KR100571237B1 - Can type secondary battery - Google Patents

Abstract

A can-type secondary battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator, a container-type can containing an electrode assembly and an electrolyte solution, and a cap assembly positioned at an upper end of the can and closing a can opening that becomes an inlet through which the electrode assembly is introduced. The thickness of the side wall of the can is formed only around the rectangular short edges or corners around the can opening having a rectangular cross section so that a low end is formed by a step inside the can opening, and the side of the cap assembly faces the low end. Disclosed is a can-shaped secondary battery, wherein a welding portion between the cap assembly peripheral portion and the can opening portion is formed on an upper surface of the cap assembly.

Description

Can type secondary battery

1 is a partial sectional view seen from the front showing an upper portion of a can type secondary battery including an electrolyte injection hole and a stopper portion of a cap plate.

2-4 are front cross-sectional partial views of techniques illustrating the form of engagement between the can opening and the cap assembly.

5 and 6 are a partial cross-sectional view and a plan view as seen from the front of the can-type secondary battery according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

11,211,311,411,511: can 12: electrode assembly

13: anode 14: separator

15: cathode 16: anode lead

17: cathode lead 18: insulating tape

110,210,310,410,510: Cap plate 118: Safety side

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 212,312,412: weld

The present invention relates to a can type secondary battery, and more particularly, to a can type secondary battery that facilitates welding of a can and a cap assembly serving as a container of an electrode assembly.

The can-type secondary battery has been rapidly developed and used in recent years due to the advantages of being rechargeable and capable of miniaturization and large capacity. The can-type secondary battery may be divided into a rectangular and a cylindrical battery according to its shape, and may be divided into a nickel-hydrogen (Ni-MH) battery and a lithium-ion (Li-ion) battery according to the electrode active material. On the other hand, the secondary battery may be divided into a case of using a liquid electrolyte and a case of using a solid polymer electrolyte or a gel-based electrolyte according to the type of electrolyte. When the liquid electrolyte is used, a can type secondary battery is usually used.

In a lithium secondary battery using a solid electrolyte, there is no problem of leakage of electrolyte, but in a can-type lithium ion battery using a liquid electrolyte, preventing leakage is an important problem as in the case of a chemical battery. In particular, the problem of leakage prevention becomes more important, considering that portable phones, computers, personal digital assistants, camcorders, etc., in which lithium ion batteries are used as power sources, are expensive precision devices.

On the other hand, when using the electrolyte due to the strong activity of the lithium component contained in the active material should use a non-aqueous electrolyte. Even in a solid electrolyte lithium secondary battery having no electrolyte problem, it is important to ensure that the electrode assembly is isolated from external moisture and air to prevent the lithium component of the electrode assembly from reacting with moisture or air to cause various defects and problems. Becomes

1 is a partial cross-sectional view showing an upper portion of a can type secondary battery including an electrolyte injection hole and a plug portion of a cap plate.

Referring to FIG. 1, the can 11 is a metal container having an open shape on an approximately rectangular parallelepiped in a rectangular lithium ion battery, and is formed by a processing method such as deep drawing. It is therefore possible for the can itself to act as a terminal. Iron can be used as a material for the can, but aluminum or aluminum alloy is preferred because it is a lightweight conductive metal and easily copes with corrosion. The can 11 becomes a container of an electrode assembly 12 and an electrolyte composed of an anode 13, a separator 14, and a cathode 15, and the electrode assembly is inserted into the can through an open top of the can, that is, an opening. The opening of the can is then sealed by the cap assembly. In a cylindrical lithium ion battery, the can is formed in a cylindrical shape.

The cap assembly is provided with a flat cap plate 110 having a size and shape corresponding to the opening of the can 11. The cap plate 110 is preferably formed of the same aluminum or aluminum alloy as the can 11 to improve weldability for bonding with the can 11. The through hole for the terminal is formed in the center portion of the cap plate 110 so that the electrode terminal can pass through. 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 insulating plate 140 is disposed on the lower surface of the cap plate near the center of the cap plate 110 and the through hole for the terminal. The terminal plate 150 is provided on the bottom surface of the insulating plate 140.

