Secondary battery

A secondary battery including: an electrode assembly including a plurality of first and second electrode plates, and a plurality of separators between the first and second electrode plates; a first electrode tab on the first electrode plate, and a second electrode tab on the second electrode plate; a case housing the electrode assembly, and the first and second electrode tabs; and first and second external lead terminals at an outer side of the case and electrically coupled to the first and second electrode tabs, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean Patent Application Serial No. 2009-0117577, filed on Dec. 1, 2009, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.

BACKGROUND

One or more embodiments of the present invention relate to a secondary battery.

2. Description of the Related Art

Secondary batteries have been esteemed as power sources for a variety of electronic and communication devices as they are rechargeable and portable.

In typical secondary batteries, electrode plates and separators are alternately stacked, or a stacked and wound-type electrode assembly is mounted in a case. In this case, an electrode tab is attached to the electrode plate of the electrode assembly, and an end portion of the electrode tab outwardly protrudes when the electrode assembly is mounted in the case. The electrode tab protruding from the case is electrically connected to an external electrode lead.

Here, leakage may occur from a contact portion with an electrode tab at an edge of a case that is a sealing portion.

Also, the electrode tab protruding from the case is welded to the external electrode lead. The electrode tab is coupled to the external electrode lead, which is located at a separate space outside the sealing portion of the case. Here, a separate space may be required, regardless of the capacity of the battery. The separate space ranges from about 15% to about 30% of the total volume of the battery pack. Accordingly, the total capacity of the battery may be reduced.

Additionally, the combination structure of the electrode tab and the external electrode lead has a mechanical safety limitation. The electrode tab and the external electrode lead are typically coupled by a welding method. Since a welding portion of the electrode tab and the external electrode lead is exposed to the outside of the case, the welding portion may be easily separated by contact with other components or external impacts.

SUMMARY

An aspect of embodiments of the present invention is directed toward a secondary battery that can inhibit reduction of sealing strength of a sealing portion caused when an electrode tab is protruded from a case.

Another aspect of embodiments of the present invention is directed toward a secondary battery with an enlarged internal capacity by excluding a space in which an electrode tab protrudes to the outside for coupling.

Another aspect of embodiments of the present invention is directed toward a secondary battery that can ensure mechanical safety at a coupling portion of an electrode tab and an external electrode lead.

An embodiment of the present invention provides a secondary battery including: an electrode assembly including a plurality of first and second electrode plates, and a plurality of separators between the first and second electrode plates; a first electrode tab on the first electrode plate, and a second electrode tab on the second electrode plate; a case housing the electrode assembly, and the first and second electrode tabs; and first and second external lead terminals at an outer side of the case and electrically coupled to the first and second electrode tabs, respectively.

The first and second external lead terminals may be encompassed by the case.

The first and second external lead terminals may be encompassed by sealing portions of the case.

Sealing portions of the case may be folded to encompass the first and second external lead terminals.

Sealing portions of the case may be folded to encompasses the first and second external lead terminal so that the first and second lead terminals are not exposed to the outside, and adhere the first or second lead terminals to the electrode assembly.

The case may include through holes corresponding to the first and second electrode tabs, respectively, and the first and second external lead terminals are coupled to the first and second electrode tabs, respectively, through the through holes.

The case may include first and second internal lead terminals between the first and second electrode tabs, and the first and second external lead terminals, respectively.

The first and second external lead terminals may be welded to the first and second internal lead terminals.

The first and second external lead terminals may be welded to the first and second internal lead terminals by ultrasonic welding or resistance welding.

The secondary battery may further include insulating layers between the case, and the first and second internal lead terminals, respectively.

The secondary battery may further include insulating layers between the case, and the first and second external lead terminals, respectively.

The electrode assembly may be a stacked-type, wherein the plurality of first electrode plates, the plurality of separators, and the plurality of second electrode plates are sequentially stacked.

The electrode assembly may be a jelly rolled-type, wherein the plurality of first electrode plates, the plurality of separators, and the plurality of second electrode plates are sequentially stacked and wound.

The first and second electrode tabs may be attached to the first and second electrode plates, respectively, at opposite sides of the electrode assembly.

The case may be a pouch-type case.

