JP2001229957A - Cylindrical lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical lithium ion battery, in which double-ply separators are used and winding slips hardly appear at winding-around. SOLUTION: Non-smooth faces of two separators made of polyethylene are overlapped in a counterposed state to each other, and the top end parts of them are welded and integrated. Then, after the top end parts of two integrated pairs of separators 24 are welded with an axial core 21, they are wound around together with an cathod plate 2 and a anode plate 23, and wound-around groups 6 are made. By using the wound-around groups 6, a cylindrical lithium ion battery is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical lithium ion battery.

[0002]

2. Description of the Related Art Lithium ion batteries are mainly used for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. In recent years, research and development of large-sized lithium-ion batteries for electric vehicles and power storage have been actively conducted. In particular, in the automobile industry, development of electric vehicles using a motor as a power source and hybrid electric vehicles using both an internal combustion engine and a motor as a power source has been promoted in order to respond to environmental issues.
Some of them are already in practical use.

[0003] However, large-sized lithium-ion batteries used for these devices have high capacity and high output,
Security is strongly required. In a conventional cylindrical lithium ion battery, since high capacity is strongly required, the number of separators between the positive electrode plate and the negative electrode plate is one. However, with one separator, a case where a short circuit occurred between the positive electrode plate and the negative electrode plate was observed. That is, during the production of a cylindrical lithium-ion battery, when foreign matter is mixed between the positive electrode plate and the separator or between the negative electrode plate and the separator, it becomes a protrusion, which breaks through the separator during winding and breaks the positive electrode plate and the negative electrode plate. In some cases, a short circuit occurred between them. In addition, when using the cylindrical lithium ion battery, a case where a short circuit was generated from a pinhole formed in advance in the separator was also recognized.

In order to solve these problems, a method of increasing the thickness of the separator has been studied. However, when the separator is thickened, short-circuiting due to foreign matter can be prevented, but short-circuiting due to pinholes formed in advance cannot be suppressed.

Therefore, a method of suppressing a short circuit by shifting the positions of pinholes by stacking a plurality of separators has been studied. However, when this method is used, there are problems in that it is difficult to align the separator, the positive electrode plate, and the negative electrode plate, and that the winding is apt to be displaced at the time of winding, thereby lowering production efficiency.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cylindrical lithium ion battery in which the alignment of the separator, the positive electrode plate and the negative electrode plate is easy, and the winding is hardly displaced during winding.

[0007]

SUMMARY OF THE INVENTION A comparison of both sides of a polyethylene separator reveals that, for manufacturing reasons, one side is smooth and the other side is slightly uneven and not smooth. . Therefore, the present invention uses a separator of 2
This is because the influence of these superimposed surfaces is taken into account when the sheets are used one after another.

That is, in the first invention, a positive electrode plate and a negative electrode plate are wound around a shaft via a separator to form a winding group, and the winding group is housed in a cylindrical battery container. In the ion battery, there are two separators between the positive electrode plate and the negative electrode plate, wherein the separator is wound with the non-smooth surfaces facing each other, The invention is characterized in that tip portions of the two separators are joined to the shaft core.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, a cylindrical lithium ion battery having the shape shown in FIG. 4 was prepared and evaluated.

[0010] 1. Preparation of positive electrode plate Lithium manganate (LiMn ₂ O ₄ ) powder, which is an active material for the positive electrode, and flaky graphite as a conductive agent (average particle size: 20 μm)
And polyvinylidene fluoride as a binder, and the mass ratio is
90: 4.5: 5.5, and this mixture was mixed with N
After adding -methyl-2-pyrrolidone, knead to form a slurry. This slurry was applied to both sides of a 20 μm-thick aluminum foil (positive electrode current collector) to form a positive electrode mixture layer.
When the slurry was applied, an uncoated portion having a width of 50 mm was left on one of the side edges in the longitudinal direction of the aluminum foil. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode plate having a width of 300 mm and a predetermined length. The thickness of the positive electrode mixture layer (however, the thickness of the current collector was not included) was 260 μm, and the coating amount of the positive electrode active material per one side of the current collector was 344 g / m ² .

