KR20060033642A - Method for treating electrode taps of stacked lithium secondary battery - Google Patents

Abstract

The present invention relates to a method for processing an electrode tab of a stacked lithium secondary battery, wherein the method comprises stacking a plurality of electrode plates having tabs formed on one side, and connecting the lead wires to one side, and then connecting the lead wires. In the electrode tab processing method of the battery, a lead wire having a predetermined length is disposed on the top surface of the stacked electrode plates, one end of which is positioned on the top surface of the stacked electrode plate, and the other end thereof coincides with the end of the electrode tab. Aligning the first step; Bonding the aligned electrode tabs and the lead wires to be integrated; A third step of first bending the junction portion of the electrode tab and the lead wire downward so that the lead wire is positioned perpendicular to the stacked electrode plates; And a fourth step of bending the lead wires to the outside of the stacked electrode plates so as to extend horizontally toward the outside of the stacked electrode plates.

Lithium Secondary Battery, Tapping, Lead Wire

Description

Electrode tab treatment method of stacked lithium secondary battery {METHOD FOR TREATING ELECTRODE TAPS OF STACKED LITHIUM SECONDARY BATTERY}

1 is an exploded view illustrating an arrangement of an electrode plate on a separator for manufacturing a stacked lithium secondary battery.

FIG. 2 is a perspective view illustrating a laminate of cells for a lithium secondary battery obtained by sequentially folding the electrode arrangement of FIG. 1. FIG.

3A to 3H are diagrams briefly illustrating a manufacturing process of a conventional lithium secondary battery cell.

FIG. 4 is a cross-sectional view of an embodiment of a lithium secondary battery cell completed by FIGS. 3A to 3H.

5 is a cross-sectional view of another embodiment of a lithium secondary battery cell completed by the prior art.

6A to 6F are cross-sectional views showing an electrode tab processing process according to the present invention.

FIG. 7 is a cross-sectional view of a cell for a lithium secondary battery of the present invention completed by FIGS. 6A to 6F.

8 is a cross-sectional view illustrating a manufacturing process of a conventional continuous lithium secondary battery.

The present invention relates to a method for processing an electrode tab of a stacked lithium secondary battery.

A battery is a device that converts chemical energy into electrical energy by an electrochemical reaction, which is largely divided into a primary battery and a secondary battery. Among secondary batteries capable of charging and discharging, lithium secondary batteries having high voltage and high energy density are currently attracting most attention. Currently, lithium secondary batteries have been variously applied to small batteries for information and communication devices such as mobile phones and laptops.

An example of a method of manufacturing a conventional lithium secondary battery is shown in FIG. 8. Lithium secondary battery according to the method is a negative electrode collector 11 in the form of a grid, a negative electrode 12 in the form of a matrix film, a separator 13 in the form of a matrix film, a positive electrode 14 in the form of a matrix film, a positive electrode collector in the form of a grid After stacking the whole 15 in sequence and passing through the laminator to integrate the elements, it is characterized in that the zigzag-fold again to have a desired structure. See US Pat. No. 5,460,904 for an example of such a method. In the lithium secondary battery produced by the above method, the electrodes are continuously connected, and thus may be referred to as "continuous lithium secondary battery". The lithium secondary battery of the above type has the advantage that the tabs are simple because the electrodes are connected to each other, but there is a problem that the damage of the electrode is necessarily accompanied in the folding process.

In order to solve this problem, examples using a plurality of negative electrode plates and a plurality of positive electrode plates are disclosed in Korean Patent Nos. 309604 and 336396 and Korean Patent Publication No. 2002-93781. At this time, a plurality of negative electrode plates and a plurality of positive electrode plates are alternately stacked, and thus are called "laminated lithium secondary batteries". This type of lithium secondary battery has the advantage that damage to the electrode (ie, detachment of the electrode material from the current collector and damage to the current collector) accompanying the folding process does not occur. However, in the case of the above-described stacked lithium secondary battery, efficient treatment of tabs located in each of the plurality of negative electrode plates and the plurality of positive electrode plates is required.

