KR20140060881A - Prismatic secondary battery employed with welding vent portion - Google Patents

Abstract

The present invention relates to a prismatic secondary battery where an electrode assembly which comprises an anode, a cathode, a separator is sealed in a prismatic battery case. The prismatic secondary battery is provided. The prismatic battery case comprises a rectangular case body which has an open upper end and consists of a metallic material, and an upper cap which is combined with the open upper end of the case body and includes an electrode terminal; the contact part of the case body and the upper end cap includes a welding surface which is bonded by laser welding. The welding surface includes a welding bending part with a relatively low binding power to discharge a gas to the outside when high pressure is generated in the battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a prismatic secondary battery employing a welding vent,

The present invention relates to a prismatic secondary battery having a welding vent portion, and more particularly, to a prismatic secondary battery in which an electrode assembly composed of an anode, a cathode, and a separator is sealed in a rectangular battery case, A case body having a rectangular shape made of a metal material, and an upper cap coupled to an open upper end of the case body and including an electrode terminal; The contact portion between the case body and the upper cap includes a welding surface joined by laser welding. The welding surface includes a welding venting portion having a relatively low bonding force so that gas is discharged to the outside when a high pressure is generated inside the battery. To a prismatic secondary battery.

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet .

The electrode assembly incorporated in the battery case is a charge / dischargeable power generating element formed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode coated with an active material, A stacked type in which a plurality of positive and negative electrodes of a size are stacked in a state in which a separator is interposed, and stacked / folded type stacked units in which unit cells such as bi-cells or pull cells are wound in separate films.

Such a secondary battery may be exposed to various environments depending on usage conditions and conditions, and it is required to prevent the risk of explosion especially for the safety of the user. Generally, the high temperature and high pressure inside the battery, which can be caused by an abnormal operating condition of the battery such as an internal short, an allowable current, a charging state exceeding a voltage, exposure to a high temperature, . Therefore, the secondary battery is provided with a high-voltage relieving means capable of relieving the high voltage which is a direct cause of the explosion of the battery despite the difference in the shape of the battery.

For example, in a cylindrical battery, a safety plate having a specific structure is installed in a cap assembly, a prismatic battery has a notch groove formed in a cap or a case of the battery, and the pouch type battery has a notch groove Sealing portion) are separated from each other.

In a general prismatic secondary battery, a closed type or a partially open type notch groove is formed in the aluminum battery case so as to be cutable.

For example, as shown in Fig. 1, the prismatic secondary battery includes a notch groove of a partially open type on the side surface of the battery case.

The notch groove 10 shown in Fig. 1 is formed in a small contour on the side edge of the rectangular-type secondary battery case 20, and is formed partially open. That is, the notch groove 10 is formed in a portion where the stress value is relatively large in the stress distribution of the case 20, so that the curve shape is designed to break when the internal pressure of the battery rises excessively.

Although the notched groove having such a structure has an advantage of reacting relatively sensitively to the high pressure generated inside the battery, there is a problem that the outer surface of the battery case is bent to increase the thickness around the battery case.

As another example of the prismatic secondary battery, there is a structure in which the notch groove is formed in the upper center portion of the battery case.

However, even in such a structure, a safety plate made of a notch groove is formed at the upper center portion of a battery case having a relatively small stress, so that the breaking pressure of the safety plate can be increased with respect to a thin- There is a problem that unnecessary breakage such as crack propagation or deformation may be caused in the region.

Furthermore, the battery case may be partially deformed in the process of forming the notch groove in the battery case.

Therefore, it is very necessary to provide a technique for a prismatic secondary battery having safety means capable of solving the complicated problems of the conventional prismatic secondary battery as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

More specifically, it is an object of the present invention to improve the safety of a battery by improving the safety of a battery by constructing a welding surface of a contact portion between a case body and a top cap with a relatively low welding force so that gas is discharged to the outside when a high- And to provide a prismatic secondary battery having a specific structure capable of eliminating bending of the outer surface of the battery case caused by the notch groove.

It is a further object of the present invention to provide a prismatic secondary battery in which the welding venting portion of the above structure can adjust only the laser welding strength in the conventional manufacturing process and does not require any additional process.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a prismatic secondary battery comprising: a prismatic secondary battery in which an electrode assembly composed of an anode, a cathode,

Wherein the battery case comprises a rectangular case body having an open top and made of a metal material, and an upper cap coupled to an open upper end of the case body and including an electrode terminal;

Wherein the contact portion between the case body and the upper cap includes a welding surface joined by laser welding and the welding surface includes a welding venting portion having a relatively low bonding force so that gas is discharged to the outside when a high pressure is generated in the inside of the battery .

Therefore, by forming a welding venting part having a relatively low bonding force at a part of the contact area between the battery case and the upper cap, gas can be easily discharged through the welding venting part when a high pressure is generated inside the battery.

Since the battery case requires ease of processing and mechanical strength of a certain level or more, it can be a metal can, preferably an aluminum can or a stainless steel can.

The laser welding is preferably performed by a YAG laser, but is not limited thereto.

In one specific example, the weld venting portion may be a structure formed by adjusting the welding strength in the laser welding process. In this case, it is possible to form a desired welding vent portion without a separate member or additional process.

The welding venting portion may be structured such that, for example, the high pressure inside the battery is opened at a pressure of three times or more the internal pressure of the battery under normal conditions.

Accordingly, when the internal pressure gradually increases and a pressure of three times higher than the normal internal pressure of the battery is generated, the stress is concentrated on the welding vent portion and is easily ruptured so that the gas is quickly discharged to the outside of the battery. As a result, have.

In one specific example, the length of the welding venting portion may be 1 to 30% of the total length of the welding surface, and the welding venting portion may be formed in a side portion of the upper end of the case body , But is not limited thereto.

