CN106207070B

CN106207070B - Secondary battery

Info

Publication number: CN106207070B
Application number: CN201510292337.9A
Authority: CN
Inventors: 曹基奉; 金东祐; 黄淳学; 李承桓; 洪镇旭; 金奎镐; 崔京泽; 孟相辰; 闵仲基; 申京秀
Original assignee: Samsung SDI Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 2015-01-28
Filing date: 2015-06-01
Publication date: 2020-12-04
Anticipated expiration: 2035-06-01
Also published as: KR102324345B1; KR20160092748A; CN106207070A

Abstract

Provided is a secondary battery which can prevent an electrode tab from being folded or torn during the winding of an electrode plate by forming a rounded 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 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 portion of the electrode tab.

Description

Secondary battery

This application claims priority from korean patent application No. 10-2015-0013523, filed in korean intellectual property office on 28.1.2015, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates to a secondary battery.

Background

In general, a secondary battery may be repeatedly charged and discharged, unlike a non-rechargeable primary battery. According to the technical development and the increase in the production of mobile devices such as mobile phones and notebook computers, the demand for secondary batteries as energy sources is rapidly increasing. Recently, research into secondary batteries used in electric vehicles or hybrid vehicles is actively being conducted as an alternative energy source to fossil fuels.

Disclosure of Invention

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

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

According to an aspect of the present invention, there is provided a secondary battery including: 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 portion of the electrode tab.

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

The electrode tab may include 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, and the first region may have a length greater than that of the second region.

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

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

The radius of the rounded 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 and negative electrode plates, which are not coated with the positive and negative active materials, through laser treatment.

As described above, the secondary battery according to the present invention may prevent the electrode tab from being bent or torn during the winding of the electrode plate by forming the rounded portion on the electrode tab.

Drawings

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

fig. 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;

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

fig. 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;

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

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

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

Detailed Description

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

Various 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 the present disclosure are provided so that this disclosure will be thorough and complete, and will convey various aspects of the disclosure to those skilled in the art.

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

Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, 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, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, for example, a first member, a first element, a first region, a first layer and/or a first portion discussed below could be termed a second member, a second element, a second region, a second layer and/or a second portion without departing from the teachings of the present disclosure.

Fig. 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 illustrating a connection relationship between each of an electrode tab, an electrode lead, and an electrode terminal in the secondary battery shown in fig. 1.

Referring to fig. 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 a 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 into a rectangular parallelepiped shape. 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 aspects of the present invention are not limited thereto. The electrolyte may serve as a moving medium for lithium ions generated through an electrochemical reaction between the positive electrode plate 111 and the negative electrode plate 112 of the secondary battery 100 during charge and discharge. 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 polyelectrolyte.

The positive electrode plate 111 may be formed by coating a positive electrode active material on at least one surface of a positive electrode collector (not shown). Similarly, the negative electrode plate 112 may be formed by coating a negative electrode active material on at least one surface of a negative electrode collector (not shown). For example, in the embodiment of the present invention, the positive electrode plate 110 may be disposed at the outermost portion of the electrode assembly 110 for the purpose of promoting heat radiation through the case 120 by disposing a positive electrode collector (not shown) generating a relatively large amount of heat adjacent to the outside of the case 120. For example, a positive current collector (not shown) may be in direct contact with the casing 120 or at least may be in thermal contact with the casing 120. Here, the expression "in 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 and

negative electrode tabs

114 and 115 may be connected to at least one or more positions of the positive and

negative electrode plates

111 and 112. The positive electrode tab 114 and the negative electrode tab 115 are generally formed to have a height in the range of 10mm to 30 mm. Throughout the description 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 non-coating portion of the positive electrode plate 111, which 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 a negative electrode uncoated portion of the negative electrode plate 112, which 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 and

negative electrode tabs

114 and 115. Here, each positive electrode tab 114 and each negative electrode tab 115 may be separately prepared 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

rounded portions

114c and 115 c. The radius of

rounded portions

114c and 115c may be in the range of 7mm to 30 mm. The

rounded portions

114c and 115c will be described in more detail later.

The positive electrode tab 114 may be connected to the cap plate 140 itself, and the negative electrode tab 115 may be connected to a negative electrode 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 to the top surface of the cap plate 140. Here, the positive electrode tab 114 may be connected to the positive electrode lead 134 to be then electrically connected to the positive electrode terminal 144. In addition, the negative electrode tab 115 may be connected to the negative electrode lead 135 to be then electrically connected to the negative electrode terminal 145. Throughout the specification of the present invention, the cathode lead 134 and the anode lead 135 may be collectively referred to as electrode leads 134 and 135.

The plurality of

electrode tabs

114 and 115 may be concentrated into a single bundle (single bundle) by spot welding (tack welding) before the

electrode tabs

114 and 115 are connected to the electrode leads 134 and 135. The

electrode tabs

114 and 115, which are concentrated into a single bundle by spot welding, can be more easily connected to the electrode leads 134 and 135.

