JPH0896829A - Secondary battery - Google Patents

Abstract

PURPOSE: To fix stacked electrodes and increase shock resistance and reliability of electrodes by welding specified parts of separators of a stacked body in the stacking direction to fix the stacked position relation of positive electrodes and the negative electrodes. CONSTITUTION: Positive electrodes and negative electrodes each of which is enveloped in a bag-shaped separator are mutually stacked to form a rectangular stacked body 14. A positive lead 2a formed by extending a current collector of the positive electrode in the rectangular stacked body 14 is welded to a positive lead body 11a having almost the same length as the longitudinal length of the positive lead 2a over the whole length. The stacked body 14 to which the positive lead body 11a and a negative lead body 12a are welded is placed in a flat square type battery case 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery suitable for use as a power source for electric vehicles and the like.

[0002]

2. Description of the Related Art In recent years, a lithium ion secondary battery which is a non-aqueous electrolyte secondary battery using lithium or a lithium alloy has been proposed as a secondary battery suitable for use as a power source for electric vehicles and the like.

This lithium ion secondary battery is shown in FIGS.
As shown in FIG. 5, the positive electrode 2 and the negative electrode 3 are packed in a bag-shaped separator 8 and formed by a laminated body 14 that is alternately stacked. The laminated body 14 including the positive electrode 2, the negative electrode 3, and the bag-shaped separator 8 is inserted into the rectangular battery case 10 and filled with an electrolytic solution to function as a secondary battery. To do.

As the positive electrode 2, for example, as shown in FIGS. 3 and 4, a composite oxide of lithium Li and a transition metal is formed on both surfaces of a current collector 5 made of an aluminum Al foil having a rectangular thickness of about 20 μm. LiCoO ₂ is deposited as the positive electrode active material 4.

As the negative electrode 3, as shown in FIGS. 3 and 4, for example, lithium L is formed on both surfaces of a current collector 7 made of a copper Cu foil (or nickel Ni foil) having a rectangular thickness of about 10 μm.
Carbon that can be doped or dedoped with i, for example, carbon having a graphite structure or carbon C such as a non-graphitizable carbon material is deposited as the negative electrode active material 6.

As the bag-shaped separator 8, for example, a microporous polyethylene film or polypropylene film having a thickness of 25 μm is bag-shaped. In this case, when packing the positive electrode 2 and the negative electrode 3 into bags, for example, the positive electrode 2
The negative electrode 3 and the negative electrode 3 are sandwiched between two films constituting a separator, and the periphery of each of the electrodes 2 and 3 is heat-sealed and bonded.

A plurality of positive electrodes 2 packed in the bag-shaped separator 8 such as 51 sheets and a plurality of negative electrodes 3 packed in the bag-shaped separator 8 such as 52 sheets are alternately stacked and laminated. After this lamination, an adhesive tape is attached to form a laminated body 14. In this case, by sticking an adhesive tape to the laminate 14, displacement between the electrodes was prevented, and thus handling of the laminate 14 until it was inserted into the battery case 10 was facilitated.

When the bag-shaped separator 8 is used, there are two microporous polypropylene films or the like between the positive electrode 2 and the negative electrode 3, the positions of the holes of the polypropylene film are different, and the probability of occurrence of an internal short circuit is increased. Get lower. When the positive electrode 2 and the negative electrode 3 are packed in the bag-shaped separator 8, the active materials 4 and 6 are prevented from falling off and scattering, respectively.
Further, since the positive electrodes 2 and the negative electrodes 3 packed in the bag-shaped separator 8 are alternately laminated, the manufacturing is easier than that in which the positive electrodes 2 and the negative electrodes 3 are laminated via the film-shaped separator.

[0009]

In such a conventional secondary battery, an adhesive tape was attached to the laminated body 14,
When the laminated body 14 is inserted into the battery case 10, the electrolytic solution 9 peels off the adhesive tape,
There is a risk that the electrodes may be displaced from each other, and reliability such as vibration resistance of the electrodes cannot be obtained.

