JP2005259511A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of obtaining a stable output property even if charging and discharging with a large current are repeated. <P>SOLUTION: In the battery of this invention, a wound electrode body 8 is housed in a closed vessel wherein a sealing plate 2 is fixed to an opening part of a battery can 1, current collectors 7, 6 are connected with an end edge on a positive electrode side and an end edge on a negative electrode side of the wound electrode body 8 respectively, the first current collector 7 located on an opening part side of the battery can 1 is connected with the sealing plate 2, and the second current collector 6 located on a bottom surface side of the battery can 1 is welded to a bottom surface of the battery can 1. The second current collector 6 has a central part 65 occupying an area where a central hole 80 of the wound electrode body 8 is projected and a ring part 66 expanding outside of the central part 65. A surface of the ring part 66 facing the bottom surface of the battery can is projection welded to the bottom surface of the battery can 1 at a plurality of parts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery configured by accommodating a wound electrode body serving as a battery element in a cylindrical sealed container, and in particular, a so-called tab that does not use a tab to connect the wound electrode body to an electrode terminal portion. This is related to a less-type battery.

In recent years, lithium ion secondary batteries having high energy density and high output density have attracted attention as power sources for portable electronic devices and electric vehicles.
For example, in the cylindrical lithium ion secondary battery shown in FIG. 5, the winding electrode body (8) is accommodated in the bottomed cylindrical battery can (1), and the opening of the battery can (1) is accommodated. The sealing plate (2) is caulked and fixed via the insulating member (3) to form an airtight container. A gas exhaust valve (22) and a positive electrode terminal (21) are attached to the sealing plate (2).

  As shown in FIG. 6, the take-up electrode body (8) is constituted by interposing a strip-shaped separator (83) between the strip-shaped positive electrode (82) and the negative electrode (81) and winding them in a spiral shape. Has been. The positive electrode (82) is configured by applying a positive electrode active material made of a lithium composite oxide on both surfaces of a strip-shaped core made of aluminum foil, and the negative electrode (81) is a carbon material on both surfaces of a strip-shaped core made of copper foil. It is comprised by apply | coating the negative electrode active material containing. The separator (83) is impregnated with a non-aqueous electrolyte.

  Here, the positive electrode (82) and the negative electrode (81) are superimposed on the separator (83) while being shifted in the width direction, and wound in a spiral shape. As a result, the core body edge of the positive electrode (82) protrudes outward from the edge of the separator (83) at one of the ends in the winding axis direction of the winding electrode body (8). At the other end, the core body edge of the negative electrode (81) protrudes outward from the edge of the separator (83).

Current collector plates (7) and (71) are joined to the positive electrode side edge and the negative electrode side edge of the winding electrode body (8), respectively. The current collector plate (7) on the positive electrode side has a central hole (70), a plurality of ridges (73) projecting in a circular arc shape toward the winding electrode body (8), and a winding electrode body (8). A plurality of cut-and-raised portions (74) projecting to the side are formed, and a strip-shaped lead portion (72) is projected. On the other hand, the negative current collector plate (71) has a plurality of protrusions (73) whose cross section protrudes in an arc shape toward the winding electrode body (8), and the winding electrode body (8) side. A plurality of cuts (74) are formed.
Then, laser welding is performed in a state where the protrusions (73) and the cuts (74) of the current collector plates (7) and (71) are pressed against the edge of the winding electrode body (8), as shown in FIG. Both current collecting plates (7) and (71) are joined to both ends of the winding electrode body (8).

  The leading end of the lead portion (72) projecting from the positive current collector plate (7) is welded to the back surface of the sealing plate (2). The current collector plate (71) on the negative electrode side is welded to the bottom surface of the battery can (1). Thereby, the battery can (1) becomes a negative electrode, and the electric power generated by the winding electrode body (8) can be taken out from the positive electrode terminal (21) and the battery can (1).

