Secondary battery

A secondary battery including: a case including an accommodation space therein; an electrode assembly housed in the case, the electrode assembly including a coating portion, a first electrode including a first non-coating portion, and a second electrode including a second non-coating portion; a short circuit induction member electrically connected to at least one of the first or second non-coating portions; and a cap plate sealing the case, the short circuit induction member including a contact maintaining part extending along a longitudinal direction of the electrode assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2012-0041659, filed on Apr. 20, 2012 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.

BACKGROUND

Aspects of embodiments of the present invention relate to a secondary battery.

2. Description of the Related Art

Lithium ion secondary batteries are widely used in electronic devices such as notebook computers and cellular phones. Such lithium ion secondary batteries are superior to other types of secondary batteries in terms of power, capacity, and weight, and are also used in hybrid vehicles and electric vehicles.

Lithium ion secondary batteries for vehicles should satisfy the requirements of safety and reliability under harsh conditions. A penetrating test, a squeezing test, and an overcharging test are the harshest of safety tests.

Of these safety tests, the penetrating test and the squeezing test are very important in predicting damage to a secondary battery due to a vehicle accident. Particularly, the penetrating test and the squeezing test require that even after a nail penetrates a secondary battery, or a secondary battery is squeezed, the temperature of the secondary battery does not excessively increase.

SUMMARY

According to an aspect of embodiments of the present invention, a secondary battery has improved safety, even after being penetrated by an external force.

According to an embodiment of the present invention, a secondary battery includes: a case including an accommodation space therein; an electrode assembly housed in the case, the electrode assembly including a coating portion, a first electrode including a first non-coating portion, and a second electrode including a second non-coating portion; a short circuit induction member electrically connected to at least one of the first or second non-coating portions; and a cap plate sealing the case, the short circuit induction member including a contact maintaining part extending along a longitudinal direction of the electrode assembly.

The contact maintaining part may be at a region of the short circuit induction member corresponding to the coating portion of the electrode assembly.

The contact maintaining part may include at least one of polyphenylene sulfide (PPS) or Teflon.

In one embodiment, the short circuit induction member further includes: a coupling part coupled to the at least one of the first or second non-coating portions; and a penetration part extending from the coupling part along the longitudinal direction of the electrode assembly, and the contact maintaining part is arranged on at least one surface of the penetration part. The coupling part may have a shape conforming with a shape of the at least one of the first or second non-coating portions.

The contact maintaining part may be formed through an injection molding process using the penetration part, or the contact maintaining part may include a tape adhered to the penetration part, or the contact maintaining part may be formed on the penetration part through laminating.

The first non-coating portion may be electrically connected to the case, and the short circuit induction member may be electrically connected to the second non-coating portion.

The first non-coating portion may be electrically connected to the cap plate and the case through a collector.

The short circuit induction member may be electrically insulated from the cap plate and the case.

In one embodiment, the first non-coating portion and the second non-coating portion are electrically insulated from the case and the cap plate, the short circuit induction member includes a first short circuit induction member and a second short circuit induction member, and the first short circuit induction member and the second short circuit induction member are electrically connected to the first non-coating portion and the second non-coating portion, respectively.

The first and second short circuit induction members may be symmetrical to each other with respect to the electrode assembly.

The first and second short circuit induction members may be arranged at opposite surfaces of the electrode assembly, respectively, and the opposite surfaces of the electrode assembly may be arranged along a direction perpendicular to the longitudinal direction of the electrode assembly.

According to an aspect of embodiments of the present invention, a secondary battery has improved safety and, as such, may be used as a motor-driving power source for propelling electric scooters, hybrid vehicles, or electric vehicles.

DETAILED DESCRIPTION

Some exemplary embodiments of the present invention are described more fully hereinafter with reference to the accompanying drawings; however, embodiments of the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

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.FIG. 3is a perspective view of a short circuit induction member of the secondary battery ofFIG. 1.FIG. 4is a cross-sectional view of the short circuit induction member ofFIG. 3, taken along the line A-A′.FIG. 5is a perspective view illustrating a conductor penetrating the secondary battery ofFIG. 1.FIG. 6is a cross-sectional view of a region “B” ofFIG. 5, showing a state in which the conductor has penetrated the secondary battery.