1 and 2 are perspective views illustrating a manufacturing process of the stacked lithium secondary battery. As shown in FIGS. 1 and 2, the positive electrode plate 2a 'or the negative electrode plate 2b' is arranged on one surface of the separator 30 'in a proper order, and then folded to fold the positive electrode plate 2a' and the negative electrode plate 2b '. This alternately positioned stack 100 'is obtained. In the laminate 100 ′ of FIG. 2, a positive electrode tab 200a ′ and a negative electrode tab 200b ′ protrude from one side of the positive electrode plate 2a ′ or the negative electrode plate 2b ′, and an efficient process therefor. Is required. That is, the space occupied by the tab must be minimized to meet the miniaturization tendency of electronic products, and a quick and accurate tapping process is required.

Korean Unexamined Patent Publication No. 2003-95519 discloses an example of a conventional electrode tab processing method, and detailed processes are described with reference to FIGS. 3A to 3G. As shown in FIG. 3A, a cell A 'formed by stacking a plurality of positive electrode plates and a negative electrode plate is stacked with a plurality of electrode tabs 200a' and 200b 'subordinate thereto. 200b ') are compressed by pushing upward, as shown in FIG. 3b. Thereafter, as shown in FIG. 3C, when the ends of the tabs do not match with each other, the ends of the plurality of overlapping positive electrode tabs 200a '(or negative electrode tabs 200b') are connected to the cutter 300 '. It is cut uniformly using the alignment as shown in Figure 3d.

Thereafter, as shown in FIG. 3E, a lead wire 4 ′ is disposed from an opposite direction of the positive electrode tab 200 a ′ (or the negative electrode tab 200 b ′), and one end of the lead wire 4 ′ is positive. The lead wire 4 'and the positive electrode tab 200a' (or negative electrode tab 200b ') are bonded to each other by being placed on the upper surface of the tab 200a' (or negative electrode tab 200b '). And wrapped with insulating material 40 '. Thereafter, as illustrated in FIG. 3F, a portion where the positive electrode tab 200a ′ or the negative electrode tab 200b ′ and the lead wire 4 ′ are welded downward is formed to form a first curved portion 40 ′. As shown in 3g, the tab portion is completed by bending the middle portion of the lead wire 4 'outward to form the second bent portion 42'. Then, as shown in FIG. 4, after receiving the tabbed cell A ′ in a predetermined case 50 ′, the lithium secondary battery B ′ is completed by filling and sealing an electrolyte solution therein.

A more preferred form is shown in FIG. In the tapping process according to FIG. 5, a third bent portion 43 ′ is additionally formed after the second bent portion 42 ′ in FIG. 3g to be bent into a substantially 'U' shape. 4, the space shown in FIG. 5 takes up less space in the tab, which contributes to the higher density of the battery. Unexplained reference numeral 44 ′ denotes a sealant for sealing.

However, the above-mentioned prior art has some problems pointed out below, and not only can not perform the tapping process quickly and accurately, but also frequently generates tapping errors.

First, the lead wires 4 'are arranged in opposite directions of the electrode tabs (i.e., opposite to the main body of the cell). The lead gaps between the electrode tabs and the lead wires 4' are generally determined depending on the operator's sense. Since it is set, it is difficult to keep this overlapping interval always constant. Therefore, the reproducibility of tapping is lowered. This lowers the reliability of the product (see FIG. 3E).

Secondly, in the configuration of a conventional production facility for arranging the lead wire 4 'in the opposite direction of the electrode tab, a work line in which the cell A' is arranged is formed on one side thereof, and the lead wire on the opposite side thereof. A work line with 4 'is arranged. Therefore, a work line for arranging lead wires is additionally required, and the space occupied by the equipment required for tapping becomes large.

Third, as shown in FIG. 5, when the electrode tab and the lead wire 4 'are bent into a' U 'shape, a restoring force is generated due to the property of returning the bent portion to its original state. The restoring force compresses the lead wire 4 'and the cell A'. Therefore, the restoring force imposes an unsuitable pressure on components (eg, electrode plate, separator, electrolyte, etc.) inside the battery, which is a factor that impairs the safety of the battery (see FIG. 5).

Fourthly, ultrasonic welding is performed to join the plurality of electrode tabs. However, in the process of applying the electrode active material to the electrode plate, a part of the electrode active material is also applied to the electrode tab, which lowers the efficiency of ultrasonic welding. Therefore, the electrode active material applied to the tab should be removed before performing the ultrasonic welding. The removal process of the electrode active material is mainly performed by manual operation. During the removal of the electrode active material, the electrode active material is scattered into the air to contaminate the working environment, and also penetrates into the battery to increase the defective rate. Occasionally, an electrode active material penetrated inside may cause a short circuit due to an unexpected chemical reaction.

