KR100571232B1 - Lead plate and can type secondary battery using the same - Google Patents

Abstract

It comprises an electrode assembly consisting of a positive electrode, a negative electrode and a separator, a metal can serving as a container for receiving the electrode assembly and the electrolyte, a cap assembly for closing the open top of the can and a protection circuit. A can-shaped secondary battery and a lead plate used therein, wherein the lead plate having a sidewall protruding with respect to the cap assembly and having a cutout portion at a contact surface in contact with the cap assembly is laser welded to the cap assembly at a portion including the cutout portion. Is initiated. In this case, the cutout may be formed as a long hole in the lead plate contact surface that is in contact with the cap assembly, it may be made to be embedded in the center of the bottom surface of the lead plate in the peripheral portion of the short side of the contact surface.

Thus, sufficient strength of the welds of the lead plate and the cap assembly can be secured to prevent the lead plate from being easily separated from the cap assembly, and sufficient welding strength can be secured between the lead plate and the cap assembly without requiring excessive laser power. Can be.

Description

Lead plate and can type secondary battery using the same}

1 is a plan view showing a conventional lead plate formed for attachment to a cap plate,

2 is a plan view of a rectangular battery showing a form in which a conventional lead plate is welded to a cap plate;

3 is an exploded perspective view illustrating a rectangular lithium ion battery in a state in which a lead plate is coupled to a unit cell according to one embodiment of the present invention;

4 is a plan view of a lead plate according to an embodiment of the present invention;

5 is a plan view illustrating a state in which a lead plate is welded to a cap assembly in a forming step of a can type secondary battery according to an exemplary embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

* Explanation of symbols for the main parts of the drawings

11: can 12: electrode assembly

13: anode 14: separator

15: cathode 16: anode lead

17: cathode lead 18: insulating tape

110: cap plate 111: through hole

112: electrolyte injection hole 120: gasket

130: electrode terminal 140: insulation plate

150: terminal plate 190: insulated case

191: lead through hole 192: electrolyte through hole

160: stopper 210: lead plate

212: bottom of the lead plate 214: side of the lead plate

216, 218: weld 219: incision

The present invention relates to a secondary battery, and more particularly, to a can type secondary battery having a lead plate and a lead plate.

Secondary batteries have been recently developed and used because they are rechargeable and have a small and large capacity. Representative secondary batteries used in recent years include nickel-hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries.

Most of the bare cells of these secondary batteries contain an electrode assembly consisting of a positive electrode, a negative electrode, and a separator in a can made of iron, aluminum, or an aluminum alloy, the can is closed with a cap assembly, and an electrolyte is injected into the can. By sealing the cap assembly. When the can is formed of aluminum or an aluminum alloy, it is advantageous in that the light weight of the aluminum makes the battery lighter and does not corrode even when used for a long time under high voltage.

In the bare cell of these secondary batteries, an electrode terminal is usually provided at an upper portion and insulated from the peripheral portion, and the electrode terminal is connected to one electrode of the electrode assembly to form a positive terminal or a negative terminal of the battery. The can itself has a polarity opposite to that of the electrode terminal.

The electrode terminals of the sealed secondary battery bare cell are electrically connected to terminals of safety devices such as a positive temperature coefficient (PTC), a thermal fuse, and a protective circuit module (PCM). Safety devices are connected to the positive and negative electrodes to cut off the current when the voltage of the battery rises rapidly due to the high temperature of the battery or excessive charge / discharge.

Typically, a conductor structure called a lead plate serves to connect the positive and negative electrodes of the cell with the electrical terminals of the safety device. As the lead plate, nickel or a nickel alloy, but stainless steel plated with nickel is used.

The safety device and the unit cell may be stored in a separate pack while being electrically connected, or may be filled with a gap between the melted resin and coated to form a battery pack.

However, a lead plate made of nickel may cause a problem in welding with the bottom surface of the can made of aluminum. That is, nickel and aluminum are very difficult to ultrasonic welding or resistance welding due to the insolubility of nickel and the excellent conductivity of aluminum. Thus, the can and lead plate are usually welded with a laser.

In the early stage, such a laser welding was brought into a state in which a lead plate and a protection circuit were connected, thereby causing a charging phenomenon and an electric shock during laser beam irradiation, and deteriorating reliability of safety devices. In recent years, the lead plate is first welded to the can-type battery, and the method of resistance welding the terminal plate on the protective circuit side to the welded lead plate is used. In US Patent No. 5,976,729, a lead lead plate made of nickel is bonded to an outer bottom surface of an aluminum can in advance by laser welding, and a separate lead plate directly connected to a protection circuit is provided to lead bonded to the outer bottom surface of the can. Techniques for resist welding and bonding of plates are presented.

