KR20030033212A - Protector and secondary battery mounting the such - Google Patents

Abstract

PURPOSE: Provided are a protection element for improving stability of a battery, which cuts off electric current perfectly by sensing the heat or ignition caused by overcharge, and a secondary battery equipped with the protection element. CONSTITUTION: The protection element(30) contains: a thermal fuse(31); a tap lead(32) welded to one end of the thermal fuse(31); a terminal lead(33) welded to the other end of the thermal fuse(31); a protection membrane layer(34) covering the thermal fuse(31) and the weld parts of the tap and terminal leads(32, 33), wherein the protection membrane layer(34) is made of a polymer resin; a sealing material(35) coated along the contact area of the protection membrane layer(34), the thermal fuse(31), and the tap and terminal leads(32, 33) to seal the gap of the contact area, wherein the sealing material(35) is a UV curing agent. And the secondary battery contains: a battery part formed by winding a cathode plate, a separator, and an anode plate; a can in which the battery part is inserted and an electrolyte is injected; a cap plate coupled with the upper part of the can; the protection element(30).

Description

Protective element and secondary battery mounting the same

The present invention relates to a secondary battery, and more particularly, to a secondary battery having an improved structure of a protection element that blocks the flow of current during overcharging of the battery.

Lithium secondary battery is a battery that can be charged and discharged rapidly and has a high operating voltage and high energy density per unit weight compared to nickel-cadmium (Ni-Cd) or nickel-metal hydride (Ni-MH) batteries. It is growing. Lithium secondary batteries can be classified into liquid electrolyte batteries and polymer electrolyte batteries according to the type of electrolyte. Generally, a battery using a liquid electrolyte is called a lithium ion battery, and a battery using a polymer electrolyte is called a lithium polymer battery.

Such a lithium secondary battery is required to have a protection device because there is a risk of explosion or fire due to heat generation or ignition due to internal short circuit or thermal runaway during overcharging.

1 illustrates a conventional lithium secondary battery having a protection element.

Referring to the drawings, the secondary battery 10 may include a can 11 in which a battery part (not shown) wound in the order of a positive electrode plate, a separator, and a negative electrode plate, a cap plate 12 coupled to the can 11, And a protection element 14 connected to the electrode terminal 13 drawn out from the cap plate 12, and a protection circuit board 15 electrically connected to the protection element 14.

An electrode terminal 13 molded in the insulator 16 protrudes from the cap plate 15, and an electrolyte injection hole for injecting an electrolyte solution is formed at one side thereof, and the electrolyte injection hole is sealed by a ball 17. It is.

The protection element 14 includes a fuse 18, a terminal lead 19 welded to the fuse 18, and a board terminal 100. The electrode terminal 13 is welded to the terminal lead 19 by laser welding. In addition, the protective circuit board 15 is electrically connected to the substrate lead 100.

In the conventional secondary battery 10 having such a structure, when the temperature inside the battery increases due to overcharging, a fuse made of a material having a relatively low melting point electrically connected through the electrode terminal 13 and the terminal lead 19 ( 18) is melted and broken to cut off the flow of current, thereby preventing the danger of explosion.

In recent years, the structure which mounts the said protection element 14 in the inside of the battery 10 is developed. When the protection element 14 is mounted inside the can 11, it may have the following problem.

Since the protection element 14 is exposed to the electrolyte injected into the can 11, the physical properties of the fuse 18 change, so that the operating range of the fuse 18 changes. As a result, the fuse 18 is not operated at a desired proper temperature, so that the safety of the battery 10 becomes unreliable.

In order to prevent this, a thin plate made of a polymer resin is ultrasonically fused to the fuse 18 and the plurality of leads 19 and 100 to be welded thereto so that the electrolyte solution does not penetrate. However, a minute gap is generated in the contact surface between the fuse 18 and the leads 19 and 100 so that the electrolyte penetrates and changes the physical properties of the fuse 18, thereby losing its function as a protection element.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a protection device and a secondary battery equipped with the same, which prevents electrolyte from penetrating into a protection device installed inside the battery, thereby improving stability of the battery.

