Secondary battery

Provided is a secondary battery including: an electrode assembly; a case housing the electrode assembly and having a case opening; a cap plate substantially sealing the case opening; a first terminal plate on the cap plate; a first collector terminal coupling the electrode assembly to the first terminal plate; and a seal gasket between the first collector terminal and the cap plate, wherein the first collector terminal includes: a lower terminal adjacent the electrode assembly, and an upper terminal adjacent the first terminal plate, the upper terminal including a first metal different from a second metal of the lower terminal, and contacting the lower terminal at an interface between the first metal and the second metal, and wherein the seal gasket covers at least a portion of a side surface of the interface between the first metal and the second metal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0009505, filed on Jan. 28, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

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

2. Description of the Related Art

Generally, unlike a primary battery that is not designed to be re-charged, a secondary battery is capable of being charged, discharged, and re-charged. The secondary battery is used as an energy source for mobile devices, electric cars, hybrid cars, electric bicycles, uninterruptible power supply apparatuses, and/or the like. Here, the secondary battery may be used in a single battery type or a battery module type, wherein a plurality of batteries are electrically coupled to each other in one unit, according to the type of external device applied to the secondary battery.

SUMMARY

One or more embodiments of the present invention include a secondary battery, wherein a corrosion-resistant characteristic of a multi-metal terminal is improved.

According to one or more embodiments of the present invention, a secondary battery includes: an electrode assembly; a case housing the electrode assembly and having a case opening; a cap plate substantially sealing the case opening; a first terminal plate on the cap plate; a first collector terminal coupling the electrode assembly to the first terminal plate; and a seal gasket between the first collector terminal and the cap plate, wherein the first collector terminal includes: a lower terminal adjacent the electrode assembly, and an upper terminal adjacent the first terminal plate, the upper terminal including a first metal different from a second metal of the lower terminal, and contacting the lower terminal at an interface between the first metal and the second metal, and wherein the seal gasket covers at least a portion of a side surface of the interface between the first metal and the second metal.

The first collector terminal may extend at least partially through a terminal hole of the cap plate, and the seal gasket may be along a side surface of the terminal hole.

The first terminal plate may include a protruding portion protruding toward the seal gasket and around a terminal hole of the first terminal plate.

The protruding portion may be continuous along a periphery of the terminal hole.

The seal gasket may contact the first terminal plate and may include a flange-shaped upper portion.

The secondary battery may further include an insulating member between the first terminal plate and the cap plate, wherein at least a portion of the upper portion of the seal gasket is compressed between the first terminal plate and the insulating member.

A width of the upper portion of the seal gasket may be larger than a width of a portion of the seal gasket in a terminal hole of the cap plate.

The seal gasket may extend along a length direction of the first collector terminal and may cover at least the interface between the first metal and the second metal.

At least a portion of an upper portion of the seal gasket may be vertically offset above the interface between the first metal and the second metal.

The upper terminal may be compressed and fixed with respect to a top surface of the first terminal plate, and the lower terminal may be coupled to a first collector member that is electrically coupled to the electrode assembly.

A top of the upper terminal may have a flange shape for engaging the first terminal plate.

The lower terminal may include a stopper having a width greater than a terminal hole of the cap plate, and the first collector terminal may extend through the terminal hole.

The first terminal plate may include a metal substantially similar to the first metal, and the first collector member may include a metal substantially similar to the second metal.

The secondary battery may further include a second collector terminal having a polarity different from a polarity of the first collector terminal.

The second collector terminal may extend through the cap plate to electrically couple the electrode assembly to a second terminal plate, and the second collector terminal may further include a lower terminal adjacent the electrode assembly and an upper terminal adjacent the second terminal plate.

The lower terminal and the upper terminal of the second collector terminal may further include a same metal or substantially similar metals.

The upper terminal of the second collector terminal may be compressed and fixed with respect to a top surface of the second terminal plate, and the lower terminal of the second collector terminal may be coupled to a second collector member that is electrically coupled to the electrode assembly.

