JPH0465496B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a sealed lead acid battery. In more detail, the amount of electrolyte is regulated so that there is no free electrolyte, and a glass fiber separator with a diameter of 0.1 to 10 μm is used, and the negative electrode plate can absorb and remove oxygen gas generated from the positive electrode plate during charging. This invention relates to a sealed lead-acid battery having a capacity ratio and a safety valve at the gas exhaust port. Conventional structure and problems This type of sealed lead-acid battery has recently been mainly used as a power source for portable equipment, etc., and has excellent storage characteristics (capacity when stored for a long time, There is a demand for batteries with excellent recovery capacity. However, when stored for a long period of time, water evaporates from the safety valve in the battery case and gas exhaust port, reducing the amount of electrolyte. It was found that a decrease in electrolyte increased the internal resistance of the battery and worsened its storage characteristics. This deterioration in storage characteristics is thought to occur because the wetting and compatibility between the negative electrode plate and the separator are worse than the wetting and compatibility between the positive electrode plate and the separator and the electrolyte. When the electrolyte in the battery decreases due to long-term storage, etc., the electrolyte is selectively lost from the areas on the surface of the negative electrode plate that are in contact with the separator, which was confirmed by measuring which areas the internal resistance increased. Ta. This is because the negative electrode plate is made of porous metal lead, which is hydrophobic, and it can be inferred that when the electrolyte decreases, the electrolyte moves to the more hydrophilic positive electrode plate and separator. A decrease in wetting and compatibility between the negative electrode plate and the separator inhibits the diffusion of sulfuric acid into the negative electrode plate, and significantly deteriorates the capacity after long-term storage. It was also found that an increase in internal resistance and a decrease in sulfuric acid diffusion made charging difficult and reduced recovery capacity. In addition, the positive electrode plate is rate-determining the initial capacity, especially in high-rate discharge, and it is thought that the capacity increases if the electrolyte becomes easier to diffuse to the positive electrode plate. This type of battery has a low electrolyte content and is usually inferior in high rate discharge compared to a liquid type battery with a rich electrolyte, such as a lead-acid automotive battery. OBJECTS OF THE INVENTION The present invention aims to prevent deterioration of storage characteristics caused by electrolyte and improve capacity during high rate discharge by improving wetting and compatibility between electrodes and separators. Structure of the Invention That is, the present invention has a structure in which the amount of electrolyte is regulated so that there is no free electrolyte, and the capacity ratio of the electrode plate is such that the oxygen gas generated from the positive electrode plate during charging can be absorbed and removed by the negative electrode plate. It is characterized in that a paper made mainly of pulp fiber is interposed between the positive and negative electrode plates and the glass fiber separator interposed between the electrode plates. A specific configuration of the electrode plate group of a battery will be explained with reference to the drawings. The figure shows an electrode plate group 1 consisting of a positive electrode plate 2, a negative electrode plate 3, and a separator 4 made of glass fiber, in which a made paper 5 mainly made of pulp fiber is sandwiched between the positive electrode plate, the negative electrode plate, and the separator. It's complicated. Pulp fiber is a natural fiber that is relatively resistant to sulfuric acid, and its true surface area is extremely large, and its ability to absorb dilute sulfuric acid is more than 10 times that of glass fiber. For this reason, by pressing paper made of pulp fibers onto the surface of the negative electrode plate, which has poor wettability with dilute sulfuric acid, it is possible to improve compatibility and improve the wettability of the negative electrode plate surface. facilitates the diffusion of sulfuric acid into the Therefore, conventionally, the electrolyte decreases during long-term storage,
We were able to remove the cause of the increase in internal resistance and poor storage characteristics. In addition, the paper pressed against the surface of the positive electrode plate facilitated the diffusion of sulfuric acid from the separator holding the electrolyte to the positive electrode plate, making it possible to increase the capacity during high rate discharge. For papermaking, natural fibers with a large surface area are effective.
Among them, pulp fiber was found to be the most effective. It should be noted that it is easier to manufacture paper if it is strong during assembly, so water-resistance agents and the like are sometimes added, but general water-resistance agents are not soluble in sulfuric acid, so the fibers will not loosen. It was found that this caused poor compatibility and adhesion with the electrode plate. However, for example, paper made using a urea-based water-resistant agent usually maintains its strength by binding the parts where pulp fibers intersect with each other through hydrogen bonds, but when dilute sulfuric acid is added, it is hydrolyzed. Hydrogen bonds are broken and the fibers break apart. For this reason, the adhesion between the electrode plate and the papermaking material was extremely good, and the above-mentioned effects could be sufficiently brought about. In addition, although papermaking has an excellent ability to absorb electrolyte, it is not possible to increase the porosity.
Electrolyte retention capacity is inferior to glass fiber separators. Therefore, increasing the thickness of paper reduces the amount of electrolyte in the battery, resulting in a decrease in capacity. Papermaking improves wetting of the electrode plate surface and serves as a medium for supplying the separator's electrolyte to the electrode plate, so as long as it can be pressed against the electrode plate surface, its thickness can be as thin as 0.1 mm. The following thickness is fine. Description of Examples Next, the battery of the present invention will be described in detail with reference to Examples. In this example, the battery plate has a length of 40 mm and a width of 30 mm.
mm, the thickness of the positive electrode plate was 3.0 mm and the negative electrode plate was 2.1 mm, and the active material was filled in the lattice and chemically formed. Furthermore, the separator used was one made of glass fiber with an average diameter of 0.7 μm and a thickness of 2.1 mm. Between the electrode plate and the separator, a 0.03 mm thick paper made of 99% or more pulp fiber and using urea formaldehyde condensation resin as a water-resistant agent was inserted. The electrode group consists of two positive electrode plates and three negative electrode plates, and has a specific gravity of 1.30 (20℃)
Add 19ml of sulfuric acid, and the electrode group will be about 20ml in the battery.
A pressure of Kg/dm ² was applied. In the first embodiment of the present invention, the above-mentioned made paper is sandwiched only between the negative electrode plate and the separator, and in the second embodiment, the made paper is sandwiched between both the positive electrode plate and the negative electrode plate and the separator. It is something that is sandwiched between them. This battery has the same configuration as a conventional battery that does not sandwich paper between the electrode plate and separator, and the initial capacity (20℃ 0, 4A discharge, 20℃ 10A discharge), storage characteristics (40℃ storage for 6 months) The following table shows the results of comparing the subsequent 20°C 0, 4A discharge (residual capacity) and the 20°C 0, 4A discharge (recovery capacity) after charging at a constant voltage of 2.45V for 6 hours at 20°C.