The electrode assembly 110 and an electrolyte (not shown) are accommodated in the case 120. The housing 120 has a top end opening and may be formed by deep drawing. The top opening of the housing 120 may be sealed by a cover plate 140. Here, the contact portions of the cap 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 electrically connects the positive tab 114, the cap plate 140, and the positive terminal 144. The positive lead 134 may be configured to bend in a substantially "L" shape. In more detail, the positive electrode lead 134 may extend in two different directions to be then bent. The first portion 134a of the cathode lead 134 may be disposed to face the bottom surface of the cap plate 140 to be subsequently bonded to the cap plate 140. In addition, a 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 coupled to the positive electrode tab 114. To form the connection between the cap plate 140 and the positive electrode tab 114, the positive electrode lead 134 may be configured to be bent in different directions to face the element coupled thereto.

The negative lead 135 electrically connects the negative tab 115 and the negative terminal 145. The negative electrode lead 135 may be configured to be bent in a substantially "L" shape. In more detail, the first portion 135a of the negative electrode 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 electrode insulating plate 132 may be interposed between the first portion 135a and the cap plate 140 such that the first portion 135a and the cap plate 140 may not be electrically connected to each other. In addition, the 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 a 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 an element coupled thereto, but aspects of the present invention are not limited thereto. For example, the negative electrode lead 135 may have a flat plate shape.

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 electrode insulating plate 132, together with a gasket 142 described later, may electrically insulate the negative electrode lead 135 and the cap plate 140. In addition, the negative electrode insulating plate 132 may prevent the cap plate 140, which is electrically connected to the positive electrode tab 114 of the electrode assembly 110, from being electrically conducted to the opposite polarity. Terminal holes 135 'and 132' for allowing the negative terminal 145 to pass therethrough may be formed in the negative lead 135 and the negative insulating plate 132.

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

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 coupling pin 141 securely couples the positive electrode lead 134 with the cap plate 140. For example, a coupling pin 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 end of the coupling pin 141 protruding from the bottom surface of the cap plate 140 may be compression-coupled to the bottom surface of the positive electrode lead 134 by riveting or rotating. For example, in the case of bonding by riveting, the bottom end of the bonding pin 141 protruding from the bottom surface of the cap plate 140 is compressed with respect to the bottom surface of the positive electrode lead 134 by striking the bottom end of the bonding pin 141 with a hammer. In the case of bonding by rotation, the bottom end of the bonding pin 141 exposed to the bottom surface of the positive electrode lead 134 is compressed with respect to the bottom surface of the positive electrode lead 134 by pressing the bottom end of the bonding pin 141 using a processing tool rotating at a high speed. Meanwhile, in other embodiments, the positive electrode lead 134 and the cap plate 140 may be bonded to each other by welding.

The positive terminal 144 may be a portion integrally protruded 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, the positive terminal 144 may have a positive polarity, similar to the cap plate 140. The positive electrode terminal 144 may be connected to the positive electrode 111 of the electrode assembly 110 through the positive electrode 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 a negative lead 135.

In more detail, the negative terminal 145 may be assembled to pass through the terminal holes 140', 132', and 135' of the cap plate 140, the insulating plate 132, and the negative lead 135, and the bottom portion of the negative terminal 145 is pressed on the bottom surface of the negative lead 135, thereby integrally coupling the cap plate 140, the insulating plate 132, and the negative lead 135 to each other in a position-aligned state.

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, and caulking or rotation is performed from the bottom of the negative electrode terminal 145 exposed to the bottom surface of the negative electrode lead 135, thereby assembling the negative electrode terminal 145 in a state where the negative electrode terminal 145 is pressed on the bottom surface of the negative electrode 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 to the bottom of the negative electrode terminal 145, thereby more closely bonding the negative electrode terminal 145 and the negative electrode lead 135 to each other. The combination of the negative terminal 145 and the negative lead 135 forms a charge/discharge path of 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, a 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 in a state in which the gasket 142 is 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 region of the terminal hole 140', thereby preventing leakage of an electrolyte (not shown) contained in the case 120 and performing a sealing function to prevent external impurities from penetrating into the cap plate 140.

Fig. 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 enlarged front view of an electrode tab in a secondary battery according to an embodiment of the present invention. Since the electrode assembly is substantially the same as described above, a repetitive description of the electrode assembly will not be given and the following description will focus on the construction of the electrode tabs.

Referring to fig. 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 then protrude upward and a negative electrode tab 115 connected to the negative electrode plate 112 to then 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 directly contacting 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 a circular portion 114c connecting the first region 114a and the second region 114 b. Here, the first region 114a preferably has a length greater than that of the second region 114 b. In addition, the rounded portion 114c is preferably formed through 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 directly contacting 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 a circular portion 115c connecting the first region 115a and the second region 115 b.

