JPH1167221A - Lithium battery and current collector used in it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the electricity conducting area in a conductive part small to suppress calorific value, and suppress temperature rising inside of a battery to ensure safety by arranging an insulating film whose both surfaces are coated with a conductive material as a current collector, and forming holes passing through the insulating film containing the conductive material on both sides. SOLUTION: A current collector 21 of a negative electrode or a positive electrode 20 is formed by vapor-depositing a conductive material 23 on both sides of an insulating material 22. For example, an aluminum layer having a thickness of about 3,000 Å is formed by vapor deposition. The insulating material 22 has a thickness of about 10 μm, a length of about 300 mm, and a width of about 40 mm. The specified number of through holes H having a diameter of about 1-5 mm are formed in the current collector 21. A pasty positive electrode mixture 24 is applied to the conductive material 23 on both surfaces and to the inside of the through holes H. The positive electrode mix 24 having a thickness of about 120 μm is formed on both surfaces. Even if a nail is stuck in a battery or outside pressure is applied to the battery, ignition or burning of the battery is prevented to increase safety.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure of a lithium battery, and more particularly to a current collector structure of an electrode capable of ensuring safety without firing or burning even under the influence of nailing, pressure and the like from outside the battery. Regarding improvement.

[0002]

2. Description of the Related Art A lithium secondary battery has a high voltage and a large capacity in a configuration in which a positive electrode having an active material applied to both sides of a current collector and a negative electrode are wound. For this reason, when a sharp conductor such as a nail is pierced into the battery, or when the battery is crushed by an external pressure, the conductive portions of the negative electrode and the positive electrode may be separated from the outside of the battery. Conduction short-circuit causes rapid temperature rise inside the battery. Then, the lithium secondary battery ignites and burns. It is necessary to prevent such ignition and combustion to enhance safety.

A wound lithium secondary battery has a wound body in which a positive electrode and a negative electrode are wound via a separator, is mounted in the battery, an electrolytic solution is injected from a sealed portion of the battery, and the battery is pressed by a press or the like. Is sealed to form, for example, an AA size wound lithium secondary battery. FIG. 8 is a structural diagram of an electrode according to the related art. This electrode is, for example, a positive electrode 20 and has a thickness of about 20 μm based on a paste-like positive electrode mixture 24.
Is coated on both sides of aluminum Al. As the positive electrode mixture 24, a lithium composite oxide such as LiV2O5 or LiCoO2 is used.

[0004]

A battery using a current collector as in the prior art is charged when a sharp conductor such as a nail is inserted into the battery in a charged state or when the battery is crushed by external pressure. If the temperature rises, the temperature rises sharply inside the battery. This is because the negative electrode and the conductive part of the positive electrode are electrically connected to each other by a nail inserted into the battery or an external pressure, thereby causing a short circuit.

FIG. 9 is a sectional view of the battery when a nail is inserted. The battery 1 is composed of a positive electrode 20 shown in FIG. 8 and a negative electrode 30 made of a lithium foil having a conductive thickness of about 100 μm via a separator 40 mainly composed of an insulating porous film having a thickness of about 25 μm. I have. The state when a conductive nail is inserted into the battery 1 is as follows.
Both the conductive surface A of the aluminum Al of the positive electrode and the conductive surface B of the metallic lithium of the negative electrode are contacted and short-circuited through the conductor nail. The larger the contact area between the nail and the conductive surface A and the conductive surface B, the larger the current passing through the short-circuited portion, the larger the amount of heat generated, causing a sharp rise in temperature.

FIG. 10 is a sectional view of the battery when the electrode is broken by an external pressure. Positive electrode 2 by external pressure P
0, the separator 40 and the negative electrode 30 are cut. Then, conduction occurs at a contact point C between the aluminum Al of the positive electrode 20 and the metallic lithium of the negative electrode 30 to cause a short circuit. The larger the area of the contact point C, the greater the current passing through the short-circuited portion, resulting in a large amount of heat generation and a sharp rise in temperature.