After the cap assembly is welded to the top of the can, the electrolyte is introduced through the electrolyte inlet 112 of the cap plate 110. The electrolyte injection hole 112 is sealed with a stopper 160 formed by inserting a ball. In order to increase the sealing reliability, the cap and the body around the periphery of the electrolyte inlet are joined by welding. The bowl is usually formed using aluminum, and a method using a laser is mainly used to weld them due to the excellent electrical and thermal conductivity of the material.

In general, in a can type secondary battery, a place where leakage fluid easily flows or a place where the sealing to the outside is easily broken may include a weld and a stopper 160 and a cap plate between the can 11 and the cap plate 110 of the cap assembly. A part of the electrolyte injection hole 112 where welding of the 110 is performed can be mentioned. Therefore, welding at these parts becomes an important key in the production of can type secondary batteries.

In welding, the welding must have a certain mechanical strength or more, the reliability of leak-free through the welding site, and the economical efficiency or efficiency of minimizing the cost and time required for welding are problematic. Factors affecting the efficiency of welding include welding method, welding equipment and material to be welded, accuracy and reliability required for welding. Together with these, the shape of the welding object and the welding position are also important factors related to the efficiency of welding.

2 through 4 are cross-sectional views of examples illustrating the form of engagement between the can opening and the cap assembly. However, the size of the weld or the gap is exaggerated for clarity.

Referring to FIG. 2, a weld 212 is formed at an interface thereof with a cap plate 210 of a cap assembly inserted into an inner surface of an opening of the can 211. This type of welding is good because the cap plate 210 is inserted into the opening of the can 211 and the laser welder can move the portion irradiated by the laser beam from the top, so that the welding convenience is good and thus the welding efficiency is improved. It can increase. However, it is difficult to control the degree of insertion of the cap plate 210 into the can 211, and thus there is a problem in that welding between the can 211 and the cap plate 210 is difficult to be performed at the correct position.

Referring to FIG. 3, a step is formed below the periphery of the cap plate 310 in contact with the opening of the can 311 so that the cap 311 and the cap plate cover the opening of the can 311. 310 is combined. By the step, the top of the can 311 and the periphery of the cap plate 310 may be coupled at the correct position.

In this case, however, the boundary between the can 311 and the cap plate 310 is exposed laterally. Therefore, the welding part 312 is formed on the side, and the laser welder welds while irradiating a beam downwardly to the boundary while rotating the can 311 lying sideways even when the laser welder is welding, or , There is a inconvenience that the laser welder rotates the can around the center axis of the can 311 on the side of the can, or the laser welder rotates and irradiates a beam to the boundary to perform welding. This is a factor that reduces the efficiency of welding.

4 has a configuration that can substantially solve the problem of FIG. 2 or FIG. That is, a taper is formed inside the upper end of the side wall of the can 411 forming the opening of the can 411, and the peripheral portion of the cap plate 410 is fixed to the taper forming portion downward for welding. In this case, since the boundary between the can 411 and the cap plate 410 is exposed upward, laser welding can be made from the upper side as in the case of FIG. Since the opening of the can 411 is narrowed toward the bottom by the tapered portion, the risk of the cap assembly being excessively inserted into the can 411 may be reduced.

However, even in this case, when the cap plate 410 is inserted into the opening of the can 411 with a slight skew, the cap plate 410 may be fixed with the skew, thereby reducing the accuracy of welding.

An object of the present invention is to provide a can-type secondary battery capable of improving welding ease and welding reliability between an upper end of the can opening and a cap plate periphery of the cap assembly.

