Rechargeable battery

A rechargeable battery includes an electrode assembly undergoing charging and discharging, a pressurization holder covering the electrode assembly and fixing the electrode assembly, a positive terminal and a negative terminal electrically connected to the electrode assembly, and a case accommodating the electrode assembly and the pressurization holder in a state in which the positive terminal and the negative terminal protrude from the case.

BACKGROUND

The present invention relates to a rechargeable battery.

2. Description of the Related Art

Unlike a primary battery that is not rechargeable, a rechargeable battery can be discharged and recharged. A small-capacity rechargeable battery is used for small portable electronic devices such as mobile phones, notebook computers, camcorders, and the like, while a large-capacity rechargeable battery is used as a motor-driving power source for a hybrid vehicle, and the like.

Recently, a high-output rechargeable battery using a non-aqueous electrolyte of high energy density has been developed, and a plurality of high-output rechargeable batteries may be connected in series to constitute a large-capacity battery module to be used for driving a motor of a device, e.g., an electric automobile or the like, that requires much power.

Also, a single large-capacity high-output rechargeable battery generally includes a plurality of rechargeable batteries connected in series, and such rechargeable batteries may have a cylindrical shape, an angular (i.e., rectangular or quadrangular) shape, a pouch-like shape, or the like.

In a typical rechargeable battery, a positive electrode and a negative electrode are generally charged by coating an active material on a base. A separator is located between the positive and negative electrodes, and are then wound and compressed to fit an angular case and housed therein.

Sometimes, however, the electrode assembly in the interior of the case expands and contracts when the rechargeable battery is charged and discharged, resulting in the active material coated on the base becoming detached or released, or degraded. In addition, when an impact from outside of the rechargeable battery is applied to the electrode assembly, the shape of the electrode assembly may be deformed, making the rechargeable battery defective.

SUMMARY

The present invention has been made in an effort to provide a rechargeable battery that stably accommodates an electrode assembly within a case and effectively protects the electrode assembly against an external impact applied thereto.

In one embodiment, a secondary battery is provided including an electrode assembly; a pressurization holder generally encompassing the electrode assembly, the pressurization holder having at least one side wall having an exterior-facing surface and an interior-facing surface, wherein at least one of the exterior-facing surface and the interior facing surface has a buffer recess; and a case housing the electrode assembly and the pressurization holder.

In one embodiment, a portion of the side wall is rounded to protrude toward the electrode assembly and the portion may be arc-shaped along at least one of a longitudinal direction or a lateral direction of the side wall. Additionally, the pressurization holder may be spaced from at least one of the case or the electrode assembly at the buffer recess.

In one embodiment, the buffer recess has a substantially planar surface that is substantially parallel to one of the interior-facing surface or the exterior-facing surface. The exterior-facing surface may include a reinforcing member generally corresponding to at least a portion of the buffer recess and the reinforcing member may protrude from the buffer recess or from the exterior-facing surface. In one embodiment, a height of the reinforcing member is less than a depth of the buffer recess.

The reinforcing member may include a plurality of protrusions or may include a plurality of ribs. The ribs may be arranged to intersect each other.

The pressurization holder may include a pair of opposing side walls, and the pair of opposing side walls may be connected by a connector. The connector may be substantially perpendicular to each of the opposing side walls. The connector may be arc-shaped.

The secondary battery may further include a cap plate on the case and wherein the connector may be located adjacent a bottom of the case substantially opposite to the cap plate. The pressurization holder may include a generally elastic and flexible material. One of the exterior-facing surface and the interior facing surface may be substantially smooth. The buffer recess may generally correspond to a center of the electrode assembly or the buffer recess may extend to an edge of the at least one side wall.

According to an exemplary embodiment of the present invention, because the electrode assembly is stably fixed by using the pressurization holder within the case, although the rechargeable battery is repeatedly charged and discharged, the electrode assembly can be prevented from excessively expanding, thus improving the life span of the rechargeable battery.

According to an exemplary embodiment of the present invention, although an external impact is applied to the rechargeable battery, because the pressurization holder stably fixes the electrode assembly, the durability of the rechargeable battery can be improved.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A rechargeable battery according to exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments disclosed hereinafter, but may be implemented in various different forms. The exemplary embodiments herein merely complete the disclosure of the present invention and fully provide explanation of the invention to the ordinarily skilled person in the art.

FIG. 1is an exploded perspective view of a rechargeable battery according to a first exemplary embodiment of the present invention,FIG. 2is a perspective view of the rechargeable battery according to the first exemplary embodiment of the present invention, andFIG. 3is a sectional view taken along line ofFIG. 2.

As shown inFIGS. 1 to 3, a rechargeable battery100according to a first exemplary embodiment of the present invention includes an electrode assembly10that is configured to undergo a charging and discharging operation, a pressurization holder20fixedly covering the electrode assembly10, terminals32and34electrically connected to the electrode assembly, and a case40receiving and accommodating the electrode assembly10in a state in which the terminals32and34protrude from the case. In one embodiment, a cap plate31is installed in an opening41, and a positive terminal32and a negative terminal34are installed through openings in the cap plate31.

