JP2007165039A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery having high performance, capable of increasing the inner volume of the battery for housing a power generation element. <P>SOLUTION: The sealed battery is formed by housing the power generation element in a cylindrical battery case with bottom, forming a groove in the battery case, and sealing an opening part of the battery case with a sealing plate through a gasket, and the sealing plate has at least a valve body and a sealing plate case, the valve body has an easily breaking part, the easily breaking part can be deformed and broken by increase of the inner pressure of the sealed battery, and the valve body does not exist in a portion interposed between the groove and the the tip part of the opening part of the battery case. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sealed battery, and particularly to a sealing structure thereof.

  In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless. As a power source for driving these devices, lithium, which is a representative of high capacity alkaline storage batteries and nonaqueous electrolyte secondary batteries, is used. Secondary batteries are suitable, and these batteries are required to be sealed batteries with high energy density and excellent load characteristics.

  Such a sealed battery can be sealed by a method of sealing the sealing plate and the opening of the battery case by laser welding, or by sealing the sealing plate and the gasket via a groove provided near the opening of the battery case. The method is adopted.

  By the way, when a high energy density sealed battery is overcharged due to a failure of a charger or the like, or overcharged or overdischarged due to misuse, a gas is generated inside the battery due to a chemical reaction, and the internal pressure of the battery increases, causing the battery to be May be in a safe state. In order to prevent the battery internal pressure from increasing, a safety mechanism is provided on the sealing plate. In particular, for the sealing plate used in the caulking sealing method, when the battery internal pressure exceeds the set value, the valve provided in the sealing plate is opened to release the gas in the battery to the outside, reducing the battery internal pressure. I try to let them. Furthermore, in the case of a non-aqueous electrolyte secondary battery, there is a possibility that the temperature rapidly increases when the battery internal pressure increases. For this reason, the sealing plate is provided with a current interrupting mechanism that interrupts the current before discharging the gas to the outside of the battery by detecting an increase in the battery internal pressure (see, for example, Patent Document 1).

  A mechanism for interrupting this current will be described with reference to FIG. In the upper valve body 1 made of metal foil, a bulging portion that protrudes downward is formed in the central portion, and an easily breakable portion that is a C-shaped thin portion is formed in the bulging portion. In the lower valve body 2 made of metal foil, a bulging portion formed at the periphery of an easily breakable portion made of a circular thin portion having a smaller diameter than the easily breakable portion of the upper valve body 1 is protruded upward at the center portion. Forming. The easily ruptured portions of the upper valve body 1 and the lower valve body 2 are overlapped so that the bulging portions face each other concentrically. An inner gasket 3 made of a ring-shaped insulating material is interposed between the peripheral portions of the upper valve body 1 and the lower valve body 2, and the peripheral edge of the sealing plate case 4 is fixed to the peripheral edge of the cap 5. Then, the sealing board provided with the electric current interruption mechanism which connected the swelling part of the center part of the upper valve body 1 and the lower valve body 2 by laser welding is formed. The upper valve body 1 and the lower valve body 2 are fixed in a state where elasticity is maintained.

  In this sealing plate, the upper valve body 1 and the lower valve body 2 are electrically connected only by a welded portion at the bulging portion formed in the central portion. The pressure at which the current is interrupted depends on the breaking strength of the easily broken portion formed by engraving. That is, when the battery internal pressure rises to a predetermined value, gas flows into the sealing plate from the vent hole provided in the sealing plate case 4, and the easily breakable portion of the lower valve body 2 is broken by the pressure. Since the bulging portion of the lower valve body 2 is welded to the upper valve body 1, the upper valve body 1 is inverted upward by the gas pressure, separated from the lower valve body 2, and the upper valve body 1 and the lower valve body 2. The current is interrupted between.

  When the battery internal pressure further increases, the easily breakable portion of the upper valve body 1 is broken, and the gas is discharged to the outside through the vent hole of the cap 5 from the broken easily broken portion.

