JPS6316550A - Separator for enclosed type lead storage battery - Google Patents

Abstract

PURPOSE:To prevent a separator from shrinking even if discharging cycles are repeated, by constructing the separator of glass fiver and a material which swells as it absorbs liquid. CONSTITUTION:A separator is constructed of a glass fiber 1 and a liquid absorbing/swelling material 2, the glass fiber 1 being partially substituted by resin fiber. If a separator is constructed of a mat body made of only fine glass fiber, and is continuously pressurized when the body has absorbed liquid, shifts amoung fibers occur so as to shrink the thickness of the body, resulting in looseness of plate groups. If the separator is however constructed of the glass fiber 1 and the material 2 which swells after it absorbs liquid, the separator tends to swell due to the swelling property of the material 2 if it is pressurized when it absorbs the liquid, and the plate groups are thereby always pressurized with a constant force.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in the composition of a separator used in a negative electrode absorption type sealed lead-acid battery.

BACKGROUND OF THE INVENTION Conventionally, separators used in sealed lead-acid batteries of this type have mainly been mats made of glass fiber. Third
The figure shows a partially enlarged schematic diagram of a conventional separator. This separator is made of fine glass fibers 6 with a fiber diameter of about 1 μm and formed into a mat shape.
are intertwined in a chaotic manner. FIG. 4 shows a cross-sectional view of an example of a conventional sealed lead acid battery using this separator.

In the figure, 7 is a positive electrode plate, which is sandwiched between two negative electrode plates 8, 8' via a U-shaped separator 9, and inserted into a resin battery case 1o made of polypropylene.

Sealed lead-acid batteries are designed to be lightweight and portable, meaning they limit the amount of electrolyte that can be used to prevent leakage even if the battery falls over. Therefore, the electrolyte is the positive electrode plate 7, the negative electrode plate 8,
8' and separator 9. For this reason, a slight decrease in electrolyte results in a significant deterioration in battery performance. Water decomposition occurs due to overcharging, but the oxygen gas generated from the positive electrode plate is absorbed by the negative electrode plate and reduced to water, and this reaction suppresses the generation of hydrogen gas from the negative electrode plate, causing water to decompose. Preventing the decline. This loss of oxygen gas in the negative electrode plate prevents deterioration in battery performance due to a decrease in the amount of liquid.

Furthermore, when some abnormality occurs and the internal pressure of the battery rises above an allowable value, a safety valve 16 provided on the lid 12 of the battery case is activated to restore the normal internal pressure. That is, the gas pushes up the rubber valve 11 at the top of the through hole 13, and the lid part 1
It escapes to the outside through the exhaust hole 13' through the hollow part 14 provided in the interior of the exhaust hole 13'.

Problems to be Solved by the Invention In such a conventional configuration, there is a problem in that the separator shrinks when charging and discharging cycles are repeated. That is, due to charging and discharging, the positive electrode becomes pbso p
To bo, the negative electrode repeats the form change of pbso, pb4 ← 2 and changes in volume, but since the dimensions of the battery case are constant, the force applied to the separator becomes stronger or weaker. Moreover, the separator is just a tangle of fine glass fibers, and once it has shrunk, it is difficult to restore, so it gradually shrinks and shrinks as the cycle goes on, making it thinner. When the separator shrinks and becomes thinner, the contact between the positive electrode plate and the separator and the negative electrode plate and the separator becomes poor, causing an increase in internal impedance and deteriorating battery performance even though the amount of electrolyte has not decreased. Raise the bottom.

The present invention is intended to solve these problems, and aims to prevent the separator from shrinking even after repeated charge/discharge cycles.

Means for Solving the Problem In order to solve this problem, the present invention comprises a separator made of glass fiber and a substance that swells when liquid is absorbed.

Function: With this configuration, the electrode plates will not loosen even if the battery is repeatedly charged and discharged. In other words, if a mat body made only of fine glass fibers continues to be pressurized while absorbing liquid, the thickness will shrink due to the misalignment between the fibers, and the electrode plate group will become loose.However, as in the present invention, the separator is made of glass fibers. and a substance that swells when it absorbs liquid, the separator tends to expand due to the swellable substance even if it is pressurized in a liquid-absorbing state, and the electrode plate group always has a constant force. This means that it is pressurized.

Embodiment FIG. 1A is an enlarged schematic diagram of a separator according to an embodiment of the present invention in a dry state, and FIG. 1B is an enlarged schematic diagram of a separator in a liquid-absorbing state. In the figure, 1 is a glass fine fiber with a fiber diameter of approximately 1 μm, and 2
is polyacrylic acid powder. When injecting electrolyte,
The electrolytic solution 3 penetrates between the glass fibers 1 by capillary action. Furthermore, the polyacrylic acid powder swells ten times or more when it holds the electrolyte inside.

When a battery is constructed using this separator, even if charge/discharge cycles are repeated, the separator does not shrink due to swelling of the polyacrylic acid powder, and good contact between the electrode plate groups can be maintained.

Figure 2 shows a capacity of 5 using the present invention and the conventional separator.
Prototype of 00 mAh battery, 1.75V at 100mA
The cycle characteristics are shown when a cycle of discharging to 120% at 100 mA and charging to 120% of the discharge amount (7) is repeated. Battery S using the conventional separator reached half its initial capacity after 650 cycles, but battery 4 using the separator of the present invention required 830 cycles to reach half its initial capacity.
times, extending the lifespan by 1.5 times compared to conventional models.

Effects of the Invention As described above, according to the present invention, since the separator has a liquid-absorbing and swelling substance, the separator does not shrink even after repeated charging/discharging cycles, and the gap between the electrode plates is maintained. The increase in internal impedance due to loosening can be suppressed, and the cycle characteristics can be increased by 1.6 times compared to the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a partial enlarged schematic diagram of a separator according to an embodiment of the present invention, where A is a dry state, B is a diagram in an absorbed state;
FIG. 2 is a comparison diagram of discharge amounts during charging and discharging cycles, FIG. 3 is an enlarged schematic diagram of a conventional separator, and FIG. 4 is a schematic cross-sectional diagram of a sealed lead-acid battery. 1...Glass fine fiber, 2...Polyacrylic acid powder, 7...Positive electrode plate, 8,8'...
...Negative electrode plate, 9...Separator. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 is the Δguru tomb (

Claims (2)

[Claims] (1) A separator for sealed lead-acid batteries composed of glass fiber and a liquid-absorbing swelling substance. (2) A separator for a sealed lead-acid battery according to claim 1, in which a portion of the glass fibers are replaced with resin fibers.