1 is an exploded perspective view illustrating a conventional secondary battery;

2 is an exploded perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention;

3 is a perspective view illustrating the protection device of FIG. 2;

<Brief description of symbols for main parts of the drawings>

10,20 ... rechargeable batteries 11,22 ... can

12,25 ... cap plate 13,26 ... electrode terminals

14,30 Protection element 21 Battery compartment

23 Cap assembly 24 Insulation plate

31 Thermal fuse 32 Tapped lead

33.Terminal lead 34.Protective layer

35 ... sealing material

In order to achieve the above object, a protective device according to an aspect of the present invention,

Thermal fuses;

A first lead welded to one end of the thermal fuse;

A second lead welded to the other end of the thermal fuse;

A protective film layer made of a polymer resin surrounding a portion where the thermal fuse and the first and second leads are coupled; And

It is characterized in that it comprises a; a sealing material for sealing the gap between the surface of the protective film layer, the thermal fuse and the first and second leads in contact with the contact.

Moreover, the seal member is characterized in that the ultraviolet curing agent cured by photocuring.

A secondary battery equipped with a protection element according to another aspect of the present invention,

A battery part wound in the order of a positive electrode plate, a separator, and a negative electrode plate;

A can which provides a space in which the battery unit is accommodated and in which an electrolyte is injected;

A cap plate coupled to the top of the can; And

It is installed in the can, the one of the electrode tab withdrawn from the battery unit and the electrode terminal withdrawn from the cap plate to conduct electricity to each other, and to block the flow of current during overcharge,

A thermal fuse, a tab lead welded to one end of the thermal fuse and electrically connected to the electrode tab, a terminal lead welded to the other end of the thermal fuse and electrically connected to the electrode terminal; And a protective device including a protective film layer made of a polymer resin surrounding the welded portion of the tab and the terminal lead.

In addition, the protective element is characterized in that the protective film layer is further formed with a sealing material cured with an ultraviolet curing agent to seal the gap between the contact surface along the contact surface of the thermal fuse and the plurality of leads.

Hereinafter, a protection device and a secondary battery equipped with the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 illustrates a lithium secondary battery 20 according to an embodiment of the present invention.

Referring to the drawings, the secondary battery 20 may include a battery unit 21, a can 22 accommodating the battery unit 21, a cap assembly 23 coupled to the can 22, and the The protection element 30 is installed in the can 22.

The battery unit 21 is wound in a jelly-roll type and includes a positive electrode plate and a negative electrode plate, and a separator interposed therebetween to electrically insulate them. The positive electrode and the negative electrode plate is composed of a current collector, and a positive electrode and a negative electrode active material layer coated on at least one surface thereof.

The positive electrode tab 21a and the negative electrode tab 21b are drawn out from the battery part 21, respectively. An insulating plate 24 having a through hole 24a through which the negative electrode tab 21b is drawn out is provided on the battery unit 21.

The cap assembly 23 is provided on the insulating plate 24.

The cap assembly 23 is provided with a cap plate 25 which is welded in contact with the can 22. The cap plate 25 is provided with a negative electrode terminal 26 to which the negative electrode tab 21b is electrically connected through the through hole 25a. The outer peripheral surface of the terminal 26 is provided with a gasket 27 made of an insulator. The negative terminal 26 may be insulated from the cap plate 25 by the gasket 27.

In addition, an electrolyte injection hole 25b is formed at one side of the cap plate 25. The electrolyte injection hole 25b is sealed by the ball 28 after the electrolyte is injected in a battery assembly process.

Meanwhile, the positive and negative electrode tabs 21a and 21b may be disposed to be opposite to each other, and both the tabs 21a and 21b may protrude toward the cap plate 25, and the positive electrode tab 21a may be a can ( 22) or various embodiments are possible depending on the design, such as being electrically connected to either of the cap plate 25.

According to a feature of the present invention, the lower portion of the cap plate 25 to electrically connect the negative electrode tab 21b and the negative electrode terminal 26 and at the same time to block the flow of current during overcharge of the battery 20 (30) is installed.

The protection element 30 includes a fuse 31, a plurality of leads 32 and 33 drawn out at both ends of the fuse 31, a protection film 34 for protecting a welding site, and the protection film 34. A seal 35 coated along the edge of the &lt; RTI ID = 0.0 &gt;

In more detail, as shown in FIG.