The case may include a laminate sheet comprising aluminum or an alloy thereof.

DETAILED DESCRIPTION

FIG. 1illustrates a perspective view of a secondary battery according to an embodiment of the present invention.FIG. 2illustrates a cross-sectional view taken along line II-II ofFIG. 1.FIG. 3illustrates a cross-sectional view taken along line III-III ofFIG. 1.FIGS. 4 through 8illustrate perspective views or plan views of a process for manufacturing a secondary battery according to an embodiment of the present invention.FIG. 4illustrates a perspective view of an electrode assembly attached with an electrode tab.FIG. 5illustrates a perspective view of first and second internal electrode leads coupled to an electrode tab.FIG. 6illustrates a plan view of an electrode assembly, an electrode tab, and first and second internal electrode leads mounted in a pouch.FIG. 7illustrates a perspective view of first and second external electrode leads coupled to a pouch.FIG. 8illustrates a perspective view of a secondary battery with folded sealing portions according to an embodiment of the present invention.

A second battery100according to an embodiment of the present invention includes an electrode assembly110having a plurality of positive electrode plates111and negative electrode plates112that are alternately stacked, a plurality of separators113interposed between the positive electrode plates111and the negative electrode plates112, a positive electrode tab assembly120having a plurality of positive electrode tabs attached to the respective positive electrode plates111, a negative electrode tab assembly130having a plurality of negative electrode taps attached to the respective negative electrode plates112, a pouch-type case (hereinafter, referred to as “pouch”)140that is sealed in a state where the electrode assembly110and the positive and negative electrode tabs assemblies120and130are mounted therein, and external positive electrode and negative electrode leads150and160that are installed at an external side of the pouch140and are respectively coupled to the positive electrode and negative electrode tab assemblies120and130.

The positive electrode tab assembly120and negative electrode tab assembly130are mechanically and electrically coupled to the external positive electrode lead150and the external negative electrode lead160, respectively, through a resistance welding, such as an ultrasonic welding or a spot welding. Here, through holes141and142are formed at portions of the pouch140corresponding to welded portions of the positive electrode tab assembly120and the negative electrode tab assembly130coupled to the external positive electrode lead150and the external negative electrode lead160, respectively. The through holes141and142may be formed to have a greater diameter than the welded portions of the positive electrode tab assembly120and the negative electrode tab assembly130coupled to the external positive electrode lead150and the external negative electrode lead160, respectively. Thus, the pouch140may not be damaged when the positive electrode tab assembly120and the negative electrode tab assembly130are coupled to the external positive electrode lead150and the external negative electrode lead160, respectively. In an embodiment of the present invention, the external positive electrode lead150may be fused with the internal positive electrode lead170, and the external negative electrode lead160may be fused with the internal negative electrode lead180.

The electrode assembly110is a stack-type electrode assembly in which the plurality of the electrode plates111and the plurality of the negative electrode plates112are alternately stacked, and the plurality of the separators113are interposed between the electrode and negative electrode plates111and112. This stack-type electrode assembly110is suitable for realizing a large capacity battery. The positive electrode plate111includes a positive electrode collector having a coated part on which a positive electrode active material is coated and an uncoated part on which no active material is coated. The separator113is interposed between the positive electrode and negative electrode plates111and112. The separator113may be formed of any materials that can enable electrons to travel. The separator113may be formed in a single layer or multiple porous layers formed of polyethylene, polypropylene, or the like.

At least one positive electrode tab of a positive electrode tab assembly120is attached to each positive electrode plate111. Also, at least one negative electrode tab assembly130is attached to each negative electrode plate112. In this case, the position of the positive electrode tab assembly120attached to the positive electrode plate111is opposite to the position of the negative electrode tab assembly130attached to the negative electrode plate112. To implement a large-capacity secondary battery according to an embodiment of the present invention, an electrode tab may be formed to have a greater width. In this case, since the electrode tabs are attached to the electrode plate in different directions, the two electrode tabs may not interfere with each other. Accordingly, the width of the electrode tabs can be increased to implement a large-capacity battery.

According to the manufacturing conditions of a battery, however, the positive electrode tab and the negative electrode tab may be attached to the positive electrode tab and the negative electrode tab in the same direction.