A sealing type battery is configured by sealing the sealing plate and the gasket 6 provided with such a mechanism by caulking through a groove provided in the vicinity of the opening of the battery case 7.
JP-A-11-144705

  However, in the conventional sealed battery, since the parts having the above-described mechanism are present in the portion sandwiched between the groove portion of the battery case and the tip of the battery case opening, the sealing portion is thick. It was. When the outer dimensions of the sealed batteries are the same, there is a problem that when the sealing portion is thick, the volume in the battery that stores the power generation element is reduced, and the battery capacity is reduced.

  Therefore, the present invention solves such a conventional problem, and an object of the present invention is to provide a sealed battery that can increase the volume in the battery that houses the power generation element and has a large battery capacity.

  In order to solve the conventional problems, a sealed battery according to the present invention includes a bottomed cylindrical battery case in which a power generation element is housed, the battery case is provided with a groove, and the opening of the battery case is a gasket. Caulking is sealed with a sealing plate. The sealing plate has at least a valve body and a sealing plate case. The valve body has an easily breakable part. The easily breakable portion can be deformed and broken when the internal pressure of the sealed battery increases. The battery case is characterized in that a valve element is not interposed in a portion sandwiched between the groove and the tip of the opening.

  According to the sealed battery of the present invention, the flange portion of the sealing plate formed using the battery case having the groove provided near the opening and the sealing plate case having the flange portion on the outer periphery is caulked through the gasket. Because it is sealed, there is only a gasket for sealing and insulation and a flange in the part sandwiched between the groove and the tip of the battery case opening. Compared to conventional sealed batteries The thickness of the sealing portion can be reduced, and the battery capacity can be increased.

  Moreover, it is preferable to have a PTC thermistor in the sealing plate of a sealed battery. That is, since the resistance of the PTC thermistor increases rapidly when a large current flows, a protection mechanism against overcharge can be configured with high reliability and low cost.

  Here, the PTC thermistor is an element in which conductive carbon and a polymer such as polyolefin and fluorine resin are blended, and when the temperature of the element rises above a certain temperature, the resistance value increases rapidly. It has a function.

  ADVANTAGE OF THE INVENTION According to this invention, the thickness of a sealing part can be made thin, the volume in the battery which accommodates an electric power generation element can be enlarged, and a sealed battery with a large battery capacity can be obtained.

  In the sealed battery according to the embodiment of the present invention, a power generation element is housed in a bottomed cylindrical battery case, the battery case is provided with a groove, and the opening of the battery case is crimped with a sealing plate via a gasket. Has been. The sealing plate has at least a valve body and a sealing plate case. The valve body has an easily breakable part. The easily breakable portion deforms and breaks when the internal pressure of the sealed battery increases. The battery case is characterized in that no valve element is interposed in a portion sandwiched between the groove and the tip of the opening.

  In this way, the gasket sandwiched between the groove and the tip of the battery case opening has only a gasket for sealing and insulation and a flange, so the thickness of the sealing portion is reduced. Is possible.

  Further, since the sealing plate case having the flange portion has a complicated shape, the material is preferably aluminum or aluminum alloy having excellent workability.

  Further, if the sealing plate has a circular shape, since the sealing portion has a circular shape, the flange portion of the gasket and the sealing plate is also circular, and the compression state of the gasket is stable during caulking, and the sealing performance. Will improve.

  The sealing plate of the sealed battery in a preferred embodiment of the present invention preferably has a PTC thermistor.

  By doing so, the temperature of the PTC thermistor rises when a large current flows through the battery, and the resistance rapidly increases accordingly, thereby adding a function of protecting the battery without flowing a large current.

  At that time, it is preferable to insert a PTC thermistor 8 between the upper valve body 1 and the cap 5 as shown in FIG. 2 in that an increase in resistance due to direct contact with the electrolyte can be avoided.

  Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings.

Lithium cobaltate (hereinafter abbreviated as LiCoO ₂ ) as a positive electrode active material, and copolymer P (VDF−) of vinylidene fluoride (hereinafter abbreviated as VDF) and hexafluoroethylene (hereinafter abbreviated as HFP) as a binder. HFP) and acetylene black (hereinafter abbreviated as AB) as a conductive material are kneaded and dispersed in N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) to prepare a positive electrode mixture paste. The positive electrode mixture paste is applied to a 15 μm thick aluminum (hereinafter abbreviated as Al) foil as a current collector, dried and rolled to produce a positive electrode plate having a thickness of 0.150 mm.