In view of the above point, the present invention has an object to enable stacking and fixing of each electrode without being affected by the electrolytic solution even in the battery case.

[0011]

The secondary battery of the present invention is, for example, a laminate in which positive electrodes 2 and negative electrodes 3 packed in a bag-like separator 8 are alternately laminated in opposition to each other as shown in FIGS. In the secondary battery including the body 14, the predetermined portions 20 of the separators 8 of the laminate 14 are welded in the stacking direction to fix the stacking positional relationship between the positive electrode 2 and the negative electrode 3.

[0012]

According to the present invention, the predetermined portions 20 of the separators 8 of the laminate 14 are welded in the stacking direction to fix the stacking positional relationship between the positive electrode 2 and the negative electrode 3, so that the electrolyte is affected. The electrodes 2 and 3 can be stacked and fixed without the need for improving the reliability of the electrodes in the battery case 10, such as vibration resistance.

[0013]

EXAMPLE An example of the secondary battery of the present invention will be described below with reference to FIGS. 1 and 2 are examples in which the present invention is applied to a lithium ion secondary battery. 1 and 2, parts corresponding to those in FIGS. 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, reference numeral 10 indicates a thickness of 300 μ, for example.
The horizontal length of the stainless steel plate is 29 m
A flat rectangular battery case of a sealed type single cell having a length of 0 mm, a length of 116 mm, and a thickness of 22 mm is shown, and 51 flat bag-shaped separators 8 are packed in the flat rectangular battery case 10. The positive electrode 2 and the negative electrode 3 packed in the bag-shaped separator 8 of 52 sheets are alternately stacked to accommodate the laminated body 14.

As shown in FIGS. 1, 2 and 4, the positive electrode 2 is made of aluminum having a rectangular shape of, for example, 265 mm × 107 mm and a thickness of about 20 μm, which corresponds to the internal shape of the flat rectangular battery case 10. A composite oxide of lithium Li and a transition metal such as LiCoO 2 is formed on both sides of the current collector 5 made of Al foil.
₂ is deposited as the positive electrode active material 4.

As the negative electrode 3, as shown in FIGS. 1, 2 and 4, for example, a copper Cu having a rectangular shape of 270 mm × 109 mm corresponding to the internal shape of the flat rectangular battery case 10 and having a thickness of about 10 μm. Carbon capable of being doped with lithium Li and dedoped from both sides of a current collector 7 made of foil (or nickel Ni foil), for example, carbon having a graphite structure or carbon C such as a non-graphitizable carbon material is deposited as the negative electrode active material 6. It was done.

The bag-shaped separator 8 is made of a microporous polyethylene film having a thickness of 25 μm or a polypropylene film having a rectangular shape of 273 mm × 112 mm, which is slightly larger than the positive electrode 2 and the negative electrode 3. 8, the positive electrode 2 and the negative electrode 3 are packed in the same manner as in the conventional case.

In this example, 51 sheets of the positive electrodes 2 packed in the bag-shaped separator 8 and 52 sheets of the negative electrodes 3 packed in the bag-shaped separator 8 are alternately laminated as shown in FIGS. Then, the rectangular laminated body 14 is formed.

Further, in the present example, a portion where only the separator 8 is laminated in the laminating direction of the laminate 14, in this example, as shown in FIGS.
The corner portion 20 is welded with a heater or an ultrasonic welding machine, for example, 103 bag-shaped separators 8 are welded in the stacking direction,
The laminated positional relationship between the positive electrode 2 and the negative electrode 3 is fixed.

Further, as shown in FIGS. 1 and 2, one side of the rectangular laminated body 14, that is, the extended positive electrode lead portion 2a of the current collector 5 of the positive electrode 2 is made of, for example, copper Cu. The length of the positive electrode lead body 11a is substantially the same as the length in the vertical direction, and the entire length is welded by ultrasonic welding.

