JP2007193966A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery of a structure securing a sealing property and enabling easy assembly. <P>SOLUTION: The battery, housing a power generating element winding around a cathode plate and an anode plate through separators in a battery case with an opening airtightly sealed with a lid body, has a tab drawn out of the power generating element and an inner terminal electrically connected, an outer terminal connected to the opening of the inner terminal by caulking, and the inner and outer terminals fixed to the lid body in a state electrically insulated from it through gaskets. The outer terminal is provided with a stepped part at a part connected with the inner terminal, and the part connected with the inner terminal is narrowed enough to be insertion-coupled with the opening of the inner terminal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery, particularly to a terminal portion thereof.

  In recent years, portable and cordless electronic devices such as AV devices, personal computers, and portable communication devices have been rapidly promoted. Conventionally, nickel cadmium batteries and nickel hydrogen batteries have been used as power sources for driving these electronic devices. However, in recent years, non-aqueous electrolyte secondary batteries represented by lithium secondary batteries capable of rapid charging, high energy density, and high safety are becoming mainstream. In this non-aqueous electrolyte secondary battery, a rectangular non-aqueous electrolyte secondary battery that is excellent in high energy density and load characteristics, is suitable for thinning electronic devices, and has good space efficiency has been extended. In the rectangular nonaqueous electrolyte secondary battery, tabs are attached to the bipolar plates of the power generation element, connected to the internal terminals, and electricity is taken out through the external terminals connected to the internal terminals. When a metal battery case is used, the tab connected to the electrode plate having the same polarity as the battery case is directly connected to the case or a metal lid joined to the case. The tab connected to the electrode plate having a polarity different from that of the battery case is connected to the internal terminal, and the internal terminal is insulated from the battery case or the metal lid by a gasket. Furthermore, the gasket also plays a role of ensuring airtightness.

The structure of a conventional battery uses a caulked external terminal in the shape of a hollow rivet. A schematic cross-sectional view around the external terminal of a conventional battery is shown in FIG. In FIG. 4, an upper gasket is disposed in an attachment hole formed in a metal lid, and a hollow rivet is inserted from above. The lower gasket and the internal terminal are inserted into the lower part of the hollow rivet, the lower end of the hollow rivet is caulked, and the hollow rivet is sealed with the upper gasket and the lower gasket (see, for example, Patent Document 1).
JP 2001-202933 A

  However, the conventional battery is sealed by caulking with a hollow rivet through an upper gasket and a lower gasket and compressing the gasket. By changing the caulking dimension, the compression ratio of the gasket changes, which affects the sealing performance. For this reason, an accurate caulking technique and a caulking method for minimizing fluctuations in caulking dimensions are required, and there is a problem that productivity does not increase.

  Therefore, the present invention solves such a conventional problem, and an object thereof is to provide a battery with improved sealing performance that does not depend on caulking dimensions.

In order to solve the above-described conventional problems, the battery of the present invention includes a battery case having an opening in which a power generation element in which a positive electrode plate and a negative electrode plate are wound via a separator is housed, and the opening of the battery case is Part is sealed with a lid,
The tab pulled out from the power generation element and the internal terminal are electrically connected, and the external terminal is connected to the opening portion of the internal terminal by caulking,
The internal terminal and the external terminal are fixed to the lid body in a state of being electrically insulated via a gasket,
The external terminal has a stepped portion at a portion connected to the internal terminal,
The portion connected to the internal terminal is thin enough to fit into the opening of the internal terminal.

  By using the external terminal of the present invention, it is possible to absorb the variation of the caulking dimension and to ensure the sealing performance.

  By providing a step on the external terminal, fluctuations in the caulking dimension are absorbed by the deformation of the external terminal, and the compression of the gasket is determined by the height of the stepped part of the external terminal, thus stabilizing the caulking dimension and improving the sealing performance. can do.

  According to the present invention, a battery with improved sealing performance can be obtained.

The non-aqueous electrolyte secondary battery in the embodiment of the present invention is
A battery case having an opening stores a power generation element in which a positive electrode plate and a negative electrode plate are wound through a separator, and the opening of the battery case is sealed with a lid,
The tab pulled out from the power generation element and the internal terminal are electrically connected,
An external terminal is connected to the opening of the internal terminal by caulking,
The internal terminal and the external terminal are fixed to the lid body in a state of being electrically insulated via a gasket,
The external terminal has a stepped portion at a portion connected to the internal terminal,
The portion connected to the internal terminal is thin enough to fit into the opening of the internal terminal.

  By doing so, variation in the caulking dimension is absorbed by deformation of the external terminal, and compression of the gasket is determined by the height of the stepped portion of the external terminal, so that the caulking dimension is stabilized and the sealing performance can be improved. .

  In the nonaqueous electrolyte secondary battery according to a preferred embodiment of the present invention, a portion connected by caulking of the external terminal and the internal terminal is welded.

