Electrode assembly and secondary battery having the same

An electrode assembly includes a first electrode plate having a first electrode active material coated on at least one surface thereof, a second electrode plate having a second electrode active material coated on at least one surface thereof, a separator between the first electrode plate and the second electrode plate, and at least one support member between the first electrode plate and the separator and outwardly protruding farther than an outermost end of the separator. A secondary battery includes the electrode assembly.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2014-0073648, filed on Jun. 17, 2014, in the Korean Intellectual Property Office, and entitled: “Electrode Assembly and Secondary Battery Having the Same,” is incorporated by reference herein in its entirety.

BACKGROUND

Embodiments relate to an electrode assembly and a secondary battery having the same.

2. Description of the Related Art

A secondary battery is a power storage system that converts electric energy into chemical energy and stores the converted energy to provide high energy density. Unlike primary batteries that cannot be recharged, a secondary battery is rechargeable. and is being widely used in IT devices, such as a cellular phone, a notebook computer, or a tablet PC. In recent years, electric vehicles are drawing attention owing to the rise in the oil price and a trend toward the use of secondary batteries as batteries for electric vehicles is growing.

SUMMARY

Embodiments are directed to an electrode assembly including a first electrode plate having a first electrode active material coated on at least one surface thereof, a second electrode plate having a second electrode active material coated on at least one surface thereof, a separator between the first electrode plate and the second electrode plate, and at least one support member between the first electrode plate and the separator and outwardly protruding farther than an outermost end of the separator.

The electrode assembly may further include a plurality of lead tabs drawn in a same direction from the first electrode plate and the second electrode plate, respectively.

When the electrode assembly is housed in a case, the support member may contact an internal surface of the case and support the first electrode plate, the second electrode plate and the separator while separating the first electrode plate, the second electrode plate and the separator from the case by a predetermined distance.

The support member may have a porous structure that allows mobile ions to move.

At least one surface of the support member may include an adhesive tape adhered thereto. The adhesive tape may be a porous tape allowing circulating ions to move.

The support member may have a bar shape.

The electrode assembly may further include a prop member protruding perpendicular to the support member from one end of the support member.

The support member may have an area that gradually increases toward its protruding direction.

Embodiments are also directed to a secondary battery including an electrode assembly including a first electrode plate, a second electrode plate, a separator between the first electrode plate and the second electrode plate and at least one support member between the first electrode plate and the separator, a case accommodating the electrode assembly, and electrode terminals electrically connected to the electrode assembly. One end of the support member outwardly protrudes from an outermost end of the separator and contacts an internal surface of the case.

The secondary battery may further include a plurality of lead tabs drawn in a same direction from the first electrode plate and the second electrode plate and electrically connected to the electrode terminals, respectively.

Directions of axes formed by the electrode terminals and the lead tabs may be parallel with a core axis direction of the electrode assembly.

The electrode assembly may include a plurality of electrode assemblies. The lead tabs drawn from the plurality of electrode assemblies may be arranged to face each other and may include bent portions facing each other. The bent portions may be electrically connected to the electrode terminals.

The support member may support the first electrode plate, the second electrode plate and the separator while separating the first electrode plate, the second electrode plate and the separator from the case by a predetermined distance.

The support member may have a porous structure that allows mobile ions to move.

At least one surface of the support member may include an adhesive tape adhered thereto. The adhesive tape may be a porous tape allowing circulating ions to move.

The support member may have a bar shape.

The secondary battery may further include a prop member protruding perpendicular to the support member from one end of the support member.

The support member may have an area that gradually increases toward its protruding direction.

DETAILED DESCRIPTION

In the drawing figures, the dimensions may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.

FIG. 1illustrates an assembled perspective view of a secondary battery according to an embodiment,FIG. 2illustrates an exploded perspective view of the secondary battery shown inFIG. 1, andFIG. 3Aillustrates a cross-sectional view taken along the line I-I′ ofFIG. 1,FIG. 3Billustrates a cross-sectional view taken along the line II-II′ ofFIG. 1, andFIG. 3Cillustrates a support member according to an embodiment.

