JPH1055792A - Thin battery - Google Patents

Abstract

(57) [Problem] To provide a thin battery capable of smoothly releasing gas when the internal pressure increases. SOLUTION: A part 5 having a small peel strength is provided in a part of an adhesive part 4 of an exterior film 1 enclosing a power generation element 2, and the part 5 having a small peel strength is small outside the adhesive part 4 and small inside the adhesive part 4. Enlarge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin battery, and more specifically, a power generating element is covered by an outer film, and when a gas generated in the battery increases the internal pressure of the battery, the gas is discharged. It relates to a structure that can be released to the outside.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and multifunctionality of portable electronic devices, batteries used as power sources have been reduced in size and weight and increased in capacity, mainly lithium batteries, and these batteries have been used. The period is also prominent for 5 to 10 years.

To cope with such a tendency, various proposals have been made regarding improvement of power generation elements such as an electrode material, a separator, and an electrolyte constituting a battery, and reduction in thickness and weight of a package. There have also been proposals for a sealing function that can maintain reliability.

In the case of a lithium battery, the above-mentioned sealing function is a function to prevent moisture and oxygen from the outside from entering through the sealing portion and to prevent the electrolyte solution from escaping through the sealing portion. Specifically, a metal foil such as aluminum is interposed in an exterior film enclosing the power generation element, and a resin with strong mechanical strength such as nylon or polyethylene terephthalate is fused to the outer surface, and a resin such as polypropylene or polyethylene is fused to the inner surface. It is known to use a laminate film having a resin having excellent properties and having a low permeability to moisture and oxygen.

The above-mentioned sealing function is also a function capable of discharging the gas to the outside when the internal pressure of the battery increases due to the gas generated in the battery.
There is one as described in JP-A-13061. According to the publication, terminal plates 4 and 5, which also function as current collectors, are arranged above and below a power generating element in which a positive electrode active material 1, an electrolyte 2, and a negative electrode active material 3 are layered. 4,5
A structure is disclosed in which the peripheral portion of is sealed by an electrically insulating sealing member 6, the adhesive strength between the sealing member 6 and the terminal plates 4 and 5 is locally reduced, and gas is released from this portion. Have been.

[0006]

The use of a laminate film for the above-mentioned exterior film is advantageous in that the battery can be made thinner, smaller and lighter. If a function of preventing the intrusion of moisture or oxygen and preventing the electrolyte from escaping and a function of releasing gas to the outside when the internal pressure of the battery is increased are required, Japanese Patent Application Laid-Open No. 5-13061 discloses When the exterior films are adhered to each other as described, there is a problem that the adhered portion may peel off when the internal pressure of the battery increases, and it is difficult to maintain the reliability of the battery.

[0007]

According to a first aspect of the present invention, there is provided a thin battery in which a power generation element is encapsulated by bonding exterior films to each other. Is provided with a portion having a small peel strength, and the portion having a small peel strength is small outside the bonding portion and large inside the bonding portion, whereby when the internal pressure of the battery increases, The internal pressure is concentrated at a portion where the peel strength is small, so that the gas can be released smoothly.

According to a second aspect of the present invention, in the thin battery according to the first aspect, a portion having a small peel strength is JIS.
The peel strength in the T-shaped peel test specified in (K6854) is 2 kg or more and 10 kg or less, whereby the adhesion is broken even by bending, vibration and impact applied during normal use. In addition, no gas is released even if the internal pressure increases so that the package expands.

According to a third aspect of the present invention, in the thin battery according to the first or second aspect, the bonding portion of the exterior film is formed by bonding a fusible resin, and the portion having a small peel strength is the fusible resin. And a non-melting substance interposed therebetween, whereby a portion having a small peel strength can be easily formed.