[Table] From this result, paper making between the positive electrode plate and the glass fiber separator is effective in increasing capacity during high rate discharge, and paper making between the negative electrode plate and the separator is effective in preventing deterioration of storage characteristics. It turns out that it is effective. Effects of the Invention The present invention improves the conformability and wettability between the electrode plate and the separator by interposing paper made mainly of pulp fibers between the electrode plate and the glass fiber separator, thereby improving storage characteristics and rapid discharge characteristics. It is an improved version.

[Brief explanation of drawings]

The figure shows a group of electrode plates in a sealed lead-acid battery according to the present invention. 1... Electrode plate group, 2... Positive electrode plate, 3... Negative electrode plate,
4... Separator, 5... Paper made mainly of pulp fibers.

Claims (1)

[Scope of Claims] 1. Positive and negative electrode plates having a capacity ratio that allows the amount of electrolyte to be regulated so that there is no free electrolyte, and the negative electrode plate absorbs and removes oxygen gas generated from the positive electrode plate during filling. It is equipped with bipolar plates, a glass fiber separator interposed between the positive and negative polar plates, and a safety valve installed at the gas exhaust port. A sealed lead-acid battery with a thin sheet of paper containing a soluble waterproofing agent. 2. The sealed lead-acid battery according to claim 1, wherein the paper has a pulp fiber content of 95% or more. 3. The sealed lead-acid battery according to claim 1, wherein the thickness of the paper is 0.1 mm or less.