CN106207070B - Secondary battery - Google Patents

Abstract

Provided is a secondary battery that can prevent the electrode tab from being folded or torn during the winding process of the electrode sheet by forming a circular portion on the electrode tab. The secondary battery includes: an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate; an electrode tab extending from each of the positive electrode plate and the negative electrode plate and protruding to the electrode assembly the upper part of the cover plate; the case, which accommodates the electrode assembly; the cover plate, which seals the top of the case; A rounded portion is formed at the side portion.

Description

Secondary battery

This application claims priority to Korean Patent Application No. 10-2015-0013523 filed in the Korean Intellectual Property Office on Jan. 28, 2015, the contents of which are hereby incorporated by reference in their entirety.

technical field

The present invention relates to a secondary battery.

Background technique

Generally, unlike primary batteries which are not rechargeable, secondary batteries can be repeatedly charged and discharged. According to technological development and increased production of mobile devices such as mobile phones and notebook computers, the demand for secondary batteries as an energy source is rapidly increasing. Recently, as an alternative energy source to fossil fuels, research into secondary batteries used in electric vehicles or hybrid vehicles is actively being conducted.

SUMMARY OF THE INVENTION

The present invention provides a secondary battery that can prevent the electrode tab from being folded or torn during the winding process of the electrode sheet by forming a circular portion on the electrode tab.

The above and other objects of the present invention will be described in or will be apparent from the following description of the preferred embodiment.

According to an aspect of the present invention, there is provided a secondary battery, the secondary battery comprising: an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate; an electrode tab, from Each of the positive electrode plate and the negative electrode plate extends and protrudes to an upper portion of the electrode assembly; a case that accommodates the electrode assembly; a cap plate that seals the top of the case; and electrode terminals that respectively protrude to the upper portion of the cap plate and are connected to electrode wiring sheet, wherein each electrode tab includes a circular portion formed into a circular shape at a side of the electrode tab.

The electrode tab may have a width gradually increasing from the top to the bottom spaced apart from the positive and negative plates.

The electrode tab may include a first region in direct contact with each of the positive electrode plate and the negative electrode plate and a second region spaced apart from the first region while being parallel to the first region, and the length of the first region may be greater than the first region. The length of the second region.

The circular portion may connect the first area and the second area to each other.

The radius of the circular portion may be 1 to 1.5 times the length of the second region.

The radius of the circular portion may be 0.35 to 1 times the height of the electrode tab.

The electrode tabs may be formed by cutting uncoated portions of the positive electrode plate and the negative electrode plate, which are not coated with the positive electrode active material and the negative electrode active material, by laser processing.

As described above, the secondary battery according to the present invention can prevent the electrode tab from being bent or torn during the winding process of the electrode sheet by forming the circular portion on the electrode tab.

Description of drawings

The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments of the present invention with reference to the accompanying drawings, in which:

1 is a perspective view of a secondary battery according to an embodiment of the present invention;

FIG. 2 is an exploded perspective view of the secondary battery shown in FIG. 1;

3 is an exploded perspective view showing a connection relationship between each of an electrode tab, an electrode lead, and an electrode terminal in the secondary battery shown in FIG. 1;

4 is a perspective view of an electrode assembly in a secondary battery according to an embodiment of the present invention;

5 is a front view of an electrode plate in a secondary battery according to an embodiment of the present invention;

6 is an enlarged front view of an electrode tab in a secondary battery according to an embodiment of the present invention;

7 illustrates stress distribution according to the configuration of the electrode tab in the secondary battery according to the embodiment of the present invention;

8 illustrates stress distributions of electrode tabs having sizes of different numerical values in a secondary battery according to an embodiment of the present invention.

Detailed ways

Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Aspects of the present disclosure may be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments of this disclosure are provided so that this disclosure will be thorough and complete, and will convey various aspects of this disclosure to those skilled in the art.