The pouch140may accept an electrode assembly110. In this case, the electrode assembly110, in which the positive electrode plates111and the negative electrode plates112are attached to the positive electrode tab assembly120and the negative electrode tab assembly130, respectively, is mounted in the pouch140.

The pouch140may be formed to have an internal space to accept the electrode assembly110. Here, the pouch140may be formed of one folded sheet, three sides of which are sealed with the electrode assembly110accepted and electrolyte injected. Alternatively, the pouch140may be formed using two sheets, four sides of which are sealed after the electrode assembly is accepted and the electrolyte is injected. In this case, three layers may be coupled to form the pouch140. That is, an internal surface layer may be formed on the inside of the pouch140. The internal surface layer may be formed of thermoplastic resin materials having suitable (or excellent) electrolyte resistance, such as polyethylene, polypropylene, and polyamide. On the other hand, an external surface layer of the pouch140may be formed of an insulating resin materials having suitable (or excellent) electric insulation property, such as polyamide-based resin and polyester-based resin. A metal layer formed of a metal having suitable (or excellent) flexibility and strength, such as aluminum and stainless steel, may be interposed between the internal and external surface layers.

The external positive electrode lead150is installed corresponding to the through hole141formed at a portion where the positive electrode tab assembly120is located in the pouch140. The external negative electrode lead160is installed corresponding to the through hole142formed at a portion where the negative electrode tab assembly130is located in the pouch140. Thus, the positive electrode tab assembly120is welded to the external positive electrode lead150through the through hole141. Also, the negative electrode tab assembly130is welded to the external negative electrode lead160through the through hold142. The external positive electrode lead150may be formed of the same material as the positive electrode tab assembly120. That is, the external positive electrode lead150may be formed of aluminum or an alloy thereof, but embodiments of the present invention are not limited thereto. The external negative electrode lead160may be formed of the same material as the negative electrode tab assembly130. That is, the external negative electrode lead160may be formed of copper, stainless steal, and/or nickel, but embodiments are not limited thereto.

An internal positive electrode lead170may be further installed at the uppermost end of the positive electrode tab assembly120, and an internal negative electrode lead180may be further installed at the uppermost end of the negative electrode tab assembly130in the pouch140. Accordingly, the positive electrode tab assembly120may be coupled to the internal positive electrode lead170to have an electrical coupling structure, and the negative electrode tab assembly130may be coupled to the internal negative electrode lead180to have an electrical coupling structure. In this structure, the external positive electrode lead150may be coupled to the internal positive electrode lead170through the through hole141, and the external negative electrode lead160may be coupled to the internal negative electrode lead180through the through hole142. The internal positive electrode lead170and the internal negative electrode lead180may be formed of the same material as the coupled components, but embodiments of the present invention are not limited thereto.

An insulating layer190may be formed between the pouch140and the internal positive and negative electrode leads170and180. A method for forming the insulating layer190may include attaching an insulating tape on the surfaces of the internal positive electrode lead170and the internal negative electrode lead180, or coating suitable insulating materials, well-known in the art, on the surfaces of the internal positive electrode lead170and the internal negative electrode lead180. The insulating layer190may serve to inhibit a short circuit of the internal positive electrode lead170or the internal negative electrode lead180. Also, the insulating layer190may serve to facilitate a sealing of the pouch140, and the internal positive and negative electrode leads170and180.

An insulating layer195may also be formed between the pouch140, and the external positive and negative electrode leads150and160. A method for forming the insulating layer195may include attaching an insulating tape on the surfaces of the external positive electrode lead150and the external negative electrode lead160or coating suitable insulating materials, well-known in the art, on the surfaces of the external positive electrode lead150and the external negative electrode lead160. The insulating layer195may serve to inhibit a short circuit of the external positive electrode lead150or the external negative electrode lead160. Also, the insulating layer190may serve to facilitate a seal (or implement a sealing) with the pouch140.

Hereinafter, a process for manufacturing a secondary battery according to an embodiment of the present invention will be described based on the fabrication order with reference toFIGS. 4 through 8.

