JP2003263977A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a laser reflectance when a collecting plate 50 is joined to an edge of a winding electrode 4 by laser welding in a secondary battery in which the collecting plate 50 is joined to the edge of the winding electrode 4 and in which an electric power of the winding electrode 4 can be supplied through the collecting plate 50. <P>SOLUTION: In the secondary battery, a plurality of circular convex portions 52 and bended pieces 53 projecting toward the winding electrode 4 side are formed on the collecting plate 50, an inner surface of the circular convex portions 52 is roughened and the circular convex portions 52 are welded to a core end 48 by laser with the circular convex portions 52 and the bended portions 53 embedded in the core end 48 of the winding electrode 4 in the collecting plate 50. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention contains an electrode body, which is a secondary battery element, housed inside a battery can, and the power generated by the electrode body can be taken out from a pair of electrode terminal portions provided on the battery can. It relates to the next battery.

[0002]

2. Description of the Related Art In recent years, lithium ion secondary batteries having high energy density have been attracting attention as power sources for portable electronic devices, electric vehicles and the like. For example, a relatively large capacity cylindrical lithium-ion secondary battery used in electric vehicles is
As shown in FIGS. 3 and 4, the lid body (12) is provided on both ends of the tubular body (11).
Inside the cylindrical battery can (1) formed by welding and fixing (12),
The winding electrode body (4) is housed. Both lids
A pair of positive and negative electrode terminal mechanisms (9) and (9) are attached to (12) and (12), and the two poles of the winding electrode body (4) and the two electrode terminal mechanisms (9) and (9) are mutually connected. Connected and wound electrode body
It is possible to take out the electric power generated by (4) from the pair of electrode terminal mechanisms (9), (9) to the outside. Also, each lid (1
A pressure opening / closing type gas discharge valve (13) is attached to 2).

The winding electrode body (4), as shown in FIG.
A strip-shaped separator (42) is interposed between a strip-shaped positive electrode (41) and a strip-shaped negative electrode (43), and these are spirally wound. The positive electrode (41) is formed by applying a positive electrode active material (44) made of a lithium composite oxide on both surfaces of a strip-shaped core body (45) made of aluminum foil, and the negative electrode (43) is a strip-shaped core made of copper foil. Anode active material containing carbon material on both sides of body (47) (46)
Is applied. The separator (42) is impregnated with the non-aqueous electrolytic solution.

Here, the positive electrode (41) and the negative electrode (43) are stacked on the separator (42) while being shifted in the width direction, and wound in a spiral shape. As a result, one of the two ends of the winding electrode body (4) in the winding axis direction is
Positive electrode (41) core (45) outward from the edge of the separator (42)
Of the core body (47) of the negative electrode (43) outward from the edge of the separator (42) while the edge (48) of the negative electrode (48) projects.
(48) is protruding. Then, a disk-shaped current collector plate (5) is joined to both ends of the winding electrode body (4), respectively, and a strip-shaped current collector plate (5) protruding from the flat plate-shaped main body (51) is provided. Lead part
(55) is connected to the base end of the electrode terminal mechanism (9) shown in FIG.

The electrode terminal mechanism (9) is, as shown in FIG. 4, an electrode terminal attached through the lid (12) of the battery can (1).
(91), and a flange (92) at the base end of the electrode terminal (91)
Are formed. An insulating packing (93) is attached to the through hole of the lid body (12) to maintain electrical insulation and sealing between the lid body (12) and the fastening member (91). A washer (94) is fitted to the electrode terminal (91) from the outside of the lid body (12), and a first nut (95) and a second nut (96) are screwed together. Then, tighten the first nut (95) to secure the electrode terminal (9
The insulating packing (93) is pinched by the flange (92) and the washer (94) of 1) to improve the sealing property.
In the current collector plate (5), the flat plate-shaped main body (51) is joined to the core body edge (48) of the winding electrode body (4) by laser welding,
The tip of the lead (55) is the flange (92) of the electrode terminal (91).
Is fixed by spot welding or ultrasonic welding.

By the way, particularly in a lithium ion secondary battery used as a power source for an electric vehicle or the like, it is necessary to reduce the internal resistance as much as possible in order to obtain a high capacity and a high output. Therefore, in order to reduce the internal resistance of the secondary battery, in the current collecting structure shown in FIG. 5, as shown in FIGS. 6 and 7, the flat plate-like main body of the current collecting plate (5) is used.
A plurality of arcuate convex portions (52) radially extending around the central hole (54) are integrally molded in the (51), and the winding electrode body (4) is formed.
It projects to the side. Further, in the flat plate-shaped main body (51), a plurality of cut-and-raised pieces (53) are formed between the adjacent arc-shaped convex portions (52) (52), respectively, and the winding electrode body (4) side Overhangs.

