Electrode assembly for lithium secondary battery and manufacturing method thereof

Abstract

A method for manufacturing a lithium secondary battery electrode assembly capable of aligning positive electrodes through adhesion between positive current collectors attached to the positive electrodes, and a lithium secondary battery electrode assembly according to the same are introduced.

Description

Technology Field

[0001] The present invention relates to an electrode assembly for a lithium secondary battery and a method for manufacturing the same. Specifically, the invention relates to a method for manufacturing an electrode assembly for a lithium secondary battery such that the alignment of the positive electrode, which is a component of the lithium secondary battery, is possible, and to an electrode assembly manufactured according to the same. Background Technology

[0003] Lithium-ion batteries are environmentally friendly as they generate less waste and can be charged and discharged more than 500 times, making them suitable for use as an energy source for electronic devices such as laptops and smartphones. They are particularly suitable as an energy source for HEVs (Hybrid Electric Vehicles) and EVs (Electric Vehicles) that require high output and a lot of energy.

[0004] A lithium-ion battery is largely composed of a positive electrode, a negative electrode, an electrolyte, and a separator. Energy is generated through the repeated intercalation and deintercalation of lithium ions at the positive and negative electrodes, while the electrolyte serves as a pathway for the movement of lithium ions, and the separator prevents short circuits from occurring within the battery where the positive and negative electrodes meet.

[0005] Meanwhile, there are various causes for short circuits within lithium-ion batteries. Short circuits can occur due to the penetration of the separator caused by lithium precipitation, or due to electrode misalignment or expansion.

[0006] Referring to FIG. 1, when the positive electrode (10) is misaligned, the positive current collector and the negative electrode (20) come into contact when the negative electrode (20) expands, and as the charge amount increases, the probability of a short circuit (S) occurring increases.

[0007] Referring to FIG. 2, due to poor alignment of the positive electrode (10), a precipitation (40) of a negative electrode material facing the edge surface of the positive electrode (10) occurs, and depending on the degree of precipitation (40), a short circuit (S) occurs between the positive current collector on the edge surface of the positive electrode (10) and the separator (30), causing the battery to degrade regardless of the charge amount, and also causing a problem with stability.

[0009] The matters described above as background technology are intended only to enhance understanding of the background of the present invention and should not be construed as an acknowledgment that they constitute prior art already known to those skilled in the art. Prior art literature

[0011] (Patent Document 0001) KR 10-2018-0097243 A The problem to be solved

[0012] The present invention is proposed to solve these problems and aims to provide an electrode assembly for a lithium secondary battery and a method for manufacturing the same, comprising a positive electrode and a negative electrode arranged at regular intervals, a separator provided between the positive and negative electrodes, and a plurality of current collectors of equal length that protrude outwardly from the positive electrode, wherein an adhesive layer for bonding between positive current collectors is formed on one side of the positive current collector to prevent misalignment of the positive electrode. means of solving the problem

[0014] In an electrode assembly for a lithium secondary battery comprising a positive electrode and a negative electrode arranged at regular intervals, a separator provided between the positive electrode and the negative electrode, and a plurality of current collectors of equal length that are formed protruding outwardly from the positive electrode, the present invention is characterized in that an adhesive layer for bonding between positive current collectors is formed on one side of the positive current collector to prevent misalignment of the positive electrode.

[0016] In an electrode assembly for a lithium secondary battery according to one embodiment of the present invention, the adhesive layer area may vary depending on the distance from the reference positive current collector, based on a flat positive current collector.

[0018] An electrode assembly for a lithium secondary battery according to one embodiment of the present invention may be characterized in that the area of ​​the adhesive layer decreases as it moves further away from a reference positive current collector.

[0020] An electrode assembly for a lithium secondary battery according to one embodiment of the present invention may be characterized in that the adhesive layer area of ​​the positive current collector located at the outermost edge is 30% or less of the adhesive layer area formed on the reference positive current collector.

[0022] An electrode assembly for a lithium secondary battery according to one embodiment of the present invention may be characterized in that the angle formed by the positive current collector located at the outermost edge and the axis perpendicular to the electrode assembly is less than 30°.