When the current collector plate (71) on the negative electrode side is welded to the bottom surface of the battery can (1), the electrode is directed from the central hole (80) of the winding electrode body (8) toward the current collector plate (71). A rod is inserted, and the central portion of the current collector plate (71) is resistance-welded to the bottom surface of the battery can (1) (see Patent Document 1).
Japanese Patent Laid-Open No. 2002-134095

  However, in the conventional secondary battery, the current collector plate (71) located on the bottom surface side of the battery can (1) has a structure in which the central portion is resistance-welded to the bottom surface of the battery can (1). The current at the time of charging / discharging concentrates on the resistance weld, and local heat is generated in the resistance weld. For example, when the battery can (1) is a negative electrode, nickel or copper is used as the material for the current collector plate (71) on the negative electrode side, while nickel plating is applied to the iron base as the material for the battery can (1). The applied one is used. Therefore, especially when charging and discharging with a large current is repeated over a long period of time, due to the difference in the thermal expansion coefficient between the battery can (1) and the current collector plate (71), which are different materials, due to the thermal cycle. The thermal stress which acts will act on a welding part repeatedly. As a result, there is a problem that defects such as cracks are generated in the welded portion, resulting in poor connection, and stable output characteristics cannot be obtained due to an increase in connection resistance.

  Therefore, an object of the present invention is to provide a battery that can obtain stable output characteristics even when charging and discharging with a large current are repeated.

In the battery according to the present invention, a battery element is formed inside a sealed container in which a sealing plate (2) is fixed to an opening of a bottomed cylindrical battery can (1) via an insulating member (3). A winding electrode body (8) is accommodated, and current collecting plates (7) and (6) are joined to the positive electrode side edge and the negative electrode side edge of the winding electrode body (8), respectively. The first current collecting plate (7) located on the opening side of 1) is connected to the sealing plate (2), while the second current collecting plate (6) located on the bottom side of the battery can (1). Is welded to the bottom surface of the battery can (1), and the electric power generated by the winding electrode body (8) can be taken out from the sealing plate (2) and the battery can (1).
The second current collector plate (6) located on the bottom surface side of the battery can (1) has a central portion (65) occupying a region projected from the central hole (80) of the winding electrode body (8), and the center An annular portion (66) extending outside the portion (65), and a surface of the annular portion (66) facing the bottom surface of the battery can is welded to the bottom surface of the battery can (1) at a plurality of locations.

  Specifically, a plurality of projections 61 project from the surface of the annular portion 66 of the second current collector plate 6 facing the bottom surface of the battery can or the bottom surface of the battery can 1. The current collector plate (6) is resistance welded (projection welded) to the bottom surface of the battery can (1) by the projection (61).

In the battery of the present invention, the current collector plate (6) located on the bottom surface side of the battery can (1) is resistance-welded to the bottom surface of the battery can (1) at the central portion (65) as in the prior art. However, since the annular portion (66) located on the outer peripheral side is resistance-welded to the bottom surface of the battery can (1), the current accompanying charging / discharging is the resistance welding portion of the annular portion (66), that is, the current collector. It flows through a wide area of the electric plate (6). Therefore, the current at the time of charging / discharging does not concentrate on the resistance welded portion as in the prior art, and the heat generation is thereby reduced.
Therefore, even when charging / discharging with a large current is repeated over a long period of time, the thermal stress acting on the resistance welded portion is smaller than before, and as a result, there is almost no risk of defects such as cracks in the welded portion. Stable output characteristics can be obtained over a long period of time.

In a specific configuration, an insulating sheet (5) is interposed between the second current collector plate (6) and the bottom surface of the battery can (1).
According to the specific configuration, in the step of resistance welding the current collector plate (6) to the bottom surface of the battery can (1), in the region other than the predetermined resistance welded portion (projection forming portion), the current collector plate (6) Since the insulation sheet (5) is interposed between the bottom surface of the battery can (1) and the electric insulation is provided, a current flows only in a predetermined resistance welding portion, and uniform resistance welding is realized.

  According to the battery of the present invention, stable output characteristics can be obtained over a long period of time even when charging / discharging with a large current is repeated.

Hereinafter, the embodiment in which the present invention is applied to a lithium ion secondary battery will be specifically described with reference to the drawings.
A lithium ion secondary battery according to the present invention, as shown in FIG. 1, accommodates a wound electrode body (8) inside a bottomed cylindrical battery can (1), and has an opening in the battery can (1). The sealing plate (2) is caulked and fixed through an insulating member (3). A gas discharge valve (22) and a positive electrode terminal (21) are attached to the sealing plate (2).

  The take-up electrode body (8) is the same as the conventional structure shown in FIG. 6, and a belt-like separator (83) is interposed between the belt-like positive electrode (82) and the negative electrode (81), respectively. It is wound up in a spiral shape.

