Secondary battery having cathode tab of pin type

Secondary battery with needle-type cathode connector

Technical field

The present invention relates to a secondary battery, in particular to a cathode joint used for a negative electrode plate of an electrode group.

The present invention claims the priority of the Korean patent application with the application number 2003-39960 filed with the Korean Intellectual Property Office on June 19, 2003, and the contents disclosed in the application are hereby incorporated by reference.

Background technique

In general, batteries are roughly classified into secondary batteries that can be repeatedly charged and discharged, and primary batteries that are not rechargeable and discarded after being exhausted. According to the shape of the target device, the battery may be formed in various shapes, such as a cylindrical shape, a prismatic shape, and a pouch shape.

Among these batteries, the cylindrical secondary battery has an electrode assembly in which the positive and negative plates are wound in the form of a jelly-roll while inserting a separator between the positive and negative plates; A cylindrical shell; and a cover assembly fixed on the top of the shell.

An insulating plate is provided between the electrode assembly and the cover assembly and between the electrode assembly and the case.

The positive plate of the electrode assembly is electrically connected to the cover assembly through the anode joint, and the negative plate of the electrode assembly is electrically connected to the casing through the cathode joint.

The cathode joint is mainly formed of a 0.05-0.1mm thick nickel strip, which is welded to the negative plate located in the outermost area of the electrode assembly and the inner bottom surface of the casing to electrically interconnect the negative plate and the casing.

However, the nickel strip used as the cathode joint is rigid, and when the electrode assembly welded with the cathode joint is inserted into the case, the cathode joint is likely to be caught in the opening part of the case, thereby causing abnormal arrangement of the electrode assembly.

In this connection, the outer diameter of the electrode assembly is designed such that when the electrode assembly is inserted into the housing, a certain distance (for example, 0.2-0.4 mm) is left between them. However, this limits the size of the electrode assembly, and therefore, the electrode assembly in the case cannot be enlarged enough to achieve the highest battery capacity.

Summary of the invention

According to an embodiment of the present invention, the secondary battery includes: an electrode assembly in which a negative plate and a positive plate are arranged by inserting a separator between the positive plate and the negative plate; and a case in which the electrode assembly is installed. The cover assembly is installed on the casing to tightly seal the casing and electrically connect it with the positive plate. The needle is inserted into the electrode assembly and brought into contact with the negative plate and the case to electrically interconnect them.

In one embodiment, the needle has a hollow shape, and protrusions are formed at one end of the needle, and these protrusions are welded to the housing. In this embodiment, the protruding portion is inclined toward the center of the needle.

In another embodiment of the present invention, a plurality of protruding parts are provided, and communication holes are provided between the protruding parts so that the inside of the needle communicates with the outside of the needle.

In one embodiment, the needle is formed of nickel or a nickel alloy.

In another embodiment, the electrode assembly is substantially in the shape of a film, and the needle is inserted into the center of the electrode assembly.

Description of the drawings

The above and other advantages of the present invention will be more apparent by detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. In the drawings: FIG. 1 is a cross-sectional view of a secondary battery according to an embodiment of the present invention; FIG. 2 shows the needle structure of this embodiment of the present invention; FIG. 3 is an electrode used in the secondary battery of this embodiment of the present invention A schematic perspective view of the assembly; Figure 4 shows another embodiment of the needle of the present invention; Figure 5 shows another embodiment of the needle of the present invention.

detailed description

Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, which exemplarily show the embodiments of the present invention.

As shown in FIGS. 1 to 3, the secondary battery has: an electrode assembly 10 in which the negative electrode plate 12 and the positive electrode plate 14 are wound in a jelly roll while the separator 13 is inserted between the negative electrode plate 12 and the positive electrode plate 14. ; A cylindrical case 20 with the electrode assembly 10 installed inside and electrically connected to the negative plate 12 of the electrode assembly 10; a cover assembly mounted to the top of the case 20 and electrically connected with the positive plate 14 of the electrode assembly 10 30; and a needle 50 inserted into the center of the electrode assembly 10 while contacting the negative plate 12 and partially welded to the bottom surface of the case 20 to electrically interconnect the negative plate 12 of the electrode assembly 10 and the case 20.