According to a fourth aspect of the present invention, in the thin battery according to the first or second aspect, the bonding portion of the outer film is formed by bonding a hot-melt resin, and the portion having a small peel strength is formed by the hot-melting resin. It is characterized by being formed by heating the conductive resin at a temperature lower than that of the other bonding portions, whereby a portion having a small peel strength can be easily formed.

According to a fifth aspect of the present invention, in the thin battery according to the first or second aspect, a portion having a small peel strength is formed by forming an unbonded portion of an exterior film. Yes, this makes it possible to easily form a portion having a small peel strength.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

FIG. 1 is a partially cutaway plan view of a thin battery according to a first embodiment of the present invention, which is characterized in that a metal foil made of aluminum is interposed in an exterior film 1 and the outer surface of the battery is formed on the outer surface. By using a laminated film in which nylon or polyethylene terephthalate and polypropylene or polyethylene are arranged on the inner surface, the outer film 1 is formed into a bag shape, the power generating element 2 is inserted therein, and the open end 3 is bonded with a fusible resin. A portion 5 having a small peel strength, which covers the power generating element 2 and is formed on a part of the bonding portion 4 at the open end 3.
Is provided by interposing a non-melting substance.

In the first embodiment, the portion 5 having a small peel strength can be provided by interposing a nickel foil 51 as a non-melting substance in a part of the bonding portion 4.

FIG. 2 is a partially cutaway plan view of a thin battery according to a second embodiment of the present invention, which is characterized in that the exterior film 1 used in the first embodiment is formed into a bag. The power generating element 2 is inserted into the inside, the open end 3 is bonded to the fusible resin, thereby enclosing the power generating element 2 and formed at a part of the bonding portion 4 of the open end 3 where the peel strength is small. 5 is provided by performing the heating of the hot-melt resin at a lower temperature than other bonding portions.

In the second embodiment, the portion 5 having a small peel strength is first heated to a temperature not lower than the softening point of the hot-melt resin and lower than the melting point of the entire bonding portion 4, and then the portion having a small peel strength is heated. The portions other than 5 can be provided by heating to a temperature higher than the melting point of the hot-melt resin.

FIG. 3 is a partially cutaway plan view (a) and a cross-sectional view (b) of a thin battery according to a third embodiment of the present invention. The power generation element 2 is inserted into the exterior film 1 used in the form in a bag shape, and the power generation element 2 is encapsulated by bonding the opening end 3 to form a part of the bonding portion 4 of the opening end 3. In addition, the portion 5 having a small peel strength is provided by making the non-adhered portion of the exterior film 1.

In the third embodiment, if the bonding of the open end 3 is the same as in the first embodiment, the portion 5 having a small peel strength may be provided with no fusible resin. In the same manner as in the second embodiment, the portion 5 having a small peel strength can be provided by disposing a heat insulating material.

In the third embodiment, when the width of the unbonded portion of the exterior film 1 is made small on the outside and large on the inside, and the thickness d is small on the outside and large on the inside, the internal pressure is easily concentrated. Thus, when the internal pressure rises, the gas is released smoothly.

[0020]

【Example】

(Example 1) Polypropylene / aluminum /
An exterior film 1 composed of a four-layer laminated film laminated in the order of polyethylene terephthalate / polypropylene is made into a bag shape, a power generation element 2 is inserted therein, and a part of a bonding portion 4 at an open end 3 is formed as a non-melting material. Saga 50
A hot plate was applied to the entire surface of the bonding portion 4 with a triangular nickel foil of μm interposed therebetween, heated to 200 to 220 ° C. to produce a sealed battery, and a 90R bending test and an overcharge test were performed. In the test, no adhesive breakage occurred even after repeated bending of 100 times, and in the overcharge test, it was recognized that gas was generated from the portion 5 where the peel strength of the bonded portion 4 was small,
No swelling was observed. When a T-shaped peel test was performed on a sample piece bonded with the same nickel foil interposed between four-layer laminated films of the same material, the peel strength was 6 to 7 kg.