Referring toFIGS. 1 to 6, a secondary battery100according to an embodiment of the present invention includes a case110, an electrode assembly120, a short circuit induction member130, a plurality of collectors140, a plurality of first insulating members150, a cap plate160, a second insulating member170, and a plurality of nuts180and181.

The case110, in one embodiment, is formed of a conductive metal, such as aluminum, an aluminum alloy, or steel plated with nickel, and has a generally hexahedron shape with an opening through which the electrode assembly120is inserted and housed in the case110. The cap plate160is coupled to an edge of the case110defining the opening thereof to seal the electrode assembly120and electrolyte in the case110.

The electrode assembly120is inserted in the case110. The electrode assembly110includes a first electrode plate, a separator, and a second electrode plate, which have a thin plate or film shape. The first electrode plate may function as a positive electrode or a negative electrode, and the second electrode plate may have the opposite polarity to that of the first electrode plate.

The first electrode plate is formed by applying a first electrode active material, such as a transition metal oxide, on a first electrode collector formed of metal foil, such as aluminum foil, and includes a region on which the first electrode active metal is not applied, at a side thereof. However, a material used to form the first electrode plate is not limited by the present invention.

The second electrode plate is formed by applying a second electrode active material, such as graphite or carbon, on a second electrode collector formed of metal foil, such as nickel or copper foil, and includes a region on which the second electrode active metal is not applied, at a side thereof.

The separator is disposed between the first electrode plate and the second electrode plate to prevent or substantially prevent short circuiting and allows the movement of lithium ions. The separator, in one embodiment, may be formed of polyethylene, polypropylene, or combined film of polypropylene and polyethylene.

The electrode assembly120and the electrolyte are accommodated in the case110. The electrolyte may include: an organic solvent, such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC); and a lithium salt such as LiPF6 or LiBF4. The electrolyte may be liquid, solid, or gel.

The electrode assembly120may be formed by winding or stacking the first electrode plate, the second electrode plate, and the separator. Regions of the first and second electrode plates on which the first and second electrode active materials are applied are disposed approximately at the longitudinal central region of the electrode assembly120, and constitute a coating portion121. The regions of the first and second electrode plates, on which the first and second electrode active materials are not applied, constitute first and second non-coating portions122and123at both ends of the electrode assembly120. The separator may envelop an outermost region of the electrode assembly120corresponding to the coating portion121. Accordingly, the coating portion121is not exposed to the outside of the electrode assembly120.

The first non-coating portion122disposed at an end of the first electrode plate, and the second non-coating portion123disposed at another end of the second electrode plate are exposed to the outside of the electrode assembly120. In one embodiment, the first non-coating portion122may be electrically connected to the case110and the cap plate160, and the second non-coating portion123may be electrically insulated from the case110and the cap plate160.

The short circuit induction member130is coupled to the second non-coating portion123, and is extended along the coating portion121. Since the coating portion121is enveloped by the separator, the coating portion121does not contact the short circuit induction member130.

In a normal state, the short circuit induction member130is electrically connected to the second non-coating portion123of the second electrode, and is electrically insulated from the case110and the first electrode. However, when a conductor10, such as a conductor having a nail or needle shape, penetrates the case110from the outside thereof, the short circuit induction member130is electrically connected to the case110through the conductor10. Accordingly, the first and second electrodes of the electrode assembly120are connected to each other to form a short circuit. The short circuit rapidly consumes inner energy of the electrode assembly120, thereby ensuring the stability and reliability of the secondary battery100.

The short circuit induction member130, in one embodiment, includes: a coupling part131disposed at an end thereof; a penetration part132extending from the coupling part131; and contact maintaining parts133and134disposed on one or more surfaces of the penetration part132.

