Secondary battery

A secondary battery includes: an electrode assembly including a first electrode plate and a second electrode plate, and electrode uncoated portions protruding at opposite sides of the electrode assembly, a case accommodating the electrode assembly; a current collector including an electrode connecting portion located at a region corresponding to an electrode uncoated portion of the electrode uncoated portions and including a coupling groove located in a surface of the electrode connecting portion, and a terminal connecting portion bent from the electrode connecting portion and extending over the electrode assembly; and a sub-tab including a first region coupled to the coupling groove, and a second region bent from the first region and connected to the electrode uncoated portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0031255, filed on Mar. 19, 2019 in the Korean Intellectual Property Office, the entire content of which is herein incorporated by reference.

BACKGROUND

Aspects of embodiments of the present disclosure relate to a secondary battery.

2. Description of the Related Art

Unlike a primary battery that cannot be charged, a secondary battery can be charged and discharged. Low-capacity secondary batteries packaged in the form of a pack including a single battery cell may be used as the power source for various portable small-sized electronic devices, such as cellular phones or camcorders, while a high-capacity secondary battery having several tens to several hundreds of battery cells connected to one another may be used as a power source for motor drives, such as those in hybrid vehicles, electric vehicles, or the like.

The secondary battery may be manufactured in any of various shapes, such as a cylindrical shape and a prismatic shape. Secondary batteries are configured such that an electrode assembly including a positive electrode plate and a negative electrode plate with a separator as an insulator positioned therebetween, and an electrolyte, are housed in a case, and a cap plate is installed on the case. The electrode assembly may be electrically connected to electrode terminals through current collectors. Here, a volume of the case may be dependent according to structures of the current collectors. Therefore, a secondary battery capable of achieving a larger capacity within a limited size may be desired.

SUMMARY

According to an aspect of embodiments of the present disclosure, a secondary battery having an improved exothermic property and an increased capacity of an electrode assembly is provided.

According to one or more embodiments of the present disclosure, a secondary battery includes: an electrode assembly including a first electrode plate and a second electrode plate, and electrode uncoated portions protruding at opposite sides of the electrode assembly, a case accommodating the electrode assembly; a current collector including an electrode connecting portion located at a region corresponding to an electrode uncoated portion of the electrode uncoated portions and including a coupling groove located in a surface of the electrode connecting portion, and a terminal connecting portion bent from the electrode connecting portion and extending over the electrode assembly; and a sub-tab including a first region coupled to the coupling groove, and a second region bent from the first region and connected to the electrode uncoated portion.

The sub-tab may have a thickness equal to a depth of the coupling groove.

The electrode connecting portion may include a first surface facing a side surface of the electrode assembly, the electrode uncoated portion extending from the side surface, and a second surface opposite to the first surface and facing the case, and the coupling groove may be located in the first surface.

The second region of the sub-tab may be bent with the electrode uncoated portion to be coupled to the electrode connecting portion.

The second region of the sub-tab may be in contact with the second surface of the electrode connecting portion.

The electrode uncoated portion may be coupled to the second surface of the electrode connecting portion through the second region of the sub-tab while facing the case.

The coupling groove may be formed by reducing a thickness of a portion of the electrode connecting portion to which the first region of the sub-tab is coupled.

The coupling groove may be formed by increasing a thickness of a region of the electrode connecting portion other than a portion to which the first region of the sub-tab is coupled.

The electrode connecting portion may be asymmetrical toward a side from a side surface of the electrode assembly.

As described above, in a secondary battery according to an embodiment, since a coupling groove coupled to a sub-tab is located in a current collector, an internal space loss can be minimized or reduced, thereby increasing a capacity of the electrode assembly within a same volume.

In addition, since a coupling groove coupled to a sub-tab is located in a current collector with a thickness of the current collector increased, an exothermic property of a secondary battery according to the present disclosure can be improved while minimizing or reducing an internal space loss.

DETAILED DESCRIPTION

Herein, some example embodiments of the present disclosure will be described in further detail. The subject matter of the present disclosure, however, may be embodied in many different forms and should not be construed as being limited to the example (or exemplary) embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete and will convey the aspects and features of the present disclosure to those skilled in the art.

