KR20060085874A - Molding-typed ptc device and secondary battery having the same - Google Patents

Abstract

The present invention provides a polymer composite exhibiting PTC characteristics in a state in which a first metal tab for electrical connection with a power generation element consisting of a positive electrode, a negative electrode, a separator, and an electrolyte and a second metal tab for electrical connection of an electrode terminal are spaced apart from each other. Provided are a PTC element that is integrally molded, and a secondary battery having the same.

Since the PTC device has a structure in which the PTC polymer composite is formed integrally between the outer surface of the first metal tab and the second metal tab while being integrally formed therebetween, the PTC polymer composite exhibits high dimensional accuracy and excellent dimensional accuracy. It is stable against external physical forces in the process, and it is stable even when exposed to a chemical environment because the PTC binding site is surrounded by the polymer composite.

Description

Molded-type PTC Device and Secondary Battery Embedding It {Molding-typed PTC Device And Secondary Battery Having The Same}             

1 is a schematic diagram of a PTC device according to one prior art;

2 is a schematic diagram of another PTC device according to the prior art;

3 is a schematic diagram of a PTC device according to one embodiment of the present invention;

4 is an exploded perspective view of a pouch-type battery according to an embodiment to which the PTC device according to the present invention is applied;

5 is a partially assembled perspective view of a rectangular battery according to an embodiment to which a PTC device according to the present invention is applied.

<Description of the symbols for the main parts of the drawings>

100, 200, 300: PTC device

110, 210, 310: PTC polymer composite

120, 220, 320: first metal tab

130, 230, 330: second metal tab

400: pouch type battery                 

500: square battery

The present invention relates to a molded PTC device and a secondary battery in which it is embedded. More particularly, the present invention provides an electrical connection between a first metal tab and an electrode terminal for electrical connection with a power generation element consisting of a positive electrode, a negative electrode, a separator, and an electrolyte. Provided are a PTC device integrally molded by a polymer composite exhibiting PTC characteristics in a state in which second metal tabs are spaced apart from each other, and a secondary battery including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Secondary batteries are classified into cylindrical batteries, square batteries, and pouch-type batteries according to their appearance, and have a variety of safety devices that can be effectively controlled when placed in abnormal operating conditions such as overcurrent and high temperature. .

Among them, a PTC (positive temperature coefficient) element is electrically connected between a power generating element and an electrode terminal, and maintains a low resistance at a temperature in a normal operating state, and flows a current, and a temperature in an abnormal state such as overcurrent or high temperature. As the resistance increases rapidly, only a small current or a small amount of current flows, thereby suppressing an increase in the battery internal pressure due to overheating.                         

In general, a PTC device has a structure in which two metal tabs for electrical connection are coupled to a composite having a PTC characteristic in which carbon black, metal fine particles and the like are dispersed in a polyolefin-based crystalline polymer substrate.

Representative structures of such PTC devices are disclosed in Korean Patent Application Publication Nos. 2004-16677 and 2004-17095. For reference, FIGS. 1 and 2 show typical structures of PTC devices according to the prior art.

Referring to FIG. 1, the conventional PTC device 100 includes metal tabs 120 at the top and bottom of the rectangular polymer composite (hereinafter sometimes abbreviated as "PTC polymer composite") 110 exhibiting PTC characteristics. , 130) is attached. As another example, the PTC device 200 of FIG. 2 has a structure in which a tube 240 is covered at a bonding portion of the PTC polymer composite 210 and the metal tabs 220 and 230.