The present invention has been made to solve the problems of the prior art, firstly, to minimize the space occupied by the tab, second, to perform the tapping process quickly and accurately, and thirdly to the workspace required for the tapping process It is to provide a tap processing method that can be kept to a minimum.

Another object of the present invention is to provide a tapping method in which a step of removing an active material applied to a tab accompanying the tapping is not required.

According to a preferred embodiment of the present invention, in the tab processing method of a lithium secondary battery comprising the step of stacking a plurality of positive electrode plates and negative electrode plates having tabs formed on one side, and connecting the leads to one side in close contact with the tabs, Placing a lead wire having a length on an upper surface of the stacked electrode plates, wherein one end is positioned on an upper surface of the stacked electrode plates, and the other end is aligned with the end of the electrode tab; Bonding the aligned electrode tabs and the lead wires to be integrated; A third step of first bending the junction portion of the electrode tab and the lead wire downward so that the lead wire is positioned perpendicular to the stacked electrode plates; And a fourth step of secondly bending the lead wires to the outside of the stacked electrode plates so as to extend horizontally toward the outside of the stacked electrode plates.                         

According to another preferred embodiment of the present invention, there is provided a method for processing an electrode tab of a stacked lithium secondary battery, wherein the bonding step of the electrode tab and the lead wire in the tapping process is performed by riveting.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

6A to 6F are cross-sectional views illustrating an electrode tab processing process according to the present invention, and FIG. 7 is a cross-sectional view of a cell for a lithium secondary battery of the present invention completed by FIGS. 6A to 6F.

First, the present invention, the positive electrode plate and the negative electrode plate is arranged sequentially on one side or both sides of the separator and then folded to stack the positive electrode plate and the negative electrode plate (cell) for lithium secondary battery (A), but a plurality of dependent on each of the positive electrode plate or negative electrode plate To form the positive electrode tab 200a or the negative electrode tab 200b (integrating the electrode tab 200) by pressing the same polarities with each other, and then connecting the lead wires 4 to the electrode tabs 200, respectively. Since the process is the same as in the prior art, a detailed description thereof will be omitted.

In the tapping method according to the present invention, the lead wires 4 are aligned with the upper ends of the electrode tabs 200, one end of the lead wires 4 is positioned on the upper surface of the stacked electrode plates, and the other end of the electrode tabs ( Aligned to the end of the line 200). That is, the end of the electrode tab 200 coincides with the one end of the lead wire 4, and the main body of the lead wire 4 is positioned above the electrode plate (see FIG. 6A). At this time, the alignment member 700 or the like may be employed to more smoothly and quickly align the lead wire 4 to the upper portion of the electrode tab 200.

After the alignment is completed, the electrode tab 200 and the lead wire 4 are joined. The bonding process may be performed by ultrasonic fusion. Ultrasonic welding, however, requires the removal of the active material applied to the tab. The removal process of the active material is mainly performed by hand. During the removal of the active material, the active material is scattered into the air to contaminate the working environment as well as penetrate into the internal space to increase the defective rate. To solve this problem, a process of physically bonding by rivets is proposed by the present inventors (see FIG. 6B). At this time, the rivet 5 comprises a head 50 and the vertical rod (52). Preferably, the rivet 5 has concave-convex portions 54a and 54b on at least one of the bottom surface of the head 50 and the outer circumferential surface of the vertical rod body 52. The uneven portions 54a and 54b make the physical fixation of the lead wire 4 and the electrode tab 200 more firm (see FIG. 6C). In addition, since the junction part by the rivet 5 may be bent through the third and fourth steps described below, unnecessary electrical contact may be generated, or an insulating material such as an insulating tape to block the junction part or to prevent damage to the junction part. It is desirable to wrap around and protect it with 400 (see FIG. 6D).

By joining, after the lead wire 4 and the electrode tab 200 are integrated, a bending process is performed. In the tapping method according to the present invention, the bending step is performed twice. The first bending causes the junction of the electrode tab 200 and the lead wire 4 to be bent downward so that the lead wire 4 is disposed perpendicular to the bottom surface of the cell (see FIG. 6E). The second bending bends the lead wires 4 in regions not overlapping with the electrode tabs 200 to the outside of the stacked electrode plates (or cells) so as to extend horizontally to the outside of the stacked electrode plates (FIG. 6F). Reference).

