JP2002050343A - Manufacturing method of secondary cell and secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method which makes it possible to make a stable structure by improving a joint intensity between an electrode and a terminal, to lower internal resistance and to improve productivity, and provide a secondary cell using such a manufacturing method. SOLUTION: When both positive and negative terminals 21, 23 are bonded to electrode metal foils 11, 13 each located at both ends of a collector 10, reed parts 11r, 13r of the electrode metal foils 11, 13 are laminated on flat bonded surfaces 21a, 23a set on an upper surface side of a periclinal part of a positive and a negative electrode terminals 21, 23, and ultrasonic energy is applied once or twice on the laminated part by an ultrasonic bonding device equipped with a ring-shaped flat chip T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a high-output secondary battery suitable for an electric vehicle or the like, and in particular, to easily obtain an electrode structure capable of efficiently extracting a current from a current collector. And a secondary battery obtained by such a manufacturing method.

[0002]

In a large-sized lithium ion secondary battery used for an electric vehicle or the like, an electrode of the battery has a structure as shown in FIG.
It was joined to the terminal as shown in FIG. 3 (b) or (c).

That is, as shown in FIG. 3A, positive and negative electrodes 11 and 13 made of strip-shaped metal foil are used.
Are not coated with the active materials 12 and 14 for the positive electrode and the negative electrode, respectively.
And the uncoated portions are processed to form strip-shaped leads 11r and 13r, respectively. Next, the separator 1 is placed between the strip electrodes 11 and 13.
In the state of sandwiching 5, these are spirally wound to form a current collector 10. Positive and negative terminals 21 and 23 are arranged at both ends of the current collector 10, as shown in FIG. By irradiating a laser beam L or pressing a chip T of an ultrasonic bonding apparatus as shown in FIG.
The strip-shaped lead portions 11r and 13r were joined to the outer peripheral portions of the terminals 21 and 23, respectively, and integrated to produce a secondary battery (Japanese Patent Application Laid-Open No. 9-99335).

A secondary battery having such a structure is characterized in that a current can be taken out evenly through the lead portion and the internal resistance is small as compared with the earlier batteries, and the secondary battery is used as a power source for electric vehicles and the like. It is suitable for large-capacity secondary batteries with high capacity. However, electric vehicles and hybrid vehicles are expected to have higher performance in the future, and it is expected that a higher output is required for a secondary battery for a power supply. At this time, the energy loss due to the internal resistance may be one of the problems for increasing the output.

However, the bonding between the positive electrode made of laminated aluminum foil and the positive electrode terminal made of aluminum and the bonding between the negative electrode made of laminated copper foil and the negative terminal made of copper are suitable for conventional laser welding in view of the material and form. However, it is difficult to secure a more stable and wider bonding area necessary for improving the performance of the secondary battery. Also, in the case of joining the outer periphery using ultrasonic joining, since the joining is repeated intermittently, it is not possible to substantially increase the joining area, and each joint has a flat contact with the chip. There is a problem that it becomes unstable because it does not exist. In addition, the intermittent ultrasonic bonding has a problem that the number of bonding points per battery is increased and productivity is lowered, and solving such a problem is a manufacturing problem in a conventional secondary battery. I was

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in joining a metal foil electrode and a terminal of a conventional secondary battery. Structure, reducing internal resistance,
It is an object of the present invention to provide a method of manufacturing a secondary battery capable of improving productivity and a secondary battery manufactured by such a manufacturing method.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing a secondary battery, wherein a separator is interposed between metal foils for a positive electrode and a negative electrode coated with respective active materials for a positive electrode and a negative electrode. At both ends of the current collector wound in a flat state, a disk plate or an annular positive electrode and a negative electrode terminal each having a flat joining surface on the peripheral edge upper surface side are arranged, and both ends of the current collector are arranged. After the metal foils for the positive electrode and the negative electrode located at the respective portions are laminated on the bonding surfaces of the positive electrode and the negative electrode terminal respectively, once or twice by an ultrasonic bonding apparatus having a ring-shaped flat chip in the laminated portion. The positive electrode and the negative electrode terminal and the metal foil for the positive electrode and the negative electrode of the current collector are joined to each other by applying ultrasonic energy to the current collector. Configure is a means for solving the conventional problems described above, such as.