The short circuit induction member130is coupled to the second non-coating portion123through the coupling part131. The coupling part131may be formed of a same material as a metal used to form the second non-coating portion123in order to increase a coupling force therebetween. For example, where the second non-coating portion123is formed of copper constituting a negative electrode, the coupling part131may also be formed of copper. The coupling part131, in one embodiment, is bent at an angle from the penetration part132and is conformed with a shape of the second non-coating portion123so as to be tightly contacted thereto. In one embodiment, the coupling part131may be electromechanically coupled to the second non-coating portion123, such as through welding. The welding may be ultrasonic welding, but is not limited thereto.

The penetration part132is connected to the coupling part131, and extends along the longitudinal direction of the electrode assembly120. The penetration part132may extend along a region of the electrode assembly120corresponding to the coating portion121. In one embodiment, the penetration part132may entirely cover the electrode assembly120. Thus, when the conductor10penetrates the case110, the conductor10may also penetrate the penetration part132.

In the normal state, the penetration part132is insulated from the case110connected to the first electrode. However, when the conductor10penetrates the penetration part132to form a through hole132a, the penetration part132is connected through the conductor10to the case110connected to the first electrode. Accordingly, the penetration part132electrically connects the second non-coating portion123to the first non-coating portion122electrically connected to the case110, thereby forming a short circuit within the electrode assembly120. Since the penetration part132has low electrical resistance, when the short circuit is formed, the penetration part132generates a small amount of heat. Thus, when the conductor10penetrates the electrode assembly120to form a short circuit, the penetration part132is heated to consume energy from the secondary battery100. Since the penetration part132has low electrical resistance, a small amount of heat is generated, thus improving the stability and reliability of the secondary battery100.

The contact maintaining parts133and134are disposed on one or more surfaces of the penetration part132. The contact maintaining parts133and134may tightly contact the penetration part132. In one embodiment, the contact maintaining parts133and134may be formed of at least one of polyphenylene sulfide (PPS) or Teflon, which have high strength and heat resistance. The contact maintaining parts133and134may be formed through an injection molding process using the penetration part132, or may be provided in the form of a tape to be adhered to the penetration part132. In another embodiment, the contact maintaining parts133and134may be formed on the penetration part132through laminating.

The contact maintaining parts133and134have an electrical resistance greater than that of the penetration part132. Thus, when the conductor10penetrates the penetration part132and electric current flows therethrough, the contact maintaining parts133and134generate a smaller amount of heat than the penetration part132does. The contact maintaining parts133and134have high heat resistance. Thus, when the contact maintaining parts133and134are heated by a short circuit, the contact maintaining parts133and134do not expand the through hole132a.

In one embodiment, since the contact maintaining parts133and134contact one or more surfaces of the penetration part132, the contact maintaining parts133and134prevent or substantially prevent expansion of the through hole132a. Thus, although heat is generated from the penetration part132, the contact maintaining parts133and134maintain a state in which the penetration part132is connected to the conductor10. Accordingly, energy from the electrode assembly120can be quickly consumed, thereby ensuring the stability and reliability of the secondary battery100even though the conductor10penetrates the secondary battery100.

The collectors140are provided in a pair to couple to the first and second non-coating portions122and123, respectively. In one embodiment, the collector140includes: a body part141extending along the longitudinal direction of the electrode assembly120; a bent part142bent from the body part141and extending in a vertical or approximately vertical direction; one or more coupling parts143extending from the bent part142and coupled to the first or second non-coating portion122or123; and a terminal part144protruding (e.g., in a vertical direction) from the body part141, and exposed to the outside of the cap plate160.

The body part141, in one embodiment, has a generally flat plate shape and extends (e.g., in a horizontal direction) above the electrode assembly120along the longitudinal direction thereof. The body parts141may have a width to cover an array of the first and second non-coating portions122and123.

The bent parts142may be bent perpendicularly from the body parts141, and are extended along the first and second non-coating portions122and123. The bent parts142may have a width to cover the first and second non-coating portions122and123.

