KR20040058917A - Lithium secondary battery having a protective mean - Google Patents

Abstract

PURPOSE: A lithium secondary battery having protection means is provided, to prevent the thermal damage of a safety vent for improving the safety of a battery. CONSTITUTION: The lithium secondary battery(20) comprises a can(21) which is made of metal and comprises a positive electrode plate, a separator and a negative electrode plate in turns; a protection plate(280) which is fixed to the outer face of the can; and a protection cladding material(290) which is joined to the exterior of the protection plate, is connected electrically with the protection device by a lead, and is made of metal other than that of the protection plate. Preferably a safety vent(29) is formed in the place corresponding to the protection plate(280), the protection plate covers completely the safety vent, and the safety vent is broken primarily in case of the increase of internal pressure.

Description

Lithium secondary battery having a protective means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having a protection plate made of a different alloy formed on a bottom surface of a can containing a battery unit.

In general, a secondary battery refers to a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used in the field of advanced electronic devices such as a cellular phone, a notebook computer, a camcorder, and the like.

In particular, the lithium secondary battery has an operating voltage of 3.6 V, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic equipment, and is rapidly increasing in terms of high energy density per unit weight. to be.

Such lithium secondary batteries mainly use lithium-based oxides as positive electrode active materials and carbon materials as negative electrode active materials. Generally, according to the kind of electrolyte solution, it classifies into the lithium ion battery which uses a liquid electrolyte, and the lithium polymer battery which uses a polymer electrolyte. Moreover, although lithium secondary batteries are manufactured in various shapes, typical shapes include a cylindrical or square shape made of a metal material of a thick film, and a pouch type made of a composite material of a metal layer and a polymer layer of a thin film.

The lithium secondary battery is equipped with a safety vent because the risk of explosion occurs when the internal pressure increases. Safety vents exist in various shapes.In the case of the square lithium secondary battery, the bottom surface of the cap plate is rolled to be thinner than other parts to be ruptured first, or a safety hole of a predetermined size is formed in the can and then The method of welding thin metal material to break this part and discharging gas is applied. In this case, a protective plate made of metal is attached to the upper portion of the safety vent to protect it during the formation process.

1 illustrates a cell 10 as disclosed in US Pat. No. 5,976,729.

Referring to the drawings, the battery 10 has a power generation element having a positive electrode, a negative electrode and a separator impregnated with an electrolyte is inserted into the can 11. The opening of the can 11 is sealed with a cover member 18 made of metal. On the outer surface of the bottom surface 11a of the can 11, a current extraction lead plate 12 is welded by laser welding.

The battery 10 having the above structure seals the opening of the can 11 with the cover member 18 after the power generation element is inserted into the can 11. Next, the lead-out lead plate 12 for taking out current is attached to the bottom surface 11a of the can 11. Subsequently, the can 11 and the lead-out lead plate 12 for current extraction are laser-welded using a laser welding device. At this time, welding is performed in two places.

The connection lead plate 15 to which the protection circuit 19 is welded is attached on the current take-out lead plate 12, and the pair of resistance welding electrodes 16 is lowered to perform welding. As a result, the current extraction lead plate 12 and the connection lead plate 15 are fixed to each other.

By the way, the conventional battery 10 has the following problems.

The battery 10 uses a metal material having excellent electrical conductivity, such as an aluminum alloy, as the raw material of the can 11. The can 11 is provided with a protective circuit 19, or in order to prevent damage to the coating when the pins for charging and discharging contacts during the battery assembly process, the lead 11 for current extraction is primarily provided on the bottom surface 11a. (12) is welded, and a PTC element (positive temperature coefficient element) and a protection circuit 19 are attached to the upper portion thereof.

Thus, when welding the connecting lead plate 15 with the protection circuit 19 mounted on the upper surface of the lead-out lead plate 12, the high temperature to the safety vent formed on the bottom surface 11a of the can 11 Heat may be transferred, which may seriously affect the safety of the battery 10.

