JPH0750602B2 - Lead acid battery - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead acid battery, and more particularly to a sealed (hereinafter referred to as a sealed) lead acid battery that absorbs oxygen gas in a negative electrode for high current discharge.

2. Description of the Related Art A negative electrode absorption type sealed lead acid battery suppresses the decrease in electrolyte solution by reacting oxygen generated from the positive electrode during charging with lead, which is the negative electrode active material, and sulfuric acid, which is the electrolytic solution, to reduce it to water. It is a battery. Most of the electrolytic solution is absorbed in the positive and negative electrode plates and the separator, and a slight amount of other flowable electrolytic solution is contained.

The matte separator used in such batteries holds the electrolyte within itself by capillarity.

Problems to be Solved by the Invention Conventional separators are considered to be better as the electrolyte retention capacity is better, and therefore efforts have been made to reduce the pore size of the separator in order to increase the capillary action.

That is, a mat-like separator with a maximum pore size of 20μ or less is used exclusively, and in order to realize that pore size, a diameter of 1μ
The following glass fibers are produced, or glass fibers having a diameter of 1 μm or less as a main component and glass fibers having a diameter of 1 μm or more mixed therein, and acrylic fibers mixed as a binder are used.

However, when examining the low temperature rapid discharge performance of this negative electrode absorption type sealed lead-acid battery, when the mat-like separator with a small pore size as described above is used, the discharge duration decreases sharply with only a slight decrease in the electrolyte. I understood it.

Further detailed examination revealed that the factor that determines the low temperature rapid discharge duration is the amount of electrolyte contained in the negative electrode active material.

Sulfuric acid can diffuse from the offshore area of the negative electrode during rapid discharge in a battery with a sufficient amount of normal electrolytic solution, but in a sealed battery, the diffusion of sulfuric acid from offshore is slow, so Determines the discharge duration.

When a conventional mat-shaped separator having a pore size of 20 μ or less is used, the electrolyte tends to concentrate on the separator because of its strong capillary action. Therefore, when the amount of the electrolyte solution decreases, the electrolyte solution of the negative electrode, which has the weakest capillary action, is lost and the duration of the low temperature rapid discharge becomes short.

Therefore, the present inventors have studied the method of reducing the capillary action of the separator contrary to the conventional method, and the duration of the low temperature rapid discharge is not shortened even when the electrolyte solution is reduced, and as a result, the following configuration was reached. did.

Means for Solving the Problems That is, the present invention uses approximately 40% of polyester resin fibers having a fiber diameter of 2 to 8 μ and approximately 40% of glass fibers having a fiber diameter of 2 to 8 μ.
40% and about 5% of acrylic fibers for binding these fibers are mixed and added, and a total amount of about 15% of silicon oxide powder having a particle diameter of 1 μ or less and diatomaceous earth having a particle diameter of 3 to 5 μ is added. Then, a mat-like separator having a maximum pore size of 30 to 60 μm is used.

While maintaining the ability to hold the electrolyte moderately by this,
Capillary action is reduced so that the duration of low temperature rapid discharge is not shortened.

A separator having a maximum pore size in this range can be obtained by using glass fibers having a diameter of 2 to 8 μ when mainly using glass fibers and acrylic fibers as in the conventional case. However, in this case, elasticity is lost as compared with a separator using glass fibers of 1 μm or less, and there arises a problem that it is difficult to apply an appropriate pressure to the electrode plate.

Action In the present invention, in order to solve this problem, a flexible polyester (PET) resin fiber is mixed with glass fiber to secure appropriate elasticity.

The fiber diameter of this PET resin fiber was 2 to 8 μm like the glass fiber was suitable for obtaining the above-mentioned maximum pore diameter.

Another problem is that when the maximum pore size becomes large, the positive electrode active material, which has been made finer during use, easily penetrates the separator to cause a short circuit in the battery.

In particular, glass fibers and PET resin fibers have a circular cross section, and the mat formed from such fibers has a simple micropore shape, and easily penetrates the finely divided active material to cause a short circuit.

In order to solve this problem, it has been found that it is effective to add an inorganic powder having a complicated shape to make the shape of the micropores in the mat complicated. There are two types of added inorganic powders, both of which are silicon oxides. One has a primary particle size of several μm and a secondary particle size of 1 μm or less. It is believed that this gels in the electrolyte and acts like a paste. The other one, which has a particle size of 3 to 5 μm and is usually called diatomaceous earth, has a complicated shape itself, so that the shape of the pores of the separator can be complicated.

Examples Hereinafter, as examples of the present invention, a mat separator having a maximum pore size of 10μ using glass fibers having a conventional fiber diameter of 0.7μ, and 40% of glass fibers having a diameter of 3μ in the separator of the present invention, PET resin fibers having a diameter of 6μ 40% and 5% acrylic fiber for binding these fibers, 5% of silicon oxide powder having a particle size of 1 μ or less and diatomaceous earth having a particle size of 3 to 5 μ, and a separator having a maximum pore size of 40 μ 5 with and
A sealed lead-acid battery with a time rate capacity of 20 Ah was constructed, and the relationship between the amount of electrolyte and low temperature rapid discharge duration was investigated. The results are shown in the figure. A is the characteristic of the battery using the separator of the present invention, and B is the characteristic of the battery using the conventional separator.

In addition, the following table shows the characteristics of the separator, the life characteristics of the battery using them, and the rapid low-temperature discharge characteristics obtained in various processes leading to the present invention.

As described above, according to the present invention, about 40% of each of the polyester resin fiber and the glass fiber having a fiber diameter of 2 to 8 μ and about 5% of the acrylic fiber for binding these fibers are used.
% To form a mat and to add a total of approximately 15% of silicon oxide powder with a particle size of 1 μm or less and diatomaceous earth with a particle size of 3 to 5 μm to complicate the shape of the holes in the mat. It was done.

This makes it possible to improve the liquid-retaining power and flexibility of the mat-shaped separator, prevent the fine active material from penetrating the separator and preventing a short circuit in the battery, and have excellent low-temperature rapid discharge characteristics and life characteristics. We can provide sealed lead acid battery,
It is extremely effective for lead-acid batteries for applications requiring rapid discharge characteristics such as lead-acid batteries for automobiles.

[Brief description of drawings]

The figure shows the relationship between the amount of electrolyte and the low temperature rapid discharge duration. (A) is a battery using the separator of the present invention, and (B) is a battery using a conventional separator.

Front page continued (72) Inventor Masayoshi Yuki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Katsuhiro Takahashi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-58-155651 (JP, A)

Claims (1)

[Claims] 1. A polyester resin fiber having a fiber diameter of 2 to 8 μ is approximately 40% and a glass fiber having a fiber diameter of 2 to 8 μ is approximately 40%.
And about 5% of acrylic fiber for binding these fibers is mixed, and about 15% of silicon oxide powder having a particle diameter of 1 μm or less and diatomaceous earth having a particle diameter of 3 to 5 μm are added in a total amount of about 15%. A lead-acid battery with a mat-shaped separator with a maximum pore size of 30 to 60μ placed between the positive and negative plates.