A positive electrode11and a negative electrode12each include coated portions of a collector formed as a thin metal foil on which an active material is coated and uncoated portions11aand12aon which the active material is not coated, respectively. The positive electrode uncoated portion11amay be formed on one side end along a lengthwise direction of the positive electrode11, and the negative electrode uncoated portion12amay be formed on the other side end along a lengthwise direction of the negative electrode12.

The positive electrode11and the negative electrode12are stacked with a separator13, which is an insulating body, located therebetween, and wound by using a winding roll or the like so as to be formed as an electrode assembly10in the form of a jelly roll. The electrode assembly10is pressurized by a press, or the like, to have a flat form, such that it can be installed in the case40.

The case40has a substantially rectangular parallelepiped shape, and has the opening41at one side thereof.

The cap plate31is formed as a thin plate that is coupled to the opening41of the case40. The cap plate31includes a sealing stopper35installed in an electrolyte injection hole33, and a vent plate39installed in a vent hole37and having a notch39athat can be opened at a pre-set pressure.

The positive terminal32and the negative terminal34are installed to penetrate the cap plate31, and include flanges32aand34aformed at lower portions thereof and supported under the cap plate31, respectively. Outer circumferential surfaces of upper columns protruded from the cap plate31are threaded. Nuts36are fastened to the positive and negative terminals32and34, and support the upper portions of the positive and negative terminals32and34.

In the present exemplary embodiment, the terminals32and34are illustrated to protrude in a columnar shape, but are not limited thereto, with the terminals32and34being able to have various other shapes. For example, the terminals32and34may protrude as a flat plate from an upper portion of the cap plate31. In addition, either one of the terminals32and34may be positioned entirely within the case40, rather than being outwardly protruded from the case40.

A gasket38ais installed between the positive terminal32and the cap plate31. In addition, a gasket38bis installed between the negative terminal34and the cap plate31. The gaskets38aand38bhermetically seal portions between the terminals32and34and the cap plate31.

The positive terminal32is electrically connected to the positive electrode11by the medium of a positive lead tab32b, and the negative terminal34is electrically connected to the negative electrode12by the medium of a negative lead tab34b. An insulating member38cmay be inserted between the positive terminal32and the positive lead tab32band between the negative terminal34and the negative lead tab34b.

The electrode assembly10is inserted into the case40in a state in which the electrode assembly10is pressurized by the pressurization holder20.

FIG. 4is a perspective view showing a state in which an electrode assembly is inserted into a pressurization holder.

As shown inFIG. 4, the pressurization holder20pressurizes both sides of the electrode assembly10to restrain the electrode assembly10from expanding in volume when the rechargeable battery100is charged and discharged. The pressurizing of the electrode assembly10by using the pressurization holder20is for restraining the electrode assembly10against expanding in volume when the rechargeable battery100is charged and discharged and to prevent separation or degradation of the electrode active material and deformation when an external impact is applied thereto.

In more detail, the pressurization holder20includes a first side wall21pressurizing one side (i.e., a front side) of the electrode assembly10, a second side wall23pressurizing the other side (i.e., a rear side) of the electrode assembly10, and a connection part25connecting the first and second side walls21and23.

The first and second side walls21and23may have substantially the same area as both sides of the electrode assembly10, and may pressurize both sides of the electrode assembly10together. That is, the first and second side walls21and23apply an overall uniform pressure to both sides of the electrode assembly10to thereby smoothly restrain the electrode assembly10from expanding. However, the present exemplary embodiment is not limited thereto, and the first and second side walls21and23may be smaller by a certain size than the area of both sides of the electrode assembly10. That is, the size of the first and second side walls21and23may be configured such that a central portion of the electrode assembly10can be stably pressurized.

One edge of the connection part25is connected to the first side wall21and the other edge of the connection part25is connected to the second side wall23. When the pressurization holder20is received in the case40, the connection part25is positioned on the bottom of the case40. Portions of the first and second side walls21and23may be bent to be connected to the connection part25. That is, in the pressurization holder20, the first and second side walls21and23and the connection part25are connected in a substantially channel-like shape, and the connection portions may have an angular corner shape.

The channel-like shaping of the pressurization holder20including the corner portions by means of the connector25serves to allow the corners of the connector25of the pressurization holder20to be positioned at the corners of a bottom surface of the case40, whereby the pressurization holder20does not significantly wobble within the case40even if an external impact is applied thereto.

The first and second side walls21and23each include a rounded portion27formed on a face contacting the electrode assembly10. The rounded portions27protrude from the first and second side walls21and23toward the electrode assembly10and smoothly transfer a pressurization force to the electrode assembly10.

Referring toFIG. 5A, the rounded portion27of the first and second side walls21and23may have an arc-shape along a longitudinal direction thereof. In another embodiment as shown inFIG. 5B, a rounded portion27′ of the first and second side walls23′ may be arc-shaped along a lateral direction thereof. Additionally, a buffer recess29′s may be formed on a surface opposite to the rounded portion27′ or, alternatively, on the same side as the rounded portion.

