Rechargeable battery having pillar terminal and battery module using the same

A rechargeable battery including a pillar terminal electrically connected to a positive or negative electrode. The pillar terminal includes a first section made of a first metal, a second section made of a second metal, and a third section between the first and second sections. The third section is made of the first metal or the second metal. The third section is welded to the first section and is electroplated to the second section.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2013-0111332, filed on Sep. 16, 2013, and entitled, “Rechargeable Battery Having Pillar Terminal and Battery Module Using The Same,” is incorporated by reference herein in its entirety.

BACKGROUND

One or more embodiments described herein relate to a battery.

2. Description of the Related Art

Unlike a primary battery, a rechargeable battery can be repeatedly charged and discharged. Low-capacity rechargeable batteries are used in portable devices such as mobile phones, notebook computers, and camcorders. High-capacity rechargeable batteries are widely used as power sources for hybrid and electric vehicles.

When used as a power source for a vehicle, a plurality of battery cells are connected by one or more bus bars to form a rechargeable battery module. Such a module includes an electrode assembly for charging and discharging. The electrode assembly includes a separator between positive and negative electrodes. The negative electrode includes a negative electrode current collector and a negative active material layer, while the positive electrode includes a positive electrode current collector and a positive active material layer.

The negative electrode current collector is made of aluminum and the positive current collector is made of copper. A negative terminal electrically connected to the negative electrode is made of aluminum, while a positive terminal electrically connected to the positive electrode is made of copper.

Because the melting point of aluminum is different from copper, it is difficult to bond the different metals by welding. In attempt to solve this problem, the terminals or bus bars of the battery module may be bonded by friction welding. However, friction welding increases manufacturing costs and decreases productivity.

SUMMARY

In accordance with one embodiment, a rechargeable battery includes an electrode assembly including a first electrode and a second electrode; a case including the electrode assembly; and a first pillar terminal electrically connected to the first electrode, wherein the first pillar terminal includes a first section made of a first metal, a second section made of a second metal, and an intermediate section made of the first metal or the second metal and located between the first and second sections.

The intermediate section may be made of the second metal and electroplated on a surface of the first section. A flange may protrude from a circumferential surface of the first section. The intermediate section may be welded to the second section.

The intermediate section may be made of the first metal and electroplated on a surface of the second section and welded to the first section. The first pillar terminal may have a substantially cylindrical shape, and the first and second sections may be elongated in a height direction of the first pillar terminal.

The intermediate section may be made of a clad metal, the intermediate section may include a first bonding layer made of the first metal and a second bonding layer made of the second metal, and the first bonding layer may be welded to the first section and the second bonding layer may be welded to the second section.

The first section may include a first coupling portion, and the second section may include a second coupling portion coupled to the first coupling portion. The first coupling portion may be formed with a groove or protrusion. The intermediate section may cover the first coupling portion.

In accordance with another embodiment, a battery module includes a plurality of rechargeable batteries and a bus bar electrically connecting the plurality of rechargeable batteries, wherein each rechargeable battery includes an electrode assembly having a first electrode and a second electrode, a case including the electrode assembly, and a first pillar terminal electrically connected to the first electrode, wherein the first pillar terminal has a first section made of a first metal and a second section made of a second metal, and an intermediate section made of the first metal or the second metal and located between the first and second sections.

The intermediate section may be made of the second metal and may be electroplated on a surface of the first section. A flange may protrude from a circumferential surface of the first section, and the intermediate section may be welded to the second section.

The intermediate section may be made of the first metal, and the intermediate section may be welded to the first section and electroplated to the second section. The intermediate section may be made of a clad metal, the intermediate section may include a first bonding layer made of the first metal and a second bonding layer made of the second metal, and the first bonding layer may be welded to the first section and the second bonding layer may be welded to the second section.

A second pillar terminal may be electrically connected to the second electrode, the second pillar terminal may be made of the second metal, and the bus bar may be made of the second metal. The first section may include a first coupling portion, and the second section may include a second coupling portion coupled to the first coupling portion.

In accordance with one embodiment, a rechargeable battery includes a first electrode; a second electrode; and a first pillar terminal electrically connected to the first electrode, wherein the first pillar terminal includes a first section made of a first metal, a second section made of a second metal, and a third section between the first and second sections and made of the first metal or the second metal. The third section may be welded to the first section. The third section may be electroplated on the second section.