In the method of manufacturing a secondary battery according to a second aspect of the present invention, the positive and negative electrode terminals and the metal foil for the positive electrode and the negative electrode are respectively connected to each other by using an ultrasonic bonding device that oscillates in the circumferential direction. In the method of manufacturing a secondary battery according to claim 3, the first bonding is performed using an ultrasonic bonding apparatus that oscillates in one direction, and then the object to be bonded or the ultrasonic bonding is performed. The second bonding is performed in a state where the chip of the device is relatively rotated by 90 degrees, and the positive and negative electrode terminals and the positive and negative metal foils are respectively bonded twice. In the method of manufacturing the next battery, ultrasonic energy is applied in a state where the upper surface and the outer peripheral surface of the metal foil laminated portion on the terminal joining surface are covered by a cap-shaped member made of the same material as the metal foil for the positive electrode and the negative electrode. And for the positive electrode The manufacturing method according to claim 5, wherein the respective cap-shaped members for the negative electrode, the metal foil, and the terminals are integrated, and in the ultrasonic bonding, the metal foil laminated portion or the cap-shaped member in contact with the outer peripheral surface of the terminals is used. It is characterized in that it is configured to hold the entire joint.

A secondary battery according to a sixth aspect of the present invention is manufactured by the above manufacturing method, wherein an angle α formed between the central axis of the current collector and the joint surface of the terminal is 45 to 90 degrees. Thus, such a configuration of the secondary battery is characterized in that it is a means for solving the above-described conventional problem.

[0010]

In the method of manufacturing a secondary battery according to the present invention, ultrasonic bonding, which is suitable for bonding thin materials such as aluminum and copper, and has a small thermal effect on the surroundings, is applied.

In the present invention, since the joining portions are joined in a state where they are in contact with each other in a plane, the joining portion is not joined to each other in a state where the joining portions are not plane-to-face. The bonding state is stabilized, and the bonding area is substantially increased. By increasing the junction area, the internal resistance is reduced, and even if a large current is taken out, the energy loss is small and a high output can be obtained. Also,
Since only one or two joinings are required, productivity is greatly improved as compared with the conventional method. Further, by appropriately selecting the chip area in accordance with the capacity of the bonding apparatus, the bonding width (bonding area) can be controlled.

In the method for manufacturing a secondary battery according to the present invention, for example, pure aluminum or an Al—Mn alloy is used for the metal foil and the terminal for the positive electrode, and the metal foil and the terminal for the negative electrode are pure copper. Or nickel, stainless steel, or the like. Examples of the positive electrode active material applied to the positive electrode metal foil such as pure aluminum include LiCoO ₂ , LiNiO ₂ , and spinel type LiMn _2.
Graphite, coke, hard carbon and the like are used as the negative electrode active material such as O ₄ .

Further, as the separator located between the metal foil for the positive electrode and the metal foil for the negative electrode, a sheet made of polypropylene, polyethylene or the like can be used.

The terminal can be suitably used as long as it has a disk shape or an annular shape, and a hole or a gap for releasing gas generated inside the battery can be appropriately provided inside. If the width of the joining portion is too small, the internal resistance increases and the output decreases. If the width is too wide, a large amount of energy is required for joining, so that the width is preferably 2 to 5 mm.

As a more specific method of manufacturing a secondary battery according to the present invention, in the method according to claim 2, the positive electrode is formed by using an ultrasonic bonding apparatus that oscillates in a circumferential direction during ultrasonic bonding. And the negative electrode terminal and the positive and negative electrode metal foils are respectively bonded at one time, and the ring-shaped bonding with the electrode metal foil at the peripheral portion of the terminal is completed by one bonding operation. Simplified,
Productivity is further improved.

In the manufacturing method according to a third aspect of the present invention, the first bonding is performed by an ultrasonic bonding apparatus which oscillates in one direction during the ultrasonic bonding, and then the chip and the chip of the ultrasonic bonding apparatus are formed. A second bonding is performed by changing the direction of one of the bonded bodies with respect to the other by 90 degrees, and the positive and negative electrode terminals and the metal foil for the positive and negative electrodes are bonded twice each. That is, by the first joining operation, a portion of the peripheral portion of the terminal that forms approximately 90 degrees with the transmitting direction, that is, about half of the ring-shaped joining with the electrode metal foil is joined, and the subsequent direction is shifted by 90 degrees. The other half is joined by the second joining operation in the state in which the terminals are joined, and the ring-like joining of the peripheral portion of the terminal is completed by the two joining operations. When this one-way oscillation bonding device is used, the actual bonding area is slightly reduced and the productivity is slightly reduced as compared with the case of using the circumferential oscillation device. Since the output performance of the battery is much improved and the device structure is simplified as compared with the bonding device oscillating in the circumferential direction, the cost such as the facility cost is reduced.

