JPH0668861A - Lithium-ion secondary battery - Google Patents

Abstract

PURPOSE:To enhance gastightness of a battery and fix its total height by providing an external can as a bottomed rectangular cylindrical body, containing agenerating element, and a sealing body having a collar portion fitted to an opening portion of the outer can by contact. CONSTITUTION:An external can 1 as a stainless steel, bottomed rectangular cylindrical body contains a generating element and also acts as a negative electrode terminal. A sealing body 3 having a collar portion 3 in the upper portion 2 is fitted to the opening portion of the external can 1 by contact. This fitting is done in excellent gastightness of the external can by lase welding together the lower surface of the collar portion and the upper end of the opening portion of the external can 1. A hole 4 opens in the middle of the sealing body 3 and therein a positive electrode pin 5 is fixed with its ends protruding from the upper and the lower surface of the sealing body 3, through glass material. The sealing body 3 is always fitted to a fixed position of the external can 1 by way of the collar portion 2, not depending on inside diameter of the external can 1 manufactured by deep drawing, so that the total height of the battery is kept fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery having a bottomed rectangular cylindrical outer can.

[0002]

2. Description of the Related Art In recent years, as video cameras, cordless phones, etc. have become smaller, lighter and more sophisticated, there has been an increasing demand for higher capacity or higher energy density of secondary batteries which are the power source for these devices. Is coming. As the secondary battery, a lead secondary battery or a nickel-cadmium secondary battery has been conventionally used, but recently, a lithium ion secondary battery has been developed as a non-aqueous electrolyte secondary battery.

Further, due to the trend toward smaller size, lighter weight, and higher performance of equipment in which the lithium ion secondary battery is used, it is only required to increase the capacity and energy density of the secondary battery. However, various restrictions have come to be given to the shape of the secondary battery. For example, a prismatic lithium-ion secondary battery having the shape of a bottomed rectangular cylinder has been increasingly demanded as a battery that can function in a limited space inside the device.

In addition, a non-aqueous electrolyte secondary battery such as the prismatic lithium ion secondary battery is required to have stable hermeticity, particularly airtightness, for a long period of time in view of its performance, and therefore has a very high airtightness. Need to take a way. Therefore, for the prismatic lithium ion secondary battery, for example, the sealing method shown in FIGS. 3 and 4 has been proposed.

The outer can 21 having a rectangular cylinder with a bottom accommodates a power generating element and also serves as one pole. The sealing body 23 having rising portions near the outer peripheral edge and near the outer peripheral edge of the hole 22 in the central portion is
The outer can 21 is fitted and is hermetically attached to the outer can 21 by laser welding the upper inner wall surface of the outer can 21 and the outer peripheral edge of the sealing body 23. Further, the other polarity pin terminal 24 has the opposite ends of the sealing body 23.
The hole 2 of the sealing body 23 so as to project from the upper and lower surfaces of
It is attached to the No. 2 via an insulating material 25 by a hermetic seal.

Although it is relatively easy to precisely process the sealing body 23 by press molding, when the outer can 21 is manufactured by deep drawing, the deeper the drawing depth of the outer can 21, the more the outer packaging. It was difficult to improve the accuracy of the inner diameter of the can 21. As a result, the outer can 2
Since the inner diameter dimension of No. 1 varies, the outer can 21
When the sealing body 23 is fitted into the upper opening of the, a gap is created between the upper inner wall surface of the outer can 21 and the outer peripheral edge of the sealing body 23. Therefore, when laser welding is performed on the upper inner wall surface of the outer can 21 and the outer peripheral edge of the sealing body 23, there is a problem that welding defects are likely to occur and the airtight reliability of the battery is deteriorated. Further, for the same reason, the sealing body 23 cannot be fitted into the outer can 21 at a fixed position, and the total height of the battery fluctuates.

Therefore, after the outer can 21 is manufactured by deep drawing, the outer can 21 is secondly processed to have the desired inner diameter, and then the sealing body 23 is attached to the outer can 21 or by a jig. After fitting the outer can 21 to the outer can 21, the outer can 21 is pressed from the outside to eliminate the gap, and then laser welding is performed to hermetically seal the battery to keep the total height of the battery constant. Was proposed.

However, these methods not only require complicated operations, but are effective only in the case of an outer can having a relatively small drawing depth in which variations in inner diameter are small.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and provides a lithium ion secondary battery having excellent airtightness and capable of keeping the total height constant. It is a thing.

[0010]

SUMMARY OF THE INVENTION The present invention is a rectangular cylinder with a bottom, which is fitted into an outer can containing a power generating element and an upper opening of the outer can, and the upper end of the opening of the outer can is attached to the upper part. And a sealing body having a flange portion that abuts against the.

According to the present invention, a thin film having a valve membrane formed on the bottom thereof by a pressure release hole opened in the sealing body and a groove provided on the outer surface of the sealing body and provided at a position corresponding to at least the hole. It is allowed to further include a safety valve mechanism consisting of

[0012]

According to the present invention, the lower surface of the collar portion is fitted to the upper end of the opening portion of the outer can by fitting the sealing body having the upper flange portion into the upper opening portion of the outer can having the bottomed rectangular tubular body. Since the outer can and the sealing body can be satisfactorily laser welded to each other, the sealing performance can be improved. Further, since the sealing body can be always fitted in a fixed position of the outer can by the collar portion, the total height of the battery can be kept constant.