An object of the present invention is to reduce the current passing therethrough by reducing the conductive area of the conductive portions of the positive electrode 20 and the negative electrode 30 even when a metal object enters and the external pressure is applied from the outside of the battery 1,
It is an object of the present invention to provide a new battery capable of ensuring safety by suppressing the amount of heat generated, thereby suppressing a rise in temperature inside the battery.

[0008]

According to a first aspect of the present invention, there is provided a lithium battery having a negative electrode and a positive electrode, wherein a current collector constituting at least one of the negative electrode and the positive electrode has a conductor on both surfaces. And a plurality of holes penetrating the insulating film including conductors on both sides thereof.

According to a second aspect of the present invention, the negative electrode and the positive electrode are arranged to face each other with a separator interposed therebetween, and a hole of the current collector provided on the negative electrode and a hole of the current collector provided on the positive electrode are provided. 3. The lithium battery according to claim 1, wherein the lithium batteries are arranged so as not to face each other. The present invention according to claim 3, characterized in that the current collector is mainly composed of an insulating film coated with a conductor on both sides, and the insulating film has a plurality of holes penetrating the conductor including both sides of the conductor. I will provide a.

[0010]

Embodiments of the present invention will be described with reference to the drawings. The same parts as those in the conventional example are denoted by the same reference numerals and description thereof will be omitted. <First Embodiment> FIG. 1 is a structural view of an electrode according to a first embodiment, for example, showing a partially broken sectional view of a positive electrode. 22 is an insulator, 23 is a conductive substance, 24 is a positive electrode mixture, and H is a through hole. The current collector 21 is made of a conductive material 2 on both sides of an insulator 22.
The positive electrode 20 is obtained by applying a positive electrode mixture 24 to both surfaces of a current collector 21.

The insulator 22 has a thickness of about 10 μm, a length of about 300 mm, and a width of about 40 mm, and may be made of polyester, polypropylene, polyethylene, polyphenylene sulfide, polyvinyl chloride, polyimide, polyamide, or the like. A conductive substance 23 is provided on both sides of the insulator 22.
Is deposited. The conductive material 23 is aluminum, titanium,
Stainless steel, carbon, etc. can be used. In the first embodiment, aluminum is deposited to a thickness of 3000 °.

Next, a predetermined number of through holes H having a diameter of about 1 to 5 mm are provided in the current collector 21. Thereafter, a paste-like positive electrode mixture 24 is applied to both surfaces of the conductive substance 23 and the inside of the through hole H. The positive electrode mixture 24 is applied to both sides with a thickness of about 120 μm on one side. The positive electrode active material as the positive electrode mixture 24 is LiCoO.
2, LiMn2O4, LiNiO2, LiMn3O6, Li
V2 O5 or the like can be used. In this embodiment, LiCoO2
A mixture in which acetylene black and polyvinylidene fluoride were mixed at a ratio of 80:10:10 (weight ratio) to (lithium cobaltate) was used.

FIG. 2 is a sectional view of the battery according to the first embodiment. The negative electrode 30 made of lithium foil is provided in contact with the lower surface of the separator 40. The positive electrode 20 is provided in contact with the upper surface of the separator 40. As the positive electrode 20, the one described in FIG. 1 was used. And separator 4
For 0, a polypropylene porous film having a thickness of about 25 μm was used.

Further, a lithium foil having a thickness of about 100 μm was used for the negative electrode 30. The positive electrode 20, the negative electrode 30, and the separator 40 were used as the wound body 10. The electrolyte used was a non-aqueous electrolyte obtained by dissolving lithium hexafluorophosphate (1 mol / 1) in a mixed solvent of propylene carbonate and 1.2-dimethoxyethane (volume ratio 1: 1).