The PTC device is getting smaller due to the large capacity and miniaturization of the battery, and the metal tabs are welded to the corresponding components of the battery and installed in the battery during assembly of the battery. The PTC devices 100 of FIGS. , 200) is susceptible to damage caused by deformation due to excessive force in the assembly process, and is susceptible to direct effects when exposed to the chemical environment. That is, the bonding sites of the PTC polymer composites 110 and 210 and the metal tabs 120, 130, 220, and 230 are limited to one side, respectively, and the bonding sites are exposed to the outside. Compared to the PTC device 100 of FIG. 1, the PTC device 200 of FIG. 2 has a relatively small problem as described above. However, the precision or dimensional stability of the device may be impaired during the mounting of the tube 240. The problem is that the process is added. In addition, the PTC devices 100 and 200 of FIGS. 1 and 2 may be formed of, for example, a PTC polymer during bending of a battery, or in a process of bending or coupling metal tabs 120, 130, 220, and 230 to other devices. In many cases, a crack is generated in the interior due to a physical force applied to the composites 110 and 210. Such cracks also cause a change in resistance and thus act as an element that inhibits the original function of the PTC device.

On the other hand, secondary batteries mounted on an external device such as a mobile phone, are divided into two types according to the external form in its final application. That is, the plastic resin housing is integrally molded on the outer surface of the battery while the terminal ("external terminal") which is electrically connected to the external device is exposed (called "hard pack battery"). ) And a form in which the housing of the plastic resin is not separately formed on the outer surface of the battery while the external terminal is exposed (called an "inner pack battery"). Since a hard pack battery is exposed to a part of its outer surface when it is mounted on an external device, at least the exposed outer housing is generally made of the same material as that of the external device. Therefore, the mounting of the battery to the external device is very easy, but according to the shape and structure of the external device has a problem that the housing of the battery to be made accordingly. On the other hand, since the inner pack battery is attached to an external case in a state where it is mounted on an external device, it may be cumbersome to install compared to a hard pack battery, but it may be used regardless of the shape and structure of the external device. have. Therefore, in recent years, the standardization work on the inner pack battery that can be used regardless of the shape and structure of the external device is in progress.                         

The PTC device used in the conventional hard pack battery is preferably a structure having a small overall thickness, such as the PTC devices 100 and 200 of FIG. 1 or 2. In particular, in a battery structure in which one of the positive and negative terminals is drawn out from the bottom of the battery, a PTC element of a small thickness is required in order to make the overall size (height) of the battery as small as possible. On the other hand, in an inner pack battery in which not only the PTC element but also the cap assembly-related elements such as the protection circuit module are mounted on the top of the cell, in the cap assembly structure for efficient arrangement and stable mounting of the device, a PTC element suitable for such a structure is provided. Required. Therefore, the PTC device, which is generally limited to a plate-like structure such as the PTC devices 100 and 200 of FIGS. 1 and 2, has a limitation in being applied to various structural changes of the cap assembly as described above.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

It is an object of the present invention to provide a PTC device which can be stably protected from physical or chemical external forces in a simple manufacturing process and can be deformed in appearance.

Another object of the present invention is to provide a secondary battery having excellent safety incorporating such a PTC element.

PTC device according to the present invention for achieving this object,                     

(a) a first metal tab in electrical connection with a power generation element comprising a positive electrode, a negative electrode, a separator and an electrolyte;

(b) a second metal tab electrically connected to the electrode terminal in a state spaced apart from the first metal tab; And

(c) a PTC polymer composite that is integrally formed while covering the facing portions of the first metal tab and the second metal tab;

It is configured to include.

As used herein, the "separated state" means that the first metal tab and the second metal tab are separated from each other by a predetermined distance, and the separation distance is such that the PTC polymer composite positioned between the two tabs can exhibit desired PTC properties. . Here, the PTC characteristic means a characteristic in which the electrical resistance rapidly increases at a specific temperature, which is a so-called switching temperature, as the PTC polymer composite increases in temperature.

The power generating element is exposed to the outside of the positive and negative tabs for electrical connection with an external element, and the first metal tab is electrically connected to such positive or negative tab (collectively referred to as "electrode tab"). . Here, the "electrical connection" includes both the case where the first metal tab is directly connected to the electrode tab as well as the case where the first metal tab is indirectly connected through other components. In the above, the connection method is generally achieved by welding, but is not limited thereto.