[0024] An electrode assembly for a lithium secondary battery according to one embodiment of the present invention may be characterized in that the positive current collector is disconnected when the angle formed by the positive current collector located at the outermost edge and the axis perpendicular to the electrode assembly exceeds a certain value.

[0026] A method for manufacturing an electrode assembly for a lithium secondary battery comprising a positive electrode and a negative electrode arranged at regular intervals, a separator provided between the positive electrode and the negative electrode, and a plurality of current collectors of equal length that are formed protruding outwardly from the positive electrode, is characterized by forming an adhesive layer for bonding between positive current collectors on one side of the positive current collectors to prevent disruption of the alignment of the positive electrodes. Effects of the invention

[0028] According to an electrode assembly for a lithium secondary battery according to one embodiment of the present invention, it is possible to prevent the alignment of the positive electrode from becoming defective, thereby suppressing the occurrence of a short circuit inside the lithium secondary battery.

[0029] In addition, the battery can be detected as defective through testing by designing the system so that when the angle between the outermost positive current collector and the axis perpendicular to the ground exceeds a certain value due to the expansion of the electrode, the positive current collector is disconnected from the positive. Brief explanation of the drawing

[0031] Figures 1 and 2 are intended to explain the occurrence of a short circuit due to a conventional anode electrode misalignment. Figure 3 is a schematic diagram of an electrode assembly constituting a lithium secondary battery. Figure 4 is an image of the stacking of the positive electrode, separator, and negative electrode during the formation of the electrode assembly. FIG. 5 is a diagram illustrating the location where an adhesive layer is formed on the positive current collector. FIG. 6 is a drawing for explaining a standard flat anode current collector. FIG. 7 is a diagram illustrating the angle formed by the anode current collector located at the outermost angle and the axis perpendicular to the electrode assembly. Specific details for implementing the invention

[0032] Hereinafter, specific details for solving the aforementioned objectives and problems will be explained in detail with reference to the attached drawings. Meanwhile, regarding the understanding of the present invention, if a detailed description of known technology in the same field does not help in understanding the core content of the invention, such description will be omitted. Furthermore, the technical concept of the present invention is not limited thereto and can be modified and implemented in various ways by those skilled in the art.

[0034] FIG. 3 shows a schematic diagram of an electrode assembly (100) constituting a lithium secondary battery. Referring to FIG. 3, the electrode assembly has a structure in which a positive electrode (10), a separator (30), and a negative electrode (20) are sequentially stacked. More specifically, a positive current collector (15) is formed to protrude outward from one end of the positive electrode (10). Additionally, a negative current collector (25) is formed to protrude outward from one end of the negative electrode (20).

[0035] As described above, an internal short circuit may occur in a lithium secondary battery due to misalignment of the positive electrode (10) and expansion of the negative electrode (20), and the present invention is intended to solve the problem of an internal short circuit occurring due to misalignment of the positive electrode (10).

[0036] The present invention is characterized by having an adhesive layer formed on one side of the positive current collector (15) for adhesion between positive current collectors (15) to prevent misalignment of the positive electrodes.

[0037] FIG. 4 is an image of the stacking of a positive electrode, a separator, and a negative electrode when forming an electrode assembly. As shown in FIG. 4, a positive electrode (10) and a negative electrode (20) are arranged with a separator (30) in between. A positive current collector (15) is welded to one end of the positive electrode (10) so as to protrude outward.

[0038] FIG. 5 is a diagram illustrating the location where an adhesive layer is formed on a positive current collector. Referring to FIG. 5, it can be seen that the adhesive layer (50) is formed on one side of the positive current collector (15). The adhesive layer (50) can be formed by applying an adhesive solution made of a polymer component capable of bonding the positive current collector (15) to one or both sides of the positive current collector (15).

[0039] Meanwhile, the electrode assembly consists of approximately 30 positive electrodes (10). Referring to FIG. 6, the electrode assembly has a positive current collector (151) that is relatively flat compared to other positive current collectors (as the positive electrodes are stacked, the positive current collector at the top and bottom has the steepest slope, and as it goes toward the center of the electrode assembly, the slope of the positive current collector gradually decreases to a slope close to 0° (or 180°)).

