JPH07272761A - Nonaqueous electrolytic secondary battery - Google Patents

Abstract

PURPOSE:To improve a heavy load characteristic, cycle characteristic and a low temperature characteristic by eliminating the wrinkle of a separator. CONSTITUTION:In a nonaqueous electrolytic secondary battery formed by superposing a positive/negative electrode plates 2, 3 opposed to each other alternately through a separator, at least this positive electrode plate 2 or negative electrode plate 3 is interposed by two sheets of separators 8a, 8a, and also the periphery of the positive electrode plate 2 or negative electrode plate 3 of two sheets of the separators 8a, 8a is fused in every other prescribed space.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery which is 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.

As shown in FIG. 6, this lithium ion secondary battery is formed by packing a positive electrode plate 2 and a negative electrode plate 3 in a bag-shaped separator 8 and stacking them alternately. Then, the laminated body composed of the positive electrode plate 2, the negative electrode plate 3 and the bag-shaped separator 8 is inserted into a battery case having a rectangular parallelepiped shape having an opening on one side, and an electrolytic solution is filled therein to recharge the secondary battery. Function as.

As the positive electrode plate 2, as shown in FIGS. 6 and 7, for example, a composite oxide of lithium Li and a transition metal is formed on both sides 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 plate 3, as shown in FIGS. 6 and 7, lithium Li is formed on both sides of a current collector 7 made of, for example, a copper Cu foil (or nickel Ni foil) having a rectangular thickness of about 10 μm.
Is a carbon that can be doped or dedoped, 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, a microporous polyethylene film or polypropylene film having a thickness of 25 μm, for example, is formed into a bag shape. As the electrolytic solution 9, an organic electrolytic solution in which LiPF ₆ is dissolved in a mixed solvent of propylene carbonate and diethyl carbonate at a ratio of 1 mol / 1 is used.

Conventionally, the bag-shaped separator 8 is arranged between the positive electrode plate 2 and the negative electrode plate 3 by packing the positive electrode plate 2 and the negative electrode plate 3 in the bag-shaped separator 8. In order to pack the positive electrode plate 2 and the negative electrode plate 3 into a bag, as shown in FIG. 8, a plurality of positive electrode plates 2 or negative electrode plates 3 (FIG. 8 shows only the positive electrode plate 2) arranged at a predetermined interval. 2 from the direction
The separator film was sandwiched between the electrode plates, and the periphery of each electrode plate was heat-sealed to bond them together.

This heat fusion is performed by pressing a heater block whose temperature is controlled. Then, as shown in FIG. 9, each of the bag-shaped electrode plates is separated from the fusion-bonded portion, and then the bag-shaped separator 8 and the bag-shaped separator 8 are bag-packed as shown in FIG. The packed negative electrode plates 3 are alternately stacked.

When the bag-shaped separator 8 is used, there are two microporous polypropylene films or the like between the positive electrode plate 2 and the negative electrode plate 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. Further, when the positive electrode plate 2 and the negative electrode plate 3 are packed in the bag-shaped separator 8, the active materials 4, 6 are prevented from falling off and scattered, and the positive electrode plate 2 and the negative electrode plate 3 packed in the bag-shaped separator 8 are alternated. Since the positive electrode plate 2 and the negative electrode plate 3 are stacked on top of each other, the manufacturing is easier than that in which the positive electrode plate 2 and the negative electrode plate 3 are stacked via a film-like separator.

[0010]

However, after the fusing, the bag-shaped separator 8 shrinks due to heat, so that the bag-shaped separator 8
Wrinkles are generated, and a plurality of positive electrode plates 2 having the bag-shaped separator 8 having the wrinkles, for example, 51 sheets and a plurality of negative electrode plates 3 having the bag-shaped separator 8 having the wrinkles, for example, 52 sheets, are alternately superposed. In such a case, the space due to the wrinkles of the bag-shaped separator 8 becomes large, and the contact deteriorates, so that the heavy load characteristic, the cycle characteristic, the low temperature characteristic, etc. are deteriorated.

