Patent Application
20100233536
The present invention relates to a safety apparatus for protecting a battery when it is short-circuited, and more particularly to a safety apparatus for use in the event of a short circuit of a high power battery, in which a positive temperature coefficient (PTC) function is integrated into the tab of a battery.
In accordance with the development of high-tech products, such as digital cameras, cellular phones, notebook computers, and hybrid automobiles, research and development on secondary batteries which are chargeable and dischargeable, unlike primary batteries, has actively been conducted. Representative secondary batteries include a Ni(nickel)-Cd(cadmium) battery, a Ni-metal hydride battery, a Ni(nickel)-H(Hydrogen) battery, a lithium ion battery, etc. Of such secondary batteries, a lithium ion secondary battery produces an operating voltage of 3.6V or more and thus is used as the main power source for portable electronic appliances or hybrid automobiles. In the case in which lithium ion secondary batteries are used in hybrid automobiles, the secondary batteries are used in the form in which a plurality of lithium ion batteries is connected in series. The lithium battery produces a voltage that is three times the voltage of a nickel-cadmium battery or a nickel-metal hydride battery, and has high energy density-to-weight ratios, so the use of the lithium battery is rapidly increasing.
The lithium ion secondary battery can be manufactured in a variety of types, for example, cylindrical type and prismatic type. The Lithium polymer batteries that have been most highly spotlighted in recent years have been generally manufactured in a pouched form having flexibility, so that they can be freely formed into a variety of shapes. The lithium polymer batteries are useful and helpful in meeting trends towards slimness and light weight of portable electronics because they are highly safe and light weight.
In such lithium ion batteries, cell resistance is reduced as low as possible in order to produce high power. Accordingly, lithium ion batteries can provide extremely high currents due to their low cell resistance when short-circuited. This causes a battery temperature to rise, resulting in the explosion of lithium ion batteries.
In order to prevent explosion when short-circuited, lithium ion batteries generally include positive temperature coefficient (PTC) elements. The PTC element starts to operate in the event of a short-circuited, and when current rapidly increases, thereby preventing explosion.
The PTC element is a device that interrupts electrical conduction by using the positive resistance-temperature characteristic, i.e. positive temperature coefficient (PTC), of a conductive polymer, which changes conductivity through heat expansion.
An exemplary polymer PTC is described with reference to
The conductive polymer 101 has the rectangular panel shape and uniform thick when it is viewed from a planar direction. The conductive polymer 101 is a polymer resin prepared by kneading polyethylene and carbon black and then performing cross-linking using radio active rays.
The conductive polymer 101 has an internal structure in which carbon black grains are coupled at room temperature, so a plurality of conduction paths through which current flows is formed therein. As a result, the conductive polymer 101 exhibits good conductance.
However, if the conductive polymer 101 is expanded by heat due to, for example, an increase in the ambient temperature or overcurrent in a conduction path, the distance between carbon black grains is increased, so the conduction path is cut and conductivity is rapidly decreased (increasing resistance).
The electrodes 102 and 103 are installed at respective end portions of the conductive polymer 101. The electrode 102 comprises an electrode member 102a made of copper and installed along the first surface 101a of the conductive polymer 101, a base part 102b connected to the electrode member 102a and installed at an end portion of the conductive polymer 101, and nickel foil 102c provided between the conductive polymer 101 and the electrode member 102a.
The electrode 103 has the same structure as the electrode 102, and comprises an electrode member 103a made of copper and installed along the second surface 101b of the conductive polymer 101, a base part 103b connected to the electrode member 103a and installed at the other end of the conductive polymer 101, and nickel foil 103c provided between the conductive polymer 101 and the electrode member 103a.
The electrode member 102a has the same width as the conductive polymer 101, and an end portion of the electrode member 102a having the rectangular shape is installed in a manner such that a parallel gap is provided between the electrode member 102a and the opposed electrode 103, particularly between the electrode member 102a and an electrode member 103d which will be described below. The base part 102b is formed by connecting the electrode member 102a formed on the first surface of the conductive polymer 101 and an electrode member 102d made of copper and remaining on the opposite surface (second surface) 101b of the conductive polymer 101 through a method of performing soldering on a cover layer 102e.