In the process of manufacturing the secondary battery having the current collecting structure, as shown in FIGS. 8 and 10, the core body edge (48) formed at the end of the winding electrode body (4) is Current collector
Press (5). As a result, the arcuate convex portion (52) of the current collector plate (5) bites into the core body end edge (48) of the winding electrode body (4) as shown in FIG. 9 to form the arcuate convex portion (52). A joining surface formed of a cylindrical surface is formed between the core body end edges (48). The cut-and-raised pieces (53) of the current collector plate (5) bite deeply into the core body edge (48) of the winding electrode body (4) as shown in FIG.
It will be crimped with 8).

In this state, as shown by an arrow in FIG. 9, a laser beam is irradiated toward the surface (inner peripheral surface) of the arcuate convex portion (52) of the current collector plate (5) to perform laser welding. Give. As a result, the arcuate convex portion (52) of the current collector plate (5) and the core body edge (48) of the winding electrode body (4) are joined to each other with a large contact area, and as shown in FIG. The crimped state between the cut-and-raised piece (53) and the core body edge (48) is maintained.

Therefore, the current collector plate (5) has the arcuate convex portions (52).
With a large contact area at the welded portion of the core edge (48) with the core edge
While being joined to (48), in a region other than the welded portion, each cut-and-raised piece (53) bites into the core body edge (48), and a good contact state is obtained, so that the current collector plate ( 5) and winding electrode body
The contact resistance between (4) becomes small. However, due to the plurality of cut and raised pieces (53) formed on the current collector plate (5), the edge of the core body is
Since current is collected from all over (48), high current collecting performance can be obtained.

[0010]

However, as shown in FIG. 9, the surface of the arcuate convex portion (52) of the current collector plate (5) is irradiated with a laser beam to wind up the current collector plate (5). In the process of laser welding to the edge (48) of the core body of the electrode body (4), the collector plate is used.
Since the laser reflectance on the surface of (5) is high,
A large laser power was required in order to give sufficient heat energy to the joint between the core body edge (48) of the winding electrode body (4) and (5). In particular, when a low resistance Cu current collector is used in place of the Ni current collector that has been used conventionally, Cu has a much higher laser reflectance than Ni, so laser welding is difficult. However, there is a problem in that the required welding strength cannot be obtained, or the strength fluctuates and reliability decreases.

To solve this problem, there has been proposed a method of lowering the laser reflectance by forming a film having low reflectance on the laser receiving surface (Japanese Patent Laid-Open No. 62-283).
No. 554), in this method, the film remains after laser welding and is exposed to the electrolytic solution in the battery can, so that the components of the film become mist, which adversely affects the battery characteristics. .

Therefore, an object of the present invention is to reduce the laser reflectance when laser welding the current collector plate to the end of the electrode body, and still maintain good battery characteristics. It is to provide a secondary battery.

[0013]

In a secondary battery according to the present invention, a strip-shaped positive electrode (41) is provided inside a battery can (1).
The electrode body (4) in which the separator (42) is interposed between the negative electrode (43) and the negative electrode (43) is housed, and the positive electrode (41) and the negative electrode (43) are accommodated.
Each of them is constituted by applying an active material to the surface of the strip-shaped core body, and the electric power generated by the electrode body (4) can be taken out from the pair of electrode terminal portions to the outside. The edge of the strip-shaped core body forming the positive electrode (41) or the negative electrode (43) at at least one of the positive electrode side end and the negative electrode side end of the electrode body (4).
(48) protrudes, a current collector plate (50) is installed to cover the edge (48), and the current collector plate (50) is laser welded to the core edge (48) of the electrode body (4). And is connected to one of the electrode terminal portions. Here, at least the light receiving surface of the laser beam is roughened on the surface of the current collector plate (50) on the side opposite to the bonding surface to the electrode body (4).

