KR100490634B1 - Secondary battery - Google Patents

Abstract

The secondary battery improves the electrical connection structure between the safety device of the battery and the can. The secondary battery of the present invention includes an electrode assembly having a positive electrode plate and a negative electrode plate, and a separator interposed therebetween; A can containing the electrode assembly together with an electrolyte solution, the top opening being sealed by a cap assembly; And a conductive member electrically connecting the can to the safety device, wherein the conductive member includes a conductive plate having one end inserted into a plate insertion groove formed at a bottom of the can.

Description

Secondary Battery {SECONDARY BATTERY}

The present invention relates to a secondary battery, and more particularly, to a secondary battery having an improved electrical connection structure between a battery safety device and a can.

In general, secondary batteries are rechargeable, compact, and large in capacity, and typically, nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries are used.

The secondary battery is formed by accommodating a power generating element consisting of a positive electrode plate, a negative electrode plate, and a separator, that is, an electrode assembly in a metal can, injecting an electrolyte into the can, and sealing the same. The secondary battery sealed in the can is usually provided with an electrode terminal insulated from the can at the top, so that the electrode terminal forms one pole of the battery, and the other electrode is the battery can itself. At this time, the other electrode is usually to be the bottom surface of the battery.

In accordance with the demand for thin weight reduction for secondary batteries, the battery cans have been changed from iron such as cold rolled steel sheets to aluminum cans using aluminum or aluminum alloy. The can is formed of aluminum or an aluminum alloy because aluminum is lighter than iron or other conductive metals, which contributes to the weight reduction of the battery and does not corrode even when used under high voltage for a long time. Because.

On the other hand, the secondary battery sealed as described above is accommodated in the battery pack with the battery safety devices such as a PTC element, a thermal fuse (thermal fuse) and a protection circuit module (PCM :), at this time, these Safety devices are connected to the negative electrode and the positive electrode, respectively, to cut off the current when the voltage of the battery rises rapidly due to the high temperature of the battery or the overcharge and discharge, etc., thereby preventing the risk of battery rupture.

These safety devices are connected to the positive and negative electrodes of the cell by leads, which are usually made of nickel or nickel alloys or nickel plated stainless steel in order to have the desired hardness and conductivity as the leads.

However, the lead provided with nickel may have some problems in welding with a can made of aluminum. In other words, nickel generally has insoluble properties, which makes it difficult to ultrasonically weld leads and cans due to the above insoluble properties. In addition, aluminum has excellent electrical conductivity and thermal conductivity, and it is very difficult to resistance weld the lead and the can because this property makes heat concentration difficult at the joint surface.

Therefore, in order to eliminate the above problems, the lead must be welded to the can using laser welding. In the case of using the laser welding, another problem occurs that the laser beam is conducted to the protection circuit, thereby lowering its reliability.

Accordingly, U.S. Patent No. 5,976,729 discloses that a conductive plate formed of nickel or a nickel alloy is bonded to a bottom surface of a can formed of aluminum or an aluminum alloy by laser welding, and the lead is welded to the conductive plate by a welding rod for resistance welding to protect the circuit. Disclosed is a secondary battery connecting safety devices.

However, in the disclosed secondary battery, since there is no criterion for the welding position of the conductive plate, an additional process for maintaining a constant welding position of the conductive plate is required, and thus workability is poor. In addition, since the lead is welded to the conductive plate in the state where the conductive plate is welded to the bottom of the can, the resistance points increase due to the welding points, thereby reducing the IR voltage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a secondary battery having improved workability by improving a connection structure between cans and leads.

Another object of the present invention is to provide a secondary battery capable of reducing a welding location and reducing a resistance element and voltage loss.

In order to achieve the above object, the secondary battery of the present invention,

An electrode assembly having a positive electrode plate and a negative electrode plate, and a separator interposed therebetween;

A can containing the electrode assembly together with an electrolyte solution, the top opening being sealed by a cap assembly;

A conductive member electrically connecting the can to a safety device;

The conductive member may include a conductive plate having one end inserted into a plate insertion groove formed at a bottom of the can.

According to a preferred embodiment of the present invention, one end of the conductive plate may be press-fit into the plate insertion groove, or may be welded and fixed after being inserted into the plate insertion groove. In this case, ultrasonic welding or laser welding may be used for the welding.