Referring to the drawings, the protection element 30 includes a thermal fuse 31 of a material having a low melting point, for example, an alloy mainly composed of lead. The thermal fuse 31 has a characteristic that when the internal temperature of the battery 20 rises, the thermal fuse 31 rises and melts.

One end of the thermal fuse 31 is welded to the tab lead 32. The tab lead 32 is electrically connected to the negative electrode tab 21b drawn out from the battery unit 21. The other end of the thermal fuse 31 is welded to the terminal lead 33. The terminal lead 33 is electrically connected to the negative terminal 26 protruding outside the cap plate 25. As a result, the negative electrode tab 21b is electrically connected to the negative electrode terminal 26 through the tab lead 32, the thermal fuse 31, and the terminal lead 33.

A protective film 34 made of a polymer resin is formed on the upper portion of the thermal fuse 31 and the tabs and the terminal leads 32 and 33. The passivation layer 34 has an appropriate thickness, and seals the coupling portion between the thermal fuse 31 and the leads 32 and 33. As the protective layer 34, it is preferable that a chemical reaction does not occur with an electrolyte such as polyethyleneterephthalate (PET). The protective film 34 is bonded to the thermal fuse 31 by ultrasonic welding.

The sealing material 35 is coated on a surface where the protective layer 34 and the tab and the terminal leads 32 and 33 are in contact with each other. That is, a portion fused with the protective film 34 and the tab lead 32, a portion fused with the protective film 34 and the terminal lead 33, a thermal fuse 31, the tab and the terminal lead 32 ( 33 and the welded portion may be a minute gap between the protective film 34.

When the electrolyte solution penetrates through this gap, the thermal fuse 31 has a change in physical properties, causing a dispersion of the melting temperature. In order to prevent this, the sealing material 35 is coated on the gap between the passivation layer 34, the leads 32, 33, and the thermal fuse 31. The sealing material 35 is a material in which no chemical reaction occurs with the electrolyte, and in this embodiment, an ultraviolet curing agent is to be applied.

When the ultraviolet curing agent is applied, the sealing material 35 is permeated through a gap that may occur at the contact surface between the protective film 34, the leads 32, 33, and the thermal fuse 31. Afterwards, when photocured, the seal 35 hardens to completely seal the gap. As a result, infiltration of the electrolyte solution into the thermal fuse 31 is essentially blocked.

When the protection device 30 manufactured in the above manner is installed inside the battery 20 and an abnormality such as an overcharge occurs and the temperature inside the battery rises, heat is transferred to the thermal fuse 31. When the thermal fuse 31 is heated up, it is melted and blown at a specific temperature. Accordingly, it is possible to forcibly block the passage of the current from the negative electrode tab 21b to the negative electrode terminal 26.

As described above, the protection element of the present invention and the secondary battery equipped with the same seal the gap between the thermal fuse and the lead welded to both ends thereof with a sealing material, so that when the battery is overheated or ignited due to overcharging, The fuse accurately detects this and completely blocks the flow of current, making the battery safe.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (4)

Thermal fuses; A first lead welded to one end of the thermal fuse; A second lead welded to the other end of the thermal fuse; A protective film layer made of a polymer resin surrounding a portion where the thermal fuse and the first and second leads are coupled; And And a sealing material for sealing the gap between the passivation layer and the surface where the thermal fuse and the first and second leads are in contact with each other. The method of claim 1, The sealing material is a protective element, characterized in that the ultraviolet curing agent cured by photocuring. A battery part wound in the order of a positive electrode plate, a separator, and a negative electrode plate; A can which provides a space in which the battery unit is accommodated and in which an electrolyte is injected; A cap plate coupled to the top of the can; And It is installed in the can, the one of the electrode tab withdrawn from the battery unit and the electrode terminal withdrawn from the cap plate to conduct electricity to each other, and to block the flow of current during overcharge, A thermal fuse, a tab lead welded to one end of the thermal fuse and electrically connected to the electrode tab, a terminal lead welded to the other end of the thermal fuse and electrically connected to the electrode terminal; And a protective element having a protective film layer made of a polymer resin surrounding the welded portion of the tab and the terminal lead. The method of claim 3, The protective element is a secondary battery, characterized in that the protective film layer is further formed with a sealing material cured with an ultraviolet curing agent to seal the gap between the contact surface along the contact surface of the thermal fuse and the plurality of leads.