The first and second side walls21and23include a buffer recess29on a face opposite to the rounded portion27. The buffer recess29serves to prevent the first and second side walls21and23from excessively contacting an inner surface of the case40if the electrode assembly10expands when the rechargeable battery100is charged and discharged. This will be described in detail as follows with reference toFIGS. 6 and 7.

FIG. 6is a sectional view of the rechargeable battery taken along line V-V ofFIG. 2, showing the electrode assembly in an unexpanded state, andFIG. 7is a sectional view showing a state in which the electrode assembly ofFIG. 6is expanded.

First, as shown inFIG. 6, when the electrode assembly10is not expanded, there may be a space between the first and second side walls21and23and an inner wall surface of the case due to the buffer recess29.

And, as shown inFIG. 7, when the electrode assembly10expands toward the case40as the rechargeable battery100is charged and discharged, the first and second side walls21and23are deformed toward the case40due to the expansion pressure of the electrode assembly10. In other words, the rounded portions27are deformed to have a nearly linear shape, while the buffer recess may be partially deformed to have a rounded shape. As such, the buffer recess29compensates for the deformation of the rounded portions27, preventing some or all of the pressure from being directly applied to the case40, thereby preventing significant deformation. In more detail, when the electrode assembly10expands according to charging or discharging of the rechargeable battery100, the first and second side walls21and23may be deformed and this deformation is compensated for by the buffer recess29. Thus, when the rechargeable battery10is charged and discharged, because the pressure that may cause the electrode assembly10to be deformed is not directly applied to the case40, the rechargeable battery100is less likely to be deformed and its stability can be improved.

In one embodiment, the buffer recess29may include reinforcing members22for reinforcing the strength of the pressurization holder20. As shown inFIG. 4, the reinforcing members22may be formed as a plurality of projections on the buffer recess29. The reinforcing members22reinforce the strength of the side wall21,23on which the buffer recess29is formed to thereby prevent the rounded portion27from being excessively deformed when the electrode assembly10expands. The reinforcing members22may protrude by less than a depth of the buffer recess29so that the pressurization holder20can be prevented from contacting the case40when the electrode assembly10expands.

The pressurization holder20may be made of a material such as polypropylene or polyphenylene sulfide. Thus, the pressurization holder20can have an elastic compressive force to thus effectively pressurize the electrode assembly10.

FIG. 8is a schematic perspective view of a pressurization holder of a rechargeable battery according to a second exemplary embodiment of the present invention. The same reference numerals as those ofFIGS. 1 to 7denote the same members. Thus, a detailed description of the same reference numerals will be omitted hereinafter.

As shown inFIG. 8, a pressurization holder120includes a first side wall121, a second side wall123, and a connector125. Here, the connector125connects the first and second side walls121and123such that the connection portions therebetween have a rounded shape. Further, the pressurization holder can be made as a single integral piece from a single material. Accordingly, formation of burrs at the corner portions of the pressurization holder120can be substantially prevented, and therefore a phenomenon in which the corner portions are broken due to stress concentrated thereto in the occurrence of an external impact can be substantially prevented.

FIG. 9is a schematic perspective view of a pressurization holder of a rechargeable battery according to a third exemplary embodiment of the present invention. The same reference numerals as those ofFIGS. 1 to 8denote the same members. Thus, a detailed description of the same reference numerals will be omitted hereinafter.

As shown inFIG. 9, a pressurization holder220according to the third exemplary embodiment of the present invention includes a buffer recess29on which a reinforcing member222is formed to have a rib-like shape. The height of the reinforcing member222in the rib-like shape according to the present exemplary embodiment is lower than a depth of the buffer recess29. Similarly to the projections22described above, the reinforcing members22in the first exemplary embodiment, the reinforcing member222does not come in to significant contact with the case40.

The rib-like shape of the reinforcing member222according to the third exemplary embodiment of the present invention may be a lattice shape formed on the buffer recess29, i.e. the ribs may intersect each other.

FIG. 10is a schematic perspective view of a pressurization holder of a rechargeable battery according to a fourth exemplary embodiment of the present invention. The same reference numerals as those ofFIGS. 1 to 9denote the same members. Thus, a detailed description of the same reference numerals will be omitted hereinafter.

As shown inFIG. 10, a pressurization holder320of a rechargeable battery according to the fourth exemplary embodiment of the present invention does not have a reinforcing member (22inFIG. 4) on the buffer recess29. Thus, although the first and second side walls21and23may move due to expansion of the electrode assembly10caused as the rechargeable battery100is charged and discharged, a pressurization force is unlikely to be transferred to the case40. That is, the first and second side walls21and23are deformed within the height of the buffer recess29, not significantly transferring a pressurization force to the case40to cause deformation.

The exemplary embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited thereto and various modifications other embodiments within the scope of the present invention can be made by a skilled person in the art. Thus, the true coverage of the present invention should be determined by the following claims.