JP5114063B2 - Sealed battery - Google Patents

Description

  The present invention relates to a structure of a battery, and more particularly to a sealed battery excellent in safety during dropping and impact.

  Various types of batteries are used as power sources for small electronic devices, and small and large-capacity sealed batteries are used as power sources for mobile phones and laptop computers. Recently, lithium-ion secondary batteries with particularly high energy density are used. A sealed battery using a non-aqueous electrolyte is used. In addition, along with the thinning of electronic devices, the use of rectangular batteries suitable for thin devices has become more space efficient, and complete sealing is essential because non-aqueous electrolyte is contained. .

  FIG. 2 is a diagram for explaining an example of a conventional sealed battery, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a cross-sectional view taken along line AA in FIG. 2 (a). FIG. 2C is a diagram for explaining the state of the inside of the battery can and the insulating plate between the lid and the battery element, FIG. 2C is a plan view of the insulating plate, and FIG. It is sectional drawing of the BB line in c). The battery shown in FIG. 2 includes a battery can 2 made of aluminum or an alloy thereof, laminated with a positive electrode and a negative electrode via a separator, wound, accommodated a molded battery element 3 and a lid 4 fitted to the battery can 2. After the laser welding. In the case of this battery, insulating plates 5 made of polyolefin resin are disposed above and below the battery element 3.

  In Patent Document 1, it is proposed to arrange an insulating plate having elasticity in order to suppress internal short circuit between the battery element, the lid, and the battery can due to dropping or impact. In Patent Document 2, the impact resistance is improved. Therefore, it has been proposed to dispose an insulating plate having a T-shaped cross section between the battery element and the battery can.

JP 200431263 A JP 2004-6363 A

  However, when the number of drop tests for confirming the safety of the battery is repeated, particularly when the drop test is repeatedly performed with the lid disposed below, an impact is applied to the upper portion of the can. 3A and 3B are diagrams for explaining a state of a conventional sealed battery after a drop test, in which FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view taken along line AA in FIG. is there. As shown in FIG. 3, when the battery element 3 moves to the lid 4 side due to a drop impact and presses the insulating plate 5, the insulating plate 5 is deformed to become a pressure valve, and the lid 4 and the insulating plate The pressure was repeatedly applied to the safety valve mechanism 6 through the non-aqueous electrolyte between 5 and 5 to cause the safety valve mechanism to open.

  There are measures to increase the operating pressure of the safety valve mechanism for opening the safety valve mechanism in such a drop test, but if the operating pressure is increased, the internal pressure of the battery will increase due to the overcharge and heating tests that were originally intended. Since the effect to prevent is remarkably impaired, it is not realistic.

  An object of the present invention is to provide a highly reliable sealed battery that prevents a safety valve mechanism from being opened due to dropping or impact.

  The sealed battery of the present invention accommodates a battery element in which a positive electrode and a negative electrode are stacked and wound through an opening of a battery can through a separator, and the opening is sealed with a lid incorporating a safety valve mechanism. In the sealed battery, an insulating plate that covers the safety valve mechanism is disposed between the battery element and the lid.

  The insulating plate is preferably made of a polyolefin-based resin having a melting point of 120 ° C. to 180 ° C., and the thickness of the portion covering the safety valve mechanism of the insulating plate is preferably the same as the height of the side wall of the insulating plate. .

  According to the present invention, by using an insulating plate having a structure covering the front surface of the safety valve mechanism of the lid body, the safety valve structure of a thin valve body having a general dome shape is improved by improving durability at the time of a drop impact. And a highly reliable sealed battery can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an embodiment of a sealed battery according to the present invention. FIG. 1 (a) is a plan view, and FIG. 1 (b) is a cross-sectional view taken along line AA in FIG. 1C is a plan view of the insulating plate, and FIG. 1D is a cross-sectional view taken along line BB in FIG. 1C. In the sealed battery 1 of the present invention, a positive electrode and a negative electrode are laminated in a rectangular battery can 2 via a separator and wound flat, and then pressed to be flattened so as to match the shape of the battery can. The battery element 3 is accommodated and sealed with a lid 4 incorporating a safety valve mechanism 6. An insulating plate 5 is disposed between the battery element 3 and the lid 4 to prevent a short circuit. The insulating plate 5 has a side wall on the lid side of the upper peripheral edge of the insulating plate 5 to avoid contact with the battery element 3 with the lid 4 and the terminal portion at the substantially central portion of the lid, and faces the safety valve mechanism 6. The portion to be provided has a thick portion 7 that covers the entire surface of the safety valve mechanism.