The needle 50 may have a hollow shape in order to obtain a gas passage. Alternatively, as shown in FIG. 4, the needle 50 may also be in the shape of a solid rod.

A plurality of communicating holes 53 are formed at the bottom end of the needle 50 to allow the inside of the needle 50 to communicate with the outside and to obtain a passage for gas and electrolyte. Of course, it is not necessary to form communicating holes (as shown in FIG. 5).

While defining the hole, a plurality of protruding portions 52 are formed at the bottom end portion of the needle 50 and between adjacent communicating holes 53.

The protruding portion 52 is welded to the housing 20 while being in contact with the bottom surface of the housing 20, and the protruding portion is inclined toward the center of the needle 50. This structure can conveniently weld the protruding part 52 to the bottom surface of the housing 20 at one point. Alternatively, as shown in FIG. 5, only a protruding portion may be formed at the bottom end portion of the needle 50 without forming the hole 53.

At the same time, the needle 50 may be composed of nickel or a nickel alloy. Compared with the housing 20, the needle 50 has excellent electrical conductivity and excellent weldability.

As shown in FIG. 3, for the electrode assembly 10, the negative electrode plate 12, the separator 13, the positive electrode plate 14, and the separator 13 are sequentially stacked from the inside of the assembly to the outside thereof, and are wound into a jelly roll form.

Subsequently, the negative electrode plate 12 is exposed inside the electrode assembly 10, and is firmly bonded to the needle 50 installed in the electrode assembly 10, thereby constituting an electrical connection thereto.

The cover assembly 30 has a cover 32 and a cover cover 34, and the cover assembly is mounted on the housing 20 by inserting a gasket 38 between the cover assembly and the housing. A rubber exhaust port 36 is provided between the cover 32 and the cover 34.

The anode lead 15 connected to the positive electrode 14 of the electrode assembly 10 is connected to the cap 34 of the cap assembly 30.

An upper insulating plate 40 is installed between the cover assembly 30 and the electrode assembly 10, and a lower insulating plate 42 is installed between the bottom surface of the case 20 and the electrode assembly 10.

The cover assembly 30, the electrode assembly 10, and the case 20 are all constructed with the structure of a conventional lithium ion battery, and therefore, detailed descriptions of them are omitted.

With the secondary battery of the above structure, the cathode tab is not installed outside the electrode assembly, and therefore, an electrode assembly having an outer diameter corresponding to the inner diameter of the case can be formed.

Therefore, with the secondary battery of the present invention, when the outer diameter of the electrode assembly is 17.10-17.20mm, compared with the conventional battery of this type, the outer diameter of the electrode assembly can be increased by 0.5-1.0%, thereby increasing the battery capacity 2-5%.

In addition, when the cathode tab is not installed outside the electrode assembly, the cathode tab can be prevented from being caught on the case during the process of inserting the electrode assembly into the case, and thus the assembly can be performed very smoothly.

For conventional batteries of this type, since the central part of the electrode assembly is hollow and has a very low strength, it is easy to deform under external compression. In contrast, the secondary battery of the present invention is provided with a needle in the center of the electrode assembly, which can absorb external pressing force, thereby preventing deformation of the electrode assembly.

In addition, for conventional batteries of this type, when the electrode assembly is tested in a hot furnace at 150°C or higher, its internal structure may be deformed, making it difficult for the gas generated inside to pass through the bottom of the case. The safety vent is released, and the battery is easy to burst. In contrast, since the secondary battery of the present invention constitutes a smooth gas passage through the needle, the gas generated inside can be smoothly discharged through the safety vent, so it can prevent the battery from bursting and meet safety standards.

The secondary battery according to this embodiment of the present invention may be formed in a cylindrical shape, a prismatic shape, or other shapes.

Although the exemplary embodiments of the present invention have been described in detail above, it should be clearly understood that those skilled in the art can easily make various changes and/or modifications on the basis of the basic inventive concept described herein, as in the appended rights As defined in the requirements, these changes and/or modifications fall within the concept and protection scope of the present invention.