A part of the uncoated portion having a width of 50 mm formed on the positive electrode plate was removed to form a rectangular portion, which was used as a lead piece 9 for current collection. Note that the width of the lead piece 9 is about 10 m
m, the interval between adjacent lead pieces 9 was set to about 20 mm.

2. Preparation of negative electrode plate Carbotron P which is amorphous carbon as the negative electrode active material
To 92 parts by mass (product name: Kureha Chemical Industry Co., Ltd.), 8 parts by mass of polyvinylidene fluoride was added as a binder, and N-methyl-2-pyrrolidone as a dispersion solvent was added thereto.
Make a slurry by kneading. This slurry has a thickness of 10μ
m of rolled copper foil (negative electrode current collector). At the time of applying the slurry, an uncoated portion having a width of 50 mm was left on one of the side edges in the longitudinal direction of the copper foil. Thereafter, drying, pressing and cutting were performed to obtain a negative electrode plate having a width of 305 mm and a predetermined length. The bulk density of the negative electrode mixture layer was about 1.0 g / cm ³ .

A notch was formed in the above-mentioned uncoated portion having a width of 50 mm formed on the negative electrode plate, a part thereof was removed, and a rectangular portion was formed to be used as a lead piece 9 for current collection. The width of the lead pieces 9 was set to about 10 mm, and the interval between the adjacent lead pieces 9 was set to about 20 mm.

In the width direction of the positive electrode plate and the negative electrode plate, the application area of the negative electrode active material is applied so as not to be displaced opposite to the application area of the positive electrode active material and the application area of the negative electrode active material. The width was about 5 mm larger than the width of the coated portion of the positive electrode active material.

3. Winding The above positive electrode plate and negative electrode plate are wound via a polyethylene separator to form a winding group 6. When comparing both sides of a polyethylene separator, for manufacturing reasons,
It was clarified that one surface was smooth and the other surface was slightly uneven and not smooth. Thus, when two separators were used, an experiment was conducted on how the influence of these superposed surfaces affects the winding deviation at the time of winding.

In this case, as will be described later, two separators each having a thickness of 25 μm are stacked and used so that the lead pieces 9 of the positive electrode plate and the lead pieces 9 of the negative electrode plate are located on the opposite sides of the winding group 6 respectively. Wound. Positive electrode plate, negative electrode plate and separator
The diameter of the wound group 6 was set to 65 ± 0.1 mm by cutting the tape into appropriate lengths.

Since the positive electrode plate is always covered with the negative electrode plate at the outermost periphery of the winding group 6, the length of the negative electrode plate is set to be 18 cm longer than the length of the positive electrode plate. The positive electrode plate and the negative electrode plate at the outermost periphery of the winding group 6 were shifted by 2.5 mm or more on one side, and were regarded as defective.

4. Fabrication of the battery As shown in FIG. 1, a lead piece led out from the positive electrode plate
9, after bending and deforming in the state of collecting and bundling,
It is brought into contact with the flange 7 formed on the positive electrode external terminal 1a. Then, in this state, the lead piece 9 and the flange 7 are electrically connected by welding using an ultrasonic welding device. In the same manner, for the negative electrode plate, the lead piece 9 and the flange portion 7 formed on the negative electrode external terminal 1b were electrically connected by ultrasonic welding.

Thereafter, the entire outer peripheral surface of the flange 7 of the positive electrode external terminal 1a, the flange 7 of the negative electrode external terminal 1b, and the winding group 6 is covered with an insulating coating 8.
Cover with. As the insulating coating 8, an adhesive tape made of polyimide having an adhesive made of hexamethacrylate coated on one side was used. After adjusting the number of turns of the adhesive tape so that the outer peripheral portion of the winding group 6 is covered with the insulating coating 8 and slightly smaller than the inner diameter of the stainless steel battery container 5, the winding group 6 is removed from the battery container. Insert into 5. The battery container 5
Has a cylindrical shape with an outer shape of 67 mm and an inner diameter of 66 mm.

