JP3371616B2 - Battery and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a sealing body for a battery, and in particular, in a normal state, the battery has a sealing function, and when the internal pressure of the battery is abnormally increased, the battery is partially ruptured to generate an internal gas. The present invention relates to an explosion-proof battery provided with a sealing body for discharging the gas to the outside of the battery.

[0002]

2. Description of the Related Art Conventionally, a battery in which an opening of a battery case containing a power generating element is sealed by using a sealing body made of a thermoplastic resin, for example, a cylindrical alkaline dry battery, an alkaline storage battery, lithium In the case of batteries, etc., when the batteries are short-circuited or in abnormal use such as over-discharge or over-charge, gas is suddenly generated inside the battery,
There is a risk that the battery may expand or rupture, damage the equipment used, or harm the human body. In order to prevent these, by forming a thin portion in a part of the sealing body,
When excessive gas is generated during abnormal use, the thin portion of the sealing body is ruptured by a low pressure before the sealing portion of the battery is ruptured, and the gas is diffused from there. The resin sealing body used at that time is molded by injection molding. That is, a thermoplastic resin heated to a temperature equal to or higher than the melting point is injection-molded in a molding die, naturally cooled, and used as a sealing body.

[0003]

With the above-mentioned structure, various studies such as the thickness of the thin portion, the shape of the sealing body itself, the sealing structure, etc. are conducted for the purpose of dissipating transient gas generation during abnormal use to the outside of the battery. However, when the battery is overcharged under certain specific environmental conditions, for example, at a high temperature of 60 ° C, the gas generated inside the battery pushes up the resin sealing body and concentrates stress on the thin wall portion. However, there is a problem in that the tensile elongation of the resin itself becomes higher than that at normal temperature in a high temperature state and the resin may not be broken.

The problem to be solved by the present invention is to secure the safety of the battery by reducing the tensile strength of the thin portion without requiring a complicated shape change and material change of the sealing body.

[0005]

In order to solve the above-mentioned problems, the battery of the present invention is a battery sealed with a synthetic resin sealing body having a thin-walled portion partially broken by gas pressure, and at least the thin-walled battery. surface portions and internal parts, characterized in that it consists of flat Hitoshitsubu径1~5μm granular crystalline resin.

The synthetic resin sealing body is preferably a polyamide resin. Further, the method for producing a battery of the present invention is a method for producing a battery which is sealed with a synthetic resin sealing body having a thin portion partially broken by gas pressure, wherein the synthetic resin sealing body is rapidly cooled after injection molding. It is characterized by

The synthetic resin sealing body is preferably a polyamide resin.

[0008]

The function of the present invention will be described below.

When a thermoplastic resin is injection-molded, the growth state of the granular crystals of the polymer in the resin-sealed body greatly changes depending on the molding conditions and the subsequent standing and cooling methods. The surface of the sealing body is amorphous or granular crystals having a particle size of about 1 μm because it is immediately cooled immediately after injection molding by contacting the molding die and the outside air, whereas the inside is large because it is gradually cooled. Spherical crystals of grain size grow. FIG. 2 is a schematic view showing a cross section of the thin portion 9 ′ of the sealing body 9 and showing an internal granular crystal 11 and an amorphous portion 12 on the surface. For example, when the sealing body is left to cool at room temperature after injection molding, and solidifies from the surface to cool the inside slowly, spherical macromolecule crystals having an average particle size of about 10 μm to 40 μm grow. When tensile stress is exerted by the internal gas pressure of the battery in a high temperature state, in the resin sealing body in which the crystal grows largely, the resin easily expands at a high temperature, the thin portion is less likely to be broken, and the battery may burst. However, when amorphous or fine granular crystals having an average grain size of 1 to 5 μm are generated by a method such as rapid cooling immediately after resin molding, the amorphous part or the grain boundaries of the fine crystals are fragilely torn. Since it easily breaks, the elongation is low even under high temperature conditions, and the thin portion 9 ′ is broken by the gas pressure and the gas inside the battery can escape to the outside of the battery.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a structural sectional view of a cylindrical alkaline battery used in this embodiment. In FIG. 1, 1 is an anode terminal,
2 is a cup-shaped separator, 3 is a positive electrode mixture made of manganese dioxide and graphite, 4 is a metal can as a positive electrode case, 5 is an outer label, 6 is a gel negative electrode in which a powdery active material is dispersed in a gel electrolyte, 7 is a current collector, 8 is a bottom plate as a negative electrode terminal, 9
Is a polyamide resin, and a resin sealing body 10 having a thin portion 9 ′ partially provided is a metal washer.