The electrode member 103a has the same width as the conductive polymer 101, and an end portion of the electrode member 103a has a rectangular shape and is formed in a manner such that a parallel gap is provided between the electrode member 103a and the opposed electrode 102, particularly the electrode member 102a of the electrode 102.
The base part 103b is formed by connecting the electrode member 103a and the electrode member 103d made of copper and remaining on the first surface of the conductive polymer 101 through a method of performing soldering on the cover layer 103e.
The resin film 104 is formed on the first surface of the conductive polymer 101 to cover the electrode member 102a, other than the base part 102b and the electrode member 102d. The resin film 105 is formed on the second surface of the conductive polymer 101 to cover the electrode member 103a, other than the base part 103b and the electrode member 103d.
The above-described polymer PTC lets current flow using the PTC characteristic of the conductive polymer 101 when the ambient temperature is lower than a predetermined temperature, which is the temperature at which the conductive polymer expands, and stops current from flowing when the ambient temperature is a predetermined temperature or higher as the conductive polymer 101 expands. The polymer PTC is a switch that is operated using the ambient temperature of the polymer PTC as the trigger of the above-described polymer PTC.
Further, the polymer PTC can use current as a trigger in such a manner that the conductive polymer 101 cuts electric conduction by expanding due to self heating caused by Joule's heat when overcurrent occurs between the electrodes 102 and 103, but the conductive state between the electrodes 102 and 103 is restored when the overcurrent is eased.
In the above-described polymer PTC, the sides and corners of the electrode member 102a and the nickel foil 102c are exposed on one side of the conductive polymer 101 in the longitudinal direction because the electrode member 102a is stacked on one surface of the conductive polymer 101.
Similarly, the sides and corners of the electrode member 103a and the nickel cladding foil 103c are exposed on the other side of the conductive polymer 101 since the electrode member 103a is stacked on one surface of the conductive polymer 101.
The above-described polymer PTC has a low capacity and was developed for small low-power electronics. In order to use the PTC for a high power lithium secondary battery producing current of 100 A or more, the PTC must have high capacity. However there is a problem in that the size of PTC increases as the PTC is made to have higher capacity. Accordingly, it is difficult to put the related PTC part to practical use in high power lithium batteries.
Accordingly, the present invention is provided in view of the above-described problem. In order to achieve the above objects and advantages, according to one aspect of the present invention, there is provided a safety apparatus for responding to a short circuit in a high power battery, in which a PTC function is integrated into a tab used in a high power battery in order to eliminate the requirement for additional space and the additional connection work for a PTC element, which implements the PTC function in a small space at low cost, and prevents explosions when short-circuited.
According to the present invention, the safety apparatus for responding to a short-circuit in a high power battery has the advantageous effect of preventing explosions in a battery when the battery is short-circuited by integrating a PTC function into the tab of a high power lithium secondary battery.
The safety apparatus for responding to a short-circuit in a high power battery has an additional advantageous effect of implementing a PTC function in a small space at low cost by eliminating the requirement for additional installation space and additional connection work for a PTC element since the PTC function is integrated into the tab of a high power lithium secondary battery.
In order to achieve the above objects, there is provided a safety apparatus for a high power battery comprising a casing, a battery part disposed inside the casing and including a first electrode plate, a separator, and a second electrode plate, a first tab connected to one of four edges of the first electrode via a first tab welding part, and a second tab connected to one of four edges of the second electrode plate via a second tab welding part, wherein one portion of the first tab ruptures when the first tab and the second tab are shorted, thus preventing a short-circuit between the first electrode plate and the second electrode plate.
The safety apparatus for a high power battery according to one embodiment of the present invention will be described with reference to
With reference to
The battery part 211 includes a positive electrode, a separator, and a negative electrode arranged in that order. This battery part 211 is wound in one direction. The battery part 211 can also have a structure in which a plurality of positive electrodes, a plurality of separators, and a plurality of negative electrodes are stacked. Each electrode is electrically connected to a positive tab 213 and to a negative tab 214 via a positive welding part 213a and a negative welding part 214a, respectively.