Then, an AA size wound lithium secondary battery was prepared. The capacity of this battery was about 900 mAh. FIG. 3 is a cross-sectional view when a nail is inserted into the battery according to the first embodiment. The inserted conductive nail is the positive electrode 2
The conductive surface 23 of the conductive material 23 and the conductive surface E of the lithium foil of the negative electrode 30 are in contact with each other and short-circuited.

FIG. 4 is a sectional view of the battery when the electrode is broken by an external pressure. The positive electrode 20, the separator 40, and the negative electrode 30 are cut by the external pressure P. Then, the conductive material 23 of the current collector 21 of the positive electrode 20 and the metallic lithium of the negative electrode 30 are brought into contact on the conductive surface F and short-circuited. However, an insulating film coated with a conductor is used, and a plurality of holes are provided in the insulating film. Further, the electrode according to the first embodiment has a conduction area of the conventional battery by depositing aluminum at a thickness of 3000 ° in the first embodiment from 20 μm of aluminum Al in the current collector region 25 of the prior art. Could be smaller.

More specifically, even when a metal object is pierced from the outside of the battery 1, the conductive material 2 of the positive electrode of the first embodiment is higher than the conductive surface A of the aluminum foil serving as the base of the conventional positive electrode.
3 can be made smaller. Further, even when the electrode is broken by an external pressure, the conductive surface F of the conductive material 23 of the positive electrode of the first embodiment can be made smaller than the conductive surface C of the aluminum foil serving as the base of the conventional positive electrode.

Therefore, by reducing the conduction area, the short-circuit current can be reduced and the heat generation can be suppressed. As a result, the temperature rise inside the battery can be suppressed, and safety can be ensured. <Second Embodiment> FIG. 5 is a structural view of an electrode according to a second embodiment, for example, showing a partial cross-sectional view of a negative electrode.

The second embodiment is different from the first embodiment in that a through hole H is provided in a current collector 21 composed of an insulator 22 and a conductive substance 23, and a negative electrode mixture 25 is applied to the conductor. This is the point of the negative electrode 30. When the negative electrode 30 has such a current collector 21 structure, the same material as the insulator 22 of the first embodiment is used.

However, as the conductive material 23, copper, nickel, chromium, stainless steel, titanium or the like is used. For example, in the second embodiment, the current collector 21 is formed by depositing copper to a thickness of about 2000 °. Next, a through hole H having a diameter of about 1 to 5 mm is formed in the current collector 21.
Are provided in a predetermined number. Further, the negative electrode mixture 2 is formed on both surfaces of the current collector 21.
5 is applied. The active material as the negative electrode mixture 25 is Li, L
i A negative electrode mixture 25 was prepared by mixing one of a lithium-carbon composite or the like based on an alloy, carbon, or graphite, for example, a mixture of graphite and polyvinylidene fluoride at a ratio of 95: 5 (weight ratio).

FIG. 6 is a sectional view of a battery according to the second embodiment. Positive electrode mixture 2 on lithium foil on top of separator 40
The positive electrode 20 provided with the electrode 4 is provided in contact with the positive electrode 20. A negative electrode 30 provided with a negative electrode mixture 25 on a current collector 21 is provided in contact with the lower surface of the separator 40. The negative electrode 30 described with reference to FIG. 5 was used.

The positive electrode 20 is obtained by coating a positive electrode mixture 24 on both sides of an aluminum foil. As the positive electrode mixture 24, a positive electrode mixture 24 in which acetylene black and polyvinylidene fluoride were mixed in a ratio of 80:10:10 (weight ratio) to LiCoO2 (lithium cobaltate) was used.