According to the embodiment of the present invention configured as described above, the assembly of the cell A to which the lead wires 4 are connected may be completed, and thus, the lithium secondary battery cell A is accommodated inside the case 500 and the lead wires ( After the end of 4) is exposed to the outside, the lithium secondary battery B is finally completed by injecting an electrolyte solution into the case 500 and then sealing it (see FIG. 7).

The shape of the electrode plate is not particularly limited under the condition of having the tab 200, and may be variously modified according to the final shape of the battery. At present, a type commonly used in PDAs or mobile phones is rectangular. The electrode plate is obtained by coating an electrode active material (specifically, a positive electrode active material and a negative electrode active material) on a current collector. It is desirable to improve the energy density by double sided coating. Preferred examples of the positive electrode active material and the negative electrode active material are described in detail in US Pat. Nos. 5,837,015, 5,635,151 and 5,501,548. Concrete _{examples, LiCoO 2, LiMn 2 O 4} , LiNiO include lithium transition metal compound of _2, LiMnO ₂ or the like. In addition, examples of the negative electrode active material include lithium metal or lithium alloy, or a material capable of inserting / desorbing lithium ions such as carbon or graphite, and preferably carbon or graphite. The positive electrode active material and the negative electrode active material are dispersed in a suitable solvent, coated on a current collector, and then cut into a predetermined size to form a positive electrode plate and a negative electrode plate, respectively. The electrode active material may be coated on one side of the current collector, but is preferably coated on both sides. Coating on both sides has the advantage that the discharge capacity per volume of the battery can be increased. Examples of metals that can be used as current collectors are not particularly limited, and are described in detail in the above-described US Pat. Nos. 5,837,015, 5,635,151 and 5,501,548. In a preferred embodiment of the present invention, aluminum foil and copper foil were used as the current collectors for the positive electrode and the negative electrode, respectively. On the other hand, the electrode active material is generally coated on the current collector with a conductive material and a binder for improving conductivity. The selection of the conductive material and the binder may be appropriately selected depending on the type of the electrode active material used, and such matters are well known to those skilled in the art.

The separator electrically insulates the positive and negative plates and provides a path for ions. Preferred examples include polyethylene films such as polyethylene, polypropylene, and the like, polyvinylidene fluoride, hexapropylene fluoride and polyethylene oxide films. Polyethylene films are most commonly used as separators. As the electrolyte, a liquid electrolyte, a gel polymer electrolyte or a solid polymer electrolyte may be widely used.

As described above, in the method for processing a tab of a cell for a lithium secondary battery according to the present invention, first, a lead wire is disposed above the cell, thereby minimizing a work space at the time of the tap processing and significantly reducing the width of the manufacturing apparatus. The device can be miniaturized.

Secondly, the end of the tab and lead wires that are cell-dependent can be easily and accurately aligned, which significantly reduces scrap.                     

Third, by bonding the electrode tab and the lead wire by rivet fixing, the closed end where the electrode active material is scattered can be blocked at the source, thereby making the working environment clean and preventing side effects due to the internal penetration of the electrode active material.

In addition, it is possible to provide a lithium secondary battery more stable and improved product reliability by the above method.

Claims (4)

In the electrode tab processing method of a stacked-type lithium secondary battery comprising the step of stacking a plurality of electrode plates having a tab formed on one side, the tab is in close contact with one side, and connecting lead wires, the electrode plate laminated a predetermined length of the lead wire A first step of arranging the lead wires so as to be disposed on an upper surface of the first electrode, one end of which is positioned on an upper surface of the stacked electrode plates, and the other end of which is aligned with an end of the electrode tab; Bonding the aligned electrode tabs and the lead wires to be integrated; A third step of first bending the junction portion of the electrode tab and the lead wire downward so that the lead wire is positioned perpendicular to the stacked electrode plates; And a fourth step of bending the lead wires to the outside of the stacked electrode plates so as to extend horizontally toward the outside of the stacked electrode plates. The method of claim 1, Wherein the second step, the electrode tab processing method of a stacked lithium secondary battery, characterized in that the aligned electrode tab and the lead wire is bonded to each other to be integrated. The method of claim 2, The rivet comprises a head and a vertical rod body, and an electrode tab processing method of a stacked lithium secondary battery, characterized in that an uneven portion is formed on the bottom surface of the head and the outer circumferential surface of the vertical rod body. The laminated lithium secondary battery in which the electrode tab was treated by the method according to any one of claims 1 to 3.

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