The positive and negative tabs 213 and 214 protrude from a sealing surface 212b of the casing 212 and are thus exposed outside. An end portion of the protruding positive tab 213 is attached to the positive tab welding part 213a. The positive tab welding part 213a serves as a connection means between the positive tab 213 and the positive electrode, and respective end portions of the positive tab welding part 213a are connected to the positive tab 213 and the positive electrode, respectively. Further, an end portion of the protruding negative tab 214 is attached to the negative tab welding part 214a. The negative tab welding part 214a serves as a connection means between the negative tab 214 and the negative electrode, and respective end portions thereof are connected to the negative tab 214 and the negative electrode, respectively.
On the outer surfaces of the positive and negative tabs 213 and 214 and the positive and negative tab welding parts 213a and 214a, a sealing tape 215 is wound in order to prevent short-circuiting from occurring between the casing 212, the tabs 213 and 214, and the positive and negative welding parts 213a and 214a at a contact portion where the sealing surface 212b and the tabs 213 and 214 and the welding parts 213a and 214b are in contact with each other.
Further, as shown in
The casing 212 is a pouch type casing comprising a middle layer made of metal foil, and an outer layer and an inner layer attached to respective surfaces of the middle layer and made of an insulating film, unlike a can type casing, such as a cylinder or a prism, which is generally manufactured through a molding method and made of gold. The pouch type casing has excellent formability, and thus it can be freely bent. The casing 212 has space 212a for receiving the battery part 211 therein, and has a sealing face 212b provided on a face formed by fusing the casing 212 along the edges of the space 212a.
With reference to the drawing, the casing 212 is a complex film comprising a metal layer 212c made of metal foil, for example aluminum foil, and an inner layer 212d and an outer layer 212e made of an insulation film and attached on the inner and outer surfaces of the middle layer 212c, respectively, in order to protect the middle layer 212c.
In the space 212a formed in the casing 212, the battery part 212 comprising the positive electrode 211a, the separator 211c and the negative electrode 211b, arranged in that order, are disposed. The positive tab 213 and the negative tab 214 extend from the positive electrode 211a and the negative electrode 211b, respectively, as shown in
An end portion of the positive tab 213 is attached to the positive tab welding part 213a. The positive tab welding part 213a serves to connect the positive tab 213 to the positive electrode 211a, and has respective end portions connected to the positive tab 213 and the positive electrode 211a.
Sealing tape 215 is wound around the outer surface of the positive tab 213 and the positive tab welding part 213a in order to prevent short-circuiting between the casing 212 and the tab 213 or between the casing 212 and the positive tab welding part 213a from occurring at a contact portion where the positive tab 213 and the positive tab welding part 213a come into contact with the sealing surface 212b.
The pouch type lithium secondary battery 210 having the above described structure is manufactured by electrically connecting the positive tab 213 and the negative tab 214 to the positive plate 211a and the negative plate 211b via the positive tab welding part 213a and the negative tab welding part 214a, and then forming the battery part 211 by arranging the positive plate 211a, the separator 211c and the negative plate 211b in that order and winding the combined structure of the plates and the separator 211a, 211c and 211b in one direction.
The positive tab 213 may be 0.1 to 0.4 millimeters thick, and more particularly 0.2 millimeters thick. In the positive tab, the length of the edge (width) that is parallel with the casing 211 is about 20 to 200 millimeters long, and the length of the edge that is perpendicular to the casing is 18 to 50 millimeters long.
The positive tab 213 preferably has a surface area ranging from 2 to 80 mm2, and has a resistance ranging from 2.36×10−4Ω to 1.64×10−5Ω.
The positive tab welding part 213a preferably has an area of 40 to 800 mm2.
In the above-described embodiment, the positive tab 213 is implemented as a safety tab, but the present invention is not limited thereto. The negative tab also can be implemented as the safety tab.
Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0017739 | Feb 2006 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR2006/005619 | 12/21/2006 | WO | 00 | 8/21/2008 |