In view of the above point, the present invention has an object to eliminate wrinkles in the separator 8 and improve heavy load characteristics, cycle characteristics, low temperature characteristics and the like.

[0012]

The non-aqueous electrolyte secondary battery of the present invention has a positive electrode plate 2 and a negative electrode plate 3 as shown in FIGS. 1 to 5, for example.
In a non-aqueous electrolyte secondary battery in which and are alternately laminated via a separator, at least this positive electrode plate 2 or negative electrode plate 3 is sandwiched by two separators 8a, 8a, and The periphery of the positive electrode plate 2 or the negative electrode plate 3 of the separators 8a, 8a is fused at predetermined intervals.

In the non-aqueous electrolyte secondary battery of the present invention, as shown in, for example, FIGS. 1 to 5, one side 2b or 3b of the positive electrode plate 2 or the negative electrode plate 3 has a predetermined width and the two separators 8a, 8a.
It is more exposed and is connected to the lead terminal 11a or 12a.

[0014]

According to the present invention, at least the positive electrode plate 2 or the negative electrode plate 3 is sandwiched by the two separators 8a, 8a, and the periphery of the positive electrode plate 2 or the negative electrode plate 3 of the two separators 8a, 8a is separated by a predetermined distance. Since they are fused every other time, after the fusion, there is almost no wrinkling of the separators 8a and 8a due to heat, and a plurality of positive electrode plates 2 and negative electrode plates 3 are provided.
There is almost no space due to the wrinkles of the separators 8a and 8a even when they are alternately superposed via a and 8a,
Heavy load characteristics, cycle characteristics, low temperature characteristics, etc. can be improved.

[0015]

EXAMPLES An example of the non-aqueous electrolyte secondary battery of the present invention will be described below with reference to FIGS. 1 to 5 are examples in which the present invention is applied to a lithium ion secondary battery. 1 to 5, parts corresponding to those in FIGS. 6 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 5, reference numeral 10 indicates a thickness of 300 μ, for example.
The horizontal length of the stainless steel plate is approximately 300m.
m shows a flat rectangular battery container of a sealed type single cell having a vertical length of about 100 mm and a thickness of 25 mm. In the flat rectangular battery container 10, 51 positive electrode plates 2 and 52 negative electrodes are shown. Laminated body 14 in which plates 3 are alternately laminated with separators 8a in between
To store.

The positive electrode plate 2 has a structure as shown in FIGS.
As shown in FIG. 7, the rectangular shape of the flat rectangular battery container 10 is approximately equal to 300 mm × 100 mm, and the rectangular shape is approximately 20 μm. A composite oxide of Li and a transition metal such as LiCoO ₂ is deposited as the positive electrode active material 4.

As the negative electrode plate 3, FIGS.
And, as shown in FIG. 7, a current collector 7 made of copper Cu foil (or nickel Ni foil) having a rectangular thickness of about 10 μm, which is approximately equal to the internal shape of the flat rectangular battery container 10 of approximately 300 mm × 100 mm. On both surfaces of the negative electrode, carbon that can be doped with lithium Li and dedoped, 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.

Further, in this embodiment, the separator is a rectangular porous film having a thickness of 25 μm, which is slightly larger than the positive electrode plate 2 and the negative electrode plate 3, as shown in FIGS. The positive electrode plate 2 and the negative electrode plate 3 are sandwiched by the two film-shaped separators 8a and 8a, respectively, and the periphery of the positive electrode plate 2 and the negative electrode plate 3 of the two film-shaped separators 8a and 8a are arranged at predetermined intervals. Then, for example, every 20 mm is fused by 3 mm (in the drawing, 8b is a fused portion).