DETAILED DESCRIPTION

FIG. 1illustrates an embodiment of a battery module100, andFIG. 2illustrates a cross-sectional view ofFIG. 1taken along line II-II. Referring toFIG. 1, battery module100includes a plurality of rechargeable batteries101and bus bars120electrically connecting the rechargeable batteries101. The batteries101are illustrated as prism-shaped lithium ion rechargeable batteries. However, batteries101may have a different shape or may be of a different type in other embodiments. For example, batteries101may be lithium polymer batteries or cylindrical batteries.

Each rechargeable battery101includes an electrode assembly10to be used for charging and discharging, a case15in which the electrode assembly10is located, a cap plate20coupled to an opening of the case15, and first and second pillar terminals22and21provided in the cap plate20. In one embodiment, electrode assembly10is formed by disposing a first electrode (e.g., a negative electrode)12and a second electrode (e.g., a positive electrode)11at respective sides of a separator13. The separators13may serve as insulators. The negative electrode12, separator13, and positive electrode11may be spirally wound, for example, in a jelly-roll shape.

The positive and negative electrodes may respectively include coated regions11aand12a, in which an active material is coated on a current collector. The positive and negative electrodes may also respectively include uncoated regions11band12bhaving exposed portions of the current collector, on which the active material is not coated.

The positive electrode uncoated region11bis formed at a lateral end of the positive electrode11along the spirally wound positive electrode11. The negative electrode uncoated region12bis formed at a lateral end of the negative electrode11along the spirally wound negative electrode12. The positive and negative uncoated regions11band12bare disposed at opposite ends of the electrode assembly10.

Case15may have, for example, a roughly cuboid shape and may be used to store the electrode assembly10and an electrolyte solution. One side of the cuboid is formed with an opening connecting inner and outer spaces thereof. The opening is formed to allow the electrode assembly10to be inserted into the case15.

The cap plate20closes and seals the case15by being disposed over the opening thereof. Case15and cap plate20may be formed, for example, of aluminum and may be welded to each other.

In addition, cap plate20may be formed with an electrolyte injection opening29, a vent hole26, and terminal holes H1 and H2. The electrolyte injection opening29enables the electrolyte solution to be injected into the case15after combining the cap plate20to the case15. The electrolyte injection opening29is closed and sealed by a sealing cap27after the electrolyte solution is injected. The vent hole26is closed and sealed by a vent plate25, which may be used to release internal pressure of the rechargeable battery101. For example, when the internal pressure of rechargeable battery10reaches a predetermined level, the vent plate25is ruptured to open the vent hole26. The vent plate25is formed with a notch that induces the rupture.

The first and second pillar terminals22and21are provided to penetrate the cap plate20. For example, first pillar terminal22is inserted into terminal hole H2 and second pillar terminal21is inserted into terminal hole H1. The first pillar terminal22is electrically connected to the negative electrode12of the electrode assembly10. The second pillar terminal21is electrically connected to the positive electrode11of the electrode assembly10. Accordingly, a charged current in the electrode assembly10is drawn out of the case15through the first and second pillar terminals22and21.

A plate terminal23is provided at an upper portion of the second pillar terminal21. The second pillar terminal21is bonded to the plate terminal23by welding while being inserted into the plate terminal23. The plate terminal23is formed with a hole, and the second pillar terminal21is inserted in the hole.

An upper insulating member31is provided between cap plate20and plate terminal23, to insulate the plate terminal23from the cap plate20.

A positive electrode gasket36is provided between the cap plate20and second pillar terminal21. The positive electrode gasket36is inserted into the terminal hole H1, to seal the space between second pillar terminal21and cap plate20and electrically insulates them.

A positive electrode lead tab51is coupled to the positive electrode11. The positive electrode lead tab51electrically connects the second pillar terminal21to the first electrode11, and may be bonded to the positive electrode uncoated region11band the second pillar terminal21, for example, by welding.

A lower insulating member61is provided between positive lead tab51and cap plate20, to electrically insulate positive lead tab51from the cap plate20. In addition, one side of the lower insulating member61is coupled to cap plate20, and the other side encloses the positive lead tab51and second pillar terminal21, to stabilize the connecting structure.

The second pillar terminal21includes a column portion21a, a flange portion21bprotruding from an external circumferential surface of the column portion21a, and a supporting protrusion21cprotruding down from a bottom side of the column portion21a. The column portion21amay be formed, for example, in a circular cylinder shape, and the flange portion21bmay be roughly formed, for example, in a square plate shape. The supporting protrusion21cis fitted into the positive lead tab51and is fixed thereto, for example, by welding.