  As shown in FIG. 1, current collector plates (7) and (6) are joined to the positive electrode side edge and the negative electrode side edge of the winding electrode body (8), respectively. The current collector plate (7) on the positive electrode side has the same structure as the conventional structure shown in FIG. On the other hand, as shown in FIG. 1, the current collector plate (6) on the negative electrode side has a circular central portion (65) occupying a region projected from the central hole (80) of the winding electrode body (8), and the central portion. And an annular portion (66) extending outward from (65).

As shown in FIG. 2, the annular portion (66) of the current collector plate (6) has a plurality of ridges (62) protruding in a circular arc shape in cross section toward the winding electrode body and a plurality of protrusions protruding toward the winding electrode body. Cutouts (63) and (64) are formed radially, and a plurality of (eight) projections (61) are formed surrounding the central portion (65). Each projection (61) protrudes toward the bottom surface of the battery can (1) as shown in FIG. In addition, it is desirable that the projections (61) are evenly arranged at 3 to 9 locations along a circumferential line having a diameter of ¼ to ¾ of the inner diameter of the bottom surface of the battery can (1).
Then, laser welding is performed in a state where the protrusions and cuts of the current collector plates (7) and (6) are pressed against the edge of the winding electrode body (8), and both current collector plates (7 ) (6) is joined to both ends of the winding electrode body (8).

  The leading end of the lead portion (72) projecting from the positive current collector plate (7) is welded to the back surface of the sealing plate (2). The current collector plate (6) on the negative electrode side is resistance welded to the bottom surface of the battery can (1). Thereby, the battery can (1) becomes a negative electrode, and the electric power generated by the winding electrode body (8) can be taken out from the positive electrode terminal (21) and the battery can (1).

In the process of assembling the lithium ion secondary battery of the present invention, after the current collector plates (7) and (6) are laser welded to the winding electrode body (8), the winding electrode body (8) is removed from the battery can. House in (1).
First, the current collector plate (6) on the negative electrode side is resistance-welded to the bottom surface of the battery can (1), and then the tip of the lead portion (72) extending from the current collector plate (7) on the positive electrode side is sealed with the sealing plate (2 ) Welded to the back. Subsequently, after injecting the electrolyte into the battery can (1), the sealing plate (2) is caulked and fixed to the opening of the battery can (1) through the insulating member (3).

In the process of resistance welding the current collector plate (6) on the negative electrode side to the bottom surface of the battery can (1), a plurality of projections (61) of the current collector plate (6) are brought into contact with the bottom surface of the battery can (1). In this state, one electrode rod is inserted from the central hole (80) of the winding electrode body (8) and brought into contact with the central portion (65) of the current collector plate (6), and the back surface of the battery can (1) The other electrode rod is brought into contact with the electrode, and electricity is applied between the two electrode rods.
As a result, current flows through the plurality of projections (61), and the current collector plate (6) is resistance-welded (projection welding) to the bottom surface of the battery can (1).

In the lithium ion secondary battery of the present invention, the current collector plate (6) located on the bottom surface side of the battery can (1) has a resistance against the bottom surface of the battery can (1) at the central portion (65) as in the prior art. Rather than being welded, it is resistance welded to the bottom surface of the battery can (1) by the projection (61) projecting from the annular portion (66) located on the outer peripheral side. It flows through a wide area where a plurality of projections (61) are formed. For this reason, the current at the time of charging / discharging does not concentrate on the resistance welded portion as in the prior art, and the heat generation is slight.
Therefore, even when charging / discharging with a large current is repeated over a long period of time, the thermal stress acting on the resistance welded portion is smaller than before, and as a result, there is almost no risk of defects such as cracks in the welded portion. Stable output characteristics can be obtained over a long period of time.

A battery can (1) having an outer diameter of 3 mm and an inner diameter of 35 mm of the present invention current collector plate is employed, and a current collector plate (6) on the negative electrode side having a diameter of 34 mm is used along a circumferential line having a radius of 9 mm. The projections (61) having a height of 0.5 mm were evenly formed at 8 locations.
In addition, as shown in FIG. 1, a polypropylene insulating sheet (5) having a thickness of 0.3 mm is interposed between the current collector plate (6) and the bottom surface of the battery can (1) to project the projection (61). The current collector plate (6) and the battery can (1) were prevented from coming into contact with each other in the other area. The insulating sheet (5) has a through hole having a diameter of 2 mm at a position corresponding to the projection (61).