The upper terminal and the lower terminal of the second collector terminal may include a same metal or substantially similar metals as the second terminal plate and the second collector member.

DETAILED DESCRIPTION

FIG. 1is a perspective view of a secondary battery according to an embodiment of the present invention.FIG. 2is an exploded perspective view of the secondary battery ofFIG. 1.

Referring toFIGS. 1 and 2, a pair of first and second electrode terminals110and120, having opposite polarities, may protrude from the secondary battery. For example, the first and second electrode terminals110and120are electrically coupled to an electrode assembly150accommodated (e.g., housed or enclosed) in the secondary battery, and may be respectively electrically coupled to a first electrode plate and a second electrode plate of the electrode assembly150to operate as a positive terminal and a negative terminal, respectively, for externally supplying discharge power accumulated in the secondary battery or for receiving charge power from outside the secondary battery. For example, the first and second electrode terminals110and120may be formed, respectively, on two sides (e.g., at opposing ends) of the secondary battery.

Alternatively, a cap plate100of the secondary battery may be electrically coupled to the electrode assembly150to operate as a terminal, and any of the first and second terminals110and120may be omitted.

FIG. 3is a cross-sectional view taken along the line III-III ofFIG. 2.FIG. 4is an enlarged cross-sectional view of the first electrode terminal110ofFIG. 3, andFIG. 5is an enlarged cross-sectional view of the second electrode terminal120ofFIG. 3.

Referring toFIG. 3, the secondary battery includes the electrode assembly150, the first and second electrode terminals110and120, and first and second collector members117and127for electrically coupling the electrode assembly150to the first and second electrode terminals110and120, respectively. Also, the secondary battery may include a case180accommodating (e.g., housing or substantially enclosing) the electrode assembly150, and the cap plate100sealing an opening of the case180where the electrode assembly150is positioned or located. The cap plate100is combined, attached, or coupled to a top of the case180where the electrode assembly150is positioned, and may substantially seal the opening of the case180. For example, the cap plate100and the case180may be welded along the edges of the cap plate100.

The cap plate100may include a bent portion108that breaks to release an internal pressure during an abnormal operation wherein an internal pressure of the case180exceeds a pressure (e.g., a predetermined pressure), and a sealing portion109for substantially sealing an electrolyte injection hole.

The electrode assembly150may be accommodated or positioned in the case180of the secondary battery, and include first and second electrode plates151and152having opposite polarities, and a separator disposed between the first and second electrode plates151and152. The electrode assembly150may have a wound structure wherein the first and second electrode plates151and152, and the separator153are wound or rolled in a jelly roll shape. Alternatively, the electrode assembly150may have a stacked structure wherein the first and second electrode plates151and152, and the separator153are alternately stacked on each other. The cap plate100may be attached or coupled to a top open portion of the case180accommodating the electrode assembly150so as to substantially seal the electrode assembly150within the case180. The first and second electrode terminals110and120may be electrically coupled to the electrode assembly150and may be formed outside the cap plate100to electrically couple the electrode assembly150to an external circuit or electrical device (not shown) or to electrically couple the electrode assembly150to a neighboring secondary battery.

The first and second electrode terminals110and120may have opposite polarities, and may be respectively electrically coupled to the first and second electrode plates151and152of the electrode assembly150.