An upper portion of the first pillar terminal22is provided with a plate terminal24. The first pillar terminal22is bonded to the plate terminal24, for example, by welding, while being inserted into plate terminal24. The plate terminal24is formed with a hole, and the first pillar terminal22is inserted into the hole.

An upper insulating member32is provided between plate terminal24and cap plate20, to insulate the plate terminal24from the cap plate20.

A negative electrode gasket37is provided between the cap plate20and the first pillar terminal22. The negative electrode gasket37is inserted into terminal hole H2, to seal the space between the first pillar terminal22and the cap plate20and electrically insulates them.

A negative electrode lead tab52is coupled to the negative electrode12. The negative electrode lead tab52electrically connects the first pillar terminal22to the negative electrode12, and is bonded to the negative electrode uncoated region12band the first pillar terminal22, for example, by welding.

A lower insulating member62is provided between the negative electrode lead tab52and the cap plate20, to electrically insulate them. In addition, one side of the lower insulating member62is coupled to the cap plate20. The other side encloses the negative electrode lead tab52and the first pillar terminal22, thereby stabilizing the connecting structure.

FIG. 3illustrates a first embodiment of the pillar terminal, andFIG. 4illustrates a vertical cross-sectional view of this pillar terminal. Referring toFIGS. 2 to 4, the first pillar terminal22includes a column portion22a, a flange portion22bprotruding from an external circumferential surface of the column portion22a, and a supporting protrusion22cprotruding down from a bottom side of the column portion22a.

The column portion22ais formed in a circular cylinder shape. The flange portion22bis roughly formed in a square plate shape. The supporting protrusion22cis fitted into the negative electrode lead tab52and is fixed thereto, for example, by welding.

The column portion22aincludes a first part22aaformed of a first metal, a second part22abformed of a second metal different from the first metal, and an intermediate layer22acdisposed between the first part22aaand the second part22ab. The flange portion22bis combined to an outer side of the first part22aa. The first metal may be copper, while the second metal may be aluminum. The first and second parts22aaand22abare combined to form a circular cylinder, and are bonded through the intermediate layer22ac.

The first and second parts22aaand22abare bonded and disposed to be elongated in a height direction of the circular cylinder. The intermediate layer22acis made of the second metal, and may be formed at a top side of the first part22aaby electroplating.

When the intermediate layer22acis formed by electroplating, the intermediate layer22acformed of aluminum can be integrally formed on the first part22aaformed of copper. The width of the intermediate layer22acmay have a thickness different from that shown, but in one non-limiting embodiment should be thick enough to allow for welding.

It has been shown to be difficult to bond different metals of different melting points by welding. This is because a welding fault may occur as a result of the different melting points. For example, a welding fault may form as a metal with a high melting point does not melt, while a metal with a low melting point melts.

However, if intermediate layer22acmade of one metal (e.g., aluminum) is formed on first part22asmade of a different metal (e.g., copper), for example, by electroplating, the first and second parts22aaand22abcan be integrally formed. The first and second parts22aaand22abmay be welded, for example, by laser welding or resistance welding, such that the interface of the intermediate layer22acand the second part22abis melted and bonded.

In the case where intermediate layer22acis made of the same material as the second part22ab, welding is easily performed and therefore sufficient strength is guaranteed at the welded part.

In one embodiment, the second pillar terminal21is formed of the second metal, which is the same metal as the second part22ab, and the bus bar120is made of the second metal. Further, the plate terminal23may coupled to second pillar terminal21may be made of the second metal. The plate terminal24coupled to the second part22abof the first pillar terminal22may be made of the second metal.

The bus bar120is welded to plate terminals23and24, to allow the second pillar terminal21to be electrically connected to the first pillar terminal22.

As described above, because the second pillar terminal21, the second part22ab, the plate terminals23and24, and the bus bar120are made of the same metal (e.g., aluminum), they can be easily welded to each other.

FIG. 5illustrates a second embodiment of a pillar terminal. The second embodiment of a rechargeable battery including the pillar terminal may have the same structure as the first embodiment of the rechargeable battery, except for first pillar terminal70.

The first pillar terminal70includes a column portion71, a flange portion72, and a supporting protrusion protruding down from a bottom side of flange portion72.

The column portion71is formed in a circular cylinder shape. The flange portion72is formed to protrude outwards from an external circumferential side of the column portion71. The column portion71includes an intermediate layer71cbetween first and second parts71aand71b.