Referring toFIGS. 1 to 3C, the secondary battery1000according to an embodiment includes an electrode assembly100, a case200and a cap assembly300.

The electrode assembly100may include a first electrode plate110, a second electrode plate120, a separator130and a support member140, which are formed as thin plates or layers. The first electrode plate110may function as a positive electrode and the second electrode plate120may function as a negative electrode, or vice versa.

The first electrode plate110may be formed by coating a first electrode active material111, such as a transition metal oxide, on a first electrode collector formed of a metal foil of, for example, aluminum. A plurality of first lead tabs113that are not coated with the first electrode active material111may extend and protrude from the first electrode collector to the cap assembly300. The first lead tabs113may be aligned at regular positions during a winding process for fabricating the electrode assembly100, providing a multi-tab configuration. The first lead tabs113may serve as paths for the flow of current between the first electrode plate110and a first external polar element.

The second electrode plate120may be formed by coating a second electrode active material121, such as graphite or carbon, on a second electrode collector formed of a metal foil of, for example, copper or nickel. A plurality of second lead tabs123that are not coated with the second electrode active material121may extend and protrude from the second electrode collector to the cap assembly300. The second lead tabs123may be aligned at regular positions during a winding process for fabricating the electrode assembly100, providing a multi-tab configuration. The second lead tabs123may serve as paths for the flow of current between the second electrode plate120and a second external polar element.

As shown inFIG. 2, the first lead tab113and the second lead tab123may be drawn from the first electrode plate110and the second electrode plate120in the same direction E1, E2to then be electrically connected to the first electrode terminal320and the second electrode terminal340of the cap assembly300, respectively, as described below. In addition, as shown inFIG. 3A, a direction C1of an axis formed by the first lead tab113and the first electrode terminal320and a direction C2of an axis formed by the second lead tab123and the second electrode terminal340may be parallel with a core axis direction C3of the electrode assembly100.

The separator130may be positioned between the first electrode plate110and the second electrode plate120to prevent short-circuits from occurring therebetween and to allow flowable ions to move. The separator130may have a width greater than that of the first electrode plate110or the second electrode plate120and may protrude upwardly and downwardly from the electrode assembly110farther than the first electrode plate110and the second electrode plate120. On the other hand, the separator130may not protrude upwardly from the electrode assembly110farther than the first and second lead tabs113and123and may not protrude downwardly from the electrode assembly110further than the support member140. The first and second lead tabs113and123may protrude upwardly from the electrode assembly100farther than the separator130, and the support member140may protrude downwardly from the electrode assembly100farther than the separator130.

The separator130may be made of polyethylene, polypropylene, or a combination of polyethylene and polypropylene, as examples.

The support member140may positioned between the first electrode plate110and the separator130or between the second electrode plate120and the separator130. The support member140may be wound together with the first electrode plate110, the second electrode plate120and the separator130to then be fixed to the electrode assembly100. The support member140may have a bar shape and may have a bottom end protruding downwardly from the electrode assembly100, thereby bearing the weight of the electrode assembly100from a bottom surface of the case200when the electrode assembly100is accommodated in the case200. The separator130may be spaced a predetermined distance D apart from the bottom surface of the case200by the support member140, such that the separator130is not brought into direct contact with the bottom surface of the case200.

In the comparative electrode assembly accommodated in a case in a core axis, an outermost end of the separator comes into direct contact with a bottom surface of the case, thereby bearing the weight of the electrode assembly. However, in the embodiment, the support member140protruding from the electrode assembly100allows the electrode assembly100to be space a predetermined distance apart from the case200and bears the weight of the electrode assembly100. Thus, it may be possible to prevent the separator130from being damaged due to the weight of the electrode assembly100, thereby improving the structural stability of the separator130.