In this example, as shown in FIG. 2, a plurality of positive electrode plates 2 or negative electrode plates 3 (FIG. 2 shows only the positive electrode plate 2) arranged at a predetermined interval are formed into two films in the thickness direction. Each positive electrode plate 2 sandwiched between the separators 8a, 8a
(Or each negative electrode plate 3) 3m at intervals of 20mm, for example
m Heat fusion is performed. In this case, this heat fusion is performed by pressing a heater block having a temperature-controlled, for example, a 20 mm interval and a 3 mm convex portion.

In this case, when a polyethylene film is used as the film-shaped separator 8a, the heater block is kept at 120 ° C. for 3 seconds. When a polypropylene film is used as the film-shaped separator 8a, the heater block is set to 160 ° C. and pressed for 3 seconds.

Further, in this example, as shown in FIGS. 1, 2 and 3, the predetermined width 2b of the current collector 5 (or current collector 7) on one side of the rectangular positive electrode plate 2 (or negative electrode plate 3). (Or 3b) is exposed from the separator 8a.

The positive electrode plate 2 (or the negative electrode plate 3) sandwiched between the two film-shaped separators 8a and 8a is heat-sealed at intervals of 20 mm for 3 mm, for example. Separate each one.

In this example, 51 sheets of the positive electrode plate 2 sandwiched between the two separators 8a, 8a fused by 3 mm every 20 mm and two separators 8a, 8a fused by 3 mm every 20 mm are sandwiched. Fifty-two negative electrode plates 3 are alternately laminated as shown in FIG. 4 to form a rectangular laminated body 14.

Further, in this example, as shown in FIG. 4, one side of the rectangular laminated body 14, that is, the exposed portion 2b having a predetermined width of the positive electrode plate 2 is made of, for example, copper Cu, and the positive electrode plate 2 is arranged in the vertical direction. Is welded over the entire length to the positive electrode lead body 11a having a length of about 100 mm by ultrasonic welding.

The side opposite to one side of the rectangular laminated body 14, that is, the exposed portion 3b of a predetermined width of the negative electrode plate 3 is made of, for example, copper Cu, and the negative electrode plate 3 has a length of about 10 in the vertical direction.
The negative electrode lead body 12a having a length of 0 mm is welded over the entire length by ultrasonic welding. 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 container 10.

Further, this closed flat rectangular battery container 10 is used.
An organic electrolytic 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 thereinto, and the organic electrolytic solution was placed between the positive electrode active material 4 and the negative electrode active material 6. 9 is filled.

In this embodiment, 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. In FIG. 5, 13
Is a safety valve for venting the gas inside the closed flat rectangular battery case 10 when the internal pressure becomes higher than a predetermined value.

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

According to this embodiment, the positive electrode plate 2 and the negative electrode plate 3 are sandwiched by two separators 8a and 8a, respectively, and the circumference of the positive electrode plate 2 and the negative electrode plate 3 of the two separators 8a and 8a is, for example, 20 mm. Since every 3 mm, the separators 8a, 8a are hardly wrinkled by heat after the fusion, and the positive electrode plate 2 is, for example, 51 sheets and the negative electrode plate 3 is, for example, 52 sheets. Even when they are alternately overlapped with each other, there is almost no space due to the wrinkles of the separators 8a, 8a, and there is an advantage that heavy load characteristics, cycle characteristics, low temperature characteristics, etc. can be improved.

Further, according to this example, the positive electrode plate 2 and the negative electrode plate 3 are sandwiched by the two separators 8a, 8a, respectively, so that the microporous polypropylene film or the like between the positive electrode plate 2 and the negative electrode plate 3 is separated by 2 pieces. The number of sheets is different, and the positions of the holes in the polypropylene film are different, which has the advantage that the probability of occurrence of an internal short circuit is low.

Further, according to this example, the positive electrode plate 2 and the negative electrode plate 3 are sandwiched by the two separators 8a, 8a, respectively, so that the positive electrode active material 4 and the negative electrode active material of the positive electrode plate 2 and the negative electrode plate 3, respectively. It prevents the falling and scattering of No. 6.