In addition, in the accompanying drawings, sizes or thicknesses of various components may be exaggerated for brevity and clarity. Like numbers 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. In addition, it is to be understood that when an element A is referred to as being “connected to” an element B, the element A may be directly connected to the element B or one or more intervening elements C may be present therebetween such that the element A and the element B are indirectly connected to each other.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is to be further understood that the terms “comprise” or “include” and/or “comprising” or “including,” when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It is to be understood that the spatially relative terms are intended to encompass different orientations of the secondary battery in use or operation in addition to the orientation depicted in the figures. For example, if the secondary battery in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “on” or “above” the other elements or features. Thus, the exemplary term “below” may encompass both an orientation of above and below.

FIG.1is a perspective view of a secondary battery according to an embodiment of the present disclosure.FIG.2is a cross-sectional view taken along the line A-A ofFIG.1.FIG.3is an enlarged cross-sectional view of a region “P” ofFIG.2.FIG.4is an exploded perspective view illustrating a coupling relationship between a current collector and a sub-tab.FIG.5is a perspective view illustrating a state in which a current collector and a sub-tab are coupled to each other.FIG.6is a cross-sectional view taken along the line B-B ofFIG.5.FIG.7is a cross-sectional view taken along the line C-C ofFIG.5.FIGS.8and9are an exploded perspective view and a perspective view, respectively, illustrating a coupling relationship between an electrode assembly and a current collector.FIG.10is a side view illustrating a state in which a current collector is coupled to an electrode assembly.FIG.11is an enlarged partial perspective view illustrating a state in which a current collector is coupled to an electrode assembly.

Referring first toFIGS.1to3, a secondary battery100according to an embodiment includes an electrode assembly110, current collectors120and130, sub-tabs140, a case150, and a cap assembly160.

The electrode assembly110may be produced by stacking a plurality of stacks each including a first electrode plate, a separator, and a second electrode plate, which are thin plates or layers. Here, the first electrode plate may operate as a positive electrode, and the second electrode plate may operate as a negative electrode. Of course, polarities of the first electrode plate and the second electrode plate may be reversed and arranged according to the option of a person of ordinary skill in the art.

In an embodiment, the first electrode plate is formed by coating a first electrode active material, such as a transition metal oxide, on a first electrode current collector formed of a metal foil made of aluminum, for example. The first electrode plate includes a first electrode uncoated portion111that is a region without the first electrode active material coated thereon. The first electrode uncoated portion provides a passage of a flow of current between the first electrode plate and an exterior of the first electrode plate.

In an embodiment, the first electrode uncoated portion111may be overlapped at a same position when multiple first electrode plates are stacked, forming a multi-tab structure. In an embodiment, the first electrode uncoated portion111may protrude to a first side of the electrode assembly110and may include a plurality of first electrode uncoated portions111welded to one another, forming a first current collector tab. In an embodiment, the first current collector tab111is integrally formed with the first electrode plate and is drawn out from each of the stacked first electrode plates, thereby increasing current collecting efficiency of the electrode assembly110. However, in another embodiment, the first current collector tab111may be separately formed from the first electrode plate according to the option of a person skilled in the art.

In an embodiment, the second electrode plate is formed by coating a second electrode active material, such as graphite or carbon, on a second electrode current collector formed of a metal foil made of copper or nickel, for example. The second electrode plate includes a second electrode uncoated portion112that is a region without the second electrode active material coated thereon.

In an embodiment, the second electrode uncoated portion112may be overlapped at a same position when multiple second electrode plates are stacked, forming a multi-tab structure. In an embodiment, the second electrode uncoated portion112may protrude to a second side of the electrode assembly110and may include a plurality of second electrode uncoated portions welded to one another, forming a second current collector tab.

The separator may be positioned between the first electrode plate and the second electrode plate to prevent or substantially prevent electrical short circuits and to allow movement of lithium ions. The separator may be made of polyethylene, polypropylene, or a composite film made of polypropylene and polyethylene. However, embodiments of the present disclosure are not limited to the materials of the separator described above.

The electrode assembly110is accommodated in the case150with an electrolyte. The electrolyte may include a lithium salt, such as LiPF6, or LiBF4, dissolved in an organic solvent, such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC). In addition, the electrolyte may be in a liquid, solid, or gel phase.