However, the laser welding of the auxiliary lead plate 25 to the outer bottom surface of the can 20 is very thin in thickness according to the tendency of thinner and lighter battery, so that the welding strength is not accurately adjusted. This may cause a problem such as leakage of the electrolyte solution from the laser welding part 27. Therefore, in recent years, a cap plate of a can-type battery, mainly a cap plate, and a part of a lead plate having a protruding structure for electrical connection with a protection circuit are often formed.

Fig. 1 is a plan view showing a conventional lead plate formed to be attached to a cap plate, and Fig. 2 is a plan view of a square battery showing a form in which a conventional lead plate is welded to a cap plate.

1 and 2, the lead plate 210 is formed in a substantially rectangular shape in plan view, and at the periphery of the bottom surface 214, a wall 212 protruding upward from the cap plate side is provided with a protective circuit terminal plate. Exist for welding. The cap assembly 110 is welded to both sides of the rectangular direct shape of the lead plate bottom surface 214. By the way, when looking at the shape of the weld 216 in more detail, the welding is made in the form of spot welding on the lead plate bottom surface 214 abuts overlapping the cap plate 110 and is not made at the edge portion.

In such welding, problems are likely to occur if the power of the laser beam for welding is not strictly controlled. For example, when the output of the laser beam is weak, only the lead plate bottom surface 214 is partially melted, and the lower cap plate 110 is not sufficiently melted, so that the strength of the welding is likely to decrease. In particular, when the lead plate bottom surface 214 is not sufficiently in contact with the cap plate 110 when the other part is protruded or the cap plate 110 is bent, such as an electrolyte inlet plug on the upper surface of the cap plate 110, the welded portion The problem that the cap plate 110 below the 216 does not melt enough becomes conspicuous. In this case, it is easy to see a case where the lead plate 210 is separated from the bare cell during the subsequent test or bending test in the battery pack.

Since the welding strength draws a statistical distribution to some extent, in order to sufficiently melt the cap plate 110 below, the laser beam output must be large and the laser beam output loss is excessive. In addition, even when the laser beam output is excessive, problems such as damage to the weld 216 may occur.

Meanwhile, when welding is performed at the periphery of the lead plate 210, the cap plate 110 and the lead plate 210 may be melted together, but the protruding wall 212 is formed at the periphery of the lead plate 210. There is a problem that welding is not easy, and if the welding part is close to the sealing weld between the can 11 and the cap plate 110, it may be considered that the problem may affect the sealing weld.

The present invention is to solve the above-described problems, can be secured to the strength of the welding portion of the lead plate and the cap assembly can can prevent the lead plate is easily separated from the cap assembly of the bare cell when an external force is applied in the battery pack It is an object to provide a secondary battery and a lead plate that can be used therein.

An object of the present invention is to provide a can-type secondary battery having a welded shape capable of securing sufficient welding strength between the lead plate and the cap assembly without requiring excessive laser power and a lead plate that can be used therein.

The can-type secondary battery of the present invention for achieving the above object, the electrode assembly consisting of a positive electrode, a negative electrode and a separator, a metal can serving as a container for receiving the electrode assembly and the electrolyte, a cap assembly for closing the open top of the can and protection In a secondary battery comprising a circuit,

The cap assembly is characterized in that a lead plate having a side wall protruding from the cap assembly cap assembly at the periphery and having a cutout portion in contact with the cap assembly is laser welded to the cap assembly at least at the portion including the cutout portion.

In the present invention, the lead plate may be welded to the cap assembly only at the incision, but can also be combined with the cap assembly by spot welding or the like at different contact surfaces.

The lead plate of the present invention for achieving the above object is a lead plate attached to the cap assembly for connecting the bare cell and the protection circuit of the can-shaped secondary battery, the bottom surface is coupled to the cap assembly is formed in a substantially rectangular shape, At least a portion of the periphery of the bottom has a wall projecting from the cap assembly surface, characterized in that the incision is formed on the contact surface in direct contact with the cap assembly in the bottom.

In the present invention, the cutout may be formed as a long hole in the lead plate contact surface that is in contact with the cap assembly, it may be made to be long embedded toward the center of the bottom of the lead plate at the periphery of the contact surface short side.

In the present invention, the lead plate is usually made of nickel or nickel alloy material, and the cap assembly, especially the cap plate, is formed of aluminum or aluminum alloy.