As shown inFIG. 4, a plurality of separators113are located between positive and negative electrode plates111and112to form a stacked electrode assembly110. A positive electrode tab assembly120is attached to the positive electrode plates111of the electrode assembly110, and a negative electrode tab assembly130is attached to the negative electrode plates112. In this case, the positive electrode tab assembly120and the negative electrode tab assembly130may be attached in different directions.

As shown inFIG. 5, an internal positive electrode lead170is installed at the uppermost end of the positive electrode tab assembly120, and an internal negative electrode lead180is installed at the uppermost end of the negative electrode tab assembly130. The internal positive electrode lead170and the internal negative electrode lead180may be coupled to the positive electrode tab assembly120and the negative electrode tab assembly130, respectively, by a welding method.

As shown inFIG. 6, the pouch140may accept the electrode assembly110attached with the positive electrode tab assembly120and the negative electrode tab assembly130, and the internal positive electrode lead170and the internal negative electrode lead180coupled to the positive electrode tab assembly120and the negative electrode tab assembly130, respectively. Then, after electrolyte is injected, three or four sides of the pouch140are sealed.

The through holes141and142are formed at both sides of the pouch140. The through hole141may be formed to correspond to the positive electrode tab assembly120and the internal positive electrode lead170. The through hole142may be formed to correspond to the negative electrode tab assembly130and the internal negative electrode lead180.

FIG. 7illustrates that the external positive electrode lead150and the external negative electrode lead160installed on the outside of the pouch140are coupled to the internal positive electrode lead170and the internal negative electrode lead180, respectively, mounted in the pouch140. Thus, the external positive electrode lead150and the external negative electrode lead160are welded to the internal positive electrode lead170and the internal positive electrode lead180, respectively, through a resistance welding method, such as an ultrasonic welding or a spot welding. In this case, the through holes141and142of the pouch140are formed greater in size than welded portions, thereby preventing the pouch140from being melted or damaged. Leakage from the through holes141and142can be inhibited by the insulating layer195between the pouch140and the external electrode leads150and160, and the insulating layer190between the pouch140and the internal electrode leads170and180.

As shown inFIG. 8, both sealing portions143and144are vertically folded in the direction of the main body145of the pouch140. Then, both ends143aand144aof sealing portions143and144are folded or bent so that the external electrode leads150and160are substantially surrounded (or encompassed) by the sealing portion143and144, respectively. At this time, the first and second external lead terminals150and160are preferably disposed in parallel with surfaces of the case140.

Thus, the external electrode leads150and160are substantially surrounded by sealing portions143and144, respectively, to be adhered to the main body145of the pouch140, thereby enabling the total size to be minimized.

Thus, an electrode tab is not protruding from a pouch, but is welded to an external electrode lead through a through hole. Accordingly, the sealing strength at a sealing portion of the pouch can be increased.

Also, since the electrode tab does not protrude to the outside and is welded to the external electrode lead, the lengths of the electrode tab and the electrode lead need not be elongated, thereby saving space. Accordingly, the capacity of a battery can be increased by about 15% to about 30%. Furthermore, the electrode tab mounted in the pouch is coupled to the external electrode lead in a stacked structure, thereby not limiting the thickness of the electrode tab.

In addition, since a welding portion of the electrode tab and the external electrode lead is not exposed to the outside by the sealing portion of the pouch, the mechanical safety can be enhanced at the coupling portion of the electrode tab and the external electrode lead.

A secondary battery according to an embodiment of the present invention has an effect of maintaining a sealing portion of a case in a good sealing state because an electrode tab is mounted in the case together with an electrode assembly.

Furthermore, the electrode tab can be mounted in the case to be coupled to the external electrode lead provided on the outside of the case. Accordingly, the welding portion of the electrode tab and the external electrode lead is not exposed to the outside, thereby increasing mechanical safety at the coupling portion of the electrode tab and the external electrode lead.

Although the electrode assembly according to the embodiment of the present invention has been described as a stacked-type of a first electrode plate, a separator, and a second electrode plate, the electrode assembly may be a jelly rolled-type in which the first electrode plate, the separator, and the second electrode plate, are successively stacked and wound. This may correspond to a variation that could be easily practiced by those skilled in the art although a separate accompanying drawing is not attached.