In this way, the method of directly welding the connection lead plate 15 having the protection circuit 19 mounted on the current extraction lead plate 12 at the center of the bottom surface 11a ensures the safety of the battery. Not desirable in

The present invention is to solve the above problems, the protection of the structure is improved to improve the safety of the battery by welding a protection means made of a different alloy on the bottom surface of the can, and welding a lead pin connected to the protection circuit thereto It is an object to provide a lithium secondary battery with a plate formed.

1 is a cross-sectional view showing a conventional battery,

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

3 is an exploded perspective view illustrating a state in which a protection unit is coupled to the battery of FIG. 2;

4 is a cross-sectional view of FIG.

5 is a sectional view showing a battery according to a second embodiment of the present invention;

6 is a partial sectional view showing a battery according to a third embodiment of the present invention.

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

20 ... lithium secondary battery 21 ... can

29 ... Safety vent 31 ... PTC element

32 ... 1st lead 33 ... 2nd lead

34 ... protection circuit 35 ... 3rd lead

280 ... protective plate 290 ... protective cladding

In order to achieve the above object, a lithium secondary battery having a protection means according to an aspect of the present invention,

A can made of a metal material for accommodating a battery part arranged in the order of a positive plate, a separator, and a negative plate;

A protection plate fixed to an outer surface of the can; And

And a protective clad material joined to the outside of the protective plate, electrically connected to the protective element by a lead, and a protective clad material made of a different kind of metal from the protective plate.

In addition, the outer surface of the can is formed with a safety vent that breaks preferentially when the internal pressure rises in a portion corresponding to the protective plate, the protective plate is characterized in that it completely covers the safety vent.

In addition, the protective clad material is formed along the outer wall of the protective plate, characterized in that the welding fixed to the outer surface of the can.

Furthermore, an end of the lead is electrically connected to an upper surface of the protective clad material.

In addition, the protective clad material is characterized in that the end of the lead is inserted and fixed when the protective clad material is melt-bonded with respect to the outer surface of the can.

In addition, the protective clad material is characterized in that the welding fixed to the outer surface of the can adjacent to the portion provided with the protective plate.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of a lithium secondary battery having a protective means according to a preferred embodiment of the present invention.

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

Referring to the drawings, the lithium secondary battery 20 may include a can 21, a battery unit 22 accommodated in the can 21, and a cap assembly 200 coupled to an upper portion of the can 21. ).

The can 21 is a rectangular metal material having a hollow formed therein, and serves itself as a terminal. The can 21 is preferably made of a thick film aluminum alloy having excellent electrical conductivity.

The battery unit 22 includes a positive electrode plate 23, a negative electrode plate 25, and a separator 24. The positive and negative plates 23 and 25 and the separator 24 each consist of one strip, and are arranged in the order of the positive plate 23, the separator 24, the negative plate 25, and the separator 24, and are wound. .

The positive electrode plate 23 includes a positive electrode current collector made of a thin aluminum foil, and a positive electrode active material layer mainly composed of lithium-based oxides coated on both surfaces thereof. The positive electrode lead 26 is welded to the positive electrode plate 23 in a region where the positive electrode active material layer on the positive electrode current collector is not coated, and an end portion of the positive electrode lead 26 protrudes above the battery part 22. .

The negative electrode plate 25 includes a negative electrode current collector made of a thin copper foil and a negative electrode active material layer mainly composed of a carbon material coated on both surfaces thereof. The negative electrode lead 27 is also welded to the negative electrode plate 25 in a region where the negative electrode active material layer on the negative electrode current collector is not coated, and an end of the negative electrode lead 27 also protrudes above the battery part 22. .

Insulating tapes 28 are wrapped in portions where the positive and negative lead 26 and 27 are led out of the battery unit 22 to prevent short circuits between the electrode plates 23 and 25.

The separator 24 is made of polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. The separator 24 may be more advantageous in forming a wider width than the positive and negative electrode plates 23 and 25 to prevent a short circuit between the electrode plates 23 and 25.

