KR20070081301A - Ptc device mounted to battery cap and secondary battery having the same - Google Patents

Abstract

A protective device capable of being combined with a battery cap for secondary battery is provided to block over-current of the secondary battery, to improve spatial utility of the battery and to increase a ratio of recharge capacity to the same volume of a battery pack for the secondary battery by fabricating the protective device in an empty space between the battery cap and the battery can. A protective device PTC(100) comprises: a layered PTC resistor(110) with first and second surfaces and a constant thickness; a cap electric conduction part(150) that is attached to one side of the layered PTC resistor; first electrode(120) arranged on the first surface to electrically insulate the first electrode from the cap conduction part; second electrode(130) arranged on the second surface to electrically insulate the second electrode from the cap conduction part; and a lead part(140) to electrically connect the first electrode. The cap conduction part is fixed on a side part of the battery cap, in order to carry PTC between the battery cap and a battery can.

Description

Protective element mountable to battery cap and secondary battery having same {PTC device mounted to battery cap and Secondary battery having the same}

1 is a perspective view showing a configuration of a protection element according to the prior art.

Figure 2 is a schematic configuration diagram of a secondary battery equipped with a protection element according to the prior art.

3 is a perspective view showing a configuration of a protection element according to a preferred embodiment of the present invention.

4 is a cross-sectional view taken along line IV-IV ′ of FIG. 3.

5 is a schematic configuration diagram of a secondary battery equipped with a protection device according to a preferred embodiment of the present invention.

<Description of Major Reference Marks in Drawing>

100 ... Protective element 200 ... Secondary battery 110 ... Layered PCT resistor

120 ... first electrode 130 ... second electrode 140 ... lead part

150 ... Cap energization 220 ... Battery can 230 a ... Battery cap

The present invention relates to a protection element that can be mounted to a battery cap, and more particularly, to a PTC element mounted in a space between a battery cap of a secondary battery and a battery can, and blocking a power supply path when an overcurrent occurs in the secondary battery.

In general, secondary batteries are batteries that can be used repeatedly through a reverse charging and discharging process that converts chemical energy into electrical energy. Examples thereof include nickel-cadmium batteries, nickel-hydrogen batteries, lithium-ion batteries, and lithium-ion batteries. Polymer batteries and the like.

Recently, the growth of secondary batteries is due to the rapid growth of new markets such as digital home appliances and portable terminals. Lithium-based small secondary batteries are applied to products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and e-bikes. Nickel-hydrogen medium and large secondary batteries are HUV (Hybrid Electric). Applicable to vehicles such as vehicles.

At this time, in view of the development of the negative electrode and the positive electrode of the secondary battery, it is 3000mAh based on the cylindrical, exceeding the first generation 2400mAh, it is expected that the lithium-based medium-large secondary battery will be commercialized in the future.

The secondary battery is classified into a rectangular, cylindrical, and pouch type according to the shape of the outer shape, an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator are stacked, a battery can accommodating the electrode assembly together with an electrolyte, and an upper opening of the battery can. It includes a cap assembly for sealing the.

The principle of charging and discharging of a secondary battery is that when a battery is charged, a metal atom moves from a positive electrode to a negative electrode through a separator, where a charging current flows. On the contrary, when discharged, metal atoms move from the cathode to the anode and discharge current flows.

Here, when the secondary battery is overcharged or an overcurrent flows, there is a risk of explosion ignition. Typically, when the secondary battery is charged based on the assembled battery voltage, a cell that is overcharged above the charging voltage may occur due to a difference in cell voltage due to a difference in characteristics (eg, capacity and state of charge) between cells connected in series. In particular, the metal material generates hydrogen gas and heat when reacted with moisture, and there is a risk of explosion.

A safety device is required as a means of protecting the secondary battery from such overcharge and overcurrent and preventing performance degradation due to overdischarge. Safety devices of secondary batteries include safety vents, positive temperature coefficients (PTCs), shut-down separators, and additives.

Here, the safety valve is a component designed in the battery can to relieve the internal pressure increased by the release of gas inside the battery, the separator is a component designed so that metal atoms can not pass when the separator itself of polypropylene or polyethylene exceeds a certain temperature. , Additives are used as materials to induce battery safety.

In particular, the PTC element has a constant temperature coefficient and can be used repeatedly, unlike a fuse, and is secondary by a lead to prevent the battery from rupturing by cutting off the current when the voltage of the secondary battery increases rapidly. It is connected to the positive and negative electrodes of the battery.