In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Here, the same reference numbers refer to the same elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that when the terms "comprising" and/or "comprising" are used in this specification, the stated features, numbers, steps, operations, elements and/or components are indicated to be present, but are not precluded the presence or addition of one or and more other features, numbers, steps, operations, elements, components and/or groups thereof.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, elements, regions, layers and/or sections, these elements, elements, regions, layers and/or sections should not be affected by these terms limits. These terms are only used to distinguish one element, element, region, layer and/or section from another element, element, region, layer and/or section. Thus, for example, a first member, element, region, layer and/or section discussed below could be termed a second member, second element, The second region, the second layer and/or the second portion.

1 is a perspective view of a secondary battery according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the secondary battery shown in FIG. 1 , and FIG. 3 is an exploded perspective view of the secondary battery shown in FIG. 1 . An exploded perspective view of the connection relationship between each of the electrode tabs, electrode leads, and electrode terminals.

1 to 3 , a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 110 , a case 120 and a cap plate 140 .

The electrode assembly 110 includes a positive electrode plate 111, a negative electrode plate 112, and a separator 113, and may be accommodated in a case 120 together with an electrolyte (not shown), and then sealed.

For example, the electrode assembly 110 may be formed by winding the stacked structure of the positive electrode plate 111 , the negative electrode plate 112 and the separator 113 into a jelly roll configuration or stacking the stacked structure in the shape of a rectangular parallelepiped. Here, the positive electrode plate 111 may be made of aluminum (Al) foil, the negative electrode plate 112 may be made of copper (Cu) foil, and the separator 113 may be made of polyethylene (PE) or polypropylene (PP), but the present invention Aspects of the are not so limited. The electrolyte may serve as a moving medium of lithium ions generated through electrochemical reaction between the positive electrode plate 111 and the negative electrode plate 112 of the secondary battery 100 during charging and discharging. The electrolyte may be a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent. In addition, the electrolyte may be a polymer using a polymer electrolyte.

The positive electrode plate 111 may be formed by coating a positive electrode active material on at least one surface of a positive electrode current collector (not shown). Similarly, the anode plate 112 may be formed by coating an anode active material on at least one surface of an anode current collector (not shown). For example, in an embodiment of the present invention, the positive electrode plate 110 may be disposed at the outermost part of the electrode assembly 110 for the purpose of arranging a positive electrode current collector (not shown), which generates a relatively large amount of heat, adjacent to the case 120 . The outer side is used for the purpose of promoting heat radiation through the housing 120 . For example, a positive current collector (not shown) may be in direct contact with the case 120 or at least may be in thermal contact with the case 120 . Here, the expression "thermal contact" may refer to allowing heat exchange between two elements in thermal contact with each other even though the two elements may not be in direct contact with each other.

The positive electrode tab 114 and the negative electrode tab 115 may be connected to at least one or more locations of the positive electrode plate 111 and the negative electrode plate 112 . The positive electrode tab 114 and the negative electrode tab 115 are generally formed to have a height in the range of 10 mm to 30 mm. Throughout the specification of the present invention, the positive electrode tab 114 and the negative electrode tab 115 may be collectively referred to as electrode tabs 114 and 115 .

In the case of a high-capacity, high-output secondary battery, a plurality of positive electrode tabs 114 and a plurality of negative electrode tabs 115 may extend from the electrode assembly 110 . In more detail, each positive electrode tab 114 may be formed by cutting a positive electrode uncoated portion of the positive electrode plate 111 that is not coated with the positive electrode active material and forming a tab. In addition, the negative electrode tab 115 may also be formed by cutting the negative electrode uncoated portion of the negative electrode plate 112 that is not coated with the negative electrode active material and forming a tab. The secondary battery can obtain high-power current through the plurality of positive electrode tabs 114 and negative electrode tabs 115 . Here, each of the positive electrode tabs 114 and each of the negative electrode tabs 115 may be prepared separately and then attached to the uncoated portions of the positive electrode plate 111 and the negative electrode plate 112 .