In the present invention, the cutout of the lead plate may be formed in one or a plurality. When formed in plural, the cutouts may be formed side by side on one portion of the bottom surface of the lead plate, or may be formed from both ends of the rectangular bottom surface.

In the present invention, it is assumed that the incision is usually made of a straight line, but is not necessarily limited to the straight line. For example, it may be a linear shape having a curved shape such as a 'b', 'b', or 'c'.

When laser welding the lead plate onto the cap assembly, the depth of welding may be typically from 0.15 to 0.4 mm depending on the thickness of the lead plate and the thickness of the cap plate and the required weld strength.

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

3 is an exploded perspective view illustrating a rectangular lithium ion battery in a state in which a lead plate is coupled to a unit cell according to an embodiment of the present invention.

Referring to FIG. 3, the rectangular lithium ion battery is coupled to the can 11, the electrode assembly 12 accommodated in the can 11, and the open top of the can 11 to seal the top of the can. It has a unit cell comprising a cap assembly.

The electrode assembly 12 is formed by winding a laminate of an anode 13, a separator 14, a cathode 15, and a separator formed in a thin plate or film form in a spiral shape.

The positive electrode 13 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, such as aluminum foil, and a positive electrode active material layer mainly composed of lithium-based oxides coated on both surfaces thereof. A positive electrode lead 16 is electrically connected to a positive electrode 13 in a region of a positive electrode current collector in which a positive electrode active material layer is not formed.

The negative electrode 15 includes a negative electrode current collector made of a conductive metal sheet, such as a copper foil, and a negative electrode active material layer mainly composed of a carbon material coated on both surfaces thereof. The negative electrode lead 17 is also connected to the negative electrode 15 in the region of the negative electrode current collector in which the negative electrode active material layer is not formed.

The positive electrode 13 and the negative electrode 15 and the positive electrode and negative electrode leads 16 and 17 may be arranged with different polarities, and the boundary portion from which the positive electrode and negative electrode leads 16 and 17 are drawn out from the electrode assembly 12. Insulation tapes 18 are wound around each other to prevent a short circuit between the two electrodes 13 and 15.

The separator 14 is made of polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene. The separator 14 is formed to be wider than the positive and negative electrodes 13 and 15, which is advantageous in preventing short circuits between the electrode plates.

The can 11 is formed of an approximately rectangular parallelepiped metal, usually aluminum or an aluminum alloy. The electrode assembly 12 is received through the open top of the can 11 so that the can serves as a container for the electrode assembly and electrolyte. The can itself may serve as a terminal, but in the present invention, the cap assembly may serve as a positive terminal.

The cap assembly is provided with a flat cap plate 110 having a size and shape corresponding to the open top of the can 11. The through hole 111 for the terminal is formed in the center portion of the cap plate 110 so that the electrode terminal 130 can pass therethrough. A tubular gasket 120 is installed outside the electrode terminal 130 penetrating the central portion of the cap plate 110 to electrically insulate the electrode terminal 130 from the cap plate 110. The insulation plate 140 is disposed on the lower surface of the cap plate 110 near the center of the cap plate 110 and the through hole 111 for the terminal. The terminal plate 150 is provided on the bottom surface of the insulating plate 140.

The electrode terminal 130 is inserted through the terminal hole 111 in a state in which the gasket 120 surrounds the outer circumferential surface. The bottom portion of the electrode terminal 130 is electrically connected to the terminal plate 150 with the insulating plate 140 interposed therebetween.

The positive lead 16 drawn from the positive electrode 13 is welded to the lower surface of the cap plate 110, and the negative lead 17 drawn from the negative electrode 15 is folded to the lower end of the electrode terminal 130 in a meandering state. Welded

On the other hand, an insulating case 190 is provided on the upper surface of the electrode assembly 12 to electrically cover the electrode assembly 12 and the cap assembly and at the same time to cover the upper end of the electrode assembly 12. . The insulating case 190 is an insulating polymer resin, preferably made of polypropylene. A lead through hole 191 is formed in the center portion of the insulating case 190 to allow the negative electrode lead 17 to pass therethrough, and an electrolyte passage hole 192 is formed at the other side thereof. The electrolyte through hole may not be separately formed, and a lead through hole for the positive electrode lead 16 may be formed next to a central lead through hole 191 for the negative electrode.

An electrolyte injection hole 112 is formed at one side of the cap plate 110. After the electrolyte is injected into the electrolyte injection hole 112, a stopper 160 is installed to seal the electrolyte injection hole.