The positive electrode tab 114 and the negative electrode tab 115 (hereinafter, collectively referred to as electrode tabs) 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 slitting device. In this manner, the

electrode plates

111 and 112 having the

electrode tabs

114 and 115 are wound in such a manner that the separator 113 is 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

first regions

114a and 115a of the

electrode tabs

114 and 115 have a length greater than that of the

second regions

114b and 115b, and the rounded portion 114c is formed between the first and

second regions

114a and 114b and the rounded portion 115c is formed between the first and

second regions

115a and 115b, thereby preventing the

electrode tabs

114 and 115, which are made of a thin, soft material, from being folded or torn by the rolls during the winding of the

electrode plates

111 and 112.

In more detail, if tension is applied to the

electrode plates

111 and 112 during the process of processing the

electrode tabs

114 and 115 or transferring the

electrode plates

111 and 112 using rollers, stress is concentrated on the

electrode tabs

114 and 115. The concentration of stress occurs at the bottom of the

electrode tabs

114 and 115, i.e., the

first regions

114a and 115 a. Here, the width of the

first regions

114a and 115a is made larger than the width of the

second regions

114b and 115b, thereby preventing concentration of stress. In addition, the rounded portion 114c is formed between the first and

second regions

114a and 114b, and the rounded portion 115c is formed between the first and

second regions

115a and 115b, so that stress can be more effectively dispersed, thereby effectively preventing folding or tearing of the

electrode tabs

114 and 115. In addition, even if the width of the

first regions

114a and 115a is increased by the

circular portions

114c and 115c, the entire width of the

electrode tabs

114 and 115 can be prevented from being excessively increased.

Referring to fig. 6, the radius a of the rounded 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 the winding of the electrode assembly 110. In addition, if the radius a of the rounded 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 excessively 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 rounded 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 114 b.

In addition, the radius a of the rounded portion 114C may be 0.35 to 1 times the height C of the positive electrode tab 114. If the radius a of the rounded portion 114C 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 the winding of the electrode assembly 110. In addition, if the radius a of the rounded portion 114C is greater than the height C of the positive electrode tab 114, the length of the first region 114a may be excessively increased. Eventually, the distance between each positive electrode tab 114 may be reduced, which is undesirable.

Meanwhile, in the case of the negative electrode tab 115, the radius of the rounded portion 115c may be 1 to 1.5 times the length of the second region 115 b. In addition, the radius of the rounded 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 repetitive description will not be given.

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

Referring to fig. 7, a winding process of electrode plates each including electrode tabs of different shapes, i.e., a rectangular electrode tab (a), a trapezoidal electrode tab b, and a circular electrode tab c, was simulated using Computer Aided Engineering (CAE), and the results thereof are shown. Here, a copper foil or an aluminum foil having a thickness of 8 to 12 μm is used as each electrode plate. In addition, an electrode tab is formed by processing an uncoated portion of the electrode plate using a rectangular laser. Further, each electrode plate was wound while passing through a roll at a winding speed of 780 mm/s. Here, the same tension is applied to the respective electrode plates. In fig. 7, circular bands appearing on the electrode tab shown in fig. 7 indicate stress distribution lines and red portions indicate regions having the highest stress. Generally, a circular nail-shaped band is formed on the electrode tab and the electrode tab may be folded or torn along the band during the process of winding the electrode plate.

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

Meanwhile, as understood from the simulation result shown in fig. 7, when the winding is performed at a high speed of 780mm/s, the electrode tab having only the circular portion is not folded. 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 rounded portion, the folding of the electrode tab can be minimized even during the high-speed winding of the electrode plate.

Referring to fig. 8, a winding process of electrode plates each including a circular electrode tab was simulated using Computer Aided Engineering (CAE) by changing the radius of each circular portion and the length of the second region on top of each electrode tab. The following table lists simulation results of the occurrence or non-occurrence of the folding of each electrode tab according to the radius of the circular portion and the length of the second region.

TABLE 1

(occurrence of folding: non-occurrence of folding: X)

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 fig. 8 and table 1, the electrode tabs d, g, and h were not folded, and a significant stress distribution line was shown in the other electrode tabs, suggesting that they were folded. That is, when the radius of the circular part is less than the length of the second region in each electrode tab, the electrode tabs a, b, c, e, f and i are folded. However, when the radius of the rounded portion is equal to or greater than the length of the second region, like 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 excessively increased, the radius of the rounded 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, which is relatively close to the electrode plate, longer than the second region. Here, the rounded portion may have a radius 1 to 1.5 times the length of the second region. In addition, the radius of the rounded portion may be 0.35 to 1 times the height of the electrode tab.

That is, a rounded portion is formed on the electrode tab to increase the length of the base of the electrode tab, thereby effectively preventing stress from being concentrated on the electrode tab during the winding of the electrode plate. Accordingly, stress concentration to 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 high speed, the electrode plate can be prevented from being folded. Accordingly, it is possible to obtain a high-quality electrode tab, thereby preventing the deterioration of the performance of the secondary battery or the ignition due to the 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 various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. It is therefore intended that the present embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.

Claims

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.