In a specific configuration, the current collector plate (50) is formed with a plurality of arcuate convex portions (52) protruding in an arcuate cross section toward the core body end edge (48) of the electrode body (4). And the core edge
A plurality of cut-and-raised pieces (53) cut and raised toward (48) are formed, and these arcuate convex portions (52) and cut-and-raised pieces (53) bite into the core body edge (48). In the secondary battery in which the arcuate protrusion (52) is welded to the core body edge (48) in this state, the surface of the arcuate protrusion (52) is roughened.

As a method for roughening the current collector plate (50), for example, at least the light receiving surface of the laser beam among all the surfaces of the current collector plate (50) is sandpaper, abrasive, blasted,
Alternatively, a method of roughening using chemical etching can be used, whereby the light receiving surface of the laser beam becomes rougher than other areas.

In the secondary battery of the present invention, the electrode body
In the step of laser welding the current collector plate (50) to the core edge (48) of (4), the laser beam receiving surface of the current collector plate (50) is roughened. The reflectance of the laser beam becomes low, and most of the energy of the laser beam is collected by the collector plate (50).
And the end of the core body (48) of the winding electrode body (4). As a result, the current collector plate (50) is satisfactorily laser-welded to the core body edge (48) of the winding electrode body (4) with sufficient energy.

As the material of the current collector (50), Cu, Al,
Ni, SUS, Cu, or an alloy thereof can be used. For example, even when the current collector plate (50) is formed using Cu, the laser beam receiving surface of the current collector plate (50) is rough. By making the surface flat, the laser reflectance can be suppressed sufficiently low.

[0018]

According to the secondary battery of the present invention, by the treatment of roughening the laser receiving surface of the current collecting plate, the laser receiving surface at the time of laser welding the current collecting plate to the winding electrode body is improved. It is possible to reduce the laser reflectance. Further, according to the roughening treatment, since the residue such as the conventional film is not generated on the laser light receiving surface, the battery characteristics are not adversely affected and the battery characteristics can be maintained well.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described below.
A concrete explanation of the embodiment of the next battery with reference to the drawings
Revealoverall structure The lithium ion secondary battery according to the present invention is shown in FIGS.
As shown in Fig. 2, the lids (12) and (12) are welded and fixed to both ends of the tubular body (11).
The winding electrode is placed inside the cylindrical battery can (1).
It is configured to accommodate the body (4). On both lids (12) (12)
Is a pair of positive and negative electrode terminal mechanism (9) (9)
There is. Each lid (12) has a pressure opening / closing type gas discharge valve (13).
It is attached. At both ends of the winding electrode body (4),
Each has a current collector plate (50) installed and laser welding as described later.
And the lead portion (55) protruding from the current collector plate (50)
The tip of the electrode constitutes the electrode terminal mechanism (9) electrode terminal (91)
Spot welded or resistance welded to the flange (92) of
There is.

[0020]Winding electrode body (4) As shown in Fig. 5, the winding electrode bodies (4) are strip-shaped.
A strip-shaped separator (42) is interposed between the positive electrode (41) and the negative electrode (43) of
It is made to exist and these are wound in a spiral shape.
It The positive electrode (41) is a strip-shaped core body (45) made of aluminum foil.
Positive electrode active material (44) composed of lithium composite oxide on both sides of
The negative electrode (43) is formed by coating, and the negative electrode (43) is a strip-shaped core made of copper foil.
Apply negative electrode active material (46) containing carbon material on both sides of (47)
It is configured. The separator (42) contains a non-aqueous electrolyte.
It is soaked.

The positive electrode (41) is provided with a coated portion coated with the positive electrode active material (44) and a non-coated portion not coated with the positive electrode active material. In addition, the negative electrode (43) also has a negative electrode active material.
The coated part of (46) and the non-coated part to which the negative electrode active material is not coated are formed. The positive electrode (41) and the negative electrode (43) are respectively shifted and overlapped on the separator (42) in the width direction, and the non-coated portions of the positive electrode (41) and the negative electrode (43) are separated from both end edges of the separator (42). Each is projected outward. The winding electrode body (4) is constructed by winding these in a spiral shape. The winding electrode body
In (4), the core body edge (48) of the non-coated portion of the positive electrode (41) is more than the one edge of the separator (42) at one of the two ends in the winding axis direction. Also protrudes outward, and at the other end, the core body edge (48) of the non-coated portion of the negative electrode (43) is the separator.
It projects more outward than the other edge of (42).