Then, an AA size wound type lithium secondary battery was prepared by using the same electrolyte and separator 40 as in the first embodiment. The capacity of this battery is 600m
Ah. <Comparative Example 1> AA size wound lithium secondary battery having the same configuration as that of the first embodiment except that a positive electrode current collector was applied to an aluminum foil having a thickness of about 20 µm and a positive electrode mixture 24 was applied. It was created. The capacity of this battery was 900 mAh. Comparative Example 2 AA size wound lithium secondary battery having the same configuration as that of the second embodiment except that a copper foil having a thickness of about 10 μm was used as a current collector of a negative electrode. The capacity of this battery was 600 mAh. <Safety Test> The batteries of Examples 1 and 2 and Comparative Examples 1 and 2 were charged to 4.2 V at 1.0 mA / square CM, and the following safety tests were performed in a fully charged state.

(1) Compression test A round bar having a diameter of 7.9 mm is used to compress the battery at a central portion up to 65% of the diameter. The compression speed is 10 mm / sec. (2) Nail penetration test A 2.5 mm diameter nail penetrates the center of the battery.

The nail penetration speed is 10 mm / sec. Table 1 shows the safety test results of the compression test and the nail penetration test of the batteries used in the first and second examples. The maximum temperature of the battery was 60 ° for the battery used in the first embodiment.
C, the temperature of the battery used in the second example rose only to 50 ° C. And did not ignite. However, the batteries used in Comparative Examples 1 and 2 had a maximum battery temperature of 50
The temperature rose to 0 ° or more. It ignited and burned. <Third Embodiment> FIG. 7 is a longitudinal sectional view of a battery according to the present invention. Both the positive electrode 20 described in the first embodiment and the negative electrode 30 described in the second embodiment are used. In this case, the through holes H of the current collector 21 provided on the negative electrode 30 and the through holes H of the current collector 21 provided on the positive electrode 20 are disposed so as not to be opposed to each other. The conductive area for short-circuiting is further reduced. Therefore, the calorific value is reduced, and a rapid temperature rise does not occur.

[0026]

As described above, the battery according to the present invention can reduce the heat generation amount by reducing the conductive area between the conductive portions of the positive electrode and the negative electrode even when a metal object enters and receives an external pressure from the outside. Therefore, temperature rise inside the battery can be suppressed, and safety can be ensured.

[Brief description of the drawings]

FIG. 1 is a structural view of an electrode according to a first embodiment,

FIG. 2 is a cross-sectional view of the battery according to the first embodiment,

FIG. 3 is a sectional view of the battery according to the first embodiment when a nail is inserted into the battery;

FIG. 4 is a cross-sectional view when the battery of the first embodiment is broken by receiving an external pressure;

FIG. 5 is a structural view of an electrode according to a second embodiment,

FIG. 6 is a sectional view of a battery according to a second embodiment,

FIG. 7 is a sectional view of a battery according to a third embodiment,

FIG. 8 is a configuration diagram of a battery according to the related art,

FIG. 9 is a cross-sectional view when a nail is inserted into an electrode according to the related art;

FIG. 10 is a cross-sectional view when a battery according to the related art is broken by receiving an external pressure.

[Explanation of symbols]

 Reference Signs List 1 battery 10 wound body 20 positive electrode 30 negative electrode 40 separator

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kensuke Yoshida 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Hiroshi Horiuchi 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 Inside Fujitsu Limited (72) Inventor Tsutomu Miyashita 4-1-1 Kamikadanaka Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited

Claims (3)

[Claims] 1. A lithium battery comprising a negative electrode and a positive electrode, wherein the current collector constituting at least one electrode of the negative electrode or the positive electrode is formed of an insulating film having both surfaces coated with a conductor, and A lithium battery, characterized in that the film has a plurality of holes penetrating the film including the conductors on both sides. 2. The negative electrode and the positive electrode are opposed to each other via a separator, and a hole of the current collector provided on the negative electrode does not face and coincide with a hole of the current collector provided on the positive electrode. The lithium battery according to claim 1, wherein the lithium battery is arranged as follows. 3. A current collector for a lithium battery, mainly comprising an insulating film coated with a conductor on both sides thereof, and having a plurality of holes penetrating the insulating film including the conductors on both sides.