The current collectors120and130include a first current collector120electrically connected to the first electrode plate and a second current collector130electrically connected to the second electrode plate.

The first current collector120is made of a conductive material, such as aluminum, and is brought into contact with the first electrode uncoated portion111extending to the first side of the electrode assembly110to then be electrically connected to the first electrode plate.

Referring toFIGS.4to7, in an embodiment, the first current collector120includes a first terminal connecting portion121and a first electrode connecting portion125, and a bent region is located between the first terminal connecting portion121and the first electrode connecting portion125.

In an embodiment, the first terminal connecting portion121is positioned above the electrode assembly110and is parallel with a cap plate161, which will later be described. For example, the first terminal connecting portion121is positioned between the electrode assembly110and the cap plate161and may be shaped of a substantially planar plate. In an embodiment, the first terminal connecting portion121includes a terminal hole122and a fuse hole123. Here, the fuse hole123is located closer to the bent region than the terminal hole122. A first terminal164, which will later be described, is coupled to the terminal hole122. The fuse hole123may be shaped as a rectangle, for example, an elongated rectangle perpendicular to, for example, the first terminal connecting portion121, but embodiments of the present disclosure are not limited thereto. The fuse hole123may be shaped to reduce the cross-sectional area of the first terminal connecting portion121. If a large amount of current flows in the secondary battery100due to an electrical short circuit occurring thereto, heat is generated in the secondary battery100, and a region where the fuse hole123is located may be fused and cut by the generated heat, thereby cutting off the flow of current. In an embodiment, a molding member124is located at an end of the first terminal connecting portion121to cover the fuse hole123. In an embodiment, the molding member124may extend from the first terminal connecting portion121to the first electrode connecting portion125. In an embodiment, the molding member124may be formed in the first terminal connecting portion121by insert-molding. In addition, the molding member124may prevent or substantially prevent an arc from being generated when the region where the fuse hole123is located is fused and cut. The molding member124may be generally made of an insulating material, such as polypropylene or polyethylene, but is not limited thereto.

The first electrode connecting portion125is bent from an end of the first terminal connecting portion121to then downwardly extend and is located at a side of the electrode assembly110. The first electrode uncoated portion111is connected to the first electrode connecting portion125.

Referring toFIGS.4to7, the first electrode connecting portion125has a first surface125aand a second surface125bopposite to the first surface125a. The first surface125afaces the electrode assembly110, and the second surface125bfaces the case150. A coupling groove126is located in the first surface125aof the first electrode connecting portion125. One of the sub-tabs140is coupled to the coupling groove126. The coupling groove126may extend in a length direction of the first electrode connecting portion125. In an embodiment, the coupling groove126has a depth equal to a thickness of the sub-tab140. Therefore, if the sub-tab140is coupled to the coupling groove126, the first surface125aof the first electrode connecting portion125is planarly formed. The coupling groove126may be provided by forming a groove at a portion of the first electrode connecting portion125, to which the sub-tab140is coupled (that is, by reducing a thickness of the portion to which the sub-tab140is coupled) or by increasing a thickness of a region other than the portion to which the sub-tab140is coupled. In the former case, the coupling groove126may reduce the thickness of a portion where the first electrode connecting portion125and the sub-tab140are coupled to each other, thereby minimizing or reducing an internal space loss and ultimately increasing the capacity of the secondary battery100. In the latter case, the coupling groove126may increase the overall thickness of the first electrode connecting portion125relative to the same volume and capacity, thereby improving the exothermic property. For example, if an electrical short circuit occurs to the secondary battery100, a large amount of current may flow in the secondary battery100and thus generates heat. As described above, heat conductivity can be reduced by increasing the thickness of the first electrode connecting portion125, thereby improving the exothermic property.

In an embodiment, the first electrode connecting portion125is bent from the end of the first terminal connecting portion121to then extend so as to be asymmetrical toward one side (that is, so as to be shifted) in view of a stacking direction of the electrode assembly110. That is, in an embodiment, the first electrode connecting portion125is formed only at one side relative to a central portion of the stacked electrode assembly110(e.g., the left or the right inFIG.9). In this way, if the first electrode connecting portion125is shifted toward one side in view of the stacking direction of the stacked electrode assembly110, the plurality of first electrode uncoated portions111may be collected together approximately at a center of the electrode assembly110to then be easily connected to the first electrode connecting portion125. In other words, since the first electrode connecting portion125is formed to be shifted toward one side in view of the stacking direction of the electrode assembly110, the length of the first electrode uncoated portion111can be minimized or reduced.