Meanwhile, the electrode tabs 114 and 115 may be formed to include circular portions 114c and 115c formed at one side and the other side thereof. In forming the electrode tabs 114 and 115, laser processing may be used to facilitate the formation of the circular portions 114c and 115c. The radius of the circular portions 114c and 115c may be in the range of 7mm to 30mm. The circular portions 114c and 115c will be described in more detail later.

The positive tab 114 may be connected to the cap plate 140 itself, and the negative tab 115 may be connected to the negative terminal 145 extending to the top surface of the cap plate 140 . For example, the positive terminal 144 and the negative terminal 145 may be exposed on the top surface of the cap plate 140 . Here, the positive tab 114 may be connected to the positive lead 134 for subsequent electrical connection to the positive terminal 144 . Additionally, the negative tab 115 may be connected to the negative lead 135 for subsequent electrical connection to the negative terminal 145 . Throughout the specification of the present invention, the positive electrode lead 134 and the negative electrode lead 135 may be collectively referred to as electrode leads 134 and 135 .

Before the electrode tabs 114 and 115 are connected to the electrode leads 134 and 135, the plurality of electrode tabs 114 and 115 may be gathered into a single bundle (single bundle) by tack welding. The electrode lugs 114 and 115 can be more easily connected to the electrode leads 134 and 135 by spot welding the electrode lugs 114 and 115 gathered into a single bundle.

The electrode assembly 110 and an electrolyte (not shown) are accommodated in the case 120 . The housing 120 has an open top end and may be formed by deep drawing. The top opening of the case 120 may be sealed by the cover plate 140 . Here, the contact portions of the cover plate 140 and the case 120 may be coupled to each other by laser welding. The housing 120 may be made of one selected from steel, aluminum, and equivalents thereof, but aspects of the present invention are not limited thereto.

The positive lead 134 is electrically connected to the positive tab 114 , the cap plate 140 and the positive terminal 144 . The positive lead 134 may be configured to bend in a generally "L" shape. In more detail, the positive lead 134 may extend in two different directions for subsequent bending. The first portion 134a of the positive lead 134 may be disposed to face the bottom surface of the cap plate 140 for subsequent bonding to the cap plate 140 . In addition, the second portion 134b extending in a different direction from the first portion 134a may be disposed to face the positive electrode tab 114 to be subsequently bonded to the positive electrode tab 114 . To form the connection between the cap plate 140 and the positive terminal tab 114, the positive lead 134 may be configured to bend in different directions to face the component to which it is combined.

The negative lead 135 is electrically connected to the negative tab 115 and the negative terminal 145 . The negative lead 135 may be configured to be bent in a generally "L" shape. In more detail, the first portion 135a of the negative lead 135 may be disposed to face the bottom surface of the cap plate 140 to be subsequently bonded to the cap plate 140 . Here, the negative insulating plate 132 may be interposed between the first part 135a and the cap plate 140 so that the first part 135a and the cap plate 140 may be electrically disconnected from each other. In addition, a second portion 135b of the negative electrode lead 135 extending in a different direction from the first portion 135a may be disposed to face the negative electrode tab 115 to be subsequently bonded to the negative electrode tab 115 . In order to form the connection between the cap plate 140 and the negative electrode tab 115, the negative electrode lead 135 may be configured to be bent in different directions to face the components combined therewith, but aspects of the present invention are not limited thereto. For example, the negative electrode lead 135 may have the shape of a flat plate.

The negative electrode insulating plate 132 is interposed between the negative electrode lead 135 and the bottom surface of the cap plate 140 to electrically insulate the negative electrode lead 135 and the cap plate 140 . The negative insulating plate 132 can electrically insulate the negative lead 135 and the cap plate 140 together with the spacer 142 described later. In addition, the negative insulating plate 132 may prevent the cap plate 140 electrically connected to the positive tab 114 of the electrode assembly 110 from conducting electricity to the opposite polarity. Terminal holes 135 ′ and 132 ′ for allowing the anode terminal 145 to pass therethrough may be formed in the anode lead 135 and the anode insulating plate 132 .