In the manufacturing method according to a fourth aspect of the present invention, ultrasonic bonding is performed in a state where the upper surface and the outer peripheral surface of the metal foil laminated portion are covered with a cap-like member made of the same material as the metal foil for the positive electrode and the negative electrode. Thus, the cap-shaped members for the positive electrode and the negative electrode, the metal foil, and the terminals are integrated. That is, for example, by installing a thin cap-shaped member on the metal foil laminated portion at the end of the current collector before joining, the adhesive strength between the foils and between the foil and the terminal is improved, so that the joining strength is also improved, and Will be stabilized. Further, the non-joined portion of the foil on the outer peripheral side surface can be fixed. The cap-shaped member may have a ring-shaped integral shape. For example, by dividing the cap into two parts, workability at the time of attachment is improved. Also,
The material of the cap member for the positive electrode and the negative electrode is preferably the same pure aluminum material and pure copper material as the current collector metal foil, respectively.
If the thickness is too large, a large energy is required at the time of joining, and if it is too thin, the workability is adversely affected, such as bending at the time of work, so that the thickness is preferably about 0.1 to 0.3 mm.

Further, in the manufacturing method according to the fifth aspect of the present invention, ultrasonic bonding is performed while holding the whole object to be bonded in the metal foil laminated portion or the cap-shaped member in contact with the outer peripheral surface of the terminal. . In the case of ultrasonic bonding, it is desirable to hold and fix the object to be bonded so that energy is concentrated on the bonding portion when applying ultrasonic waves, but when holding the entire side surface of the wound current collector, In this case, a supporting force is applied to the metal foil portion to which the active material is applied, and problems such as falling off of the active material and cracking of the metal foil occur.
In this respect, since the active material is not applied to the strip-shaped lead portion of the metal foil laminated on the outer peripheral portion of the terminal, there is no danger of falling off, especially if the foil is held with the cap-shaped member covered, cracking of the foil may occur. Will be prevented. In addition, since the object to be joined is held at a position close to the joint, the working efficiency is good.

A secondary battery according to a sixth aspect of the present invention is manufactured by the above-described manufacturing method according to the present invention, and includes an angle α formed between the central axis of the current collector and the joint surface of the terminal. Is 45 to 90 degrees, so that the joining strength is improved without impairing the workability. That is, in ultrasonic bonding, it is most desirable that the angle between the bonding surface and the pressing direction of the chip is 90 degrees from the viewpoint of workability and bonding strength. However, the joining is not necessarily a right angle, and the joining is possible even if there is a certain angle. If the joining is performed in an oblique state, the joining area increases accordingly, and there is a favorable tendency. However, if the inclination of the joining surface is too large, the applied energy efficiency tends to be low and the joining tends to be impossible, so the range of 45 to 90 degrees is preferable.

[0020]

According to the method for manufacturing a secondary battery according to the first aspect of the present invention, since the joining portion between the metal foil for an electrode and the terminal can be made flat, the joining state is stable and the substantial joining area is increased. In addition, the internal resistance of the battery is reduced, and a secondary electrode suitable for high output can be obtained. Improving battery output not only increases the output of electric vehicles, but also reduces energy loss during large-current discharge, suppresses battery heat generation, and reduces the number of joints, thus improving productivity. This brings about an extremely excellent effect that the cost can be reduced.

In the method of manufacturing a secondary battery according to the second aspect of the present invention, the ring-shaped bonding between the electrode metal foil and the terminal is performed once by using an ultrasonic bonding device that oscillates in the circumferential direction. Since the operation is completed, the process can be further simplified, and the productivity can be further improved.
In the manufacturing method according to the third aspect, the ultrasonic bonding device that oscillates in one direction is used, so that the bonding is performed twice by changing the direction. The apparatus structure becomes simpler and the equipment cost can be reduced, and in the manufacturing method according to claim 4, a cap-shaped member made of the same material as the respective metal foils for the positive electrode and the negative electrode during ultrasonic bonding. Since the members are integrated with the respective metal foils and terminals, the adhesion between the metal foils and the terminals can be improved and the bonding strength can be increased, and further stabilization can be achieved, Furthermore, in the method of manufacturing a secondary battery according to claim 5, the metal foil laminated portion in contact with the outer peripheral surface of the terminal or, when a cap-shaped member is used, the portion to be joined at the cap-shaped member. Since the ultrasonic bonding is performed while the entire body is held, the object to be bonded is firmly held without causing problems such as falling off of the active material and cracking of the metal foil, and more reliable ultrasonic bonding An even better effect is that it can be done.

A secondary battery according to a sixth aspect of the present invention is manufactured by the above manufacturing method, wherein an angle α formed between the central axis of the current collector and the joint surface of the terminal is 45 to 90. Therefore, there is an effect that the joining strength can be reliably improved with good workability.