The cap plate 200 is provided with a cap plate 210. The cap plate 210 is a metal plate having a size and shape corresponding to the opening of the can 21. A terminal through-hole 211 having a predetermined size is formed in the center of the cap plate 210. An electrolyte injection hole 212 is formed at one side of the cap plate 210. The ball 220 is hermetically coupled to the electrolyte injection hole 212.

An electrode terminal, for example, a negative electrode terminal 230, is inserted into the terminal through hole 211. The outer surface of the negative electrode terminal 230 is provided with a tubular gasket 240 for insulation of the cap plate 210.

An insulating plate 250 is installed on the lower surface of the cap plate 210. The terminal plate 260 is provided on the bottom surface of the insulating plate 250. A bottom portion of the negative terminal 230 is electrically connected to the terminal plate 260.

An insulating case 270 is installed on the battery unit 22 to electrically insulate the battery unit 22 and the cap assembly 200 from each other. The insulating case 270 is a polymer resin which is an insulating material, and preferably made of polypropylene.

Here, a safety vent 29 is formed on the bottom surface 21a of the can 21. The safety vent 29 is a portion formed in a central portion of the bottom surface 21a with a predetermined size, and is formed thinner than other portions of the can 21. The safety vent 29 is broken more preferentially than other parts when the internal pressure rises due to overcharging of the battery 20, thereby improving the safety of the battery 20.

A protection plate 280 is formed on the bottom surface 21a of the can 21 in which the safety vent 29 is formed. The protective plate 280 is made of a metal plate having excellent conductivity, for example, a metal material mainly containing nickel. In addition, the protective plate 280 has a size and width that can cover the bottom surface 21a on which the safety vent 29 is formed, and has a substantially rectangular shape.

According to a feature of the invention, a protective plate 28 made of nickel is welded to the bottom surface 21a of the can 21 made of aluminum, and a protective cladding material 290 made of a different alloy is welded to the outside thereof. In this way, a safety device such as a PTC element is directly welded to the protection plate 28 located in the center of the bottom surface 21a, thereby preventing the safety valve 29 from being deformed.

In more detail as follows.

3 illustrates a state after the battery 20 of FIG. 2 is assembled, and FIG. 4 is a cross-sectional view of FIG. 3.

3 and 4, a safety vent 29 is formed at the center of the bottom surface 21a of the can 21 of the battery 20. A protection plate 280 is attached to the top surface of the bottom surface 21a to protect it. The protective plate 280 is located at a portion opposite to the safety vent 29.

At this time, the protective cladding material 290 is bonded to the side wall of the protective plate 280. The protective clad material 290 is a metal material having excellent electrical conductivity and oxidation resistance, and is a different kind of metal from the protective plate 28. Preferably, carbon steel or nickel alloy may be used.

The thickness of this protective cladding material 290 is preferably within the range of approximately 0.05 micrometers to 10 micrometers. When the thickness of the protective cladding material 290 is thinner than 0.05 micrometers, welding defects occur such as deformation occurs during welding. On the contrary, when the thickness of the protective cladding material 290 becomes thicker than 10 micrometers, problems such as welding may occur due to poor melt adhesion during welding.

The protective plate 280 and the protective clad material 290 are fixed to the can 21 by resistance welding, laser welding, ultrasonic welding, or the like. That is, the protection plate 280 is directly welded to the bottom surface 21a of the can 21 corresponding to the upper portion of the safety vent 29, and the bottom surface corresponding to the outside where the protection plate 280 is located. The protective clad material 290 is welded to 21a. As such, the protection plate 280 and the cladding material 290 are welded to the bottom surface 21a of the can 21 in duplicate.

In addition, a PTC element 31 is connected to the protective cladding material 290. The PTC element 31 is electrically connected to the protection circuit 34. For this electrical connection, each lead is connected between the protective cladding material 290, the PTC element 31, and the protective circuit 34.