The coupling parts143extend (e.g., in a vertical direction) from the bent parts142. The coupling parts143contact the first and second non-coating portions122and123, and may be parallel thereto. In one embodiment, side surfaces of the coupling parts143contact side surfaces of the first and second non-coating portions122and123, and may be parallel thereto and electromechanically connected thereto.

The terminal parts144protrude (e.g., in a vertical direction) from the body parts141. The terminal parts144protrude from the upper portion of the cap plate160to form electrode terminals. In one embodiment, screw threads are formed on the outer circumferential surfaces of the terminal parts144, such that the nuts180and181may be coupled to the upper portions of the terminal parts144. The terminal parts144may be integrally formed with the body parts141, or may be separately formed and coupled thereto.

The first insulating members150are disposed on the collectors140, particularly, on upper portions of the body parts141. The first insulating members150are disposed between the cap plate160and the collectors140. The first insulating members150seal the peripheries of terminal holes163and164formed in the cap plate160, to prevent or substantially prevent the electrolyte from leaking therethrough. The first insulating members150electrically insulate the cap plate160and the collectors140from each other. The first insulating members150include terminal holes therein, such that the terminal parts144may be exposed to the upper side of the cap plate160through the terminal holes of the first insulating members150.

The cap plate160is coupled to the upper portion of the case110. The cap plate160seals the case110to prevent or substantially prevent the electrolyte from leaking out of the case110. The cap plate160, in one embodiment, may include an injection hole at a region thereof to inject the electrolyte, and an injection plug161closing the injection hole after the injection of the electrolyte. The cap plate160, in one embodiment, includes a safety vent162, such as approximately at a central portion thereof. When the secondary battery100is overcharged, gas may be generated within the case110such that an inner pressure of the case110is increased to be greater than a reference pressure. In this case, the safety vent162is opened earlier than the other portions of the cap plate160so as to discharge the gas, thereby reducing the possibility of explosion due to increased pressure within the case110. The terminal parts144protrude to the upper side of the cap plate160through the terminal holes163and164of the cap plate160.

The second insulating member170, in one embodiment, is disposed on the top surface of the cap plate160and surrounds the terminal part144of the collector140that is connected to the second non-coating portion123. The nut181coupled to the terminal part144above the cap plate160is electrically insulated from the cap plate160by the second insulating member170.

The nuts180and181, in one embodiment, are coupled to the terminal parts144from the upper side thereof. Screw threads formed in the nuts180and181engage with the screw threads of the terminal parts144. The nuts180and181are coupled to the terminal parts144, respectively, to fix the terminal parts144to the cap plate160. Accordingly, the electrode assembly120coupled to the collectors140is also fixed within the case110.

As described above, the first non-coating portion122of the first electrode of the electrode assembly120is electrically connected to the case110, and an end (i.e. the coupling part131) of the short circuit induction member130extending along the longitudinal direction of the electrode assembly120is connected to the second non-coating portion123of the second electrode. When the conductor10penetrates the secondary battery100, a short circuit is formed between the first and second electrodes through the case110, the conductor10, and the penetration part132. In this case, since the contact maintaining parts133and134are attached to one or more surfaces of the penetration part132, the contact maintaining parts133and134prevent or substantially prevent expansion of the through hole132ato maintain the short circuit, thereby quickly discharging the secondary battery100.

A configuration of a secondary battery according to another embodiment of the present invention is described below.

FIG. 7is an exploded perspective view of a secondary battery according to another embodiment of the present invention. Like reference numerals denote like elements throughout, and components and features of the secondary battery ofFIG. 7that are different from those of the secondary battery100described above are principally described below.

Referring toFIG. 7, a secondary battery200according to another embodiment of the present invention includes a case110, an electrode assembly120, a plurality of short circuit induction members130and230, a plurality of collectors140, a plurality of first insulating members150, a cap plate160, a plurality of second insulating members170and270, and a plurality of nuts180and181.

In the secondary battery200according to an embodiment of the present invention, the short circuit induction members130and230are provided in a pair. The short circuit induction members130and230include the short circuit induction member130(i.e. a first short circuit induction member) and a second short circuit induction member230.