US Patent No. 5,976,729 discloses a PCT device mounted on the bottom surface of a battery can, and Korean Patent Publication No. 2004-110598 (Secondary Battery) discloses a PTC device that adheres to the bottom surface of a battery can. Korean Patent Publication No. 447552 (Protective Device and Lithium Secondary Battery Having the Same) discloses a PTC device in close contact with an outer surface of a battery can.

1 is a perspective view showing the configuration of a protection element according to the prior art, Figure 2 is a schematic configuration diagram of a secondary battery equipped with a protection element according to the prior art.

Referring to FIG. 1, in the conventional PTC device 10, a layered PCT resistor 1 is sandwiched between two electrode terminals 2 and 3 to form a chip, and the chip is formed by welding. It is attached to two leads 4 and 5 extending from both ends.

Here, the two leads 4 and 5 are electrically connected to the secondary battery so that the PTC element 10 can function as a protective device or an interconnecting device of the secondary battery.

Referring to FIG. 2, the PCT element 10 is mounted in the battery can 20 to block overcurrent flowing in the secondary battery. At this time, one end of the lead wire 4 is electrically connected to the battery can forming one electrode of the secondary battery, and the other end of the lead wire 5 is electrically connected to the protection circuit 40 of the secondary battery. In this case, the protection circuit 40 is electrically connected to the battery cap 31 forming the second electrode of the secondary battery.

However, the secondary battery of the above-described configuration has a problem that the space utilization is lowered by the thickness t of the PCT element 10 to increase the size of the secondary battery pack, or the charge capacity is reduced compared to the same volume. Although the figure illustrates the case where the layered resistor of the PCT element is mounted on the bottom of the battery can, the same problem occurs when the layered resistor of the PCT element is mounted on the side of the battery can of the secondary battery. In addition, the PTC element 10 has a problem that the efficiency of detecting heat from the secondary battery is reduced.

In addition, by improving the connection structure of the PCT element 10 and efficiently disposed in the secondary battery, efforts have been made to reduce the volume of the secondary battery and maximize the electric capacity.

The present invention was devised to solve the above problems, and arranged in a structure in which the PTC element can be mounted in the space between the battery cap and the battery can, thereby mounting the battery cap to increase the charging capacity of the secondary battery. It is an object of the present invention to provide a possible protection device and a secondary battery having the same.

The protection device according to the present invention for achieving the above object is a PTC device for blocking overcurrent of a secondary battery having a battery cap and a battery can, the layered PTC resistor having a thickness and a first surface and a second surface ; A cap energizing part attached to one side of the layered PTC resistor; A first electrode attached to the first surface to be electrically insulated from the cap conducting portion; A second electrode attached to the second surface to be electrically connected to the cap conducting unit; And a lead part electrically connecting the first electrode, wherein the cap conduction part is attached to a side surface of the battery cap so that the protection element is accommodated in a space between the battery cap and the battery can.

Preferably, a non-conductive gap Gap is formed between the first electrode and the cap conducting portion. Alternatively, an insulator is interposed between the first electrode and the cap conducting portion.

In the present invention, the layered PTC resistor is made of a polymer-based conductive composite having a constant temperature coefficient characteristic.

Preferably, the polymeric conductive composite consists of a mixture of polymer polymer, conductive filler, antioxidant and peroxide crosslinker.

According to the present invention, the cap conducting portion is made of nickel, nickel plated alloy or nickel plated copper foil, the lead portion is made of nickel or nickel plated alloy, and the first and second electrodes are nickel or copper metal Electrolytic or electroless plating forms a thin film.

A secondary battery according to the present invention for achieving the above object is an electrode assembly having a positive electrode lead and a negative electrode lead, a battery can of a conductive metal material accommodating the electrode assembly therein, a cap assembly for sealing the battery can and the cap A layered PTC resistor having a battery cap formed in the assembly and having a thickness with the first and second surfaces; A cap energizing part attached to one side of the layered PTC resistor; A first electrode attached to the first surface to be electrically insulated from the cap conducting portion; A second electrode attached to the second surface to be electrically connected to the cap conducting unit; And a lead unit electrically connecting the first electrode, wherein the cap conduction unit is attached to a side surface of the battery cap such that the protection element is accommodated in a space between the battery cap and the battery can. It is characterized by.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, which can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

3 is a perspective view showing the configuration of a protection element according to a preferred embodiment of the present invention.