Next, a second ceramic washer 3b having a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 25 mm at a portion in contact with the outer surface of the battery lid 4 is connected to the positive external terminal 1a and the negative external terminal 1b.
Into each tip. Then, the first ceramic washer 3a is placed on the battery cover 4, and each of the positive external terminal 1a and the negative external terminal 1b is connected to the first ceramic washer 3a.
Through.

Thereafter, the peripheral end surface of the battery lid 4 having a disk shape is fitted into the opening of the battery container 5 and the entire area of the contact portion between the battery lid 4 and the battery container 5 is laser-welded. At this time, the positive external terminal
1a, the negative electrode external terminal 1b protrudes outside through a hole in the center of the battery lid 4. And the thickness is 2mm, inner diameter is 1
6mm, 28mm outside diameter plate-shaped first ceramic washer 3
a, a metal washer 11 smoother than the bottom surface of the nut 2 is fitted into the positive external terminal 1a and the negative external terminal 1b in this order. The battery lid 4 is provided with a cleavage valve 10 that is cleaved in response to an increase in the internal pressure of the battery.
kg / cm ² . As described above, the present battery is not provided with a current cutoff mechanism that operates in response to a rise in pressure inside the battery.

A metal nut 2 is screwed to the positive external terminal 1a and the negative external terminal 1b, respectively, and the battery cover 4 is connected via the second ceramic washer 3b and the first ceramic washer 3a.
Is fixed between the collar 7 and the nut 2. The tightening torque value at this time is 6.86 N · m. By compressing the O-ring 12 made of rubber (made of EPDM) interposed between the back surface of the battery lid 4 and the flange portion 7 at the time of tightening, the power generating elements and the like inside the battery container are shut off from the outside air.

After a predetermined amount of electrolyte is injected into the battery container 5 from the liquid inlet 13 provided in the battery cover 4, the liquid inlet 13 is sealed to complete a cylindrical lithium ion battery. The electrolyte was prepared by mixing ethylene carbonate, dimethyl carbonate and diethyl carbonate at a volume ratio of 1: 1: 1, and then adding 1 mol of lithium hexafluorophosphate (LiPF ₆ ).
/ l dissolved organic electrolyte was used.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail. (Example 1) After two polyethylene separators each having a thickness of 25 μm are overlapped so that the non-smooth surfaces 31 face each other (FIG. 1), one end thereof is welded to form a two-sheet separator. I do. This two-ply separator is
As shown in FIG. 3, as shown in FIG. 3, the tip portions of the respective separators 24 are welded to two places of the shaft core 21, and then wound with the positive electrode plate 22 and the negative electrode plate 23 inserted, and the winding deviation during winding is performed. Was measured. The separator 24 is attached to the shaft 21.
By welding the front end portions, the positioning with the positive electrode plate and the negative electrode plate is facilitated, and the winding is facilitated. Other fabrication conditions and test conditions for the cylindrical lithium ion battery are as described above. (Comparative Example 1) Two polyethylene separators each having a thickness of 25 μm are stacked so that the non-smooth surface 31 and the smooth surface 30 face each other (FIG. 2), and one end thereof is welded to form two sheets. Create an overlay separator. As shown in FIG. 3, two sets of the two-layer separators are used, and the front ends of the respective separators 24 are welded to two places of the shaft core 21.
The film was wound with the 22 and the negative electrode plate 23 inserted, and the rate of occurrence of winding deviation during winding was measured. Other manufacturing conditions and test conditions of the cylindrical lithium ion battery are exactly the same as those of the first embodiment. (Comparative Example 2) Two polyethylene separators having a thickness of 25 µm are stacked so that the smooth surfaces 30 face each other (not shown), and one end thereof is welded to form a two-layer separator. I do. As shown in FIG. 3, two sets of the two stacked separators are used, and the tip portions of the respective separators 24 are welded to two places of the shaft core 21 and then wound with the positive electrode plate 22 and the negative electrode plate 23 inserted. The rate of occurrence of winding deviation during winding was measured. Other fabrication conditions and test conditions for the cylindrical lithium ion battery are as described above.