Referring toFIGS. 4 and 5, the first electrode terminal110may include a first collector terminal115, and a first terminal plate111combined or coupled to the first collector terminal115. Similarly, the second electrode terminal120may include a second collector terminal125and a second terminal plate121combined or coupled to the second collector terminal125. Hereinafter, collector terminals115and125may collectively denote the first and second collector terminals115and125, or may selectively denote one of the first and second collector terminals115and125. Also, terminal plates111and121may collectively denote the first and second terminal plates111and121, or may selectively denote one of the first and second terminal plates111and121. For example, the terminal plate111combined or coupled to the first collector terminal115may denote the first terminal plate111, and the terminal plate121combined or coupled to the second collector terminal125may denote the second terminal plate121. As will be described below, the first and second collector terminals115and125are respectively combined or coupled to the first and second collector members117and127, and collector members117and127may collectively denote the first and second collector members117and127, or may selectively denote one of the first and second collector members117and127. For example, the collector member117combined to the first collector terminal115may denote the first collector member117, and the collector member127combined to the second collector terminal125may denote the second collector member127.

The first and second collector terminals115and125may extend at least partially outside the cap plate100through the cap plate100. Accordingly, the cap plate100may include a terminal hole100′ into which the first and second collector terminals115and125are inserted and assembled. In detail, the first and second collector terminals115and125may be inserted through the terminal hole100′ of the cap plate100from bottom to top of the cap plate100.

The first and second collector terminals115and125may include upper terminals115aand125a, which form top portions along length directions of the first and second collector terminals115and125and are combined or coupled to the first and second terminal plates111and121, and lower terminals115band125b, which form bottom portions of the first and second collector terminals115and125and are combined or coupled to the first and second collector members117and127. For example, the upper terminals115aand125amay denote portions formed relatively close to the first and second terminal plates111and121along the length directions of the first and second collector terminals115and125, and the lower terminals115band125bmay denote portions formed relatively close to the electrode assembly150along the length directions of the first and second collector terminals115and125.

The first and second collector terminals115and125extend to penetrate through the cap plate100, and may electrically couple the electrode assembly150below the cap plate100and the first and second terminal plates111and121above the cap plate100to each other. The lower terminals115band125bof the first and second collector terminals115and125may be electrically coupled to the electrode assembly150through the first and second collector members117and127below the cap plate100, whereas the upper terminals115aand125aof the first and second collector terminals115and125may be electrically coupled to the first and second terminal plates111and121above the cap plate100.

The first and second collector terminals115and125may be respectively coupled to opposite polarities of the electrode assembly150, and may have differentiated structures. Here, because the first and second collector terminals115and125are combined or coupled to different first and second metals of the electrode assembly150(or the first and second collector members117and127combined or coupled to the electrode assembly150) according to the polarities, the first and second collector terminals115and125may have the differentiated structures to be combined or coupled to similar metals. By being combined or coupled to the similar metals, deterioration of binding strength, such as deterioration of welding joints, may be fundamentally prevented or reduced.

In detail, the upper and lower terminals115aand115bof the first collector terminal115ofFIG. 4may include different dissimilar metals. In other words, the upper terminal115amay be formed by mainly using the first metal and the lower terminal115bmay be formed by mainly using the second metal different from the first metal. Unlike the first collector terminal115, the upper and lower terminals125aand125bof the second collector terminal125ofFIG. 5may include same metals. In other words, the upper and lower terminals125aand125bmay be formed by mainly using the second metal.

For reference, throughout the specification, when a component is formed of or includes a first or second metal, the first or second metal may be a certain metal or an alloy mainly including the certain metal. For example, the first metal may be aluminum or an aluminum alloy mainly including aluminum, and the second metal may be copper or a copper alloy mainly including copper.

A structure of the first collector terminal115will now be described first, and then a structure of the second collector terminal125will be described. Referring toFIG. 4, the upper terminal115aof the first collector terminal115is combined or coupled to the first terminal plate111, and the lower terminal115bis combined or coupled to the first collector member117. Here, the upper and lower terminals115aand115bare formed of different dissimilar metals, such that similar metals are combined or coupled between the first terminal plate111and the upper terminal115aincluding the first metal, and similar metals are combined or coupled between the first collector member117and the lower terminal115bincluding the second metal. Because the similar metals are combined or coupled between the first terminal plate111, the first collector terminal115, and the first collector member117, which are mutually combined or coupled to each other, deterioration of binding strength caused due to combination or coupling of dissimilar metals, for example, welding of dissimilar metals, may be fundamentally prevented or reduced. Also, corrosion generated on an interface between different dissimilar metals may be prevented or reduced.