The secondary battery includes a positive electrode terminal or a negative electrode terminal (commonly referred to as an “electrode terminal”) on the outer surface of the battery for use as a power source for an external device, wherein the second metal tab is electrically connected to the electrode terminal. . Here, the electrical connection is a concept that includes both indirect connection as well as direct connection.

As such, the first metal tab and the second metal, except for the portion (part of the first metal tab) for the electrical connection with the electrode tab and the portion (part of the second metal tab) for the electrical connection with the electrode terminal. The tabs face each other in a nested state.

As exemplarily shown in FIG. 3, in the PTC device 300 of the present invention, the PTC polymer composite 310 surrounds the facing portions of the first metal tab 320 and the second metal tab 330 therebetween. It is molded integrally with the outer surface. Thus, the PTC polymer composite 310 forms contact surfaces with the upper and lower surfaces of each of the metal tabs 320 and 330, and thus exhibits excellent dimensional accuracy with high bonding force, and thus is stable to external physical forces. In addition, since the bonding sites of the PTC polymer composite 310 and the metal tabs 320 and 330 are surrounded by the PTC polymer composite 310, the PTC polymer composite 310 is stable even when exposed to a chemical environment.

In FIG. 3, the shape of the PTC polymer composite 310 is represented by a rectangular shape, but may be manufactured in an outer shape that can be easily coupled to other elements disposed around it, or an outer shape that can be stably mounted on such a structure. It may be.

The PTC polymer composite in the present invention preferably has a structure in which conductive fine particles are dispersed in a polymer substrate.

The polymer substrate is a component for forming a three-dimensional matrix for dispersing the conductive fine particles, for example, polyethylene; Polypropylene; Ethylene / propylene copolymers; Ethylene-based copolymers such as ethylene- (meth) acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer and ethylene-vinylacetate copolymer; Polyvinyl polymers such as polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, and polyvinylidene fluoride; Other thermoplastic polymers such as other polyamides, polystyrenes, polyacrylonitriles, silicone resins, polyesters, modified celluloses, polysulfones and the like can be used. Preferably, the polymer substrate is made of a polyolefin-based crystalline polymer.

As the conductive fine particles, a component that provides electrical conductivity to the PTC polymer composite, for example, a metal such as carbon black, acetylene black, nickel, copper, gold, silver, or an alloy of these or other components may be used. Preferably carbon black can be used. The conductive fine particles may preferably be used having a particle diameter of approximately 10 to 500 nm, but are not limited only to such a range, and various shapes such as needles may be used in addition to spherical shapes. The content of the conductive fine particles is preferably in the range of 5 to 80% by weight based on the total weight of the composite.

The PTC device according to the present invention can be manufactured by various methods. For example, a composite melt is prepared by adding and dispersing conductive fine particles in a molten state of a polymer substrate, and preparing a first metal tab and a second metal tab. It can be prepared by injecting the composite melt in the state of being placed in the mold.

The present invention also provides a secondary battery incorporating the PTC device. The PTC device according to the invention can be used particularly suited for square cells and pouch cells. The PTC device of the present invention can be particularly preferably used for the inner pack battery as described above.

For reference, FIGS. 4 and 5 illustrate one exemplary configuration when the PTC device according to the present invention is installed in a pouch-type battery and a square battery. However, these drawings are provided for the purpose of understanding the present invention, and the scope of the present invention is not limited thereto.

Referring to FIG. 4, which shows an exploded perspective view of the pouch-type battery, the pouch-type battery 400 includes a battery pack 402 and a battery pack in which the electrode group and the electrolyte of the positive electrode, the negative electrode, and the separator are sealed. A case body 404 for accommodating 402, and an upper cover 406 coupled to the case body 404 to seal the battery pack 402.

The battery pack 402 is exposed with the positive electrode tab 410 and the negative electrode tab 412, and the positive electrode tab 410 is connected to the protection circuit module (PCM) 420 via the positive electrode lead 414, and the negative electrode tab ( 412 is connected to PCM 420 via a cathode lead 416 connected to PTC device 300 according to the present invention.