The intermediate layer71cis formed at a bottom side of the second part71b, for example, by plating and is formed of a different material from the second part71b. In one embodiment, intermediate layer71cmay be formed by chemical plating. Various methods can be applied to form, for example, a copper layer by chemical plating. In one embodiment, the first part71ais made of copper, the second part71bis made of aluminum, and the intermediate layer71cis made of copper. The flange portion72is coupled to a lower end of an external circumferential surface of the first part71a.

As described above, because the second part71bis formed with intermediate layer71cformed of the same material as the first part71a, the first pillar terminal70(with its upper and lower parts being formed of different materials) can be easily made, for example, by welding the intermediate layer71cand the first part71atogether.

FIG. 6illustrates a third embodiment of a pillar terminal, andFIG. 7illustrates a vertical cross-sectional view of the pillar terminal. Referring toFIGS. 6 and 7, because the rechargeable battery including the pillar terminal has the same structure as the first embodiment of the rechargeable battery, except for a first pillar terminal80.

The first pillar terminal80includes a column portion81, a flange portion82, and a supporting protrusion83protruding from a bottom side of flange portion82. The column portion81is formed in a circular cylinder shape, and the flange portion82is formed to protrude outwards from an external circumferential side of the column portion81.

The column portion81includes a first part81a, a second part81b, and an intermediate layer81cdisposed between the first and second parts81aand81b. The flange portion82is coupled to a lower end of an external circumferential surface of the first part81a. The intermediate layer81cis made of a clad metal, and includes a first bonding layer81caand a second bonding layer81cb. The intermediate layer81cis formed in a disk shape.

The first part81ais made of the first metal, and the second part81bis made of the second metal. In addition, the first bonding layer81cais made of the first metal, and the second bonding layer81cbis made of the second metal. For example, the first metal may be copper and the second metal may be aluminum.

The first bonding layer81cais disposed to contact the first part81a, and the second bonding layer81cbis disposed to contact the second part81b. The first bonding layer81cais bonded to the first part81aby welding, and the second bonding layer81cbis bonded to the second part81bby welding.

Because the first bonding layer81cais made of the same material as the first part81aand the second bonding layer81cbis made of the same material as the second part81b, the first part81aand the intermediate layer81ccan be easily welded and the second part81band intermediate layer81ccan be easily welded.

FIG. 8illustrates a fourth embodiment of a pillar terminal. Because a rechargeable battery including the pillar terminal has the same structure as the first embodiment of the rechargeable battery, except for a first pillar terminal90.

The first pillar terminal90includes a column portion91, a flange portion92, and a supporting protrusion93protruding from a bottom side of flange portion92. The column portion91is formed in a circular cylinder shape, and the flange portion92is formed to protrude outwards from an external circumferential side of the column portion91.

The column portion91includes an intermediate layer91cbetween first and second parts91aand91b. The flange portion92is coupled to a lower end of an external circumferential surface of the first part91a. The intermediate layer91cis formed at a top side of the first part91a, for example, by plating and is made of a different material from the first part91a.

When the intermediate layer91cis formed by plating, the intermediate layer91c(formed of a different material from the first part91a) may be integrally formed with the first part91a. The first part91ais made of the first metal, and the second part91band the intermediate layer91care made of the second metal. For example, the first metal may be copper and the second metal may be aluminum.

A first coupling portion95is formed at a center of the first part91a. A second coupling portion94, to be fitted into the first coupling portion95, is formed in the second part91b. In one embodiment, the first coupling portion95is formed with a protrusion, while the second coupling portion94is formed with a groove.

However, the first coupling portion95and the second coupling portion94may be fitted into each other. In this case, the first coupling portion95may be formed with a groove, and the second coupling portion94may be formed with a protrusion. In one embodiment, the first coupling portion95is formed in a quadrangular prism shape. However, the first coupling portion95may be formed to have a different shape (e.g., a polygonal column shape) in other embodiments.

The intermediate layer91cis formed to enclose the first coupling portion95. A convex portion96covering the first coupling portion95is formed in the intermediate layer91c.

As described above, when the first and second coupling portions95and94are formed, the contact area of the second part91band the intermediate layer91cincreases to thereby decrease resistance. As a result, the first pillar terminal90is prevented from being broken, for example, due to external impact and vibration. Further, when the intermediate layer91cand the second part91bare welded together, they can be easily aligned.

When the first and second coupling portions95and94are welded together while being fitted into each other, the strength of the first pillar terminal90is improved. As a result, the welded part can be prevented from being broken as a result external impact or vibration.