Throughout the specification, when the upper terminal115aand the first terminal plate111of the first collector terminal115, which are mutually combined or coupled to each other, are formed of the same type of the first metal, the first collector terminal115and the first terminal plate111may be both formed of the first metal or may mainly include the first metal.

Similarly, when the lower terminal115band the first collector member117of the first collector terminal115, which are mutually combined or coupled to each other, are formed of the same type of second metal, the lower terminal115band the first collector member117may be both formed of the second metal or may mainly include the second metal.

The first collector terminal115may be formed by integrating the upper terminal115aand the lower terminal115bthat include different dissimilar metals. For example, the upper terminal115aand the lower terminal115bmay be combined or coupled to each other via any one of various combining or coupling methods, such as friction stir welding, riveting, caulking, spinning, press-fitting concave and convex portions, and screwing. For example, in the friction stir welding, when the upper and lower terminals115aand115bthat include different dissimilar metals contact each other and are relatively rotated at a high speed, frictional heat is generated on an interface of the upper and lower terminals115aand115band contacting portions of the upper and lower terminals115aand115bare locally melted and mixed (e.g., fused together), and thus the upper and lower terminals115aand115bmay be strongly welded to each other.

Because the first terminal plate111and the first collector member117at the first collector terminal115are respectively formed of the first and second metals, which are different from each other, a so-called multi-metal terminal that includes different types of metals according to locations is formed. However, as shown inFIG. 5, because the second terminal plate121and the second collector member127at the second collector terminal125are formed of the second metal, the second collector terminal125may be formed of a single material including the second metal. In detail, the upper and lower terminals125aand125bof the second collector terminal125may include the second metal.

In more detail, the first collector terminal115may correspond to a negative terminal, and thus the first collector member117and the first terminal plate111, which are coupled to the first collector terminal115, may form a negative region. Here, the first collector member117may be formed of copper like the negative region of the electrode assembly150, and the first terminal plate111may be formed of aluminum. Also, the upper terminal115aof the first collector terminal115, which electrically couples the first collector member117to the first terminal plate111, may include aluminum, and the lower terminal115bmay include copper. Accordingly, the upper terminal115aof the first collector terminal115and the first terminal plate111may be combined or coupled to each other between similar metals, i.e., aluminum, and the lower terminal115bof the first collector terminal115and the first collector member117may be combined or coupled to each other between similar metals, i.e., copper.

Meanwhile, a positive region and a negative region of the first and second terminal plates111and121may be both formed of aluminum. For example, in a module structure wherein a plurality of secondary batteries are electrically coupled to each other, the first and second terminal plates111and121of the neighboring secondary batteries may be electrically coupled to each other through a bus bar (not shown), and thus the neighboring secondary batteries are coupled to each other in series. Accordingly, the first and second terminal plates111and121may be formed of aluminum like the bus bar.

The second terminal plate121may correspond to a positive terminal, and thus the second collector member127and the second terminal plate121, which are coupled to the second collector terminal125, may form a positive region. Here, the second collector member127may be formed of aluminum like the positive region of the electrode assembly150, and the second terminal plate121may also be formed of aluminum. Also, by forming both the upper and lower terminals125aand125bof the second collector terminal125, which electrically couples the second collector member127to the second terminal plate121, to each other using aluminum, the upper terminal125aof the second collector terminal125and the second terminal plate121may be combined or coupled to each other using similar metals, e.g., aluminum or an aluminum alloy, and the lower terminal125bof the second collector terminal125and the second collector member127may be combined or coupled to each other using similar metals, e.g., aluminum or aluminum alloy.