Referring to FIG. 3, the protection device 100 according to the present invention may include a layered PTC resistor 110 having a first and second surfaces and a predetermined thickness, and a first surface formed on the first surface of the layered PTC resistor 110. Of the electrode 120, the second electrode 130 formed on the second surface of the layered PTC resistor 110, the lead portion 140 formed on the first electrode 120, and the layered PTC resistor 110. It includes a cap energizing portion 150 formed on one side.

Here, the cap conducting unit 150 is electrically insulated from the first electrode 120 and electrically connected to the second electrode 130 and the layered PTC resistor 110.

In this case, a non-conductive gap (Gap) is formed between the first electrode 120 and the cap conducting unit 150 or an insulating material is interposed, so that the first electrode 120 is connected to the cap conducting unit 150. It can be electrically insulated.

More specifically, the layered PTC resistor 110 is made of a polymer-based conductive composite. The polymer-based conductive composite is composed of a mixture of a polymer, a conductive filler, an antioxidant, and a peroxide crosslinking agent. Preferably, the polymer may include high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinylidene fluoride (PVDF), polypropylene (PP), and Ethylene / PP polymer having a melt index of 1 to 10, The conductive filler may be made of metal such as carbon black, nickel, or metal oxide.

In this case, since the carbon black particles are interconnected to each other at room temperature, the layered PTC resistor 110 may form a plurality of conductive paths through which current flows, thereby exhibiting good conductivity. On the other hand, when a thermal runaway occurs due to an increase in the ambient temperature or an excess of the current flowing through the conductive path, the gap between the carbon black particles due to thermal expansion is widened so that the conductive path is blocked, so that the conductivity rapidly decreases. There are number characteristics.

In addition, first and second electrodes 120 and 130 for passing a current through the first and second surfaces of the layered PTC resistor 110 are closely formed.

The first and second electrodes 120 and 130 may be formed of a thin film by electrolytic or electroless plating of nickel or copper metal.

The lead portion 140 is attached to the upper surface of the first electrode 120 by solder or a conductive adhesive, and is formed such that the attachment region covers a part or the entirety of the first electrode according to ease of attachment and temperature treatment. . In addition, the lead portion 140 is formed to extend beyond a portion of the edge of the layered PTC resistor 110, it is preferably made of a conductive metal material of nickel or nickel plating alloy.

The cap conducting part 150 is attached to one side of the layered PTC resistor 110, and the metal foil is pressed or processed so that the resistance at the junction with the battery cap to be described later may be reduced, or the conductive metal may be a conductive adhesive. Is bonded to form a conductive layer, and as the conductive metal material that can be used, nickel, nickel plated alloy, or nickel plated copper foil is preferable.

Again, referring to FIG. 4, a cross-section of the protection device 100 cut into the IV-IV ′ plane of FIG. 3 is described. The first electrode 120 and the second electrode 130 are centered around the layered PTC resistor 110. ) Is oppositely attached, and the cap energization part 150 is attached to one side thereof. In addition, the first electrode 120 is electrically insulated from the upper end of the cap conducting unit 150 by a predetermined distance, and the second electrode 130 is joined to the lower end of the cap conducting unit 150. Electrically connected. In addition, a lead unit 140 is attached to an upper surface of the first electrode 120 to be electrically connected to a protection circuit (PCM) or a charge / discharge circuit described later.

The protective device 100 and the components 110 to 150 of the present invention are indicated in the form of a strap, but are not necessarily limited thereto.

The protection device 100 according to the present invention is preferably accommodated in the space between the battery cap and the battery can of the secondary battery, the schematic configuration of the secondary battery equipped with the protection device 100 will be described with reference to FIG. Is as follows. Here, the reference numerals of FIG. 5 are applied in the same manner as those used in FIG.

As shown in FIG. 5, the secondary battery 200 includes a battery can 220 accommodating an electrode assembly (not shown) therein, a cap assembly 230 sealing the battery can 220, and It includes a battery cap (230a) formed in the cap assembly 230.

Here, according to the stacking method of the electrode assembly and the structure of the secondary battery 200, it is obvious that the negative electrode and the positive electrode of the lead wire (not shown) which are components of the electrode assembly (not shown) may be configured to be interchanged. That is, of course, the present invention may be modified to electrically connect the negative electrode lead wire (not shown) with the battery cap 230a and the positive electrode lead wire (not shown) with the battery can 220.

The secondary battery 200 is manufactured by an electrode manufacturing process, an assembly process, an activation process, an inspection process, and a battery pack manufacturing process. In particular, the protection element 100 according to the preferred embodiment of the present invention is mounted in the manufacturing process of the battery pack. In addition, a protection circuit (not shown) or a charge / discharge circuit (not shown) that is electrically coupled with the protection element 100 to protect the secondary battery 200 is additionally installed.

