JP2571064B2 - Sealed lead-acid battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a sealed lead-acid battery, and an object of the present invention is to provide a sealed lead-acid battery excellent in high-rate and low-rate discharge performance. is there.

2. Description of the Related Art Conventional technology and its problems One characteristic of sealed lead-acid batteries is that the electrolyte is fixed to prevent leakage of sulfuric acid, which is a corrosive electrolyte. Currently, two methods are used for this immobilization, one of which is a method of gelling and non-fluidizing by adding a gelling agent such as silica, and is generally called a gel-type sealed lead storage battery. Others use a porous absorbent as an isolator and absorb and retain all the electrolyte in the positive / negative electrode and the isolator, thereby eliminating the flowing liquid.

Fine glass fiber mats are generally used as a liquid-absorbing separator in a sealed sealed lead-acid battery, but it is considerably more expensive than conventional separators for lead-acid batteries, and the amount of electrolyte is reduced by the electrode plate and the separator. Therefore, it is not possible to arrange a sufficient electrolyte solution in the space around the electrode plate group. For this reason, there is a disadvantage that the low rate discharge capacity is limited by the amount of the electrolyte and is not so large.
On the other hand, in a gel-type sealed lead-acid battery, since the electrolyte itself is made non-fluidized by the gelling agent, it is possible to arrange the electrolyte in the space around the electrode plate, and the low-rate discharge performance is improved. Since the electrolyte present in the vicinity of the plate is also non-fluidized, the moving speed of sulfate ions is slow, and the high-rate discharge capacity is inferior to that of the closed lead-acid battery of the retainer type. When a reference electrode was inserted into this gel-type sealed lead-acid battery and the unipolar potential during high-rate discharge was measured, it was found that the discharge capacity was limited by the positive electrode plate.

Means for Solving the Problems The present invention uses a separator having a two-layer structure of a mat made of thick fibers in contact with the negative electrode and a mat made of fine fibers in contact with the positive electrode, thereby reducing the cost of the separator. At the same time, the flowable electrolyte is held in the pores of the electrode plate and the fine fiber mat, while the non-flowable electrolyte is placed in the thick fiber mat portion and the space around the electrode group to achieve high efficiency. An object of the present invention is to provide a sealed lead-acid battery that solves the above-mentioned drawbacks by exhibiting performance similar to that of a sealed sealed lead-acid battery in discharging, while exhibiting performance similar to that of a gel-type sealed lead-acid battery in low-rate discharging. In other words, the positive electrode has a structure similar to that of a retainer battery, and the positive electrode, which is a cause of capacity limitation in high-rate discharge, has the same performance as a retainer battery.

Embodiment Hereinafter, an embodiment of the sealed lead-acid battery of the present invention will be described in detail.

Using a 3.5 mm-thick positive electrode plate and a 2.5 mm-thick negative electrode plate, a battery having three positive electrodes / four negative electrodes was assembled with the distance between the electrode plates being 2.0 mm. The average fiber diameter 21μ as separators, 1.0mm thick glass fiber mat with an average fiber diameter 1.1μ (hereinafter spacing member thickness indicated by thickness at 30 Kg / dm ² load.), The 1.0mm thick glass fiber mat What was arranged to form a two-layer structure, average fiber diameter 21μ,
2.0mm thickness single layer glass fiber mat and average fiber diameter 1.0
Single-layer glass fiber mats of μ and 2.0 mm thickness were used, respectively. The lower part of these glass fiber mats was immersed in dilute sulfuric acid having a specific gravity of 1.30 and left for 2 hours. The suction height of dilute sulfuric acid was 268 mm for a single-layer glass fiber mat having an average fiber diameter of 1.1 μm and a thickness of 2.0 mm. However, the single-layer glass fiber mat having an average fiber diameter of 21 μm and a thickness of 2.0 mm had little liquid retention of 8 mm.