[0040] Based on this flat positive current collector (151), the area of ​​the adhesive layer formed on the positive current collector (15) at a distance from the reference flat positive current collector (151) may differ.

[0041] Specifically, it is desirable that the area of ​​the adhesive layer (50) decreases as it moves further away from the reference flat positive current collector (151). This is because the lengths of the positive current collectors (15) formed in the present invention are all the same, and accordingly, the area where the positive current collector (15) can come into contact with other positive current collectors (15) becomes increasingly narrow as it moves further away from the reference positive current collector (151).

[0042] In particular, the adhesive layer area of ​​the positive current collector located at the outermost edge may be characterized as being 30% or less of the adhesive layer area formed on the standard flat positive current collector (151).

[0043] If the width of the positive current collector (15) used is 1 mm and the length is 10 mm, and the reference flat positive current collector (151) has an area (non-contact area) of 4 mm that does not come into contact with other positive current collectors (15). 2 If so, the area of ​​the adhesive layer (50) formed on the standard flat positive current collector (151) is 6mm 2 And the area of ​​the adhesive layer (50) formed on the outermost positive current collector is 6mm 2 1.8mm, which is 30% of 2It can be made to be less than or equal to. In this case, the non-contact area of ​​the outermost positive current collector is 8.2 mm 2 This is what it becomes.

[0044] Accordingly, in an electrode assembly for a lithium secondary battery according to one embodiment of the present invention, the positive current collector (152) located at the outermost edge and the axis (160) perpendicular to the electrode assembly form a specific angle, and with reference to FIG. 7, this angle may be, for example, less than 30°.

[0045] According to the present invention, by adjusting the area of ​​the adhesive layer (50) and the length of the positive current collector (15) used, the positive current collector (152) located at the outermost angle and the axis (160) perpendicular to the electrode assembly can be designed to form a specific angle. Accordingly, the design is such that if the angle formed by the positive current collector (152) located at the outermost angle and the axis (160) perpendicular to the electrode assembly exceeds a certain value, the positive current collector (152) located at the outermost angle is disconnected. This allows for the detection of a defective battery, as the positive current collector (152) located at the outermost angle is disconnected when the angle between the positive current collector (152) located at the outermost angle and the axis (160) perpendicular to the electrode assembly exceeds a specific angle due to expansion of the negative electrode or other causes.

[0047] Although specific embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that the present invention can be modified and changed in various ways without departing from the technical spirit of the invention as provided by the following claims. Explanation of the symbols

[0049] 10 ; positive electrode 15: Positive current collector 20: Cathode 25: Cathode current collector 30: Separator 50: Adhesive layer 151: Reference flat anode current collector 152: The positive current collector located at the outermost edge 160: Axis perpendicular to the electrode assembly

Claims

Claim 1 An electrode assembly for a lithium secondary battery comprising a positive electrode and a negative electrode arranged at regular intervals, a separator provided between the positive electrode and the negative electrode, and a plurality of current collectors protruding outwardly from the positive electrode and having the same length, wherein an adhesive layer for bonding between positive current collectors is formed on one side of the positive current collector to prevent misalignment of the positive electrodes, wherein, based on a flat positive current collector, the area of ​​the adhesive layer decreases according to the distance from the reference positive current collector, and wherein the angle formed by the positive current collector located at the outermost angle and the axis perpendicular to the electrode assembly is less than 30°, and the positive current collector is disconnected when the angle formed by the positive current collector located at the outermost angle and the axis perpendicular to the electrode assembly exceeds a certain value. Claim 2 delete Claim 3 delete Claim 4 An electrode assembly for a lithium secondary battery according to claim 1, characterized in that the adhesive layer area of ​​the positive current collector located at the outermost edge is 30% or less of the adhesive layer area formed on the reference positive current collector. Claim 5 delete Claim 6 delete Claim 7 delete

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