Welding the cap assembly 110 to the periphery of the cap plate 110 and the side wall of the can 11 is performed by coupling the cap assembly with the can 11. After the cap assembly is coupled to the can 11, the upper end portion of the sidewall of the can 11, which forms the opening of the can 11, may be bent inward to have a flange shape over the cap plate 110.

After the cap assembly is welded to the can, the lead plate 210 is coupled to the cap plate 110 of the cap assembly around the electrolyte injection hole 112 by welding or the like.

Figure 4 is a plan view of a lead plate according to an embodiment of the present invention, Figure 5 is a plan view showing a state in which the lead plate is welded to the cap assembly in one step of forming a can-shaped secondary battery according to an embodiment of the present invention.

Referring to FIGS. 3 to 5, the lead plate bottom surface 214 having an approximately rectangular stepped portion or an intermediate portion is opened on the cap plate 110 as shown in FIG. 4. The lead plate 210 is partially formed at two periphery of the rectangular shape with sidewalls 212 formed to be parallel to the bottom surface 214. A portion of the bottom surface 214 of the lead plate 210 that is in contact with the cap plate 110 is formed with a linear cutout 219 that is long recessed from the short edge to the center of the bottom surface. The lead plate 210 is typically welded to the portion around the stopper 160 of the cap plate 110.

Welding is made by laser welding, in the can-shaped secondary battery embodiment of the present invention as shown in FIG. 5, the long side of the rectangular bottom surface 214 of the lead plate 210 in either of the two sides of the circular turning point as conventional There is a welded welded portion, and on the other side of the center is a welded portion 218 which is pre-welded along the periphery of the linear incision. In the conventional welding form as shown in FIG. 2, one of the two portions of the circular spot portion 216 is replaced with a straight weld 218 along the boundary of the cutout 219. Although not shown, a long hole may be installed instead of an indentation inserted at the periphery, and welding may be performed along a boundary of the hole. In addition, when the middle portion of the lead plate rectangular bottom surface is removed, the cutout portion may be formed to be long recessed from the middle boundary to the bottom portion that is in contact with the cap plate.

As another example, the lead plate may form two parallel cutouts in the bottom face that abut the cap plate, with the stopper at the center of the bottom of the leadplate, and may be a straight weld on four parallel boundaries, two per cut. In addition to the parallel linear welding as described above, a welding line may be formed in a "-" shape, a "c" shape, etc. as needed.

Thereafter, a protective circuit board equipped with a protective circuit for preventing overcharging and discharging of the battery, and other battery parts are connected to the battery in a state where the lead plate is welded. At this time, the lead plate serves as an anode and the electrode terminal serves as a cathode. The electrode structure and polarity may vary depending on the embodiment. Depending on the type and shape of the protective circuit board and the battery accessories, the cells in which they are combined may be stored in a separate exterior body, or the space between the substrate and the cap plate may be hot melted using a low temperature molding resin. It can be molded into a pack battery by filling or coating the overall resin.

According to the present invention, the strength of the welded portion of the lead plate and the cap assembly can be sufficiently secured to prevent the lead plate from being easily separated from the cap assembly in the process when an external force is applied from the battery pack or after welding the lead plate.

In addition, the present invention can ensure sufficient weld strength between the lead plate and the cap assembly without requiring excessive laser power.

Claims (5)

In a can-type secondary battery comprising an electrode assembly consisting of a positive electrode, a negative electrode and a separator, a metal can serving as a container for accommodating the electrode assembly and an electrolyte, a cap assembly closing an open upper portion of the metal can, and a protection circuit. A can plate having a side wall protruding from the cap assembly surface with a periphery and a lead plate having a cutout at a contact surface in contact with the cap assembly is laser-welded to the cap assembly at least at a portion including the cutout. Secondary battery. In the lead plate attached to the cap assembly for connecting the bare cell and the protection circuit of the can-shaped secondary battery, The bottom surface coupled with the cap assembly is formed in a rectangular shape, At least a portion of the peripheral portion of the bottom has a wall protruding with respect to the cap assembly surface, A lead plate, characterized in that a cutout is formed on the contact surface of the bottom surface in direct contact with the cap assembly. The method of claim 2, The cutout is formed as a long hole in the contact surface, or the lead plate, characterized in that formed in the long side toward the center of the bottom from the periphery of the short side of the rectangular bottom. The method of claim 2, Lead plate, characterized in that formed in plural. The method of claim 2, The cut plate is characterized in that the lead plate made of a straight.

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