The support member140may include a plurality of support members provided in the electrode assembly100. In such a case, the position and number of the support members140may be selected so as to allow the electrode assembly100to maintain a balance within the case200. For example, the position and number of the support members140may be selected such that the support members140are symmetrically arranged in view of the core axis of the electrode assembly100. If more support members140than required were to be provided, contact areas between electrode active materials and the separator130could be excessively reduced, thereby lowering battery efficiency. If the support members140were to be asymmetrically arranged, the weight of the electrode assembly100may not be uniformly distributed to the respective support members140but may concentrate on a support member located at a particular position. According to embodiments, the support members140may be arranged to be horizontally symmetrical with each other in view of the core axis of the electrode assembly100.

The support member140may be appropriately sized. For example, if the width and thickness of the support member140were to be unduly large, contact areas between electrode active materials and the separator130could be excessively reduced, thereby lowering battery efficiency. According to embodiments, the support member140may have a porous structure to allow mobile ions, such as lithium ions, to move. The support member140may be shaped as a frame having an opening to allow for the movement of mobile ions. In this case, however, the bearing capacity of the weight of the electrode assembly100may be reduced. Accordingly, the mobility of mobile ions and weight bearing capacity of the electrode assembly100may both be taken into consideration in fabricating the support member140.

The support member140may be made of a hard material so as to maintain a predetermined distance D between the separator130and the bottom surface of the case200. In addition, the support member140may be made of an insulating material so as to achieve insulation stability of the secondary battery1000.

As shown inFIG. 3C, an adhesive tape142may be formed on at least one surface of the support member140. The adhesive tape142may allow the support member140to be fixed well to the electrode assembly100. If the support member140has a porous structure, the adhesive tape142may also have porosity to allow mobile ions, such as lithium ions, to move. In other implementations, the adhesive tape142may include a plurality of adhesive tapes so as to minimize an adhesion area.

The electrode assembly100may be housed in the case200with an electrolyte solution. The electrolyte solution may include an organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), or the like, and a lithium salt such as LiPF6or LiBF4. The electrolyte solution may be a liquid, a solid or a gel phase.

The case200may be made of a conductive metal such as aluminum, aluminum alloy or nickel plated steel, and may have an approximately hexagonal shape that defines an opening through which the electrode assembly100is inserted and placed in the case200. The case200may have an inner surface subjected to an insulating treatment to be insulated from the electrode assembly100.

The cap assembly300may be coupled to the case200. The cap assembly300may include a cap plate310, a first electrode terminal320, a first lower insulation member330, a second electrode terminal340, a second lower insulation member350, an upper insulation member360, a short-circuit plate370, a safety vent380and a plug390.

The cap plate310may seal the opening of the case200and may be made of the same material as the case200. The cap plate310may include a first electrode terminal hole311, a second electrode terminal hole312, a short-circuit hole313, a vent hole314, and an electrolyte injection hole315. The cap plate310may be coupled to the case200by laser welding.

The first electrode terminal320may include a first electrode terminal member321, a first electrode plate322, a first terminal plate323and a first seal gasket324. The first electrode terminal member321may pass through the first electrode terminal hole311and may have a lower portion connected to the first electrode plate322and an upper portion connected to the first terminal plate323. The upper portion of the first electrode terminal member321may be fitted into a coupling hole of the first terminal plate323to be riveted and coupled to the first terminal plate323. A bottom surface of the first electrode plate322may be welded to the first lead tab113to then be electrically connected to the first electrode plate110. The first seal gasket324may be made of an insulating material and may seal a gap between the first electrode terminal member321and the first electrode terminal hole311.

The first lower insulation member330may be positioned between the cap plate310and each of the first electrode terminal member321and the first electrode plate322and may prevent unnecessary short-circuits from occurring therebetween.