Comparative current collector A comparative current collector similar to the current collector of the present invention except that projections with a height of 0.5 mm were uniformly formed at eight locations along a circumferential line with a radius of 2.5 mm. An electric plate was produced.

As shown in FIG. 4, the current collector plate (6) of the present invention was resistance-welded to the bottom surface of the battery can (1) (invention example) and the comparative current collector plate was resistance-welded to the bottom surface of the battery can. An energization test was conducted on the object (comparative example). The insulating sheet (5) was interposed between the current collector plate and the bottom surface of the battery can.

In the energization test, a copper energization lead (91) having a thickness of 1 mm and a width of 2 cm is laser welded to the current collector plate (6) as shown in FIG. 4, and the back surface of the battery can (1) is energized. A nut (9) was attached, and the connection resistance between the current collector plate (6) and the battery can (1) was measured at an alternating current of 1 kHz.
Thereafter, energization of 200 A for 10 seconds and rest for 1 minute were repeated 200 times, and then the connection resistance was measured again. The results (average value of 10 samples) are shown in Table 1 below.

  As is clear from Table 1, in the present invention example, the amount of increase in resistance before and after the energization test is smaller than that in the comparative example, which realizes a stable connection state between the current collector plate and the battery can. It is confirmed that it is done.

  As described above, according to the secondary battery of the present invention, the current accompanying charging / discharging flows through a wide area of the current collector plate (6), so that the concentration of current is low, thereby generating little heat. It will be a thing. Therefore, even when charging / discharging with a large current is repeated over a long period of time, the thermal stress acting on the resistance welded portion is smaller than before, and as a result, there is almost no risk of defects such as cracks in the welded portion. Stable output characteristics can be obtained over a long period of time.

  Further, according to the configuration in which the insulating sheet (5) is interposed between the current collector plate (6) and the bottom surface of the battery can (1), the current collector plate (6) is resistance to the bottom surface of the battery can (1). In the welding process, since electric insulation is performed by the insulating sheet (5) in the region other than the projection forming portion, a current flows only in the projection forming portion. As a result, the height of the projection and the thickness of the current collector plate are not limited, and a connection by uniform resistance welding is possible.

It is sectional drawing of the lithium ion secondary battery which concerns on this invention. It is a back view of a current collecting plate. It is an expanded sectional view of a projection formation part. It is sectional drawing which shows the structure at the time of connection resistance measurement. It is sectional drawing of the conventional lithium ion secondary battery. It is a disassembled perspective view of a winding electrode body and a current collecting plate.

Explanation of symbols

(1) Battery can
(2) Sealing plate
(3) Insulation material
(5) Insulation sheet
(6) Current collector
(61) Projection
(65) Central part
(66) Annular part
(7) Current collector
(8) Winding electrode body
(80) Through hole

Claims (3)

  A wound electrode body (8) serving as a battery element is placed inside a sealed container in which a sealing plate (2) is fixed to an opening of a bottomed cylindrical battery can (1) via an insulating member (3). A current collector plate (7) (6) is joined to the positive electrode side edge and the negative electrode side edge of the winding electrode body (8), respectively, and is positioned on the opening side of the battery can (1). The first current collector plate (7) is connected to the sealing plate (2), while the second current collector plate (6) located on the bottom side of the battery can (1) is connected to the battery can (1). In the battery which can be taken out from the sealing plate (2) and the battery can (1) and the electric power generated by the winding electrode body (8) can be taken out from the sealing plate (2) and the battery can (1), the second is located on the bottom side of the battery can (1). The current collector plate (6) includes a central part (65) occupying a region projected from the central hole (80) of the winding electrode body (8), and an annular part (66) extending outside the central part (65). The surface of the annular portion (66) facing the bottom surface of the battery can has a plurality of locations on the battery can (1). Cell characterized by being welded to the surface.   A plurality of projections (61) project from the surface of the annular portion (66) of the second current collector plate (6) facing the bottom surface of the battery can or the bottom surface of the battery can (1). The battery according to claim 1, wherein the current collector plate (6) is resistance-welded to the bottom surface of the battery can (1) by (61). The battery according to claim 1 or 2, wherein an insulating sheet (5) is interposed between the second current collector plate (6) and the bottom surface of the battery can (1).

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