If the top cover 406 is made of stainless steel, there is a possibility of an electric short when it comes in contact with the PCM 420, the electrode leads 414 and 416, the PTC 300, etc., so that the insulating member 430 is installed therebetween. do. In addition, between the case body 404 and the battery pack 402 and the top cover 406 so that the battery pack 402 can be stably fixed in a state in which the battery pack 402 is embedded in the case body 404 and the top cover 406. The double-sided tape 432 is provided between the battery packs 402.                     

A plurality of fasteners 440 are formed at the side end of the upper cover 406 in the direction of the case body 404, and the fastening grooves 442 at the corresponding positions of the fasteners 440 at the case body 404. Is formed.

The battery pack 402 is welded to the inside of the case body 404 by welding the connection portions of the electrode tabs 410 and 412 and the electrode leads 414 and 416, and the connection portions of the PCM 420 and the electrode leads 414 and 416, respectively. With the top cover 406 positioned in the case body 404 with it seated in the space, the fasteners 440 of the top cover 406 are inserted into the corresponding fastening grooves 442 of the case body 404. By this, assembling can be performed. After the assembly is completed, the immersion label 450 is attached to the top of the case body 404.

Referring to FIG. 5, in which a perspective view of a partially assembled state of a square battery is illustrated, a square battery 500 includes a power generation element (not shown) including a positive electrode, a negative electrode, a separator, and an electrolyte embedded in a rectangular can 502. It is made of a structure that the cap plate 504 is coupled to the top in the state. An electrode (eg, a cathode) of one of the power generating elements is electrically connected to the PCM 506 mounted on the cap plate 504 with its tab protruding upwards, and the other electrode (eg, an anode) Its tab protrudes downwards and is electrically connected to the cap 502 so that the can 502 itself serves as a terminal. The PTC device 300 according to the present invention is installed by spot welding the first metal tab 320 to the can 502, for example by spot welding the second metal tab 330 to the nickel lead 508. . Nickel lead 508 is connected to PCM 506 insulated from cap 502.

The foregoing has been described above with reference to some embodiments according to the present invention, but those skilled in the art to which the present invention pertains to various applications and modifications within the scope of the present invention based on the above contents It will be possible.

As described above, the PTC device according to the present invention has a structure in which the PTC polymer composite is formed integrally between the outer surface of the first metal tab and the second metal tab while being integrally molded between the first metal tab and the second metal tab. It exhibits dimensional accuracy, and is stable to external physical force during battery assembly, and has a merit of being stable even when exposed to a chemical environment because the bonding site is surrounded by a PTC polymer composite. In addition, due to the structural features of the PTC device is very easy to manufacture, can be manufactured in a variety of outer surface shapes, by the dimensional stability of the secondary battery embedded therein provides excellent safety.

Claims (7)

(a) a first metal tab in electrical connection with a power generation element comprising a positive electrode, a negative electrode, a separator and an electrolyte; (b) a second metal tab electrically connected to the electrode terminal in a state spaced apart from the first metal tab; And (c) a PTC polymer composite that is integrally formed while covering the facing portions of the first metal tab and the second metal tab; PTC element configured to include. The PTC device according to claim 1, wherein the first metal tab is directly or indirectly connected to an electrode tab of a power generation element, and the second metal tab is directly or indirectly connected to an electrode terminal of a battery. . The PTC device according to claim 1, wherein the PCT polymer composite has a structure in which carbon black as conductive fine particles is dispersed in a polyolefin-based crystalline polymer substrate. The PTC device according to claim 1, wherein the PCT polymer composite has an outer surface shape that is easy to fasten or couple to peripheral devices or peripheral structures. A secondary battery containing the PTC device according to claim 1. The secondary battery according to claim 5, wherein the battery is a square battery or a pouch battery. The secondary battery of claim 5, wherein the battery is an inner pack battery.

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