The battery safety device may be a protection circuit module, and the other end of the conductive plate may be soldered to the protection circuit module or connected to the safety device through a lead.

On the other hand, the can is preferably formed of aluminum or aluminum alloy, the conductive plate is preferably formed of nickel or nickel alloy. In addition, the conductive plate preferably has a thickness of 1 mm or less.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exploded perspective view illustrating a rectangular secondary battery according to an exemplary embodiment of the present invention, and FIG. 2 is a side view illustrating a state in which a safety device is installed in the secondary battery of FIG. 1.

Referring to the drawings, a secondary battery according to an embodiment of the present invention is a can 10 having an opening 12 on one surface thereof, and an electrode assembly accommodated in the can 10 through the opening 12. 20).

The electrode assembly 20 is formed by the positive electrode plate 22 and the negative electrode plate 24 via the separator 26. According to an exemplary embodiment of the present invention, as shown in FIG. 1, the positive electrode plate 22 is formed. And a jelly roll electrode assembly 20 wound up after the negative electrode plate 24 is laminated via the separator 26.

At this time, the negative electrode plate 24 includes a negative electrode current collector made of a strip-shaped metal thin plate, and a copper thin plate may be used as the negative electrode current collector. A negative electrode coating part coated with a negative electrode mixture including a negative electrode active material is formed on at least one surface of the negative electrode current collector, and a carbon material is used as the negative electrode active material, and may contain a binder, a plasticizer, a conductive material, and the like to form a negative electrode mixture. have.

In addition, the positive electrode plate 22 includes a positive electrode current collector made of a strip-shaped metal thin plate, and an aluminum thin plate may be used as the positive electrode current collector. At least one surface of the positive electrode current collector is formed with a positive electrode coating portion coated with a positive electrode mixture including a positive electrode active material, the lithium active material is used as the positive electrode active material, containing a binder, a plasticizer, a conductive material, etc. Can be achieved.

The positive electrode tab 28 and the negative electrode tab 28 ′ that are electrically connected to the positive electrode plate 22 and the negative electrode plate 24 are respectively drawn out on the electrode assembly 20 as described above. Nickel thin film may be used as the negative electrode tab 28 ′, and aluminum thin film may be used as the positive electrode tab 28, but is not limited thereto. Values of the positive electrode tab 28 and the negative electrode tab 28 'may be provided as opposed to FIG. 1.

On the other hand, the can 10 may be made of a metal material having a substantially rectangular parallelepiped shape, and thus can itself serve as a terminal. According to the present embodiment, the can 10 may be formed of Al or an Al alloy, which is a lightweight conductive metal. In addition, one side of the can 10 may be opened to have an opening 12, through which the electrode assembly 20 may be received into the can 10.

The can 10 may be provided in an angled square of the side edge portion thereof, and although not shown in the drawing, the can 10 may be provided in a round shape in which the edge portion is rounded.

The cap assembly 30 is installed and sealed in the opening 12 of the can 10 as described above. The cap assembly 30 is directly welded to the opening 12 to seal the can 10. (32) is provided. The can 10 and the cap plate 32 may be provided with the same metal material for ease of welding.

The cap assembly 30 is formed with a terminal pin 36 formed through the gasket 34 to be insulated from the cap plate 32. An insulating plate and a terminal plate (not shown) are formed below the terminal pin 36. C) is further formed to insulate the terminal pin 36 from the cap plate 32. The negative electrode tab 28 'drawn out from the negative electrode plate 24 is welded to the lower portion of the terminal pin 36, and the terminal pin 36 functions as a negative electrode terminal portion.

Meanwhile, the positive electrode tab 28 drawn from the positive electrode plate 22 is directly connected to the lower surface of the cap plate 32 or the inner surface of the can 10 so that the whole of the outside of the battery except the terminal pin 36 is positive. Function as a terminal part. However, the structures of the positive electrode terminal and the negative electrode terminal are not necessarily limited thereto, and the structure of the positive electrode terminal portion may be formed through a separate terminal pin like the structure of the negative electrode terminal portion, and any other structure may be applied. have.

On the other hand, after the electrode assembly 20 is inserted into the can 10, a protective case 38 made of an insulating material is further installed between the electrode assembly 20 and the cap assembly 30 to provide an electrode. The assembly 20 can be more firmly fixed.

After the cap assembly 30 is welded to the opening 12 of the can 10, an electrolyte is injected through an electrolyte injection hole (not shown) formed in the cap plate 32, and then a plug (not shown) is inserted. Seal it through.