Meanwhile, similar to the case where the negative electrode insulating plate 132 is provided between the cap plate 140 and the negative electrode lead 135 , the positive electrode insulating plate 131 may be provided between the cap plate 140 and the positive electrode lead 134 . The positive insulating plate 131 may be provided to establish balance with respect to the negative insulating plate 13 . That is, the positive insulating plate 131 may be inserted to maintain a balance between the height between the cap plate 140 and the positive electrode lead 134 and the height between the cap plate 140 and the negative electrode lead 135 . In addition, the positive insulating plate 131 may be interposed between the cap plate 140 and the positive lead 134 to increase the bonding strength during compression bonding using a bonding pin 141 described later.

The cover plate 140 may be a metal plate sized and shaped to correspond to the top opening of the housing 120 . The cap plate 140 includes a coupling pin 141 , a positive terminal 144 , a negative terminal 145 and a gasket 142 .

The bonding pin 141 securely bonds the positive electrode lead 134 to the cap plate 140 . For example, the bonding pins 141 protruding from the bottom surface of the cap plate 140 may be assembled to pass through the positive electrode lead 134, and the bottom ends of the bonding pins 141 protruding from the bottom surface of the cap plate 140 may be compression-bonded to the positive electrode lead 134 by riveting or rotating the bottom surface. For example, in the case of bonding by riveting, the bottom ends of the bonding pins 141 are compressed with respect to the bottom surface of the positive electrode lead 134 by hitting the bottom ends of the bonding pins 141 protruding from the bottom surface of the cap plate 140 with a hammer. In the case of bonding by rotation, the bottom ends of the bonding pins 141 are compressed with respect to the bottom surface of the positive electrode lead 134 by pressing the bottom ends of the bonding pins 141 exposed to the bottom surface of the positive electrode lead 134 using a processing tool that is rotated at a high speed . Meanwhile, in other embodiments, the positive lead 134 and the cap plate 140 may be bonded to each other by welding.

The positive terminal 144 may be a portion integrally protruding from the cap plate 140 or may be formed as a separate member combined to cover the top surface of the cap plate 140 . In addition, similar to the cap plate 140, the positive terminal 144 may have a positive polarity. The positive terminal 144 may be connected to the positive electrode 111 of the electrode assembly 110 through the positive lead 134 .

The negative terminal 145 may be assembled to pass through the cap plate 140 . The negative terminal 145 may establish an insulating connection with the cap plate 140 and may extend to the top surface of the cap plate 140 . The negative terminal 145 may be connected to the negative electrode 112 of the electrode assembly 110 through the negative lead 135 .

In more detail, the negative terminal 145 may be assembled to pass through the cap plate 140 , the insulating plate 132 and the terminal holes 140 ′, 132 ′ and 135 ′ of the negative lead 135 , and the bottom portion of the negative terminal 145 is pressed against the bottom of the negative lead 135 surface, so that the cap plate 140 , the insulating plate 132 and the negative electrode lead 135 are integrally bonded to each other in a state of alignment.

For example, the cap plate 140 , the insulating plate 132 and the negative electrode lead 135 are stacked to cover each other, the negative electrode terminal 145 is continuously inserted into the terminal holes 140 ′, 132 ′ and 135 ′ from the top of the cap plate 140 to be assembled with each other, from the negative electrode terminal 145 The bottom of the anode lead 135 exposed to the bottom surface of the anode lead 135 is riveted or rotated, thereby assembling the anode terminal 145 in a state where the anode terminal 145 is pressed against the bottom surface of the anode lead 135 .

The bottom of the negative terminal 145 is compression bonded to the bottom surface of the negative lead 135 . However, welding is also performed on the bottom of the negative electrode terminal 145, thereby bonding the negative electrode terminal 145 and the negative electrode lead 135 to each other more closely. The combination of the negative terminal 145 and the negative lead 135 forms a charge/discharge path for the negative electrode. Meanwhile, the top of the negative terminal 145 protrudes from its cylindrical body in the shape of a plate, and is then compressed with respect to the top surface of the cap plate 140 .

