] In addition, as described above, the thickness of the uncoated portion of the electrode increases, thereby increasing the overall average thickness of the current collector, so the electrode resistance can be reduced and heat dissipation through the current collector can be effectively achieved.

[0056] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. Explanation of the symbols

[0057] 10: Electrode assembly 100: Electrode 110: Active substance 120: Whole house A: The entire house located in the maintenance area B: The entire house located in the non-existent area C: Connection formed throughout the house B': Conductor piece W_A: Thickness of the entire house located in the maintenance section W_B: Thickness of the entire house located in the non-existent area

Claims

Claim 1 An electrode comprising a retaining portion formed by coating an active material on one or both sides of a current collector, and a non-retaining portion on the current collector in which the active material is not coated, wherein the current collector has a thickness greater than the thickness of the current collector located in the non-retaining portion, and the electrode has a shape having a single non-retaining portion and a single retaining portion, wherein the area of ​​the non-retaining portion is smaller than the area of ​​the retaining portion, and the non-retaining portion is arranged to exist at one end of the retaining portion. Claim 2 An electrode according to claim 1, wherein the active material is continuously applied, the thickness of the current collector located in the retaining portion is constant, and the thickness of the current collector located in the non-retaining portion is constant. Claim 3 In claim 1, the current collector comprises a connecting portion formed between the current collector located in the retaining portion and the current collector located in the non-retaining portion, and the connecting portion is an electrode that becomes thicker as it extends from the retaining portion toward the non-retaining portion. Claim 4 In claim 1, the electrode, wherein the thickness of the current collector located in the non-retaining portion is equal to or smaller than the combined thickness of the current collector located in the retaining portion and the active material. Claim 5 In paragraph 1, the above-mentioned portion is an electrode electrically connected to an electrode tab. Claim 6 In claim 1, the current collector located in the above-mentioned non-conductive portion is an electrode formed by stacking a plurality of conductor pieces. Claim 7 A method for manufacturing an electrode comprising: 1) a step of preparing a current collector in the form of a flat plate; 2) a step of forming a thickness difference in the current collector such that the thickness of the current collector in the area corresponding to the non-current portion of the current collector is greater than the thickness of the current collector in the area corresponding to the retaining portion of the current collector; and 3) a step of applying an active material to the area corresponding to the retaining portion of the current collector in which the thickness difference is formed; wherein the electrode manufactured by the method for manufacturing an electrode comprises a single non-current portion and a single retaining portion, wherein the area of ​​the non-current portion is smaller than the area of ​​the retaining portion, and the non-current portion is arranged to exist at one end of the retaining portion. Claim 8 A method for manufacturing an electrode according to claim 7, wherein in step 2), the region corresponding to the retaining portion of the current collector is rolled, the region corresponding to the retaining portion of the current collector is stretched, or one or more conductor pieces are stacked in the region corresponding to the non-retaining portion of the current collector, thereby forming the current collector thickness of the region corresponding to the non-retaining portion of the current collector to be thicker than the current collector thickness of the region corresponding to the retaining portion of the current collector. Claim 9 A method for manufacturing an electrode comprising: 1) a step of preparing a current collector in the form of a flat plate; 2) a step of applying an active material to an area corresponding to a retaining portion of the current collector; and 3) a step of forming a thickness difference such that the thickness of a current collector not coated with the active material is greater than the thickness of the current collector coated with the active material; wherein the electrode manufactured by the method for manufacturing an electrode comprises, when the portion of the current collector not coated with the active material is called a non-coated portion, having a single non-coated portion and a single retaining portion, wherein the area of ​​the non-coated portion is smaller than the area of ​​the retaining portion, and the non-coated portion is arranged to exist at one end of the retaining portion. Claim 10 A method for manufacturing an electrode according to claim 9, wherein in step 3), one or more conductor pieces are stacked in the region corresponding to the non-conducting portion of the current collector, so that the thickness of the current collector in the region corresponding to the non-conducting portion of the current collector is formed to be thicker than the thickness of the current collector in the region corresponding to the retaining portion of the current collector. Claim 11 A secondary battery comprising an electrode assembly in which an anode current collector including a retaining portion coated with an anode active material and a non-retaining portion not coated with the anode active material; and a cathode current collector including a retaining portion coated with a cathode active material and a non-retaining portion not coated with the cathode active material are alternately stacked, wherein at least one of the anode current collector and the cathode current collector is formed such that the thickness of the current collector of the retaining portion coated with the anode active material or the cathode active material is smaller than the thickness of the current collector of the non-retaining portion, and the electrode constituting the electrode assembly has a single non-retaining portion and a single retaining portion, wherein the area of ​​the non-retaining portion is smaller than the area of ​​the retaining portion and the non-retaining portion is arranged such that it exists at one end of the retaining portion. Claim 12 A secondary battery according to claim 11, wherein the non-bonded portions of the positive current collector and the non-bonded portions of the negative current collector are formed in mutually opposite directions and are alternately stacked, each non-bonded portion of the positive current collector is joined by welding at one end, and each non-bonded portion of the negative current collector is joined by welding at the other end. Claim 13 In claim 11, the positive current collector or the negative current collector further comprises a connecting portion having a gradually decreasing thickness, said connecting portion corresponding to a retaining portion of an adjacent current collector, a secondary battery.

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