The side of the rectangular laminated body 14 facing one side of the negative electrode 3, that is, the extended negative electrode lead portion 3a of the collector 7 of the negative electrode 3 is made of, for example, copper Cu. The negative electrode lead body 12a having the same length as the entire length is welded by ultrasonic welding over the entire length. The laminated body 14 to which the positive electrode lead body 11a and the negative electrode lead body 12a are welded is housed in the flat rectangular battery case 10.

Further, the closed flat battery case 1
An organic electrolyte solution 9 in which LiPF ₆ was dissolved in a mixed solvent of propylene carbonate and diethyl carbonate at a ratio of 1 mol / 1 was injected into 0, and the organic electrolyte solution was placed between the positive electrode active material 4 and the negative electrode active material 6. 9 is filled.

In this example, the positive electrode lead body 11a and the negative electrode lead body 12a are connected to the external positive electrode terminal 11 and the external negative electrode terminal 12, respectively, as shown in FIG. Figure 1
In FIG. 13, 13 is the closed flat battery case 10
This is a safety valve that releases the gas inside when the internal pressure becomes higher than a predetermined value.

According to the lithium ion secondary battery in this example, it is possible to obtain a battery having an average voltage of 3.5 V and 50 Ah.

According to this example, the separators 8 of the four corners 20 of the separator 8 of the laminate 14 are welded in the laminating direction to fix the laminating positional relationship between the positive electrode 2 and the negative electrode 3. The electrodes 2 and 3 can be laminated and fixed without being affected by the electrolytic solution 9, and the reliability such as vibration resistance of the electrodes 2 and 3 in the battery case 10 is improved.

Further, in this example, since the separators 8 of the laminate 14 are welded together in the laminating direction, it is possible to prevent the displacement between the electrodes without sticking the adhesive tape and to insert the laminate 14 into the battery case 10. Will be easier to handle.

Further, according to this embodiment, the positive electrode 2 and the negative electrode 3 are packed in the bag-shaped separator 8 respectively, so that the microporous polypropylene film or the like between the positive electrode 2 and the negative electrode 3 is 2 pieces.
The number of sheets becomes different, and the positions of the holes in the polypropylene film and the like are different, which has the advantage that the probability of occurrence of an internal short circuit is reduced.

Further, according to this embodiment, the positive electrode 2 and the negative electrode 3 are packed in the bag-shaped separator 8, respectively.
Also, the positive electrode active material 4 and the negative electrode active material 6 of the negative electrode 3 are prevented from falling off and scattering.

In the above-mentioned embodiments, an example in which the present invention is applied to a lithium ion secondary battery has been described, but it goes without saying that the present invention can be applied to other secondary batteries.
Further, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0030]

According to the present invention, since the separators 8 at predetermined portions of the separator 8 of the laminated body 14 are welded in the laminating direction to fix the laminated positional relationship of the positive electrode 2 and the negative electrode 3, the electrolytic solution It is possible to stack and fix each electrode without being affected by, and there is an advantage that reliability such as vibration resistance of the electrode in the battery case 10 is improved.

Further, according to the present invention, since the separators 8 of the laminate 14 are welded together in the laminating direction, it is possible to prevent the displacement between the electrodes without using an adhesive tape and to laminate them until they are inserted into the battery case 10. The benefit is that bundling of the body 4 is facilitated.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a secondary battery of the present invention.

FIG. 2 is a partially cutaway perspective view showing an example of a main part of FIG.

FIG. 3 is a cross-sectional view showing an example of a conventional secondary battery.

FIG. 4 is a diagram provided for explaining a lithium ion secondary battery.

[Explanation of symbols]

 2 Positive electrode 2a Positive electrode lead 3 Negative electrode 3a Negative electrode lead 8 Bag separator 10 Battery case 11 External positive electrode terminal 12 External pressure negative electrode terminal 14 Laminated body

Claims (1)

[Claims] 1. A secondary battery comprising a laminated body in which positive electrodes and negative electrodes packed in a bag-like separator are alternately laminated to face each other, and predetermined portions of the separators of the laminated body are welded in a laminating direction. The secondary battery is characterized in that the positional relationship between the positive electrode and the negative electrode is fixed.