In this embodiment, the case where a polyamide resin (Nylon 66 manufactured by DuPont) is used as the resin sealing body 9 will be described as an example. First, nylon 66 is supplied to an injection molding machine, and a predetermined temperature, in this embodiment, 250 ° C. to 270 ° C.
Was melted and supplied to a resin mold, and a resin sealing body 9 having a thin portion 9'on a part thereof was injection-molded. The resin sealing body 9 released from the mold was immediately immersed in circulating ice water at about 0 ° C. and completely cooled within 2 minutes until the surface temperature of the resin sealing body 9 became 0 ° C. to 20 ° C.

Next, the resin sealing body 9 thus obtained was cut, the surface was polished, and the size of the crystal was measured by a deflection microscope.

After that, the moisture content of the resin sealing body 9 was adjusted by a drying process, and then a battery was assembled using this to conduct a safety test. As this safety test, in a circuit of four alkaline dry batteries in series, only one of them was connected in the reverse direction to short-circuit. In such a circuit, since the battery connected in reverse is charged by the remaining three batteries, the electrolysis reaction of water proceeds in the battery, hydrogen gas and oxygen gas are generated, and the pressure inside the battery is increased. Rising,
As a result, in the room temperature region, the thin portion 9'is torn and gas is dissipated to prevent the battery from bursting. In this embodiment, the resin condition of the thin portion 9'is changed to 20
This safety test was conducted for each 20 sets under each temperature condition of ° C, 45 ° C, 60 ° C and 80 ° C. The results are shown in Table 1. In the table, the denominator shows the number of test sets and the number of sets ruptured in the numerator.

[0015]

[Table 1]

As shown in Table 1, in Comparative Examples 1 and 2, 2
In the room temperature region of 0 ° C, all the thin-walled parts did not break and burst, but in the high-temperature region of 45 ° C or higher, the thin-walled parts did not break and burst. However, in Examples 1 and 2, all the thin-walled portions 9 ′ were broken in a wide temperature range including a high temperature, the gas inside the battery could be released to the outside of the battery, and it did not burst. That is, it was confirmed that if the average grain size of the granular crystals on the surface portion and inside of the thin portion is 5 μm or less, the thin portion is broken and safety can be secured.

Although nylon 66 was used as the sealing body in the examples, almost the same results were obtained with polyethylene and polypropylene.

The same effects can be obtained by manufacturing the resin sealing body by a method other than this embodiment, for example, by changing the molding conditions.

Needless to say, the same effect can be obtained in other battery systems having an explosion-proof thin wall portion that breaks due to gas pressure, such as lithium batteries and prismatic batteries.

[0020]

As described above, according to the present invention, even if the inside of the battery has a high pressure, the thin portion of the resin sealing body is surely torn in a wide temperature range including a high temperature to dissipate the gas inside. It is possible to provide a battery with excellent safety that does not burst.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a cylindrical alkaline dry battery according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a cross section of a thin portion of a resin sealing body of the cylindrical alkaline dry battery of FIG.

[Explanation of symbols]

1 Anode terminal 2 separator 3 Positive electrode mixture 4 metal cans (positive electrode case) 5 Exterior label 6 Gel negative electrode 7 Electronic 8 Bottom plate (negative electrode terminal) 9 Resin sealing body 9'thin wall 10 metal washers 11 Granular crystals inside the thin part 12 Amorphous part of thin surface

─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Takeshi Okubo 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-1-173565 (JP, A) JP-A-56- 132765 (JP, A) JP-A-56-136453 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 2/08 H01M 2/12 101 B29C 33/42 B29C 45/00

Claims (5)

(57) [Claims] 1. A battery was sealed with synthetic resin sealing member having a thin portion breaking by gas pressure to a portion, the surface portion and the interior of at least a thin portion, a flat Hitoshitsubu径1~5μ
A battery made of m crystalline resin. 2. The battery according to claim 1, wherein the synthetic resin sealing body is a polyamide resin. 3. A method for producing a battery, which is sealed with a synthetic resin sealing body having a thin portion partially broken by gas pressure, the method comprising:
A method for manufacturing a battery, characterized in that the synthetic resin sealing body is rapidly cooled after injection molding. 4. The synthetic resin sealing body released from a mold,
Within 2 minutes until the surface temperature of the resin sealing body reaches 0 to 20 ℃
The electric power according to claim 3, wherein the electric power is cooled and rapidly cooled.
Pond manufacturing method. 5. A method according to claim 3 or 4 manufacturing method of battery, wherein said synthetic resin gasket is a polyamide resin.