The second current collector130is made of a conductive material, such as nickel, and is brought into contact with the second electrode uncoated portion112extending to the second side of the electrode assembly110to then be electrically connected to the second electrode plate. The second current collector130includes a second terminal connecting portion131and a second electrode connecting portion135. Here, a bent region is located between the second terminal connecting portion131and the second electrode connecting portion135. In addition, a second terminal165is electrically connected to the second terminal connecting portion131. In an embodiment, the second current collector130has the same configuration as the first current collector120, and repeated explanations thereof will not be given.

The sub-tabs140are electrically coupled to the first electrode connecting portion125and the second electrode connecting portion135, respectively. In an embodiment, the sub-tabs140coupled to the first and second electrode connecting portions125and135may have a same configuration but may be made of different materials. For example, the sub-tab140coupled to the first electrode connecting portion125may be made of aluminum or an aluminum alloy, and the sub-tab140coupled to the second electrode connecting portion135may be made of copper or a copper alloy. The following description will be made by way of example with respect to the sub-tab140coupled to the first electrode connecting portion125.

The sub-tab140includes a first region141coupled to the coupling groove126of the first electrode connecting portion125, and a second region142bent from the first region141. The first region141may first be coupled to the coupling groove126located in the first surface125aof the first electrode connecting portion125and then fixed to the first electrode connecting portion125by welding. In an embodiment, the sub-tab140and the first electrode connecting portion125may be welded to each other by laser welding, resistance welding, or ultrasonic welding. In an embodiment, the sub-tab140has a smaller thickness than the first electrode connecting portion125so as to be easily bent in a subsequent process. The second region142is bent (e.g., vertically bent) from the first region141in an L-shaped configuration. The first electrode uncoated portion111of the electrode assembly110is welded to the second region142. In an embodiment, the second region142of the sub-tab140and the first electrode uncoated portion111is bent again to be coupled to the second surface125bof the first electrode connecting portion125. Here, the second region142is bent to be brought into contact with the second surface125bof the first electrode connecting portion125. That is, the first electrode uncoated portion111welded to the second region142is positioned to face the case150. Thus, as shown inFIGS.3to11, the first region141of the sub-tab140, the first electrode connecting portion125, the second region142of the sub-tab140, and the first electrode uncoated portion111are arranged in that order between the electrode assembly110and the case150.

Referring toFIGS.8and9, a coupling relationship between the first electrode uncoated portion111and the first current collector120will now be described according to an embodiment. First, as shown inFIG.8, the first current collector120is coupled to the cap assembly160, and the first region141of the sub-tab140is fixed to the coupling groove126of the first electrode connecting portion125by welding. Then, the second region142of the sub-tab140is bent perpendicular to the first region141to have the generally L-shaped configuration. Of course, the sub-tab140may be welded to the coupling groove126in a state in which the first region141and the second region142are positioned perpendicular to each other. Next, the first electrode uncoated portion111protruding to the first side of the electrode assembly110is welded to the second region142of the sub-tab140. Here, a plurality of first electrode uncoated portions111may be welded to one another, forming a single current collector tab.

Next, as shown inFIG.9, the sub-tab140is bent such that the second region142of the sub-tab140comes into contact with the second surface125bof the first electrode connecting portion125. Therefore, the sub-tab140may be bent approximately in a U-shaped configuration. In an embodiment, the sub-tab140and the first electrode uncoated portion111may be fixed to the first electrode connecting portion125by welding.

As described above, the sub-tab140is coupled to the coupling groove126of the first electrode connecting portion125so as not to protrude from the first electrode connecting portion125to thus minimize or reduce an internal space loss, thereby increasing the capacity of the secondary battery100.