The first and second collector terminals115and125extend to penetrate through the cap plate100, and electrically couple the first and second collector members117and127below the cap plate100and the first and second terminal plates111and121above the cap plate100to each other. Also, the first and second collector terminals115and125include the lower terminals115band125bcombined or coupled to the first and second collector members117and127below the cap plate100, and the upper terminals115aand125acombined or coupled to the first and second terminal plates111and121above the cap plate100.

The upper terminals115aand125amay fix (or secure) locations of the first and second collector terminals115and125, for example, with respect to top surfaces of the first and second terminal plates111and121via a riveting method. In detail, a length (e.g., a predetermined length) of the upper terminals115aand125amay protrude from the top surface of the cap plate100to penetrate through the first and second terminal plates111and121, and may pressurize and contact the top surfaces of the first and second terminal plates111and121to be combined to the first and second terminal plates111and121. A concave groove (not shown) may be formed on a top of each of the upper terminals115aand125aaccording to pressurization of a processing tool (not shown) that rotates at a high speed, and the tops of the upper terminals115aand125amay adhere to the top surfaces of the first and second terminal plates111and121while being forced in a lateral direction, according to the pressurization of the processing tool. For example, concave grooves (not shown) may be formed on inner tops of the upper terminals115aand125a, thereby allowing flange shapes to extend in a lateral direction at outer tops of the upper terminals115aand125aafter applying the pressurization of the processing tool to the upper terminals115aand125a.

The lower terminals115band125bmay respectively include stoppers115ba and125ba having a flange shape extending in a wider outer circumference than the terminal hole100′, such that the first and second collector terminals115and125do not slip through the terminal hole100′ of the cap plate100. Here, the first and second collector terminals115and125are assembled to be inserted into the terminal hole100′ from the bottom of the cap plate100, and the locations of the first and second collector terminals115and125may be fixed by riveting the tops of the upper terminals115aand125aexposed above the cap plate100while the first and second collector terminals115and125are supported below the cap plate100through the stoppers115ba and125ba of the lower terminals115band125b.

The first and second collector terminals115and125may be inserted into the terminal hole100′ of the cap plate100while being electrically insulated from the cap plate100. For example, seal gaskets113and123may be inserted into the terminal hole100′, and the first and second collector terminals115and125may be insulated from the cap plate100as the first and second collector terminals115and125are inserted into the terminal hole100′ through the seal gasket113and123. The seal gaskets113and123seal around the terminal hole100′ so as to prevent an electrolyte in the case180from leaking, and also to prevent external impurities or contaminants from penetrating into the case180.

According to an embodiment, the first collector terminal115may be a multi-metal terminal including different dissimilar metals. Here, the seal gasket113formed along or around a circumference of the first collector terminal115may prevent corrosion between the dissimilar metals by covering and protecting an interface115cof the upper and lower terminals115aand115bformed of the dissimilar metals and blocking moisture. In detail, the seal gasket113surrounds a side surface of the first collector terminal115so as to hermetically seal the side surface of the first collector terminal115and the terminal hole100′. The seal gasket113covers the interface115cof the upper and lower terminals115aand115bso that external harmful materials, such as moisture, do not penetrate into the interface115c. When the interface115chas a height H1so that the interface115cis not exposed, a top113aof the seal gasket113may have a height H2at least higher than the height H1. In other words, because the seal gasket113covers the height H2higher than the height H1, the seal gasket113may sufficiently cover the interface115c. Here, the heights H1and H2may be measured along the length direction of the first collector terminal115, and a level of measuring the heights H1and H2are not limited, and for example, the heights H1and H2may be measured from a bottom surface of the secondary battery.