  By so doing, fluctuations in internal resistance can be suppressed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the present invention is not limited to the examples described below.

(Embodiment 1)
FIG. 1 is a cut front view showing a lithium ion secondary battery according to an embodiment of the present invention, and FIG. 2 is a cut right side view of the battery. The battery case 1 is made of an aluminum alloy, is a rectangular outer can having an opening at the upper end, and also serves as a positive electrode terminal. Further, the battery case 1 may be made of iron whose surface is nickel-plated, and in that case, also serves as a negative electrode terminal.

  Inside the battery case 1, a power generation element 2 is housed in an electrically insulated state with respect to the bottom surface by means of insulating tape or the like (not shown). An upper insulating plate 3 is inserted for electrical insulation. Although not shown, the power generation element 2 is flattened corresponding to the rectangular battery case 1 by press molding after winding the positive electrode plate and the negative electrode plate into a non-circular spiral shape with a separator interposed therebetween. The winding shaft is inserted into the battery case so that its winding axis is perpendicular to the opening surface of the battery case 1.

The positive electrode plate may be prepared by a conventionally known method. A paste obtained by kneading and dispersing a positive electrode active material, a conductive agent, and a binder in a solvent is applied to both surfaces of an aluminum foil current collector, dried, and rolled. To make.

As the positive electrode active material, the conductive agent, the binder, and the solvent, conventionally known materials may be used. In this embodiment, the positive electrode active material is lithium cobaltate (LiCoO ₂ ), the conductive agent is acetylene black, the binder is polyvinylidene fluoride (PVDF) and its copolymer, and the solvent is N -Methyl-2-pyrrolidone (NMP) is preferred. The negative electrode plate may be prepared by a conventionally known method. A paste obtained by kneading and dispersing a negative electrode active material, a conductive agent, and a binder in a solvent is applied to both sides of a copper foil current collector, dried, and rolled. To make.

  A conventionally well-known substance may be used for a negative electrode active material, a electrically conductive agent, a binder, and a solvent. In the present embodiment, the negative electrode active material is preferably a carbon material such as graphite, the conductive agent is acetylene black, the binder is PVDF and a copolymer thereof, and the solvent is NMP.

  The separator is preferably a microporous polyolefin resin such as polyethylene (PE) resin or polypropylene resin.

  The method of press-molding the power generating element 2 is heated to a temperature equal to or lower than the softening point of the binder used for the electrode plate and pressed at a pressure of 1.0 MPa to 7.0 MPa.

  The opening of the battery case 1 is sealed by laser welding the welded portion 5 after the metal lid 4 is fitted. Further, the lid 4 has a safety valve 6. The safety valve 6 may be a conventionally known one, but when the gas pressure inside the battery becomes abnormally high, it is a non-returning type that releases gas by destruction. Specifically, the clad plate type or the stamp type is cheaper Therefore, it is preferable because the lid 4 can be installed even if it is thin. A positive electrode tab 7 is connected to the lid 4.

  Furthermore, the rivet-shaped external terminal 9 is inserted into the opening portion of the internal terminal 8 and caulked to be fixed to the lid body 4. The opening portion of the internal terminal 8 passes through the shaft tip of the external terminal 9 and stays at the stepped portion. The internal terminal 8 is electrically insulated from the lid 4 by the lower gasket 10 and the upper gasket 11. As shown in FIG. 2, a negative electrode tab 12 drawn out from the gap 20 of the upper insulating plate 3 is connected to the internal terminal 8. A lower gasket 10 and a U-shaped upper insulating plate 3 are arranged so as to close the negative electrode tab 12.

  As the material for the internal terminals 8 and the external terminals 9, it is preferable to use stainless steel, iron whose surface is nickel-plated, or copper or copper alloy with good formability in order to facilitate electrical connection between the terminals. The above materials are also preferable when welding the external terminal and the external lead, which is mainly nickel, and the internal terminal and the negative electrode tab. The upper gasket 11 uses a fluororesin having a high heat resistance temperature as a main material in order to prevent leakage of the non-aqueous electrolyte due to the influence of heat when the battery case 1 and the lid 4 are fitted and laser-welded. Is preferred. On the other hand, for the same reason as the upper gasket 11 described above, the lower gasket 10 is preferably made of a fluororesin having a high heat resistance as a main material. Depending on the size and shape of the battery width, polypropylene (PP) or polyphenylene sulfide is preferable. It is preferable to use different resins such as (PPS).