First, for a battery using a single-layer glass fiber mat having an average fiber diameter of 1.1 μm, 52 cc of dilute sulfuric acid having a specific gravity of 1.30 was injected, in which all pores were almost completely saturated, to produce a closed lead storage battery of the retainer type. Next, for a battery using a single-layer glass fiber mat having an average fiber diameter of 21 μm and a thickness of 2.0 mm, a solution in which 5% by weight of SiO ₂ was mixed with dilute sulfuric acid having the same specific gravity as 59 cc so that the electrode group was completely immersed. The solution was injected to produce a gel battery. This electrolyte was completely non-fluidized after one hour. For a battery using a two-layer separator with a thick fiber mat in contact with the negative electrode and a fine fiber mat with the positive electrode, the amount of dilute sulfuric acid having a specific gravity of 1.30 was completely absorbed and retained, and no fluid was generated, i.e., 44
cc was injected.

It should be noted that the liquid absorbing speed of these electrode plates was approximately 0 in about 5 minutes.
The electrolyte was absorbed and retained in the positive and negative electrode plates and the fine fiber mat portion, and the fluid disappeared. Some batteries were subjected to the test in this state, and other batteries were further injected with 15 cc of a solution obtained by mixing 5.0 wt% of SiO ₂ with dilute sulfuric acid of the same specific gravity until the electrode assembly was completely immersed. The additional injected electrolyte almost gelled after 30 minutes and did not flow at all after 1 hour even if a little vibration was applied. The electrolyte around the gelled electrode was taken out and analyzed.
The SiO ₂ concentration was 4.9 weight percent. This suggests that the initially absorbed and retained dilute sulfuric acid and the additionally injected gel electrolyte are hardly mixed.

It should be noted that 5% of SiO ₂ was directly
A gel battery in which 59 cc of the liquid mixed by weight percent was injected was also prepared.

The above five types of batteries were sealed using a safety valve, and after supplementary charging, the batteries were allowed to stand for 30 days and then discharged at a 30-hour rate and a 1-hour rate current. Table 1 shows the results.

As is apparent from Table 1, dilute sulfuric acid was absorbed and retained in the liquid-retaining fine fiber mat portion in contact with the positive electrode and in the positive and negative electrode plates using the separator having a two-layer structure. There is no thick fiber mat part or around the electrode plate.The sealed lead-acid battery according to the present invention, which has an electrolyte made by adding SiO ₂ to diluted sulfuric acid and made non-fluidized, has a low rate discharge performance equivalent to that of the gel-type sealed lead-acid battery. In addition, the high-rate discharge performance is equal to that of the closed lead storage battery of the retainer type, and has both excellent characteristics.

On the other hand, when 59 cc of a solution containing 5% by weight of SiO ₂ necessary for completely defluidizing the electrolyte around the electrode plate was directly added to a battery using a two-layered separator using a fine fiber, The high rate discharge performance could not be improved because the SiO ₂ concentration in the pores of the mat and the positive and negative electrode plates also increased.

Since the separator material becomes more expensive as the diameter of the used fiber becomes smaller, liquid retention is not required on the side facing the negative electrode having a two-layer structure. Fiber diameter suffices. On the other hand, on the side facing the positive electrode, a mat having an average fiber diameter of at least 8μ or less in order to maintain sufficient liquid absorption for the electrode plate group height of about 50mm of the currently marketed small sealed lead-acid battery It is necessary to use

Effects of the Invention As described above, the sealed lead-acid battery according to the present invention has the advantages that the cost of the separator can be reduced and the performance of both low-rate and high-rate discharge is excellent.

Claims (1)

(57) [Claims] 1. A battery in which a separator having a two-layered structure in which a fiber mat having an average fiber diameter facing the negative electrode of 10 μ or more and a mat having an average fiber diameter of 8 μ or less facing the positive electrode are arranged, wherein The electrolyte in the pores of the fiber mat and around the electrode plate is non-fluidized by the gelling agent, and
A sealed lead-acid battery, characterized in that the following fiber mats and pores of the positive and negative electrode plates are filled with an electrolyte substantially free of a gelling agent.