The top113aof the seal gasket113has a flange shape extending in the lateral direction substantially parallel to the first terminal plate111. As shown inFIG. 6, the top113amay have the flange shape as the top113ais pressed in the lateral direction according to downward pressurization of the first terminal plate111while the first terminal plate111and the first collector terminal115are combined or coupled to each other via pressurization from upper and lower dies D1and D2. For example, the top of the upper terminal115ais pressurized and compressed to the top surface of the first terminal plate111while pressing the first terminal plate111downward. Accordingly, the top113aof the seal gasket113touching a protruding portion111aof the first terminal plate111is pressed and pushed to the lateral side, and thus forms the flange shape at the bottom surface of the first terminal plate111.

The protruding portion111amay be formed to press the seal gasket113, around a terminal hole111′ of the first terminal plate111. As shown inFIG. 7, the protruding portion111amay be formed along a circumference of the terminal hole111′, or along an outer circumference of the terminal hole111′ according to a circular shape of the terminal hole111′. The protruding portion111amay protrude downward from a bottom surface of the first terminal plate111, i.e., towards a direction of the seal gasket113. The protruding portion111amay be continuously formed along or around the circumference of the terminal hole111′, but is not limited thereto. Alternatively, the protruding portion111amay be locally formed on a part of the circumference of the terminal hole111′ or intermittently formed along the circumference of the terminal hole111′ while pressing the top113aof the seal gasket113.

Returning toFIG. 4, the protruding portion111amay press the top113aof the seal gasket113so that the top113ahas the flange shape. In other words, the protruding portion111alocally presses the top113aof the seal gasket113so that the top113ahas the flange shape, and may compactly seal around the first terminal plate111adjacent to the seal gasket113or around an upper insulating member112adjacent to the seal gasket113. When the top113aof the seal gasket113is locally pressed, moisture may be effectively prevented from penetrating through the top113aof the seal gasket113, and when the top113aof the seal gasket113has a wide flange shape, a path of moisture penetration may be long, and thus moisture penetration may be suppressed or delayed.

The top113aof the seal gasket113contacts the bottom surface of the first terminal plate111, wherein a width W1of the top113acontacting the bottom surface of the first terminal plate111is wider than a width across a perimeter of the seal gasket113, and thus the top113ahas the flange shape. In detail, the width W1of the top113acontacting the first terminal plate111is wider than a width W2of the seal gasket113around a terminal hole110′ surrounding the first collector terminal115. Because the top113aof the seal gasket113is widely formed in the flange shape, the path of the moisture penetration may be relatively long, thereby effectively suppressing or reducing the moisture penetration. Meanwhile, the top113aof the seal gasket113contacts the bottom surface of the first terminal plate111, wherein a part of the top113amay be compressed between the first terminal plate111and the upper insulating member112.

The protruding portion111aof the first terminal plate111and the flange shape of the top113aof the seal gasket113may operate to protect the first collector terminal115(which is a multi-metal terminal), by forming an effective corrosion preventing (or reducing) structure to protect the interface115cfrom moisture or other contaminants. Such a corrosion preventing structure may also be applied to the second collector terminal125formed of the similar metals so as to suppress moisture penetration and prevent or reduce corrosion. According to an embodiment, the protruding portion111aand the flange shape of the top113amay be selectively applied to the first collector terminal115that is a multi-metal terminal that may need to be protected from moisture and prevented from being corroded.

Referring toFIGS. 4 and 5, lower insulating members114and124may be disposed between the first and second collector terminals115and125and the cap plate100, and may insulate the first and second collector members117and127from the cap plate100. The seal gaskets113and123are disposed around the terminal holes100′ through which the first and second collector terminals115and125penetrate, and the lower insulating members114and124are disposed between the first and second collector terminals115and125and the cap plate100, and thus the first and second collector terminals115and125may be insulated from the cap plate100. The lower insulating members114and124may be extended between the first and second collector members117and127and the cap plate100.

The first and second collector terminals115and125may be electrically coupled to the electrode assembly150through the first and second collector members117and127. The first and second collector members117and127may include first and second collector plates117band127bthat form bottom portions of the first and second collector members117and127and are combined or coupled to the electrode assembly150, and first and second lead portions117aand127athat form top portions of the first and second collector members117and127and are combined or coupled to the first and second collector terminals115and125.