The lid 4 is provided with a liquid injection hole 13 for injecting a nonaqueous electrolytic solution. A nonaqueous electrolytic solution (not shown) is injected into the battery case 1 from the injection hole 14. The nonaqueous electrolytic solution is composed of a nonaqueous solvent and an electrolyte salt, and the nonaqueous solvent is composed of a mixture of a cyclic carbonate and a chain carbonate as main components. The cyclic carbonate is preferably ethylene carbonate (EC), and the chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). As the electrolyte salt, for example, a lithium salt having a strong electron withdrawing property is used. Specifically, LiPF ₆ , LIBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F _{5 are used.} ) ₂ etc. These electrolyte salts may be used in combination of two or more, and are preferably dissolved at a concentration of 0.5 to 1.5 mol / L in the non-aqueous solvent.

  When the injection of the non-aqueous electrolyte is finished, the injection hole 13 is fitted with a sealing plug 14 formed by integrally molding an aluminum plate and a rubber plug, and hermetically sealed by laser welding.

In the embodiment, the lithium ion secondary battery is taken as an example, but the power generation element itself may be another battery system such as an alkaline storage battery.
In addition, although an example using an upper insulating plate having a U-shaped cross section was given, the negative electrode tab may be used in combination with a U-shaped lower gasket and a flat upper insulating plate, or in other shapes. Any structure may be used as long as the case is insulated.

(Embodiment 2)
FIG. 3 is a cut front view of a sealing structure portion according to another embodiment of the present invention. A rivet-shaped external terminal 9 is inserted into the opening portion of the internal terminal 8 and caulked to be fixed to the lid body 4. Thereafter, the external terminal 9 and the internal terminal 8 are welded. By so doing, fluctuations in internal resistance can be suppressed.

  In the case of maintaining continuity by contact of components inside the battery, it is desirable to perform welding in order to improve reliability. FIG. 5 shows a cut front view of a sealing structure portion in which a solid external terminal 209 without a step is caulked. When the external terminal 209 having a solid rivet shape without a stepped portion is used and the opening portion of the internal terminal 208 is inserted and caulked through the external terminal 209, the tip diameter of the external terminal 209 is the opening portion of the internal terminal 208. About 0.01 to 0.2 mm larger than the diameter. After caulking with an external terminal having no stepped portion, when the interface between the external terminal and the internal terminal is laser-welded, as described above, the difference between the tip diameter of the external terminal 209 and the aperture diameter of the internal terminal 208 is extremely large. Since it is small, the laser light enters between the corners of the external terminal 209 and the internal terminal 208, melts the lower gasket 210 or the upper gasket 211, and the airtightness of the battery is lowered. Therefore, in the structure according to the present invention, when the interface between the external terminal 9 and the internal terminal 8 is laser-welded, the welded portion is on the internal terminal 8 and the stepped portion of the external terminal 9 (the internal terminal stays) even if the penetration becomes deep. Surface), the gasket is not melted, and the sealing performance is not lowered. Here, the difference between the tip diameter and the root diameter of the stepped external terminal is preferably 0.2 mm or more.

  The battery of the present invention is useful for an electronic device using a high energy density sealed battery. 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.

Cutting front view of the battery shown in Embodiment 1 of the present invention Cut right side view of the battery shown in Embodiment 1 of the present invention Cutting front view of the sealing structure shown in Embodiment 2 of the present invention Cutting front view of a sealing structure in a conventional battery (hollow external terminal) Cutting front view of the sealing structure in a conventional battery (solid external terminal, welding)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Power generation element 3 Upper insulating plate 4 Cover body 5 Welding part 6 Safety valve 7 Positive electrode tab 8 Internal terminal 9 External terminal 10 Lower gasket 11 Upper gasket 12 Negative electrode tab 13 Injection hole 14 Sealing plug 20 Upper insulating plate gap 21 Welded part of external terminal and internal terminal 104 Cover of conventional example (hollow external terminal) 108 Conventional example (hollow external terminal) Internal terminal 109 External terminal of conventional example (hollow external terminal) (hollow rivet)
110 Conventional gasket (hollow external terminal) lower gasket 111 Conventional gasket (hollow external terminal) upper gasket 204 Lid of conventional example (solid external terminal) 208 Internal terminal of conventional example (solid external terminal) 209 Conventional example ( External terminal (solid rivet)
210 Lower gasket of conventional example (solid external terminal) 211 Upper gasket of conventional example (solid external terminal)

Claims (2)

In a battery case having an opening, a power generation element in which a positive electrode plate and a negative electrode plate are wound via a separator is housed, and the opening of the battery case is sealed with a lid,
The tab pulled out from the power generation element and the internal terminal are electrically connected,
An external terminal is connected to the opening of the internal terminal by caulking,
The battery in which the internal terminal and the external terminal are fixed to the lid body in a state of being electrically insulated via a gasket,
The external terminal has a stepped portion at a portion connected to the internal terminal,
The battery which is thin to such an extent that the portion connected to the internal terminal fits into the opening of the internal terminal. The battery according to claim 1, wherein the external terminal is welded at a portion connected to the internal terminal by caulking.