The case body of the prismatic secondary battery can be distinguished from both sides corresponding to the long axis and both sides corresponding to the minor axis in a horizontal cross section. The side portion of the upper end of the case body, in which the welding venting portion is formed, Or < / RTI > both sides.

The thickness of the welding venting portion may be, for example, 0.05 to 0.15 mm, and the thickness of the welding venting portion is preferably 0.1 mm.

In some cases, an exterior film may be further attached to the outer surface of the battery case to protect the battery from external impact and maintain the electrically insulated state.

The electrode assembly may have a stacked structure as well as a jelly-roll structure. Of these, the jelly-roll is advantageous in that it is easy to manufacture and has a high energy density per unit weight. However, the electrode assembly is not limited thereto .

The secondary battery having such a structure is more preferably a lithium secondary battery.

The present invention also provides a device using the prismatic secondary battery as a power source.

Preferred examples of the device that can be used in the prismatic secondary battery according to the present invention include an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

Electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric power storage devices, etc. are well known in the art, and a detailed description thereof is omitted here.

As described above, in the prismatic secondary battery according to the present invention, the welding surface of the contact portion between the case body and the upper cap is constituted by a welding venting portion having a relatively low bonding force so that gas is discharged to the outside when a high pressure is generated inside the battery, And the occurrence of bending of the outer surface of the battery case caused by the conventional notch groove can be prevented.

In addition, the welding venting part according to the present invention has merits in that it does not require a separate additional process since it controls only the laser welding strength in the conventional manufacturing process.

1 is a schematic view of a conventional prismatic secondary cell having a notch groove formed therein;
2 is a schematic view of a prismatic secondary battery used in the present invention;
3 is a perspective view of an assembling step of a secondary battery according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings, but the scope of the present invention is not limited thereto.

FIG. 2 shows a structure of a prismatic secondary battery according to an embodiment of the present invention.

Referring to FIG. 2, the prismatic secondary battery 100 includes a jelly-roll structure having a structure in which a sheet-like positive electrode and a negative electrode are wound with a separator interposed therebetween in a rectangular cell case 200 serving as a negative terminal, An electrode assembly 300 having a stacked structure in which an anode, a cathode, and a separator are stacked, or a stack / folding structure in which unit cells are wound in a separation film is inserted.

The battery case 200 includes a rectangular case body 210 having an open upper end and a metallic material and an upper cap 220 provided with an anode terminal 400 at an open upper end of the case body 210 Structure. The positive electrode terminal may be the case body 210 or the top cap 220 itself, which is electrically insulated from the negative electrode terminal 400.

In order to manufacture such a prismatic secondary battery 100, the electrode assembly 300 is first inserted into the case body 210, the upper cap 220 is seated in the opening of the case body 210, Is sealed by laser welding. The electrolyte solution is injected into the battery case 200 through the injection port 230 formed at one side of the upper cap 220. A ball member 600 made of aluminum or the like is inserted into the injection port 230 and a separate thin metal plate 610 is placed on the ball member 600, The upper surface of the upper case 220 and the upper surface of the battery case 200 are sealed by laser welding along the contact surface 250 which is in contact with the upper surface of the battery case 200.

3 and 4 are schematic perspective views of a secondary battery assembling step according to an embodiment of the present invention.

Referring to FIGS. 3 and 4 together with FIG. 2, the secondary battery 100 includes an insulating upper cap 500 according to the present invention in a prismatic battery case 200 in which an electrode assembly (not shown) .

The upper cap 500 is a rectangular structure having a shape corresponding to the open top 210 of the battery case 200 and includes a cathode terminal 520 at the center and an electrolytic solution injection port 530 formed at one side thereof have. The upper cap 500 is fastened to the open top 210 of the battery case 200 and then joined together by laser welding along the upper contact surface 250 of the battery case 200 contacting the upper cap 500 do.

Here, since the welding venting part 700 having a relatively low bonding force is formed on the contact surface 250 to have a thickness of 0.1 mm on the side surface of the contact surface 250 of the battery case 200, when the gas expands inside the battery, Can be easily discharged to the outside through the venting part (700).

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (13)

1. A prismatic secondary battery in which an electrode assembly composed of an anode, a cathode and a separator is sealed in a rectangular battery case, wherein the battery case has a rectangular case body made of a metal material and an open top, And an upper cap including an electrode terminal;
The contact portion between the case body and the upper cap includes a welding surface joined by laser welding. The welding surface includes a welding venting portion having a relatively low bonding force so that gas is discharged to the outside when a high pressure is generated inside the battery. . The prismatic secondary battery according to claim 1, wherein the case body is a metal can. The prismatic secondary battery according to claim 1, wherein the laser welding is performed by a YAG laser. The prismatic secondary battery according to claim 1, wherein the welding vents are formed by adjusting a welding strength in a laser welding process. The prismatic secondary battery according to claim 1, wherein the welding venting portion is opened at a pressure of three times or more the internal pressure of the battery under normal conditions of high pressure inside the battery. The prismatic secondary battery according to claim 1, wherein the length of the welding vent portion is 1 to 30% based on the total length of the weld surface. The prismatic secondary battery according to claim 1, wherein the welding venting portion is formed at a side portion of an upper end of the case body. The prismatic secondary battery according to claim 1, wherein the thickness of the welded bending portion is within a range of 0.05 to 0.15 mm. The prismatic secondary battery according to claim 1, wherein an outer film is attached to an outer surface of the battery case. The prismatic secondary battery according to claim 1, wherein the electrode assembly is a stacked type or jelly-roll type. The prismatic secondary battery according to claim 1, wherein the secondary battery is a lithium secondary battery. 11. A device comprising a prismatic secondary battery according to any one of claims 1 to 11 as a power source. 13. The device of claim 12, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

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