Meanwhile, the gasket 142 is interposed between the negative terminal 145 and the cap plate 140 . That is, the negative terminal 145 is assembled with the cap plate 140 by inserting the gasket 142 between the negative terminal 145 and the cap plate 140 . Here, a terminal hole 140 ′ for allowing the negative terminal 145 to pass therethrough is formed in the cap plate 140 . The negative terminal 145 is inserted into the terminal hole 140 ′ of the cap plate 140 with the gasket 142 inserted between the negative terminal 145 and the cap plate 140 , thereby electrically insulating the negative terminal 145 from the cap plate 140 . The gasket 142 seals the peripheral area of the terminal hole 140 ′, thereby preventing leakage of an electrolyte (not shown) accommodated in the case 120 and performing a sealing function to prevent penetration of external impurities into the cap plate 140 .

4 is a perspective view of an electrode assembly in a secondary battery according to an embodiment of the present invention, FIG. 5 is a front view of an electrode plate in a secondary battery according to an embodiment of the present invention, and FIG. 6 is an implementation of the present invention An enlarged front view of an electrode tab in an example secondary battery. Since the electrode assembly is substantially the same as that described above, a repeated description of the electrode assembly will not be given and the following description will focus on the configuration of the electrode tab.

4 to 6 , the electrode assembly 110 includes a positive electrode plate 111 , a negative electrode plate 112 , and a separator 113 interposed between the positive electrode plate 111 and the negative electrode plate 112 . In addition, the electrode assembly 110 includes a positive electrode tab 114 connected to the positive electrode plate 111 to subsequently protrude upward, and a negative electrode tab 115 connected to the negative electrode plate 112 to subsequently protrude upward.

The positive electrode tab 114 is formed to protrude to the top of the positive electrode plate 111 . Here, the positive electrode tab 114 includes a first region 114a in direct contact with the positive electrode plate 111, a second region 114b spaced apart from the first region 114a while being parallel to the first region 114a, and connecting the first region 114a and the second region 114b Circular portion 114c of region 114b. Here, the first region 114a preferably has a larger length than that of the second region 114b. In addition, the rounded portion 114c is preferably formed by a rounding process.

The negative electrode tab 115 may have the same configuration as that of the positive electrode tab 114 . That is, the negative electrode tab 115 includes a first region 115a in direct contact with the negative electrode plate 112, a second region 115b spaced apart from the first region 115a while being parallel to the first region 115a, and connecting the first region 115a and the The circular portion 115c of the second region 115b.

The positive electrode tab 114 and the negative electrode tab 115 (hereinafter, collectively referred to as electrodes) may be formed by cutting uncoated portions of the positive electrode plate 111 and the negative electrode plate 112 (hereinafter, collectively referred to as electrode plates) using a laser notching device. lugs). In this manner, the electrode plates 111 and 112 having the electrode tabs 114 and 115 are wound with the separator 113 interposed between the electrode plates 111 and 112 , thereby forming the electrode assembly 110 . Here, the electrode plates 111 and 112 and the separator 113 are wound using a plate winding device (not shown) including a plurality of rollers for conveying the electrode plates 111 and 112 and the separator 113 .

The lengths of the first regions 114a and 115a of the electrode tabs 114 and 115 are greater than the lengths of the second regions 114b and 115b, the circular portion 114c is formed between the first and second regions 114a and 114b, and the circular portion 115c is formed between the first and second regions 114a and 114b. Between the first region 115a and the second region 115b, thereby preventing the electrode tabs 114 and 115 made of thin, soft materials from being folded or torn by the rollers during winding the electrode plates 111 and 112.