[0023]

The present invention will be described below in more detail with reference to examples.

Battery Manufacturing Procedure First, 75% of spinel-type LiMn ₂ O ₄ having an average particle size of about 1 μm as the active material 12 for the positive electrode, 10% of acetylene black as a conductive aid, and 15% of polyvinylidene fluoride as a binder (above) Mass ratio), N-methylpyrrolidone as a solvent was added thereto, and then mixed to prepare a slurry. Using a coater, a 20 μm-thick pure aluminum foil electrode (positive electrode) 1
On the other hand, the slurry was applied and dried while leaving the non-application area 11a on one side. Then, as shown in FIG. 3A, the non-coated area 11a of the pure aluminum foil electrode 11 was cut and pressed so as to obtain a predetermined strip-shaped lead portion 11r, and cut into a predetermined width by a slitter. . In addition,
The total thickness at this time was about 65 μm.

On the other hand, the negative electrode active material 14 has an average particle size of 4
90% of hard carbon of about μm and 10% of polyvinylidene fluoride (above mass ratio) as a binder have a thickness of 10 μm.
m of pure copper foil electrode (negative electrode) 13 and dried. Then, a strip-shaped lead portion 13r was formed by performing the same processing on the non-coating region 13a of the copper foil electrode 13. The total thickness at this time was about 45 μm.

Next, the design capacity of the secondary battery is set to 3 Ah
The positive and negative electrodes 11 and 13 are wound with a polypropylene microporous separator 15 interposed therebetween,
No current collector 10 of 38 mmφ × 68 mm, FIG. 1 (a)
Alternatively, as shown in FIG. 1B, the positive and negative terminals 2 of the same material as the electrode metal foil of each of the positive and negative electrodes are provided at both ends of the current collector 10.
Nos. 1 and 23 (26 mm diameter x 4 mm height) were provided.

Then, after the strip-shaped lead portions 11r and 13r of both electrodes 11 and 13 are laminated on the upper surface side of the peripheral portion of the positive and negative terminals 21 and 23, if necessary, each electrode is placed on this laminated portion. With the cap-shaped members 31 and 33 made of the same material as the metal foil being covered, the chip T of the ultrasonic bonding apparatus was applied, and each was ultrasonically bonded to a bonding width of 3 mm. At this time, the outer peripheral portion of the laminated portion of the metal foil lead portions 11r and 13r or the side surface portions of the cap-like members 31 and 33 were pressed and held by the holding devices 41 and 42 from both left and right directions.

In this manner, the current collector 10 having the positive and negative terminals 21 and 23 joined at both ends is housed in a battery can, the positive and negative terminals are insulated from the can body and taken out, and the lid is welded. The sealed structure was adopted. After evacuation of the entire can body, a predetermined amount of an electrolytic solution was injected from the injection port, and the injection port was closed to form a secondary battery. The output performance of the obtained battery was comparatively evaluated. In this performance evaluation, an internal temperature of 3
After fully charged in a 5 ° C thermostat, 10C
The output after 10 seconds when discharging at a current value of was measured.

Embodiment 1 Joining surfaces 21a and 23a are formed on the upper surface side of the peripheral portions of the terminals 21 and 23 (that is, the angle α = 90 degrees in FIG. 1B), and the cap-like members 31 and 3 are formed on the laminated portions.
3 and the positive and negative electrode terminals 21 and 23 and the positive and negative electrode metal foils 11 and 13 are respectively bonded once using an ultrasonic bonding device that oscillates in the circumferential direction without covering the secondary metal foil 3. I got a battery.

Embodiment 2 FIG. 1 shows the laminated portions of the strip-shaped leads 11r and 13r.
As shown in (a), the cap-like members 31 and 33 are covered, and the upper surfaces 31a, 3
A secondary battery was obtained by performing bonding in the same manner as in Example 1 except that the chip T of the ultrasonic device was applied to 3a and bonded. The positive electrode cap member 31 was made of a pure aluminum material having a thickness of 0.2 mm, and the negative electrode cap member 33 was made of a pure copper material having a thickness of 0.15 mm.

Example 3 Positive and negative terminals 21, 23 and positive and negative metal foils 11,
A secondary battery was obtained by performing ultrasonic bonding in the same manner as in Example 1 except that each of the secondary batteries was bonded twice.

Example 4 A secondary battery was obtained by performing ultrasonic bonding in the same manner as in Example 1 except that the angle α of the bonding surface was set to 45 degrees.