Further, according to this example, the positive electrode plate 2 and the negative electrode plate 3 are sandwiched by two separators 8a, 8a, respectively, and fused at predetermined intervals, and the positive electrode sandwiched by the two separators 8a, 8a. Since the plate 2 and the negative electrode plate 3 are laminated, there is an advantage that the handling is easier and the manufacturing is easier than that of the conventional one in which the positive electrode plate 2 and the negative electrode plate 3 are laminated via a film-like separator.

Further, in the above-mentioned example, since the positive electrode lead body 11a and the negative electrode lead body 12a are provided over the entire length of the opposite sides of the rectangular laminate 14 composed of the rectangular positive electrode plate 2 and the negative electrode plate 3, respectively. There is an advantage that the current collection efficiency is improved as compared with the conventional one side where the positive electrode lead part and the negative electrode lead part are provided.

In the above-mentioned embodiments, the example in which the present invention is applied to the lithium ion secondary battery is described, but it goes without saying that the present invention can be applied to other non-aqueous electrolyte secondary batteries. Further, in the above-described embodiment, the positive electrode plate 2 and the negative electrode plate 3
Both of them are sandwiched by two separators 8a, 8a, respectively, and the periphery of the positive electrode plate 2 and the negative electrode plate 3 of the two separators 8a, 8a is fused by, for example, 3 mm at intervals of 20 mm. Adhesion may be performed at predetermined intervals as needed, and the separators 8a, 8a may be provided on either the positive electrode plate 2 or the negative electrode plate 3, and when provided on either one of them, the same operation as described above is performed. It can be easily understood that the effect can be obtained.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0037]

According to the present invention, at least one of the positive electrode plate 2 and the negative electrode plate 3 is sandwiched by the two separators 8a and 8a, and the positive electrode plate 2 and the negative electrode plate 3 of the two separators 8a and 8a are sandwiched. Since the periphery is fused at a predetermined interval, after the fusing, the separators 8a, 8a are hardly wrinkled by heat, and the positive electrode plate 2 is, for example, 51 sheets and the negative electrode plate 3 is, for example, 52 sheets. , 8a, the separators 8a, 8a
There is almost no space due to the wrinkles of a, and there is an advantage that heavy load characteristics, cycle characteristics, low temperature characteristics, etc. can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a main part of an embodiment of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a diagram for explaining a manufacturing example of the example of the main part of FIG.

FIG. 3 is a cross-sectional view of an example of a main part of FIG.

FIG. 4 is a perspective view for explaining an example of a main part of the present invention.

FIG. 5 is a cross-sectional view showing an example of the non-aqueous electrolyte secondary battery of the present invention.

FIG. 6 is a diagram provided for explaining an example of a conventional non-aqueous electrolyte secondary battery.

FIG. 7 is a diagram provided for explaining a lithium ion secondary battery.

FIG. 8 is a diagram for explaining FIG. 6;

9 is a diagram used to explain FIG. 6. FIG.

[Explanation of symbols]

 2 Positive Electrode Plate 3 Negative Electrode Plate 4, 6 Active Material 5, 7 Current Collector 8a Separator 8b Fused Section 10 Oblate Square Battery Container 11 External Positive Electrode Terminal 11a Positive Electrode Lead Body 12 External Negative Electrode Terminal 12a Negative Lead Body

Claims (2)

[Claims] 1. A non-aqueous electrolyte secondary battery in which a positive electrode plate and a negative electrode plate are alternately laminated with a separator interposed therebetween, and at least the positive electrode plate or the negative electrode plate is sandwiched by two separators. A non-aqueous electrolyte secondary battery, characterized in that the positive electrode plate and the negative electrode plate of the two separators are fused at predetermined intervals. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein one side of the positive electrode plate or the negative electrode plate is exposed from the two separators with a predetermined width and is connected to a lead terminal. And a non-aqueous electrolyte secondary battery.