That is, the first lead 32 is connected between the protective cladding material 290 and the PTC element 31. One end portion 32a of the first lead 32 is directly welded to the upper surface of the protective cladding material 29 in a bent state. The end 32a of the first lead 32 to the cladding material 29 may be fixed by resistance welding by the tip 300 for a welder. The other end 32b of the first lead 32 is electrically connected to the PTC element 31. At this time, the PTC element 31 is located on the outer side wall in the longitudinal direction of the can 21.

The second lead 33 is connected between the PTC element 31 and the protection circuit 34. One end 33a of the second lead 33 is electrically connected to the PTC element 31. The other end 33b of the second lead 33 is electrically connected to the protection circuit 32. The protection circuit 32 is located on the upper side of the cap assembly 200 where the negative terminal 230 is located. In the protection circuit 32, an IC chip, a charge / discharge switch, a current fuse, etc. capable of controlling the current during overcharge or overdischarge are circuitized.

Meanwhile, both ends of the third lead 35 are also connected between the negative electrode terminal 230 and the protection circuit 34.

Accordingly, the can 21 serving as the anode is connected to the protection circuit 34 by being connected to the protective cladding material 290, the first lead 32, the PTC element 31, and the second lead 33 in this order. The negative terminal 230 is connected to the third lead 35 and connected to the protection circuit 34 to maintain the flow of current.

The battery 20 having the above structure is damaged when the safety valve 29 is broken, the resistance of the PTC element 31 is rapidly increased, or the protection circuit ( The current control means in 34 can prevent the battery from igniting or exploding in advance.

5 shows a battery 50 according to a second embodiment of the present invention.

Here, the same reference numerals as in the above-described drawings indicate the same members having the same function.

Referring to the drawings, the battery 50 includes a can 21, a battery unit 22 inserted into the can 21, and a cap assembly 200 installed on an upper portion of the can 21. .

The battery unit 22 is disposed in the order of the positive electrode plate 23, the separator 24, and the negative electrode plate 25, and is wound in a jelly-roll type.

The cap assembly 22 is disposed on the cap plate 210, an electrode terminal 230 which is surrounded by an outer circumferential surface of the gasket 240, and is insulated from the cap plate 210, and a lower end of the electrode terminal 230. The insulation plate 250 and the terminal plate 260 are provided.

The positive and negative lead 26 and 27 drawn from the electrode plates 23 and 25 of the battery unit 22 are separated from the cap plate 210 and the terminal plate 260, respectively, and are electrically connected to each other. . The negative lead 27 is bent meandering to reduce the internal space. An insulating case 270 is mounted on the top surface of the battery unit 22.

In this case, a safety vent 29 is installed at the center of the bottom surface 21a of the can 21 to form a thinner thickness than other portions so that the battery breaks preferentially when the internal pressure of the battery rises. The protection plate 580 is welded to the upper surface of the safety vent 29. The protective plate 580 is a metal material different from the can 21 made of aluminum, for example, a nickel plate.

In addition, the protective plate 580 has a size that can completely cover the safety valve (29). The upper surface of the protective plate 580 is later contacted with the pins for charging and discharging during the battery assembly process to perform the chemical conversion process.

A protective clad material 590 is formed on the bottom surface 21a of the can 21 adjacent to the protective plate 580. The cladding material 59 is a dissimilar metal material different from the protection plate 580 and is made of nickel alloy or carbon steel, which is excellent in oxidation resistance and electrical conductivity. In addition, the thickness of the cladding material 59 is within the range of 0.05 micrometers to 10 micrometers as mentioned in the first embodiment.

The cladding material 590 is formed only toward one side edge of the bottom surface 21a of the can 21. This area is the minimum area to which the lead 52 which is electrically connected with the PTC element 31 which will be described later is weldable.

One end 52a of the first lead 52 is electrically connected to an upper surface of the clad material 590, and the other end 52b of the first lead 52 is connected to the PTC element 31. have. The PTC element 31 is located on one side wall in the longitudinal direction of the can 21.

The PTC element 31 and the protection circuit 54 are connected by the second lead 53. One end 53a of the second lead 53 is electrically connected to the PTC element 31, and the other end 53b of the second lead 53 is connected to the protection circuit 54. . The protection circuit 54 is located on the negative terminal 230 insulated from the cap plate 210.