  In the sealed battery 1 of the present invention, the thickness of the thick portion 7 of the insulating plate 5 that covers the entire portion facing the safety valve mechanism 6 is the same as that of the side wall of the insulating plate 5, thereby receiving impact such as a drop test. When the battery element 3 is moved, the battery element 3 moves to the lid 4 side, and deformation caused by pressing the insulating plate 5 is reduced. In addition, when abnormality arises by heat_generation | fever of a battery, since an insulating board softens or fuse | melts, there is no trouble in opening of a safety valve mechanism.

  Next, an embodiment will be described with reference to FIG. A battery can 5 made of an aluminum alloy having a length of 49.1 mm, a width of 33.8 mm, a thickness of 4.2 mm, and a thickness of 0.2 mm is laminated with a positive electrode and a negative electrode through a separator of a microporous polypropylene film, and spirally formed. The battery element 3 having a length of 45.5 mm, a width of 32.6 mm, and a thickness of 3.7 mm, which was wound around the container, was accommodated, the lid was fitted into the can via the insulating plate 5, and laser welding was performed. The insulating plate has a plate-like portion having a thickness of 0.3 mm, and a side wall having a thickness of 0.3 mm and a height of 1.2 mm is provided on the peripheral portion of the length of 3.7 mm and the width of 32.2 mm, and the portion facing the safety valve mechanism The one provided with a thick portion 7 having a height of 1.2 mm was prepared. Next, an electrolyte solution was injected from an inlet provided in the lid 4 to produce a lithium ion battery.

(Comparative example)
Next, a comparative example will be described. An insulating plate having a plate-like portion having a thickness of 0.3 mm and a peripheral edge portion having a length of 3.7 mm and a width of 32.2 mm provided with a side wall having a thickness of 0.3 mm and a height of 1.2 mm is prepared. A lithium ion battery was produced as a comparative example in the same manner as in the example except that it was used.

  The lithium ion batteries of Examples and Comparative Examples produced as described above were packaged with a case made of a molded resin together with a protective circuit to obtain a battery pack. Each of the three battery packs obtained was mounted on a MC nylon (registered trademark) jig weighing 80 g assuming a mobile phone, and the direction of the battery lid was controlled to the bottom, starting from a height of 1 m on the plywood A drop test was conducted. Table 1 shows the number of drops when the safety valve mechanism is opened by repeating the drop test.

  From the results in Table 1, it was confirmed that the drop durability was improved in the sealed battery in which the present invention in which the insulating plate having a structure covering the entire surface facing the safety valve mechanism was provided was implemented.

  Next, a test was conducted on opening the safety valve mechanism by heating. As a pre-treatment, the lithium ion batteries produced according to the examples and comparative examples were discharged at a constant current of 0.2 C to a final voltage of 3.0 V, and then the battery voltage was 4.25 V and the current was 1 C in a 20 ° C. atmosphere. The battery was charged with a constant current and a constant voltage for 5 hours. A heating test was performed in which each of the three charged lithium ion batteries was heated to 150 ° C. at a rate of 5 ° C./min and held at 150 ° C. for 3 hours. The results are shown in Table 2.

  From the results shown in Table 2, it was confirmed that the safety valve was opened even in the sealed battery in which the present invention in which the insulating plate having a structure covering the entire surface facing the safety valve mechanism was provided, and there was no problem.

  The sealed battery according to the present invention has a structure that covers the entire surface of the insulating plate between the battery element and the cover, which faces the safety valve mechanism, and requires high durability without opening the safety valve mechanism even when subjected to a drop impact. It can be used as a sealed battery.

FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1C is a diagram illustrating an embodiment of a sealed battery according to the present invention. The top view of an insulating board, FIG.1 (d) is sectional drawing of the BB line in FIG.1 (c). FIG. 2 (a) is a plan view, FIG. 2 (b) is a cross-sectional view taken along line AA in FIG. 2 (a), and FIG. 2 (c) is an insulating plate. FIG. 2D is a plan view, and FIG. 2D is a sectional view taken along line BB in FIG. The figure explaining the state after the drop test of the conventional sealed battery, Fig.3 (a) is a top view, FIG.3 (b) is sectional drawing of the AA line in Fig.3 (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealed battery 2 Battery can 3 Battery element 4 Lid 5 Insulation plate 6 Safety valve mechanism 7 Thick part

Claims (1)

By laminating a positive electrode and the negative electrode via the separator from the opening of the battery can accommodating the battery element wound, the opening, the sealed cell comprising sealed by incorporating the lid with a safety valve mechanism,
Between the lid and the battery element, the safety valve mechanism, arranged an insulating plate covering over the entire surface of the safety valve mechanism,
The insulating plate is made of a polyolefin resin having a melting point of 120 ° C to 180 ° C,
The sealed battery according to claim 1, wherein a thickness of a portion of the insulating plate covering the safety valve mechanism is the same as a height of a side wall of the insulating plate .

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