Further, a pressure release hole opened in the sealing body and a thin film which is attached to the outer surface of the sealing body and has a valve membrane formed on the bottom thereof by a groove provided at least at a position corresponding to the hole. If the battery is provided with a safety valve mechanism that is configured as follows, it is possible to prevent the battery outer can from being ruptured or deformed due to the safety valve mechanism reliably operating due to the improvement of the sealing property and the battery internal pressure rising excessively. A highly reliable lithium-ion secondary battery can be provided.

[0014]

EXAMPLE A prismatic lithium ion secondary battery to which the present invention is applied will be described with reference to FIGS.

The power generating element is housed in the outer can 1 which is made of, for example, stainless steel and has a bottomed rectangular cylinder, and also serves as a negative electrode terminal, for example. The sealing body 3 made of, for example, stainless steel, which has the flange portion 2 on the upper portion, is fitted into the upper opening portion of the outer can 1 by bringing the flange portion 2 into contact with the upper end of the opening portion of the outer can 1. The outer surface of the outer can 1 is hermetically attached to the outer can 1 by laser welding the contact portion between the lower surface of the portion 2 and the upper end of the opening of the outer can 1. A hole 4 is opened near the center of the sealing body 3. For example, the positive electrode pin terminal 5 made of stainless steel is attached to the hole 4 through the glass insulating material 6 by a hermetic seal so that both ends of the positive electrode pin terminal 5 project from the upper and lower surfaces of the sealing body 3, and serves as a negative electrode terminal. The can 1 and the positive electrode pin terminal 5 are insulated from each other.

For example, a circular hole 7 is opened in the portion of the sealing body 3 apart from the hole 4. For example, the thin film 8 having a circular shape is airtightly attached to the outer surface of the sealing body 3 by laser welding so as to cover the hole 7. Groove 9
Is provided at a position corresponding to the hole 7, and has, for example, a straight portion and both ends thereof are V-shaped. The groove 9
Is formed by pressing the thin film 8 with a punch having the same shape as the groove 9 or etching the thin film 8. The bottom of the groove 9 functions as a valve leaflet 10. A safety valve mechanism 11 is formed from the hole 7 and the thin film 8 having the valve film 10 formed at the bottom thereof by the groove 9 provided at a position corresponding to the hole 7.

According to such a structure, by fitting the sealing body 3 having the collar portion 2 on the upper portion of the outer can 1, the collar portion 2 abuts on the upper end of the opening of the outer can 1. As a result, good welding can be achieved by laser welding the contact portion between the lower surface of the collar portion 2 and the upper end of the opening portion of the outer can 1, so that the airtightness of the battery can be improved. it can. In addition, since the sealing body 1 is always fitted in a fixed position of the outer can 1 by the collar portion 2 without depending on the inner diameter of the outer can 1 manufactured by deep drawing, the total battery The height can be kept constant.

Further, a hole 7 opened in the sealing body 3.
And the groove 9 which is airtightly attached to the outer surface of the sealing body 3 by laser welding and is provided at a position corresponding to the hole 7.
The thin film 8 having the valve membrane 10 formed on the bottom thereof by
By providing the battery with the safety valve mechanism 11 formed by the above, an abnormal current flows due to a short circuit due to overcharge or misuse, the temperature inside the battery rises, and the battery is housed in the outer can 1. When the electrolyte of the power generation element is decomposed and gas is generated to increase the internal pressure of the outer can 1, the gas is formed in the sealing body 3 without escaping to the outside because the airtightness of the battery is high. Pressure is applied to the leaflet 10 of the thin film 8 through the circular hole 7 of the safety valve mechanism 11,
Can be reliably broken by the pressure (operating pressure). As a result, it is possible to prevent the battery outer can from being ruptured or deformed due to an excessive increase in the battery internal pressure, and it is possible to obtain a highly safe lithium ion secondary battery.

In the above embodiment, the safety valve mechanism is provided with the hole 7 and the groove 9 provided at a position corresponding to the hole 7.
The thin film 8 having the valve membrane 10 formed on the bottom thereof by
However, the present invention is not limited to this. For example, several arc-shaped holes formed concentrically with the center of the sealing body 3, a ring-shaped circular groove provided at a position corresponding to the hole 7, and the circular groove intersecting with the circular groove are provided. The safety valve mechanism may be composed of a thin film having a valve film formed on the bottom thereof by a linear groove extending radially from the center of 3.

[0020]

As described above in detail, according to the present invention, it is possible to provide a lithium ion secondary battery having excellent airtightness and having a constant total height and improved safety. .

[Brief description of drawings]

FIG. 1 is a perspective view of a sealing body of a prismatic lithium-ion secondary battery that is a present embodiment.

FIG. 2 is an enlarged sectional view of FIG.

FIG. 3 is a perspective view of a sealing body of a lithium-ion secondary battery that is a conventional example of the present invention.

FIG. 4 is a sectional view of FIG.

[Explanation of symbols]

 1 ... Battery outer can, 2 ... Collar part, 3 ... Sealing body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masamichi Kawabe, 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Stock Company, Toshiba Horikawa-cho factory (72) Inventor Masataka Yamashita 1-3, Yokou, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 Asahi Kasei Co., Ltd. (72) Inventor Shigeo Kasahara 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Inventor Takashi Takayama 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd.

Claims (2)

[Claims] 1. A closure having a bottomed rectangular tubular body having an outer can that houses a power generating element, and a flange portion that is fitted into an upper opening of the outer can and that abuts on an upper end of the opening of the outer can. A lithium-ion secondary battery comprising: a body. 2. A pressure release hole opened in the sealing body,
The lithium ion according to claim 1, further comprising a safety valve mechanism attached to the outer surface of the sealing body, the safety valve mechanism including a thin film having a valve film formed on a bottom portion thereof by a groove provided at a position corresponding to at least the hole. Secondary battery.