[0022]Electrode terminal mechanism (9) As shown in FIG. 1, the electrode terminal mechanism (9) is a lid for the battery can (1).
A battery consisting of bolts mounted through the body (12).
It has a pole terminal (91). At the base end of the electrode terminal (91)
Has a disc-shaped flange (92). Lid (12)
An insulating packing (93) is attached to the through hole of the
The electrical insulation and sealing property between the fastener and the fastening member (91) are maintained.
ing. Wash the electrode terminal (91) from the outside of the lid (12).
The first nut (95) and the second nut
(96) is screwed. Then tighten the first nut (95).
Attach the flange (92) and washer (94) of the electrode terminal (91).
The insulation packing (93) is clamped by
It has a high quality.

[0023]Current collecting structure The positive and negative electrode side current collecting plates (50) are circular plates as shown in FIG.
A disk-shaped main body (51) having a diameter of 40 mm,
It is formed to a thickness of 0.5 mm. On the flat body (51)
The central hole (54) is opened and the central hole (54)
A plurality of arcs (4 in the example) that extend radially as the center
-Shaped convex part (52) is integrally molded and protrudes to the winding electrode body (4) side.
I have put it out. In addition, the disc-shaped main body (51) has an adjacent arc shape.
Plural lines (two lines in the embodiment) between the convex portions (52) and (52), respectively.
The cut-and-raised piece (53) is formed on the winding electrode body (4) side.
It is protruding. The end of the flat plate-shaped body (51) has a strip shape.
The lead portion (55) of the is protruded. In addition, the collector plate (50)
The surface (inner peripheral surface) of the arcuate convex portion (52) has a surface roughness of # 240.
Roughening treatment is performed by using paper. Incidentally, positive
The collector plate (50) on the pole side is made of aluminum and
The electric plate (50) is made of copper.

[0024]Manufacturing process The battery can (1), electrode terminal mechanism (9), and winding power shown in FIG.
An electrode body (4) and a pair of current collector plates (50) and (50) were prepared, respectively.
After that, as shown in FIGS. 8 and 10, the winding electrode body (4)
Push the collector plate (50) onto the core edge (48) formed on each end.
Discipline. As a result, the arcuate convex portion (52) of the current collector plate (50)
Is the core body edge (48) of the winding electrode body (4) as shown in FIG.
It bites into, and between the arc-shaped convex part (52) and the core body edge (48),
A joining surface formed of a cylindrical surface is formed. Also, of the current collector (50)
The cut-and-raised pieces (53) are wound electrode bodies as shown in FIG.
It digs deep into the core edge (48) of (4) and presses against the core edge (48).
I will wear it.

In this state, as shown by an arrow in FIG. 9, a laser beam is irradiated toward the inner peripheral surface of the arcuate convex portion (52) of the current collector plate (50) to perform laser welding. Here, the arc-shaped protrusion (5
Since the inner peripheral surface of 2) is roughened, the reflectance of the laser beam on the inner peripheral surface becomes low, and most of the energy of the laser beam is the same as that of the current collector plate (50). Winding electrode body
It is applied to the joint portion of the core body edge (48) of (4). As a result, the collector plate (50) causes the core body edge (48) of the winding electrode body (4).
Laser welding will be excellent. As a result, the arcuate convex portion (52) of the current collector plate (50) and the winding electrode body (4)
11 and the core body edge (48) are joined to each other with a large contact area, and the cut and raised piece (53) and the core body edge (48) shown in FIG.
The crimped state between the two is maintained.

After fixing the current collectors (50) (50) to both ends of the winding electrode body (4) in this manner, the tips of the lead portions (55) of each current collector (50) are used as electrodes. The winding electrode body (4) is welded to the flange (92) of the terminal (91) and is housed inside the cylindrical body (11) shown in FIG. Then, after the lid body (12) is installed in each opening of the cylindrical body (11) and the electrode terminal mechanism (9) is assembled, the lid body
The (12) is welded and fixed to the tubular body (11). Finally, after injecting the electrolytic solution into the battery can (1), the safety valve (13) is screwed into each lid (12) to complete the lithium ion secondary battery of the present invention.

In the above lithium-on secondary battery, the material of the current collector plate (50) on the negative electrode side is C instead of conventional Ni.
u is adopted, and the specific resistance of Ni is 6.84 × 10.
^-6 Ω · cm, Cu has a specific resistance of 1.67
Since it is as small as × 10 ⁻⁶ Ω · cm, the internal resistance of the battery is small. Although Cu is a material having a high laser reflectance, since the laser reflectance of the laser receiving surface is reduced by the above-described roughening treatment, the Cu current collector plate (50)
It is easy to perform laser welding on the winding electrode body (4), and sufficient welding strength can be obtained.