The present invention provides a can-type secondary battery which can improve the accuracy of the welded part by accurately positioning the relative position between the upper end of the can opening and the cap plate periphery of the cap assembly, and prevent leakage of electrolyte, leakage of external moisture and inflow of air. It aims to do it.

An object of the present invention is to provide a can-type secondary battery that can improve welding operation, space and equipment efficiency, and can increase conversion efficiency when used for welding other types of batteries.

The can-type secondary battery of the present invention for achieving the above object,

A can-type secondary battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator, a container-type can containing an electrode assembly and an electrolyte solution, and a cap assembly positioned at an upper end of the can and closing a can opening that becomes an inlet through which the electrode assembly is introduced. In

The thickness of the sidewall of the can is thinly formed only on the short side or the corner of the rectangle formed by the cross section of the rectangular can around the can opening, so that a low end is formed by a step inside the can opening, and the side of the cap assembly faces the low end. It is fitted inside the can, characterized in that the welding portion between the cap assembly peripheral portion and the can opening is formed on the upper surface side of the cap assembly.

In the present invention, the can can be divided into a case of a rectangular can, a case having only rounded corners and a case in which the entire short side is treated as a round, and a case in which the can is completely angled. Among these, an angled battery having an inner round is advantageous in forming a step since a margin can be secured at a distance between the outer surface and the inner round surface at the corners.

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Method for forming a secondary battery of the present invention for achieving the above object,

In a can-type secondary battery comprising an electrode assembly consisting of a positive electrode, a negative electrode, and a separator, a container-type can containing an electrode assembly and an electrolyte solution, and a cap assembly positioned at an upper end of the can and closing a can opening that becomes an inlet through which the electrode assembly is introduced. A method of welding cans and cap assemblies,

Preparing a can of varying thickness so that a step is formed in at least a portion inside the can opening;

Inserting the cap assembly inside the opening until it stops by a step,

And sealing the boundary of the periphery of the cap assembly and the top of the can with welding that irradiates a laser beam from the top of the cap assembly.

In the present invention, a method of inserting a cap assembly into an opening may include inserting a portion (side) corresponding to a portion of the can in which the step of the cap assembly is formed along the inner wall of the can, and then stopping the cap assembly when the portion touches the stepped portion. One can press a different part of the assembly to fit the entire cap assembly into the can opening. Alternatively, a method of inserting the cap assembly into the opening while pressing the overall cap may be used.

The size of the cap assembly in the present invention may be slightly greater than 0.02 mm in each direction (horizontal or vertical) on the plane than the size of the can opening into which it is fitted. With this minor size difference, the cap assembly can be inserted into the can's opening by forced press.

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

5 and 6 are a partial front cross-sectional view and a plan view of a can-type secondary battery at the step of inserting the cap assembly in the can opening in the middle according to an embodiment of the present invention.

In the step of preparing the can 511, the thickness is thinly formed by a predetermined distance of the end inside the short side portion of the opening of the rectangular can 511, the thickness is formed thick in the lower portion of the lower side to generate a step. In order to form such a step, a method of forming a thin end in the step of deep drawing the can 511 may be used, and once the can 511 is formed to the same thickness, the end portion may be partially hot or Cold rolling may also be considered.

A cap assembly (cap plate) 510 having a size difference in each direction within 0.02 mm from the opening of the can 511 is fitted in the opening. Under overall pressure the cap assembly is inserted into the opening. Even when the cap assembly is slightly larger than the can 511 opening, it is possible to press the cap assembly into the can 511 opening. Of course, the operation of inserting the electrode assembly into the can 511 through the opening is preceded by inserting the cap assembly into the opening of the can 511. The electrode assembly is usually made of an ellipse-shaped jelly roll having a large eccentricity by winding after stacking a membrane-shaped or plate-shaped anode, separator, and cathode.

