JP2009087900A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small lithium ion secondary battery having an electrolyte leakage detection function. <P>SOLUTION: The lithium ion secondary battery has a cover sheet 2 on the surface of a first fixing member 3, an acid alkali indicating sheet 5 in a safety valve counter part on the backside, an insulating sheet 4 in a part other than the safety valve counter part on the backside, and an insulating member 1 having a second fixing member 6 is formed on the header part side of the insulating sheet 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery, and more particularly to a lithium ion secondary battery in which a header portion is covered with an insulating member.

  In recent years, electric devices such as mobile phones, digital cameras, and MP3 players are required to be used for a long time, downsized, and reduced in weight. The lithium ion secondary battery used as the power supply unit has similar requirements.

  Further, since lithium ion secondary batteries have high energy per unit area, they are often used in familiar products, and safety is required.

  Lithium ion secondary battery has high energy per unit area, so if an abnormal condition occurs inside the battery, it may cause a chemical reaction and generate gas, and if the internal pressure rises, to prevent explosion Some headers have a safety valve. This safety valve is thinner than other joint parts of the outer can of lithium ion secondary battery, that is, the negative electrode pin part of the header part, the seam part joining the header part and the can, etc. When the internal pressure rises, the structure is easily opened.

  3 and 4 are perspective views for explaining a conventional lithium ion secondary battery. As shown in FIG. 3, the negative electrode pin 33, the safety valve 32, and the liquid injection port are arrange | positioned at the header part of the lithium ion secondary battery. When using an aluminum battery can in the exterior of the lithium ion secondary battery 30, the negative electrode pin 33 serves as the negative electrode, and the other header and battery can parts serve as the positive electrode. This prevents short circuits when manufacturing battery packs. Therefore, it is necessary to cover the periphery of the negative electrode pin 33 with the insulating member 31 in the header portion.

  However, if a part or the like touches the safety valve during the battery pack assembly process, the safety valve may be opened. Therefore, as shown in FIG. 4, there is also a lithium ion secondary battery 40 having a structure in which the entire header portion is covered with an insulating member 41 including the safety valve 42 except for the periphery of the negative electrode pin 43.

  In addition, a minute crack or the like may occur in the safety valve during the battery pack assembling process or the battery manufacturing process. In the case of a minute crack, it is difficult to find it visually, and it cannot be visually recognized after the safety valve is covered with an insulating member. If a micro crack or the like occurs in the safety valve, there is a possibility that the performance of the lithium ion secondary battery may be deteriorated due to leakage of the electrolyte from the inside of the battery can or penetration of moisture from the outside. is there.

  Therefore, as a battery in which electrolyte leakage can be easily confirmed, Patent Document 1 discloses a technique of providing an insulating member formed by bonding a transparent or translucent insulating sheet and acid-alkali indicator paper on a header portion. Yes. However, in order to ensure the insulating properties originally required for this insulator, an insulating sheet having a thickness of 0.1 to 0.5 mm such as modified PPE or PPS and an acid having a thickness of 0.1 to 0.5 mm are used. Since the alkali indicator paper is pasted, the thickness increases, which is not preferable for downsizing. Further, when an insulating sheet such as thin modified PPE or PPS is used, there is a problem that the insulating property is inferior. Further, in order to fix the acid / alkaline indicator paper to the header portion, a fixing member is used to closely contact the sheet. Therefore, the safety valve portion is closed, which is not preferable from the viewpoint of opening the safety valve.

JP 2005-251597 A

  The present invention has been made to solve the above problems, and a technical problem thereof is to provide a small-sized lithium ion secondary battery having a leakage detection function.

  The lithium ion secondary battery of the present invention is a lithium ion secondary battery provided with an insulating member so as to cover a header portion provided with a safety valve, the insulating member has a cover sheet on the surface of the first fixing member, It has acid-alkaline indicator paper on the safety valve facing part on the back surface, has an insulating sheet on a portion excluding the safety valve facing part on the back surface, and has a second fixing member on the header portion side of the insulating sheet, To do.

  According to the present invention, the header portion of the lithium ion secondary battery is reliably insulated, and the safety valve that may occur in the battery pack assembly process is prevented from being contacted from the outside, and a micro crack or the like is temporarily entered. In this case, the acid / alkaline indicator paper that detects leakage of electrolyte from the lithium ion secondary battery is held by the thin cover sheet on the front side, so there is no need to attach it to the header side. By creating a gap in the header part, there is an advantage that the size can be reduced without affecting the operation of the safety valve.