The second electrode terminal340may include a second electrode terminal member341, a second electrode plate342, a second terminal plate343, and a second seal gasket344. The second electrode terminal member341may pass through the second electrode terminal hole312and may have a lower portion connected to the second electrode plate342and an upper portion connected to the second terminal plate343. The upper portion of the second electrode terminal member341may be fitted into a coupling hole formed at one side of the second terminal plate343to be riveted and coupled to the second terminal plate343. The other side of the second terminal plate343may extend to a position corresponding to the short-circuit hole313. A bottom surface of the second electrode plate342may be welded to the second lead tab123to be electrically connected to the second electrode plate120. The second seal gasket344may be made of an insulating material and may seal a gap between the second electrode terminal member341and the second electrode terminal hole312.

The second lower insulation member350may be positioned between the cap plate310and each of the second electrode terminal member341and the second electrode plate342, thereby preventing short-circuits from occurring therebetween.

The upper insulation member360may be formed to surround side and bottom portions of the second terminal plate343and may insulate the second terminal plate343from the cap plate310. An opening corresponding to the short-circuit hole313may be formed on a bottom surface of the upper insulation member360.

The short-circuit plate370may be installed in the short-circuit hole313of the cap plate310to have the same polarity with the cap plate310. When the internal pressure of the secondary battery1000exceeds a preset pressure, the short-circuit plate370may be inverted and may protrude convexly upward to be brought into contact with a bottom surface of the other side of the second terminal plate343, resulting in occurrence of a short-circuit. If the short-circuit occurs, the amount of current flowing in the secondary battery1000increases to generate heat, and a fuse (not shown) may be melted by the generated heat, thereby interrupting the flow of current through the secondary battery1000.

The safety vent380may be installed in the vent hole314of the cap plate310and may have a notch381configured to be opened at a preset pressure.

The plug390may be installed to seal the electrolyte injection hole315of the cap plate310.

The first electrode plate322and the first lead tab113may be coupled to each other, and the second electrode plate342and the second lead tab123are coupled to each other, thereby allowing the first and second electrode terminals320and340to share the capacity of bearing the weight of the electrode assembly100and supporting the electrode assembly100.

FIGS. 4A to 4Cillustrate a secondary battery according to a modified embodiment.

The secondary battery shown inFIGS. 4A to 4Cis substantially the same with the secondary battery1000shown inFIGS. 1 to 3C, except for a configuration of a support member140′. InFIGS. 4A to 4C, the same functional components are denoted by the same reference numerals with those of the previous embodiment, and detailed descriptions thereof will not be repeated.

According to the modified embodiment, the support member140′ may further include a prop member141connected to a bottom end contacting a bottom surface of a case200. The prop member141may have a roughly plate-like shape and may be positioned to be perpendicular to the support member140′. The prop member141may be provided for reinforcing the bearing capacity of the support member140′ against the weight of the electrode assembly100. The prop member141may be made of the same material as the support member140′. As shown inFIG. 4C, an adhesive tape142′ may be adhered to the support member140′. Other details of the support member140′ may be understood by referring to the aforementioned support member140.

FIGS. 5A to 5Cillustrate a secondary battery according to another modified embodiment.

The secondary battery shown inFIGS. 5A to 5Cmay be substantially the same as the secondary battery1000shown inFIGS. 1 to 3C, except for a configuration of a support member140″. InFIGS. 5A to 5C, the same functional components are denoted by the same reference numerals with those of the previous embodiment, and detailed descriptions thereof will not be repeated.

According to this modified embodiment, the support member140″ may have an area that gradually increases toward a lower portion of the electrode assembly100, that is, in a protruding direction of the electrode assembly100. For example, as shown inFIG. 5A, the support member140″ may be shaped as a trapezoid having a lower width d2greater than an upper width d1. With this configuration, the support member140″ may have an increased bearing capacity against the weight of the electrode assembly100. In addition, as shown inFIG. 5C, an adhesive tape142″ may be adhered to the support member140″. Other details of the support member140″ may be understood by referring to the aforementioned support member140.