COMPARATIVE EXAMPLE The joining position was determined by the side surfaces of the terminals 21 and 23 (the angle α of the joining surface).
= 0 °), and bonding is performed using an ultrasonic bonding device that oscillates in one direction, that is, 20 points are intermittently bonded in the circumferential direction in the manner shown in FIG. Obtained.

Table 1 summarizes the bonding modes of the above Examples and Comparative Examples. FIG. 2 shows the output performance of the obtained battery. Note that the battery output performance according to each example shown in FIG. 2 is represented by an index when the output of the secondary battery of Comparative Example is set to 100.

[0035]

[Table 1]

As is apparent from the results shown in FIG. 2, in the secondary battery in which the metal foil electrode and the terminal are ultrasonically bonded on the upper surface side of the outer edge of the terminal by the manufacturing method according to the present invention, the terminal side portion is formed. It was confirmed that a higher output was obtained as compared with the comparative example joined by the above method. According to the manufacturing method of the present invention, it has been confirmed that the time required for bonding is also remarkably reduced from 1/20 to 1/10 as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 (a) is a schematic view showing the procedure of ultrasonic bonding between a metal foil electrode and a terminal in a method for manufacturing a secondary battery according to the present invention. (B) It is explanatory drawing which shows the angle of a joining surface and the collector current center axis.

FIG. 2 is a graph showing the output performance of a secondary battery obtained in an example of the present invention in comparison with a comparative example.

FIG. 3A is a perspective view illustrating a structure of a current collector of a lithium ion secondary battery. (B) It is the schematic which shows the joining method by the laser of the metal foil electrode and terminal in the conventional lithium ion secondary battery. (C) It is the schematic which shows the joining point of the ultrasonic bonding of the metal foil electrode and terminal in the conventional lithium ion secondary battery.

DESCRIPTION OF SYMBOLS 10 Current collector 11 Positive electrode metal foil 12 Positive electrode active material 13 Negative electrode metal foil 14 Negative electrode active material 21 Positive terminal 21 a Joining surface 23 Negative terminal 23 a Joining surface 21 a, 23 a Joining surface 31 Positive cap member 33 Cap member for negative electrode T chip (ultrasonic bonding equipment)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenji Hamada 2nd Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 5H022 AA09 AA18 BB17 CC02 CC08 CC12 CC16 5H028 AA01 AA07 BB05 BB07 BB14 CC05 CC12 5H029 AJ06 AJ14 AK03 AL07 BJ02 CJ05 CJ28 DJ05 DJ07 EJ01 HJ00

Claims (6)

[Claims] 1. A current collector formed by winding a metal foil for a positive electrode and a negative electrode coated with an active material for each of a positive electrode and a negative electrode with a separator interposed therebetween, at both ends of a current collector, A disk or annular positive electrode and negative electrode terminals each having a flat bonding surface are arranged, and the positive electrode and negative electrode metal foils located at both ends of the current collector are joined to the positive electrode and negative electrode terminals, respectively. After being laminated on the respective surfaces, the ultrasonic energy is applied once or twice by an ultrasonic bonding device having a ring-shaped flat chip on the laminated portion to apply the ultrasonic energy to the positive and negative terminals and the current collector. A method for manufacturing a secondary battery, comprising joining a body metal foil for a positive electrode and a metal foil for a negative electrode. 2. The method according to claim 1, wherein the positive and negative electrode terminals and the positive and negative electrode metal foils are respectively bonded once by using an ultrasonic bonding device that oscillates in a circumferential direction. Manufacturing method of secondary battery. 3. The first bonding is performed using an ultrasonic bonding apparatus that oscillates in one direction, and then the object to be bonded or the chip of the ultrasonic bonding apparatus is rotated by 90 degrees for a second time. 2. The method for manufacturing a secondary battery according to claim 1, wherein the positive electrode and the negative electrode terminal and the metal foil for the positive electrode and the negative electrode are bonded twice each. 4. A method of applying ultrasonic energy while covering an upper surface and an outer peripheral surface of a metal foil laminated portion on a terminal joining surface with a cap-shaped member made of the same material as a metal foil for a positive electrode and a negative electrode. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein each of the cap-shaped members for the negative electrode, the metal foil, and the terminal are integrated. 5. The ultrasonic bonding method according to claim 1, wherein the whole object to be bonded is held by a metal foil laminated portion or a cap-shaped member in contact with the outer peripheral surface of the terminal.
The method for producing a secondary battery according to any one of the above. 6. The method according to claim 1, wherein an angle α between a central axis of the current collector and a bonding surface of the terminal is 45 to 90 degrees. Secondary battery.