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

  1A and 1B are diagrams for explaining an insulating member used in the lithium ion secondary battery of the present invention. FIG. 1A is a perspective view and FIG. 1B is an exploded perspective view. FIG. 2 is a perspective view illustrating the lithium ion secondary battery of the present invention.

  The lithium ion secondary battery of the present invention includes an insulating member 1 provided with a relief pin 1a for a negative electrode pin at the center as shown in FIG. 1A, and a lithium ion secondary battery 20 as shown in FIG. The upper header portion has a structure in which a relief hole is provided in the negative electrode pin 23. Next, the insulating member will be described in detail. The insulating member is a cover sheet 2 having a relief hole 2a in the central portion from the surface side, a first fixing member 3 having a relief hole 3a in the central portion, an insulating sheet 4 having a relief hole 4a in the central portion, and a corresponding portion of the safety valve 22 And the second fixing member 6 having the escape hole 6a in the center portion is superimposed on the portion without the insulating sheet, and the relief holes 2a, 3a, 4a, 6a of the respective negative electrode pins are provided. In addition, an insulating sheet and a second fixing member are not provided in the corresponding part of the safety valve, but an acid / alkali indicator paper is provided.

  The cover sheet 2 is formed of an insulating material such as modified PPE or PPS having a thickness of 0.01 to 0.05 mm by connecting the insulating sheet 4 and the acid / alkaline indicator paper 5 via the first fixing member 3. A transparent material is used so that the reaction of the acid-alkali indicator paper 5 can be confirmed.

  The first fixing member 3 is a member for connecting the cover sheet 2, the insulating sheet 4, and the acid / alkaline indicator paper 5, and is made of a double-sided tape, an adhesive, or the like having a thickness of 0.01 to 0.05 mm. Note that a neutral member is used to suppress unnecessary reaction of the acid-alkali indicator paper 5.

  The acid-alkali indicator paper 5 is litmus paper, PH indicator paper, or the like, and confirms the presence or absence of a crack or the like of the safety valve by discoloring in response to electrolyte leakage from the safety valve. The acid / alkaline indicator paper 5 is connected to the first fixing member 3 and provided only at the corresponding portion of the safety valve.

  Since the insulating sheet 4 has an insulating function between a conductor such as a Ni tab connected to the negative electrode pin (negative electrode) of the battery when manufacturing the battery pack, and the battery header portion (positive electrode) excluding the negative electrode pin, the insulating sheet 4. An insulating material such as modified PPE or PPS having a thickness of 1 to 0.5 mm is used. The insulating sheet 4 is connected to the first fixing member 3 except for the portion provided with the acid / alkali indicator paper 5 of the corresponding part of the safety valve.

  The 2nd fixing member 6 is a member for fixing the insulating sheet 4 and a battery header part, and consists of a double-sided tape, an adhesive agent, etc. of 0.01-0.05 mm thickness. A second fixing member is not provided under the acid-alkali indicator paper 5, and the thickness of the acid-alkali indicator paper 5 is set to be equal to or less than the thickness of the insulating sheet 4, so Make a gap. This makes it easier to release the pressure from the safety valve.

The figure explaining the insulating member used for the lithium ion secondary battery of this invention, Fig.1 (a) is a perspective view, FIG.1 (b) is a disassembled perspective view. The perspective view explaining the lithium ion secondary battery of this invention. The perspective view explaining the conventional lithium ion secondary battery. The perspective view explaining the conventional lithium ion secondary battery.

Explanation of symbols

1, 31, 41 Insulating member 2 Cover sheet 3 First fixing member 4 Insulating sheet 5 Acid-alkali indicator paper 6 Second fixing member
1a, 2a, 3a, 4a, 6a Relief hole 20, 30, 40 Lithium ion secondary battery 23, 33, 43 Negative electrode pin 22, 32, 42 Safety valve

Claims (1)

  In a lithium ion secondary battery in which an insulating member is provided so as to cover a header portion provided with a safety valve, the insulating member has a cover sheet on the surface of the first fixing member, and acid-alkaline instructions are provided on the back surface of the safety valve facing portion. A lithium ion secondary battery comprising paper, having an insulating sheet on a portion of the back surface excluding the safety valve facing portion, and having a second fixing member on the header portion side of the insulating sheet.

Images