In more detail, in the process of processing the electrode tabs 114 and 115 or transferring the electrode plates 111 and 112 using rollers, if tension is applied to the electrode plates 111 and 112 , stress is concentrated on the electrode tabs 114 and 115 . The concentration of stress occurs at the bottoms of the electrode tabs 114 and 115, that is, the first regions 114a and 115a. Here, the widths of the first regions 114a and 115a are made larger than the widths of the second regions 114b and 115b, thereby preventing the concentration of stress. In addition, the circular portion 114c is formed between the first region 114a and the second region 114b, and the circular portion 115c is formed between the first region 115a and the second region 115b, which can disperse the stress more effectively, thereby effectively preventing the electrode Folding or tearing of tabs 114 and 115. In addition, even if the widths of the first regions 114a and 115a are increased by the circular portions 114c and 115c, the overall width of the electrode tabs 114 and 115 can be prevented from being extremely increased.

6, the radius A of the circular portion 114c may be 1 to 1.5 times the length B of the second region 114b. If the radius A of the circular portion 114c is smaller than the length B of the second region 114b, the effect of dispersing stress is weak, and the positive electrode tab 114 may be folded or torn during winding of the electrode assembly 110. In addition, if the radius A of the circular portion 114c is greater than 1.5 times the length B of the second region 114b, the length of the first region 114a may be extremely increased. That is, since the length of the first region 114a is increased, the distance between each positive electrode tab 114 is decreased, which is not desirable.

Meanwhile, since the radius A of the circular portion 114c is 1 to 1.5 times the length of the second region 114b, the length of the first region 114a may be 3 to 4 times the length of the second region 114b.

In addition, the radius A of the circular portion 114c may be 0.35 to 1 times the height C of the positive electrode tab 114 . If the radius A of the circular portion 114 c is less than 0.35 times the height C of the positive electrode tab 114 , the effect of dispersing stress is weak, and the positive electrode tab 114 may be folded or torn during winding of the electrode assembly 110 . In addition, if the radius A of the circular portion 114c is greater than the height C of the positive electrode tab 114, the length of the first region 114a is extremely increased. Eventually, the distance between each positive tab 114 may decrease, which is not desirable.

Meanwhile, in the case of the negative electrode tab 115, the radius of the circular portion 115c may be 1 to 1.5 times the length of the second region 115b. In addition, the radius of the circular portion 115c may be 0.35 to 1 times the height of the negative electrode tab 115, which is substantially the same as the case of the positive electrode tab 114, and a repeated description will not be given.

7 illustrates stress distribution according to the configuration of the electrode tab in the secondary battery according to the embodiment of the present invention.

7, the rolls of electrode plates each including electrode tabs of different shapes (ie, rectangular electrode tabs (a), trapezoidal electrode tabs b, and circular electrode tabs c) were simulated using computer-aided engineering (CAE). around the process and show its results. Here, copper foil or aluminum foil having a thickness of 8 μm to 12 μm is used as each electrode plate. In addition, electrode tabs were formed by processing the uncoated portion of the electrode plate with a rectangular laser. In addition, each electrode plate was wound while passing through the roll at a winding speed of 780 mm/s. Here, the same tension is applied to each electrode plate. In Fig. 7, the circular bands appearing on the electrode tabs shown in Fig. 7 indicate stress distribution lines and the red portions indicate regions with the highest stress. Typically, a circular fingernail-like band is formed on the electrode tab and the electrode tab is folded or torn along the band during winding of the electrode plate.

As shown in FIG. 7 , the larger the base of the electrode tab (ie, the first region of the electrode tab), the smaller the stress. Therefore, the larger the first area of the electrode tab, the least folding of the electrode tab can be expected. In particular, significantly reduced stress concentrations are exhibited. The electrode tab c having the rounded portion exhibits the highest stress dispersing effect, wherein the electrode tab c has a relatively wide first region as the base of the electrode tab while the overall width of the electrode tab is not increased. Therefore, in the case of using an electrode tab having a circular portion, folding of the electrode tab is minimized during winding of the electrode plate.