The thickness of the short side portion of the can 511 is 0.25 mm in the thin portion at the end of the opening and 0.4 mm in the thick portion thereof at the bottom, and the step is 0.15 mm (shown at intervals between the arrows in the figure). Forming a stage having such a thickness difference in the long side portion of the can 511 may be contrary to the light weight thinning tendency of the battery, so it is preferable to form a step only on the short side. At this level, the cap assembly can no longer be inserted at the normal pressure of inserting the cap assembly into the opening of the can 511. When the thickness of the upper portion of the can 511 is about 1 mm and the thickness of the cap plate 510 of the cap assembly is about 1 mm, the upper surface of the cap plate 510 and the upper end of the can 511 are at the same level. The boundary between the top of the can 511 and the cap plate 510 is shown as a small square in the outer contour of the can 511 in FIG. 6 seen from above the cap assembly with the cap assembly inserted in the can.

In this state, laser welding is performed by laser beam irradiation above the cap assembly, while facing the boundary. The boundary part is partially welded during laser welding to form a weld part having a depth of about 0.2 to 0.3 mm. Laser beam welding may have a line welding speed of about 10 to 20 mm per second depending on the output of the laser beam in the form of line welding.

Thereafter, the electrolyte is injected through the electrolyte injection hole 160 to form a battery, and the electrolyte injection hole 160 is press-fitted and welded to form a bare cell. The bare cell is connected to a lead plate, a protection circuit, and the like, and the resultant is placed in a case to form a secondary battery in a hard pack state. The secondary battery in a hard pack state is repeatedly charged and discharged a predetermined number of times during the chemical conversion process, thereby completing a secondary battery having proper characteristics.

Considering the size of the laser beam generator and the path to which the laser beam is irradiated, welding while circulating the laser beam around a battery having a boundary as shown in FIG. 2 requires excessive welding space. In addition, welding a single battery with a plurality of laser welders has a problem of high equipment burden. Therefore, the welding method of the present invention, which moves the cell and the laser beam relatively along the boundary from the upper side, allows the assembly of the can and cap assembly to be accurately formed through the top step of the can while simultaneously welding the can and cap assembly. This can be said to be relatively superior in that it can be easily made.

In addition, in the case of the welding operation of the present invention as shown in FIG. 3 or FIG. 4, the welding operation of the present invention does not take much time for resetting the equipment, but the can 211-cap plate 210 as shown in FIG. The laser welding machine used for welding a battery having a boundary requires a lot of time for resetting when performing a welding operation like the present invention. In other words, there is a problem that the facility operation rate is lowered for the laser welding machine reset. Therefore, according to the present invention, the flexibility and the switchability of welding according to the battery model are improved.

According to the present invention, the ease of welding and the welding reliability between the upper end constituting the opening of the can and the cap plate periphery of the cap assembly can be increased, and the welding efficiency can be improved.

In addition, the relative position between the upper end of the can opening and the cap plate periphery of the cap assembly can be corrected to increase the accuracy of the welded portion and prevent leakage of electrolyte, external moisture, and inflow of air.

As another effect of the present invention, the present invention can increase the welding operation, space and equipment efficiency, and can be used to increase the efficiency of the conversion when used for welding different types of batteries.

Claims (6)

A can-type secondary comprising an electrode assembly consisting of a positive electrode, a negative electrode, and a separator, a container-type can containing the electrode assembly and an electrolyte, and a cap assembly positioned at an upper end of the can to close a can opening that is an inlet through which the electrode assembly is introduced. In the battery, The can is a rectangular can having a rectangular cross section, and the thickness of the sidewall of the can is thinly formed only at a short side portion or a corner portion of the rectangle to form a low end portion due to a step inside the can opening portion, and the side of the cap assembly is formed at the bottom end. The can-shaped secondary battery is inserted into the can so as to face the portion, the welding portion between the cap assembly peripheral portion and the can opening is formed on the upper surface side of the cap assembly. The method of claim 1, The can-shaped secondary battery, characterized in that the width of the bottom end is formed in the can side wall is the same as the thickness of the cap plate of the cap assembly. delete delete delete delete

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