Table 1 shows the measurement results of the occurrence of winding deviation during winding of the cylindrical lithium ion battery. Example 1 was good with little winding deviation. On the other hand, Comparative Examples 1 and 2 are not preferable because of large winding deviation.
Using the present invention, the uneven surface of the two separators
It is considered that the separators are less likely to slip due to the contact between the separators 30 and that the smooth surface 30 of the separator is in contact with the positive electrode plate or the negative electrode plate, and that this portion is slippery, so that winding deviation can be reduced.

[0026]

[Table 1]

In this embodiment, an example of a large-sized cylindrical lithium-ion battery is shown. However, the same applies to a relatively small-sized lithium-ion battery in which a bottomed cylindrical battery container is used and the upper lid is closed by caulking. Good results were obtained.

In this embodiment, a polyimide adhesive tape coated with an adhesive made of hexamethacrylate on one side is used for the insulating coating 8, but the present invention is not limited to this. That is, an adhesive tape in which an acrylic adhesive such as hexamethacrylate or butyl acrylate is applied to one or both surfaces of a polyolefin such as polypropylene or polyethylene, or a tape made of polyolefin or polyimide to which no adhesive is applied can also be used.

In this embodiment, an example in which lithium manganate is used as the positive electrode active material has been described, but a lithium-cobalt composite oxide, a lithium-nickel composite oxide, or the like can also be used. Further, as the active material for the negative electrode, a carbon material such as natural graphite, artificial graphite, and coke can be used, and their particle shapes are not particularly limited.

In this embodiment, poly (vinylidene fluoride) was used as a binder, but Teflon, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber,
Styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes, polymers such as acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene and mixtures thereof can also be used.

As the electrolyte, LiCl
O ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li
And mixtures thereof. In addition, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3
Dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitonyl, or a mixed solvent of two or more of these is also used.

[0032]

The cylindrical lithium ion battery using the present invention is excellent because the positioning of the separator, the positive electrode plate and the negative electrode plate is easy, and the winding is less likely to be displaced during winding.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in which two separators of Example 1 are stacked.

FIG. 2 is a cross-sectional view in which two separators of Comparative Example 1 are stacked.

FIG. 3 is a schematic diagram at the time of winding using two stacked separators.

FIG. 4 is a cross-sectional view of a cylindrical lithium ion battery for an electric vehicle.

[Explanation of symbols]

1a: positive external terminal, 1b: negative external terminal, 2: nut, 3a: first ceramic washer, 3b: second ceramic washer, 4: battery cover, 5: battery container,
6: wound group, 7: flange, 9: lead piece, 10: cleavage valve, 11: metal washer, 12: O-ring, 13: injection port, 20: cylindrical lithium ion battery, 21: shaft core, 22: Positive electrode plate, 23: Negative electrode plate, 24: Separator, 25: Welding part, 26: Adhesive part, 27: Adhesive tape 30: Smooth surface, 31: Non-smooth surface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Higashimoto 2-8-7 Nihonbashi Honcho, Chuo-ku, Tokyo F-term in Shin-Kobe Electric Machinery Co., Ltd. 5H028 AA05 BB08 BB17 CC12 5H029 AJ00 AK03 AL06 BJ02 BJ14 CJ07 DJ04 DJ11

Claims (2)

[Claims] 1. A cylindrical lithium ion battery in which a positive electrode plate and a negative electrode plate are wound around an axis through a separator to form a winding group, and the winding group is housed in a cylindrical battery container. A cylindrical lithium-ion battery, wherein two separators are present between a positive electrode plate and the negative electrode plate, and the separator is wound with non-smooth surfaces facing each other. 2. A cylindrical lithium ion battery according to claim 2, wherein the tip portions of said two separators are joined to said shaft core.