Meanwhile, both ends of the third lead 55 are electrically connected to the cathode terminal 230 and the protection circuit 54.

As such, the battery 50 is welded with a protective plate 580 to protect a region in which the safety valve 29 is formed on the bottom surface 21a of the can 21, and a can (adjacent to the protective plate 580). The protective clad material 59 is welded to the bottom surface 21a of the 21. Thereby, welding in the center of the bottom surface 21a of the can 21 can be avoided.

6 shows a battery 60 according to a third embodiment of the present invention.

Here, only the features of the present embodiment will be referred to and mentioned.

Referring to the drawings, a safety vent 29 is formed at the center of the bottom surface 21a of the can 21 so as to be thinner than other portions so that the battery breaks preferentially in the presence or absence of a battery.

The can 21 and a protective plate 680 made of a different metal are welded to the upper surface of the bottom surface 21a on which the safety vent 29 is formed. The protective clad material 690 is welded to the edge of the protective plate 680. The protective cladding material 69 is a nickel alloy or a metal material having excellent oxidation resistance and electrical conductivity, such as carbon steel.

According to a feature of the present invention, one end portion 63a of the first lead 63 is melted and bonded to the protective clad material 69. That is, as in the first embodiment, one end portion 63a of the first lead 63 which electrically connects the protective clad material 69 and the PTC element 31 is welded to the upper surface of the protective clad material 69. Instead, the one end portion 63a of the first lead 63 is buried at the time of joining the bottom surface 21a of the can 21 by melting the cladding material 690 by the welding tip 300. It is setting the position.

In the battery 60 having the above structure, the first lead 63 electrically connecting the protective cladding material 69 and the PTC material 31 can be more firmly fixed without misalignment.

As described above, the lithium secondary battery having the protection means of the present invention forms a protective cladding material separate from the protective plate attached to the bottom surface of the can is formed safety vents, thereby forming a protective element such as a PTC element and electrical The lead connected to the welding is fixed by welding, it is possible to prevent thermal damage to the safety vent in advance. This improves the reliability of the safety of the battery.

Second, since the PTC element is fixed by setting the position on the side wall of the can, it is possible to realize the thin and light battery.

Third, the part which contacts the charger pin during the battery assembly process is protected by the protection plate.

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 (11)

A can made of a metal material for accommodating a battery part arranged in the order of a positive plate, a separator, and a negative plate; A protection plate fixed to an outer surface of the can; And Lithium secondary having a protective means, comprising: a protective clad material bonded to the outside of the protective plate, electrically connected to the protective element by a lead, and made of a different kind of metal from the protective plate. battery. According to claim 1, On the outer surface of the can is formed a safety vent that breaks preferentially when the internal pressure rises in a portion corresponding to the protective plate, the protective plate completely covers the safety vents, lithium secondary battery having a protective means . The method of claim 2, The protective clad material is formed along the outer wall of the protective plate, the lithium secondary battery having a protective means, characterized in that the welding is fixed to the outer surface of the can. The method of claim 3, wherein Lithium secondary battery having a protective means characterized in that the upper end of the protective clad material is electrically connected to the end of the lead. The method of claim 3, wherein In the protective cladding material, a lithium secondary battery having protection means, characterized in that the end of the lead is inserted and fixed when the protective cladding material is melt-bonded with respect to the outer surface of the can. The method of claim 2, And the protective clad material is welded and fixed to an outer surface of a can adjacent to a portion provided with the protective plate. The method of claim 6, And an end portion of the lead is electrically connected to an upper surface of the protective clad material. The method of claim 2, The protective plate is a lithium secondary battery having a protective means, characterized in that the nickel material. The method of claim 2, The protective clad material is a lithium secondary battery having a protective means, characterized in that made of a nickel alloy. The method of claim 2, The protective clad material is a lithium secondary battery having a protective means, characterized in that the carbon steel. The method of claim 2, The protective clad material has a thickness of about 0.05 to 10 micrometers lithium secondary battery.