  Easily graphitized carbon as a negative electrode active material and P (VDF-HFP) powder as a binder are kneaded and dispersed in a mixed organic solvent composed of acetone and cyclohexanone to prepare a negative electrode mixture paste. The negative electrode mixture paste is applied to a copper foil having a thickness of 12 μm as a current collector, dried and rolled to produce a negative electrode plate having a thickness of 0.160 mm.

  The positive electrode plate and negative electrode plate thus prepared are used as separators to form an electrode group through a microporous polyethylene resin having a thickness of 25 μm.

  A bottomed cylindrical battery case made of iron with nickel plating is produced. The battery case has an outer diameter of 18.0 mm, a bottom plate thickness of 0.3 mm, and a side plate thickness of 0.2 mm.

  The electrode group was inserted into a battery case together with a polypropylene (hereinafter abbreviated as PP) disk-shaped bottom insulating plate, and the negative electrode lead connected to the negative electrode plate by resistance welding and the bottom surface of the battery case were connected by resistance welding.

  Furthermore, after inserting a PP disk-shaped upper insulating plate above the electrode group, a U-shaped groove having a width of 1.0 mm and a depth of 1.5 mm is formed in the circumferential direction by plastic working in the vicinity of the opening of the battery case. To do.

Thereafter, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte is dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) so as to have a concentration of 1.0 mol / L. Adjust the electrolyte. A predetermined amount of the adjusted non-aqueous electrolyte is injected into the battery case containing the electrode group.

  After injecting the non-aqueous electrolyte, the positive electrode lead connected to the positive electrode plate by ultrasonic welding and the sealing plate inserted in the polypropylene (PP) gasket are connected by laser welding. Thereafter, while the positive electrode lead is folded, the sealing plate is inserted into the opening of the battery case, and caulking is performed through the groove to produce a sealed battery.

  Hereinafter, an embodiment of the sealing plate in the sealed battery of the present invention will be described in detail.

Example 1
As shown in FIG. 2, the sealing plate is an upper valve body 1 made of aluminum (hereinafter abbreviated as Al) having a thickness of 0.15 mm and an outer diameter of 12.0 mm, and the upper valve body 1. Thickness 0.1 mm, outer disk 12.7 mm Al disc-shaped lower valve body 2, and thickness 0.4 mm interposed between the peripheral portions of upper valve body 1 and lower valve body 2 A ring-shaped polypropylene (hereinafter abbreviated as PP) inner gasket 3 and a ring-shaped PTC thermistor 8 having a thickness of 0.3 mm and an outer diameter of 11.9 mm, which are superimposed on the upper surface of the peripheral portion of the upper valve body 1; By performing caulking by inserting the iron (hereinafter abbreviated as Fe) cap 5 having an exhaust hole with a thickness of 0.4 mm mounted on the PTC thermistor 8 and inserting each of the above-described members in a stacked state, Thickness 1.8mm on the outer periphery that holds those members Thickness 0.4mm which arranged flange 4a having a vent hole of the outer diameter of 16.6 mm, and a sealing plate casing 4 made of Al outside diameter 13.0 mm. The inner gasket 3 has a shape in which a cylindrical portion extends upward from a peripheral end of a ring-shaped peripheral portion.

  The upper valve body 1 is a C-shaped easily breakable thin-walled portion formed by using a C-shaped inscription around a concave portion whose central portion bulges downward in a curved shape. And have. The lower valve body 2 has an easily breakable thin portion around the center portion by circular marking. These thin-walled portions have a breaking strength that can be broken when the battery internal pressure reaches a predetermined value. The breaking region of the thin portion of the lower valve body 2 is set lower than the breaking strength of the thin portion of the upper valve body 1.

  The central portions of the upper valve body 1 and the lower valve body 2 are connected by laser welding. The upper valve body 1 and the lower valve body 2 are electrically connected by a connecting portion.

  A sealed battery was produced using this sealing plate.