(Embodiment 2) The same exterior film 1 as in Embodiment 1 is formed into a bag, a power generating element 2 is inserted therein, and a hot plate is applied to the entire surface of the bonding portion 4 at the opening end 3 to cover the entire bonding portion 4. 130-1
After heating to 40 ° C. and bonding, a portion 5 with low peel strength
When the battery was sealed by heating at 200 to 220 ° C. so as not to hit the hot plate and subjected to the same bending test and overcharge test as in Example 1, the same results as in Example 1 were obtained. . In addition, a T-type peel test was performed on two types of sample pieces in which a four-layer laminate film of the same material was adhered under the same conditions. The peel strength was 14 to 17 kg.

(Example 3) The same exterior film 1 as in Example 1 is formed into a bag shape, a power generating element 2 is inserted therein, and the hot plate does not hit a portion 5 where the peel strength of the bonding portion 4 at the open end 3 is small. A battery sealed by heating to 200 to 220 ° C. as described above was manufactured, and the same bending test and overcharge test as in Example 1 were performed. As a result, the same result as in Example 1 was obtained.

(Comparative Example 1) The entire surface of the bonding portion 4 is 200 to 22
A battery was fabricated under the same conditions as in Example 2 except that the battery was heated to 0 ° C. and subjected to the same bending test and overcharge test as in Example 1. As a result, no adhesive failure occurred in the bending test. In the charging test, swelling occurred.

(Comparative Example 2) The temperature at the time of the first bonding was 120
A battery was fabricated under the same conditions as in Example 2 except that the temperature was changed to ° C., and the same bending test as in Example 1 was performed. When subjected to a shape peel test, the peel strength was 0.5 to
It was 1.5 kg.

Comparative Example 3 A battery was manufactured under the same conditions as in Example 1 except that the shape of the portion 5 having a small peel strength was rectangular, and the same bending test and overcharge test as in Example 1 were performed. No adhesion failure occurred in the bending test, but swelling occurred in the overcharge test.

From the above Examples and Comparative Examples, the bonded portion 4 was subjected to a T-shaped peeling test according to JIS (K6845). It was found that swelling occurred because the gas could not be released smoothly. Also,
It has been found that when the portion 5 where the peel strength of the bonding portion 4 is low is smaller outside the bonding portion and larger inside the bonding portion, the gas can be more smoothly released.

[0027]

As described in detail above, the thin battery of the present invention can smoothly release gas when the internal pressure increases,
It is excellent in reliability and safety.

[Brief description of the drawings]

FIG. 1 is a partially cutaway plan view of a thin battery according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway plan view of the thin battery according to the second embodiment.

FIGS. 3A and 3B are a partially cutaway plan view (a) and a cross-sectional view (b) of a main part of the thin battery according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exterior film 2 Power generation element 3 Open end 4 Adhesive part 5 Part with small peeling strength

Claims (5)

[Claims] In a thin battery in which a power generating element is encapsulated by bonding exterior films to each other, a portion having a small peel strength is provided in a part of a bonding portion of the exterior film,
A thin battery wherein the portion having a small peel strength is made small outside the bonding portion and large inside the bonding portion. 2. The thin battery according to claim 1, wherein the portion having a small peel strength has a peel strength of 2 kg or more and 10 kg or less according to a T-shaped peel test specified by JIS (K6854). Shaped batteries. 3. The thin battery according to claim 1, wherein the bonding portion of the exterior film is formed by bonding a fusible resin, and a portion having a small peel strength has a non-fusible substance interposed in the fusible resin. A thin battery characterized by being formed by: 4. The thin battery according to claim 1, wherein the bonding portion of the exterior film is formed by bonding a hot-melt resin, and the portion having a small peel strength is heated by another bonding of the hot-melt resin. A thin battery formed by performing at a temperature lower than the temperature of a part. 5. The thin battery according to claim 1, wherein the portion having a small peel strength is formed as an unbonded portion of an exterior film.