The first and second collector plates117band127bmay be respectively combined or coupled to two edges of the electrode assembly150, and may be welded to an active-material-non-coated portion formed on the edge of the electrode assembly150, i.e., active-material-non-coated portions of the first and second electrode plates151and152where an electrode active material is not formed. For example, the first collector plate117bmay be combined or coupled to the active-material-non-coated portion of the first electrode plate151, and the second collector plate127bmay be combined or coupled to the active-material-non-coated plate of the second electrode plate152.

The first and second lead portions117aand127amay bend and extend from the first and second collector plates117band127bto face the first and second collector terminals115and125, and may have terminal holes117′ and127′ (shown, e.g., inFIG. 2) for coupling the first and second lead portions117aand127ato the first and second collector terminals115and125, respectively. For example, bottom portions of the first and second collector terminals115and125may be inserted into the terminal holes117′ and127′ of the first and second lead portions117aand127a, and welding may be performed around the terminal holes117′ and127′ where the first and second collector terminals115and125and the first and second lead portions117aand127acontact each other so as to combine or couple the first and second collector terminals115and125and the first and second lead portions117aand127ato each other.

The first and second terminal plates111and121may be disposed on the cap plate100. The first and second terminal plates111and121may be electrically coupled to the first and second collector terminals115and125, and may provide wider terminal regions than the first and second collector terminals115and125. The first and second terminal plates111and121may be coupled to the first and second collector terminals115and125via riveting, but alternatively, the first and second terminal plates111and121may be coupled to the first and second collector terminals115and125via any one of various methods, such as welding and screwing.

The first and second terminal plates111and121may have terminal holes111′ and121′ through which the first and second collector terminals115and125penetrate through. For example, the protruding portion111afor pressing the seal gasket113may be formed around the terminal hole111′ of the first terminal plate111. In detail, the protruding portion111aprotruding downwards, i.e., towards the seal gasket113, is formed on the bottom surface of the first terminal plate111. For example, the protruding portion111amay extend along the outer circumference of the terminal hole111′ according to the circular shape of the terminal hole111′. By continuously forming the protruding portion111aaround the terminal hole111′, locations around the top113aof the seal gasket113inserted into the terminal hole100′ may be pressed such that the top113aof the seal gasket113has an overall flange shape, which may reduce or prevent moisture or external contaminants from penetrating past the seal gasket113. Also, by continuously forming the protruding portion111aalong the circumference of the terminal hole111′, the upper portion of the seal gasket113may be pressed in overall such that the first terminal plate111adjacent to the seal gasket113or the upper insulating member112adjacent to the seal gasket113tightly contacts the seal gasket113. Alternatively, the protruding portion111amay be continuously or intermittently formed along the circumference of the terminal hole111′ or may be formed on a local location along the circumference of the terminal hole111′ as long as the top113aof the seal gasket113inserted into the terminal hole100′ is pressed.

Upper insulating members112and122may be disposed between the first and second terminal plates111and121and the cap plate100. The upper insulating members112and122may insulate the first and second terminal plates111and121from the cap plate100. According to another embodiment, the upper insulating members112and122may be omitted if the first and second terminal plates111and121and the cap plate100have a same polarity.

As described above, according to the one or more of the above embodiments of the present invention, corrosion that may be generated on an interface between dissimilar metals of a collector terminal can be fundamentally prevented or reduce by using a seal gasket insulating the collector terminal to protect the interface between the dissimilar metals in case of introducing the collector terminal formed of a multi-metal terminal to increase a binding strength and workability through binding of similar metals.

Further, although exemplary embodiments of the present invention have been described, it should be understood that the present invention should not be limited to these exemplary embodiments, but various changes and modifications can be made by one having ordinary skill in the art within the spirit and scope of the appended claims, and their equivalents.