FIG. 6illustrates a cross-sectional view of a secondary battery according to another embodiment.

Referring toFIG. 6, the secondary battery1000′ according to this embodiment may include a pair of first and second electrode assemblies100aand100bdisposed to face each other. As described above, unlike in the secondary battery1000according to the previous embodiment, including one electrode assembly100, in the secondary battery1000′ including a plurality of electrode assemblies100aand100b, lead tabs drawn from the respective electrode assemblies100aand100bmay be disposed to face each other. For example, as shown inFIG. 6, the first lead tab113aof the first electrode assembly100aand the first lead tab113bof the second electrode assembly100bmay be disposed to face each other. The first lead tab113amay include a first bent portion113a′ having an upper portion that is bent, and the second lead tab113bmay include a second bent portion113b′ having an upper portion that is bent. The first and second bent portions113a′ and113b′ may be bent to face each other and may be electrically connected to the first electrode plate322′.

In other aspects, the secondary battery1000′ according to the present embodiment may be substantially the same as the secondary battery1000according to the previous embodiment in view of configurations, and detailed descriptions thereof will not be repeated.

The embodiments have been described with regard to the secondary battery for use in an automotive vehicle by way of example. In other implementations, embodiments may also be applied to any type of secondary battery having an electrode assembly accommodated in a case in a core axis direction.

By way of summation and review, secondary batteries are classified into a lead storage battery, a Ni—Cd battery, a Ni-MH battery, a lithium ion battery, a lithium polymer battery, and so on. Specifically, the lithium ion battery or the lithium polymer battery provide a high energy density per unit weight than other kinds of batteries, such that they can be rapidly applied for use in portable IT devices.

The recent trend toward growth in the use of secondary batteries for electric vehicles, has made it desirable for the secondary battery to have advantageous characteristics such as a high density, high output and stability.

An electrode assembly of the lithium ion battery or the lithium polymer battery includes a positive electrode plate, a negative electrode plate and a separator. The positive electrode plate is formed by coating a lithium-based positive electrode active material on an aluminum base and the negative electrode plate is formed by coating a carbonaceous negative electrode active material on a copper base. The separator may separate the positive electrode plate and the negative electrode plate from each other and may be formed of a polymer material having actively moving ions.

The lithium ion battery or the lithium polymer battery may be fabricated in a cylindrical, prismatic or pouch type. A secondary battery, such as a secondary battery for use in an automotive vehicle, may be fabricated such that an electrode assembly is housed in a prismatic can. As indicated, for this and other uses, a high capacity and high output characteristics are desirable. In order to fabricate a high-capacity secondary battery, it is desirable to wind electrode plates coated with as much positive/negative electrode active materials as possible in a given volume of the can. To this end, a secondary battery may be configured to accommodate as many as electrode plates as possible in a given volume of a can by directly connecting the electrode plates to electrode terminals without an electrode assembly.

In order to connect the electrode plates of an electrode assembly to the electrode terminals, the electrode assembly may be configured to be inserted into the can toward a core axis of the electrode assembly. In such a case, an end of a separator may be brought into contact with a bottom surface of the can to bear the weight of the electrode assembly. Since the weight derived from the electrode plates and active materials is directly applied to the separator, structural stability of the electrode assembly may be adversely affected. In addition, the weight derived from the electrode plates and active materials may also be applied to connected portions between the electrode plates and the electrode terminals, and the structural stability of the electrode assembly may also be adversely affected by the weight.

Embodiments provide an electrode assembly having improved structural safety by assembling a support member for bearing the weight of the electrode assembly, electrode plates and a separator by being wound together, and a secondary battery having the electrode assembly. According to embodiments, a support member for bearing the weight of the electrode assembly, electrode plates and a separator are wound together and assembled, thereby providing an electrode assembly having improved structural safety and a secondary battery having the electrode assembly.