The case150may be made of a conductive metal, such as aluminum, an aluminum alloy, or a nickel-plated steel, and may have a generally hexahedron shape having an opening through which the electrode assembly110is inserted and placed in the case150. The cap plate161is coupled to the opening of the case150to seal the case150. In an embodiment, the interior surface of the case150is subjected to insulation treatment to prevent or substantially prevent an electrical short circuit from occurring inside the case150. In addition, according to some embodiments of the present disclosure, an electrode of the electrode assembly110may be electrically connected to the case150through the cap plate161. In this case, the insulation treatment of the interior surface of the case150may also make it possible to prevent or substantially prevent an internal electrical short circuit. In an embodiment, the case150may operate as, for example, a positive electrode.

The cap assembly160is coupled to a top portion (opening) of the case150. In an embodiment, the cap assembly160includes the cap plate161, an electrolyte injection hole162, a safety vent163, the first terminal164, the second terminal165, a gasket166, a first terminal plate167, a second terminal plate168, a fastening plate169and a lower insulation member170.

The cap plate161may seal the opening of the case150and may be made of a same material as the case150. As an example, the cap plate161may be coupled to the case150by laser welding. In addition, the cap plate161may be electrically independent, or may be electrically connected to one of the first current collector120and the second current collector130in some cases.

In an embodiment, the electrolyte injection hole162for injecting an electrolyte is located in the cap plate161. The electrolyte is injected into the case150through the electrolyte injection hole162, and the electrolyte injection hole162is then sealed by a plug162a.

In an embodiment, the safety vent163having a smaller thickness than other regions of the cap plate161is located approximately at a center of the cap plate161. When an internal pressure of the case150is higher than a certain pressure (e.g., a preset rupture pressure), the safety vent163is ruptured, thereby preventing or substantially preventing the secondary battery100according to an embodiment of the present disclosure from exploding.

The first terminal164and the second terminal165are formed to pass through the cap plate161, respectively. The first terminal164is coupled to the terminal hole122of the first terminal connecting portion121to then be electrically connected to the first current collector120. Similarly, the second terminal165is coupled to a terminal hole of the second terminal connecting portion131to then be electrically connected to the second current collector130.

The gasket166is located between each of the first and second terminals164and165and the cap plate161. The gasket166is configured to cover the exterior side of each of the first and second terminals164and165and is made of an insulating material. The gasket166seals a gap between each of first and second terminals164and165and the cap plate161. The gasket166prevents or substantially prevents external moisture from penetrating into the secondary battery100and prevents or substantially prevents the electrolyte accommodated in the secondary battery100from flowing out.

The first terminal plate167is coupled to the first terminal164upwardly protruding from the cap plate161. After the first terminal plate167is coupled to the first terminal164, a top portion of the first terminal164may be riveted or a boundary surface between the first terminal plate167and the first terminal164may be welded to then be fixed to the first terminal164.

The second terminal plate168is coupled to the second terminal165upwardly protruding from the cap plate161. After the second terminal plate168is coupled to the second terminal165, a top portion of the second terminal165may be riveted or a boundary surface between the second terminal plate168and the second terminal165may be welded to then be fixed to the second terminal165.

The fastening plate169is located between the cap plate161and the first terminal plate167and between the cap plate161and the second terminal plate168. The fastening plate169may be made of an electrically conductive material or an insulating material. For example, the fastening plate169located under the first terminal plate167may be may be made of an electrically conductive material, and the fastening plate169located under the second terminal plate168may be made of an insulating material. In this case, the first terminal164may have the same polarity as the cap plate161. In addition, if the fastening plate169is made of an insulating material, the first terminal164and the second terminal165may be electrically disconnected from the cap plate161.

The lower insulation member170is located between the first current collector120and the cap plate161and between the second current collector130and the cap plate161, thereby electrically insulating the first and second current collectors120and130from the cap plate161.

In embodiments, since the coupling groove126having the sub-tab140coupled thereto is formed in the current collector120, the secondary battery100according to the embodiment of the present disclosure can minimize or reduce an internal space loss, thereby increasing the capacity of the electrode assembly110within a same volume.

In addition, the secondary battery100according to an embodiment of the present disclosure includes the coupling groove126formed in the current collector120, the coupling groove126having the sub-tab140coupled thereto in such a manner that the thickness of the current collector120increases, thereby improving the exothermic property while minimizing or reducing the internal space loss.

While the secondary battery according to the present disclosure has been particularly shown and described with reference to one or more example 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 disclosure as set forth by the following claims.