Further, the positive electrode side and negative electrode side current collector plates (50) have a large contact area at the welded portion of each arcuate convex portion (52) and the core body end edge (48) with a large contact area (48). ), The cut-and-raised pieces (53) bite into the core end edge (48) in a region other than the welded portion, and a good contact state is obtained, so that the current collector plate (50) The contact resistance between the winding electrode body (4) and the winding electrode body (4) is reduced, which further reduces the internal resistance of the battery. Of course,
By the plurality of cut-and-raised pieces (53) formed on the current collector plate (50), current is collected from the entire area of the core edge (48), and thus high current collecting performance is obtained. A high output secondary battery will be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a secondary battery according to the present invention.

FIG. 2 is a plan view of a current collector plate.

FIG. 3 is a perspective view showing the appearance of a secondary battery.

FIG. 4 is a cross-sectional view showing a main part of a conventional secondary battery.

FIG. 5 is a partially exploded perspective view of a winding electrode body.

FIG. 6 is a plan view of a conventional current collector plate.

FIG. 7 is an enlarged cross-sectional view of a main part of the current collector plate.

FIG. 8 is a perspective view of a step of pressing the arcuate convex portion of the current collector plate against the core edge of the winding electrode body.

FIG. 9 is an enlarged cross-sectional view showing a state where the arcuate convex portion of the current collector plate is pressed against the end edge of the core body of the winding electrode body.

FIG. 10 is a perspective view of a step of pressing the cut-and-raised pieces of the current collector plate against the core body edge of the winding electrode body.

FIG. 11 is an enlarged cross-sectional view of a state in which a cut-and-raised piece of a current collector plate is pressed against a core body end edge of a winding electrode body.

[Explanation of symbols]

(1) Battery can (11) Cylindrical body (12) Lid (4) Winding electrode body (48) Core edge (50) Current collector (51) Flat body (52) Circular convex (53) Cut and raised piece (54) Central hole (55) Lead part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiyuki Noma             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Ikuro Ikuro             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 5H022 AA09 BB17 BB21 CC12 CC13                       CC16 CC19 CC22                 5H029 AJ02 BJ14 CJ05 DJ05 DJ07                       EJ01

Claims (5)

[Claims] 1. A battery can (1) contains therein an electrode body (4) in which a belt-shaped positive electrode (41) and a negative electrode (43) are respectively laminated with a separator (42) interposed therebetween. Each of the positive electrode (41) and the negative electrode (43) is formed by coating an active material on the surface of the strip-shaped core body, and the electric power generated by the electrode body (4) can be taken out from the pair of electrode terminal portions to the outside. In the next battery,
The end edge (48) of the strip-shaped core body forming the positive electrode (41) or the negative electrode (43) projects from at least one of the positive electrode side and negative electrode side ends of the electrode body (4). A current collector plate (50) is installed so as to cover the edge (48), and the current collector plate (50) is bonded to the core edge (48) of the electrode body (4) by laser welding. ,
In the secondary battery connected to one electrode terminal part,
A secondary battery, characterized in that at least a light receiving surface of a laser beam is roughened on a surface of the current collector plate (50) opposite to a bonding surface to the electrode body (4). 2. The current collector plate (50) is provided with a plurality of arc-shaped projections (52) protruding in an arc cross-section toward the core body edge (48) of the electrode body (4). In addition, a plurality of cut-and-raised pieces (53) cut and raised toward the core body end edge (48) are formed, and these arc-shaped convex portions (52) and cut-and-raised pieces (53) are used as the core body. Edge (48)
The arc-shaped convex portion (52) is welded to the core body edge (48) in a state of biting into the core, and the surface of the arc-shaped convex portion (52) is roughened. Secondary battery. 3. The secondary battery according to claim 1, wherein the laser beam receiving surface of the entire surface of the current collector plate (50) is a rougher surface than other areas. 4. A sandpaper, an abrasive, a blast treatment, a laser beam receiving surface of the entire surface of the current collector plate (50),
Alternatively, the secondary battery according to any one of claims 1 to 3, which has been roughened by chemical etching. 5. The current collector plate (50) is made of Cu, Al, Ni, SU.
The secondary battery according to any one of claims 1 to 4, which is formed from S, Cu, or an alloy thereof.