JPS6161228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a paste-type electrode for a lead-acid battery.

Currently, the most popular type of secondary battery is a lead-acid battery, and the mainstream is a so-called paste-type lead-acid battery, in which the electrode plates are obtained by applying paste to a grid. The first reason for this is that the manufacturing method is simple and the electrode structure is simple, resulting in low cost. The second reason is that it has excellent performance.

The present invention provides an effective method for maintaining the high performance of such a paste-type lead-acid battery and making it possible to extend its life.

In paste-type lead batteries, the active material is bonded to the active materials or the active material and the lattice through a chemical reaction that partially generates lead sulfuric acid from lead oxide when the paste is applied. It is said that Therefore, in terms of characteristics, it is not necessary to particularly contain an insulating material such as a binder, and since there is no partition wall like a clad type, both discharge utilization efficiency and potential are excellent. However, when charging and discharging are repeated, it is weak against contraction and expansion, and the bond strength gradually weakens, and eventually the active material softens and falls off, causing a short circuit and reaching the end of its life. It had the disadvantage of short lifespan.

Various studies have been made to improve the above drawbacks, and one of them has been proposed to include a dispersion of fluororesin, particularly polytetrafluoroethylene, added to the paste. Paste is usually made by adding water to the lead active material and slowly adding dilute sulfuric acid while thoroughly kneading it. When dispersed in water to be added to the active material, added at the same time as the water, and further mixed with dilute sulfuric acid, the fluororesin becomes fibrous, and fibers are present in the active material. The paste kneaded in this way is filled into a grid made of lead alloy, dried and solidified to form an electrode plate, which is extremely strong and has a much longer charging and discharging life than one without fluororesin additives. Become.

However, although the paste containing fluororesin dispersion has strong rubber-like elasticity and increases the binding force between the active material powders, it does not easily adhere to the lead alloy grid, making it difficult to fill. When smoothing the surface, it is difficult to flatten the surface, making it difficult to obtain a uniform thickness. In this respect, work efficiency becomes extremely poor, and cracks may appear between the lattice and the active material, resulting in variations in capacity.

The present invention eliminates the above-mentioned drawbacks and provides a paste-type electrode with a long life.

That is, the present invention is characterized in that when a fluororesin dispersion is added to the paste and kneaded, a surfactant is added at the same time as the fluororesin dispersion. According to the present invention, the surfactant further promotes fiberization of the fluororesin, and an active material layer having a network structure tightly intertwined with the lead active material can be obtained. On the other hand, it is possible to increase the amount of fluororesin added to extend the service life, but in this case, the paste becomes rubber-like and elastic, which poses a problem in workability. In other words, kneading in the presence of a surfactant is different from simply adding more fluororesin; rather, the fluororesin forms very thin fibers, forming a network between the particles of the lead active material rather than a rubbery one. spread,
It exhibits an excellent effect in terms of retention of active materials.

The present invention will be explained in more detail below using examples.

First, a lead alloy grid body containing 2% by weight of antimony and having a size of 110×110 mm and a thickness of 1.5 mm is used as a support for the electrode plate. On the other hand, for 1 kg of lead active material, 3 c.c.
(Resin content: 2.7 g), 2 g of polyethylene oxide, and 150 c.c. of water were added to the kneader. Knead thoroughly using Next, gradually add 100 c.c. of dilute sulfuric acid with a specific gravity of 1.35 and mix.
Apply to the above grid. After this, it is aged and dried in high humidity.

Five positive electrode plates obtained as described above, a known paste, six formula negative electrode plates, and a cellulose-based separator were combined to form an electrode plate group, and the battery was placed in a battery container with dilute sulfuric acid.

The amount of the above surfactant per 1 kg of lead active material
Batteries using positive electrodes of 0.5, 1, 2, 5, and 10 g are designated as A ₁ , A ₂ , A ₃ , A ₄ , and A _{5 ,} respectively. On the other hand, a battery using a positive electrode made without adding a surfactant is designated as B. After forming the above A and B, rapid discharge was performed at a low temperature of -15° C. with a current of 150 A, and the discharge duration up to 1 V was examined. The results are shown in FIG. As is clear from the figure, batteries A ₁ to _{A 4} exhibited similar performance to B. In A ₅ , it is slightly lower than in B, but this may be due to the fact that the concentration of surfactant has increased so that the fiberization of the fluorine resin has progressed too much and becomes a resistance during discharge, or the surfactant has some kind of negative effect during discharge. It seems that it was

Next, charge and discharge the above battery by discharging it with a current of 20A for 1 hour and charging it with a current of 5A for 5 hours, and the cycle ends when the discharge voltage drops to 1.7V after 1 hour.The charge/discharge cycle life I conducted a test. The results are shown in FIG. As is clear from the figure, adding a surfactant has an effect on life span. This is thought to be because the presence of the surfactant causes the fluororesin to become fibrous, forming a network structure within the electrode plate and preventing the active material from falling off. _A1 shows the same characteristics as B, and the appropriate amount of surfactant to be added is 2 to 5 g per 1 kg of active material, including low-temperature rapid discharge characteristics.

As is clear from the results of the low-temperature rapid discharge characteristics and repeated charge/discharge characteristics shown above, the paste-type electrode plate according to the present invention has excellent characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram comparing the capacities of lead batteries using various positive electrodes during low-temperature rapid discharge, and FIG. 2 is a diagram comparing the charge/discharge life.

Claims (1)

[Claims] 1. To the lead active material powder, add a fluororesin dispersion, 2 to 5 g of surfactant per 1 kg of the active material powder, and water and knead to form a paste, then gradually add sulfuric acid and knead. A method for producing a paste-type electrode for a lead battery, characterized by applying the mixed mixture onto a grid.