In the secondary battery as described above, according to the preferred embodiment of the present invention, an end insertion groove 16 into which an end of the conductive plate 40 is inserted is formed in the bottom portion 14 of the can 10.

According to a preferred embodiment of the present invention, the conductive plate 40 is formed in a "┘" shape, one end is inserted into the end insertion groove 16 of the can 10. The conductive plate 40 may be made of nickel or a nickel alloy mainly containing nickel as a lead, and may be formed of any material that may be used as a lead.

In this case, the conductive plate 40 is preferably formed to a thickness t of about 15 to 25%, preferably about 20%, of the thickness T of the bottom portion 14 of the can 10. For example, when the bottom thickness T of the can 10 is 5 to 6 mm, the conductive plate 40 may be formed to a thickness t of about 1 mm.

Meanwhile, the width w of the end insertion groove 16 may be formed to be equal to or less than the thickness t of the conductive plate 40 so as to press-fit the end of the conductive plate 40. Of course, in order to secure the end of the conductive plate 40 to the can 10, the end of the conductive plate 40 is inserted into the end insertion groove 14 of the can 10, as shown in FIG. Alternatively, it is possible to join using laser welding. In Fig. 3, reference numeral P denotes a welding point.

As described above, the other end of the conductive plate 40 having one end fixed to or bonded to the end insertion groove 14 is bonded to the battery safety device 50 that cuts off the current when the battery malfunctions. 1 and 2, the safety device 50 is a protection circuit module 52, and the other end of the conductive plate 40 may be directly soldered to the protection circuit module 52. . The protection circuit module 52 has a connection lead 54 bonded to the terminal pin 36 serving as the other electrode of the battery. The battery is overcharged. Eliminate the risk of

According to the present invention, the conductive plate 40 connected to the protective circuit module 52 extends integrally from the bottom of the can 10, which is one electrode of the battery, without an intermediate welding point, thereby protecting the protective circuit module 52. Since it is connected to, it is possible to prevent the resistance increase and the voltage drop due to the intermediate welding point, and to shorten the process.

In addition to the safety device 50, a PTC element 56 or the like may be further added. As shown in FIG. 3, the PTC element 56 may include a connection lead 58 connected to the protection circuit module 52; It may be provided between the conductive plates 40.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the secondary battery according to the present invention can maintain the welding position of the conductive plate constantly because the end insertion groove provided at the bottom of the can serves as a reference for the welding position of the conductive plate. In addition, when the end portion of the conductive plate is press-fitted to the end insertion groove in the end insertion groove, a separate welding process can be eliminated, thereby improving workability and reducing the resistance element due to the reduction of the welding point. It works.

1 is an exploded perspective view showing a lithium secondary battery according to an embodiment of the present invention.

Figure 2 is a side view showing a state in which the safety device is coupled to the secondary battery of Figure 1;

Figure 3 is a side view showing a state in which the safety device is coupled to the secondary battery according to another embodiment of the present invention.

Claims (10)

An electrode assembly having a positive electrode plate and a negative electrode plate, and a separator interposed therebetween; A can containing the electrode assembly together with an electrolyte solution, the top opening being sealed by a cap assembly; A conductive member electrically connecting the can to a safety device; The secondary battery of claim 1, wherein the conductive member comprises a conductive plate having one end inserted into a plate insertion groove formed at a bottom of the can. The secondary battery of claim 1, wherein one end of the conductive plate is pressed into the plate insertion groove. The secondary battery of claim 1, wherein one end of the conductive plate is welded and fixed after being inserted into the plate insertion groove. The secondary battery of claim 3, wherein ultrasonic welding or laser welding is used for the welding. The secondary battery of any one of claims 1 to 4, wherein the safety device includes a protection circuit module. The secondary battery of claim 5, wherein the other end of the conductive plate is soldered to the protection circuit module. The secondary battery of claim 5, wherein the safety device further comprises a PTC element. The secondary battery of claim 7, wherein the PTC device is provided between a connection lead connected to a protection circuit module and a conductive plate. The rechargeable battery of claim 7, wherein the can is formed of aluminum or an aluminum alloy, and the conductive plate is formed of nickel or a nickel alloy. The secondary battery of claim 9, wherein the conductive plate has a thickness of 15 to 25% of a thickness of a bottom portion of the can.