(Comparative Example 1)
As shown in FIG. 1, the sealing plate has an Al disc-shaped upper valve body 1 having a thickness of 0.15 mm and an outer diameter of 15.0 mm, and a thickness of 0.1 mm opposed to the upper valve body 1. An Al disk-shaped lower valve body 2 having an outer diameter of 15.7 mm, and a ring-shaped PP inner with a thickness of 0.4 mm interposed between the peripheral portions of the upper valve body 1 and the lower valve body 2 A gasket 3, a ring-shaped PTC thermistor 8 having a thickness of 0.3 mm and an outer diameter of 14.9 mm superimposed on the upper surface of the peripheral portion of the upper valve body 1, and a plate thickness of 0.4 mm placed on the PTC thermistor 8 And an air hole having a plate thickness of 0.4 mm and an outer diameter of 16.6 mm, which holds the members by inserting the above-described members 5 in a laminated state and caulking them. An Al cylindrical sealing plate case 4 having

  As in Example 1, after injecting the nonaqueous electrolyte, the positive electrode lead connected to the positive electrode plate and the sealing plate inserted in the gasket were connected by laser welding, and the positive electrode lead was folded and the sealing plate was opened to the case It inserted in the part and sealed by caulking through the groove part.

  A sealed battery was produced using this sealing plate.

Total battery height (cap top surface to case bottom surface), sealing portion thickness (thickness of a portion that is caulked with a gasket via a groove), and effective height (battery case) of the sealed batteries of Example 1 and Comparative Example 1 The inner bottom of the groove to the bottom surface) were measured, and the results are shown in Table 1.

  Moreover, the current interruption operating pressure, the internal pressure operating pressure, and the leakage resistance characteristics of these sealed batteries were evaluated.

  The current interruption operating pressure and the internal pressure operating pressure were measured as follows. A sealed battery excluding the electrode group and the non-aqueous electrolyte was manufactured, nitrogen gas was injected into the battery, and the pressure when nitrogen gas leaked from the sealing portion was measured. The average value of battery n = 5 was calculated.

  In terms of leakage resistance, 100 batteries were left in an environment of 60 ° C. for 30 days. After leaving the battery, the presence of leakage was confirmed with a magnifier.

The current interruption operating pressure was 0.91 MPa in Comparative Example 1, whereas it was 0.90 MPa in Example 1. The internal pressure working pressure was 1.95 MPa in Comparative Example 1, whereas it was 1.95 MPa in Example 1. From this result, the performance of the current interruption operating pressure and the internal pressure operating pressure in the sealing plate was equivalent. As for the liquid leakage resistance, no liquid leakage was confirmed in both Example 1 and Comparative Example 1.

  From the above, the effective height in the battery, that is, the volume in the battery that can store the power generation element is increased without changing the performance of the current cutoff operating pressure, the internal pressure operating pressure, and the leakage resistance characteristic of the sealing plate. Thus, a sealed battery that can be obtained can be obtained.

  In addition, although the Example demonstrated the cylindrical sealed battery, it does not specifically limit about the shape of a sealed battery, It can apply to any, such as a button shape, a flat shape, and a square shape.

  Since the sealed battery of the present invention can reduce the thickness of the sealing portion and increase the volume of the battery that houses the power generation element, the sealed battery is useful for electronic devices that use a sealed battery with a high energy density. For example, it is suitable for use as a main power source for consumer mobile tools such as mobile phones and laptop computers, a main power source for power tools such as an electric screwdriver, and an industrial main power source such as an EV car.

Schematic cross-sectional view of a conventional sealed battery 1 is a schematic cross-sectional view of a sealed battery according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper valve body 2 Lower valve body 3 Inner gasket 4 Sealing plate case 4a Flange 5 Cap 6 Gasket 7 Battery case 8 PTC thermistor

Claims (2)

  A power generation element is housed in a bottomed cylindrical battery case, the battery case is provided with a groove, and an opening of the battery case is sealed with a sealing plate via a gasket, The sealing plate has at least a valve body and a sealing plate case, the valve body has an easily breakable portion, and the easily breakable portion is deformed by an increase in internal pressure of the sealed battery. A sealed battery that can be broken and does not include the valve element in a portion of the battery case that is sandwiched between the groove and the tip of the opening. The sealed battery according to claim 1, wherein the sealing plate has a PTC thermistor.