The first short circuit induction member130, in one embodiment, has the same configuration as described above with respect to the secondary battery100. The first short circuit induction member130extends along a surface of the electrode assembly120. The first short circuit induction member130includes: a coupling part131at an end thereof to connect to a second non-coating portion123of a second electrode of the electrode assembly120; and a penetration part132extending from the coupling part131along the longitudinal direction of the electrode assembly120. As described above, the first short circuit induction member130includes contact maintaining parts133and134on one or more surfaces of the penetration part132to continually maintain a short circuit formed by a conductor10penetrating the penetration part132.

The second short circuit induction member230, in one embodiment, is symmetrical to the first short circuit induction member130. The second short circuit induction member230is disposed on the opposite surface of the electrode assembly120to that of the first short circuit induction member130. The conductor10may penetrate both the first and second short circuit induction members130and230. In this case, the second short circuit induction member230is connected to the first short circuit induction member130through the conductor10and thereby forms a short circuit between the first electrode and the second electrode of the electrode assembly120. The short circuit rapidly consumes inner energy of the electrode assembly120, thereby ensuring stability and reliability of the secondary battery200.

In one embodiment, the second short circuit induction member230includes: a coupling part231coupled to a first non-coating portion122of the first electrode of the electrode assembly120; a penetration part232extending from the coupling part231; and contact maintaining parts234disposed on one or more surfaces of the penetration part232. The coupling part231and the penetration part232may be formed of aluminum to correspond to a collecting plate forming the first electrode of the electrode assembly120. The contact maintaining parts234disposed on one or more surfaces of the penetration part232may prevent or substantially prevent expansion of a through hole formed by the conductor10penetrating the penetration part232. As described above with respect to the contact maintaining parts133and134of the short circuit induction member130, the contact maintaining parts234may be formed of at least one of polyphenylene sulfide (PPS) or Teflon, which have high strength and heat resistance. The contact maintaining parts234may be formed through an injection molding process using the penetration part232, or may be provided in the form of a tape to be adhered to the penetration part232. In another embodiment, the contact maintaining parts234may be formed on the penetration part232through laminating.

Thus, when the conductor10penetrates the secondary battery200, the second short circuit induction member230forms a short circuit with the first short circuit induction member130and maintains the short circuit, thereby stably consuming energy from the electrode assembly120.

The second insulating members170and270are disposed between the cap plate160and the nuts181and180, respectively. The second insulating members170and270insulate the nuts181and180from the cap plate160, respectively. Thus, in a normal state, the case110and the cap plate160are electrically insulated from the electrode assembly120.

As described above, the first and second short circuit induction members130and230are coupled to the second and first non-coating portions123and122, respectively, and the contact maintaining parts133and134, or234are disposed on one or more surfaces of each of the first and second short circuit induction members130and230. Thus, through holes formed by the conductor10penetrating the first and second short circuit induction members130and230are prevented or substantially prevented from expanding so as to stably consume energy from the electrode assembly120.

According to an embodiment of the present invention, a first non-coating portion of a first electrode of an electrode assembly is connected to a case, and an end of a short circuit induction member extending along the longitudinal direction of the electrode assembly is connected to a second non-coating portion of a second electrode. When a conductor penetrates a secondary battery, a short circuit is formed between the first and second electrodes through the case, the conductor, and a penetration part. In this case, since contact maintaining parts are attached to one or more surfaces of the penetration part, the contact maintaining parts prevent or substantially prevent expansion of a through hole of the penetration part to maintain the short circuit, thereby quickly discharging the secondary battery.

According to another embodiment of the present invention, first and second short circuit induction members are coupled to second and first non-coating portions of an electrode assembly, respectively, and contact maintaining parts are disposed on one or more surfaces of each of the first and second short circuit induction members. Thus, through holes formed by a conductor penetrating the first and second short circuit induction members are prevented or substantially prevented from expanding so as to stably consume energy from the electrode assembly.

While some exemplary embodiments of a secondary battery have been described herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as set forth in the following claims and equivalents thereof.