Meanwhile, as understood from the simulation results shown in FIG. 7 , when the winding was performed at a high speed of 780 mm/s, the electrode tab having only the circular portion did not fold. Therefore, it is understood that the electrode tab exhibits the most desirable characteristics based on the winding speed. That is, in the case of using the electrode tab having the round portion, the folding of the electrode tab can be minimized even during high-speed winding of the electrode plate.

8 illustrates stress distributions of electrode tabs having sizes of different numerical values in a secondary battery according to an embodiment of the present invention.

Referring to Figure 8, the winding of electrode plates each comprising circular electrode tabs was simulated using computer aided engineering (CAE) by varying the radius of each circular portion and the length of the second region on top of each electrode tab craft. The following table lists the simulation results for the occurrence or non-occurrence of folding of each electrode tab according to the radius of the circular portion and the length of the second region.

Table 1

(○: folding occurs, ×: folding does not occur)

In Table 1, the length of the second region and the radius of the circular portion were all measured in millimeters, and the electrode tab had a fixed height of 28 mm.

As shown in Figure 8 and Table 1, the electrode tabs d, g, and h were not folded, and distinct stress distribution lines were shown in the other electrode tabs, suggesting that they were folded. That is, when the radius of the circular portion in each electrode tab is smaller than the length of the second region, the electrode tabs a, b, c, e, f and i are folded. However, when the radius of the circular portion is equal to or greater than the length of the second region, as in the electrode tabs d, g, and h, folding does not occur. Therefore, based on the simulation results, it is understood that the radius of the circular portion is preferably greater than or equal to the length of the second region. In addition, in order to prevent the length of the first region corresponding to the base of the electrode tab from being extremely increased, the radius of the circular portion is preferably less than 1.5 times the length of the second region.

As described above, in the secondary battery according to the embodiment of the present invention, the circular portion is formed in the electrode tab to make the first region of the electrode tab that is longer than the second region relatively close to the electrode plate. Here, the circular portion may have a radius of 1 to 1.5 times the length of the second region. In addition, the radius of the circular portion may be 0.35 to 1 times the height of the electrode tab.

That is, the circular portion is formed on the electrode tab to increase the length of the base body of the electrode tab, thereby effectively preventing stress from concentrating on the electrode tab during winding of the electrode plate. Therefore, stress concentration on the electrode tab can be prevented, thereby minimizing folding or tearing of the electrode tab. In addition, even in the process of winding the electrode plate at a high speed, the folding of the electrode plate can be prevented. Therefore, a high-quality electrode tab can be obtained, thereby preventing deterioration or ignition of the performance of the secondary battery due to failure of the electrode tab.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that This makes various changes in form and detail. It is therefore intended that the given embodiments be considered in all respects to be illustrative and not restrictive, and that reference made to the claims rather than the foregoing description indicates the scope of the invention.

Claims (4)

1. A secondary battery, comprising:

an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate;

an electrode tab extending from each of the positive and negative electrode plates and protruding to an upper portion of the electrode assembly;

a case accommodating the electrode assembly;

a cover plate sealing the top of the case; and

electrode terminals respectively protruding to an upper portion of the cap plate and connected to the electrode tabs,

wherein each of the electrode tabs includes a circular portion formed in a circular shape at a side of the electrode tab;

wherein the electrode tab includes a first region directly contacting each of the positive and negative electrode plates and a second region spaced apart from the first region while being parallel to the first region, the first region having a length greater than that of the second region;

wherein the radius of the rounded portion is 1 to 1.5 times the length of the second region; and is

Wherein the electrode tab has a width gradually increasing from a top to a bottom spaced apart from the positive and negative electrode plates.

2. The secondary battery according to claim 1, wherein the rounded portion connects the first region and the second region to each other.

3. The secondary battery according to claim 1, wherein the radius of the rounded portion is 0.35 to 1 times the height of the electrode tab.

4. The secondary battery according to claim 1, wherein the electrode tab is formed by cutting uncoated portions of the positive and negative electrode plates, which are not coated with the positive and negative electrode active materials, by laser processing.

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