Specifically, the protection device 100 is accommodated in the empty space of the battery cap 230a and the battery can 220 of the secondary battery 200, the cap conduction unit 150 of the protection device 100 Is electrically connected to one side of the battery cap 230a, and the lead unit 140 of the protection device 100 is electrically connected to the protection circuit or the charge / discharge circuit.

The current generated by the electrode assembly of the secondary battery 200 is transferred to the battery can 220 through the battery cap 230a, the protection device 100, the protection circuit (PCM) and the charge and discharge circuit. In more detail, the secondary battery 200 equipped with the protection device 100 includes a battery cap 230a, a cap conducting part 150, a second electrode 130, a layered PTC resistor 110, and a first The electrode 120, the lead unit 140, the protection circuit PCM, the charge / discharge circuit, and the battery can 220 form a conductive path electrically connected to each other. In this case, when overcurrent occurs in the process of charging and discharging the secondary battery 200, the layered PTC resistor 110 blocks the flow of current to protect the secondary battery 200 by opening the conductive path.

Here, the insulating plate 230 of the secondary battery 200 prevents the electrical contact between the battery cap 230a and the battery can 220 so that the protection device 100 is disposed between the battery cap 230a and the battery can 220. Allows overcurrent to be blocked without short circuit in space. For example, the battery cap 230a, the cap conduction unit 150, the second electrode 130, the layered PTC element 110, the first electrode 120, the lead portion 140, the protection element, the charge and discharge circuit And in the order of the battery can 220, the current may flow without a short circuit, and when the overcurrent occurs in the secondary battery 200, the protection element 100 to block the path of the overcurrent.

In this case, a protection circuit electrically connected to the protection element 100 may include a charge / discharge circuit for overvoltage, overcurrent, and / or overheating together with the protection device 100 during charging and discharging of the secondary battery 200. It is operated to protect the secondary battery 200.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

As described above, the present invention has an advantage that the protective element is mounted between the battery cap and the battery can to utilize the empty space of the secondary battery. In addition, the space utilization of the secondary battery is improved, thereby reducing the size of the secondary battery pack as compared with the related art, thereby substantially increasing the charging capacity with respect to the same volume.

Claims (9)

In the PTC element for blocking the overcurrent of the secondary battery having a battery cap and a battery can, A layered PTC resistor having a thickness with the first and second surfaces; A cap energizing part attached to one side of the layered PTC resistor; A first electrode attached to the first surface to be electrically insulated from the cap conducting portion; A second electrode attached to the second surface to be electrically connected to the cap conducting unit; And And a lead part electrically connecting the first electrode. And the cap conduction unit is attached to a side surface of the battery cap such that the protection element is accommodated in a space between the battery cap and the battery can. The method of claim 1, A non-conductive gap (Gap) is formed between the first electrode and the cap conducting portion, the protection element mountable to the battery cap, characterized in that. The method of claim 1, The protection element mountable to the battery cap, characterized in that an insulating material is interposed between the first electrode and the cap conducting portion. The method of claim 1, The layered PTC resistor is a protective element that can be mounted on the battery cap, characterized in that made of a polymer-based conductive composite having a constant temperature coefficient characteristics. The method of claim 4, wherein The polymer-based conductive composite is a protective element that can be mounted on the battery cap, characterized in that made of a mixture of a polymer polymer, a conductive filler, an antioxidant and a peroxide crosslinking agent. The method of claim 1, The cap conducting unit is a protective element mountable to the battery cap, characterized in that made of nickel, nickel plated alloy or nickel plated copper foil. The method of claim 1, The lead portion is a protective element mountable to the battery cap, characterized in that made of nickel or nickel plating alloy. The method of claim 1, The first and second electrodes may be formed of a thin film by electrolytic or electroless plating of nickel or copper metal. A secondary battery comprising an electrode assembly having a positive electrode lead and a negative electrode lead, a battery can made of a conductive metal material accommodating the electrode assembly therein, a cap assembly for sealing the battery can, and a battery cap formed in the cap assembly. A layered PTC resistor having a thickness with the first and second surfaces; A cap energizing part attached to one side of the layered PTC resistor; A first electrode attached to the first surface to be electrically insulated from the cap conducting portion; A second electrode attached to the second surface to be electrically connected to the cap conducting unit; And A protection element further comprises; a lead portion electrically connecting the first electrode, And the cap conduction unit is attached to a side surface of the battery cap so that the protection element is accommodated in a space between the battery cap and the battery can.

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