JPS6155749B2 - - Google Patents

Description

[Detailed description of the invention]

The main electrode plates for lead-acid batteries that use sulfuric acid as the electrolyte are paste-type plates and clad-type plates. Among these electrode plates, paste-type electrode plates are easy to manufacture, have relatively good discharge characteristics, and are inexpensive, but have a rather short lifespan. On the other hand, the clad type plate has a robust structure and long life, but its rapid discharge characteristics are somewhat inferior and it is relatively expensive. The purpose of the present invention is to particularly improve the low-temperature rapid discharge characteristics and extend the life of a paste-type electrode plate. Paste-type lead electrode plates are usually made by mixing lead powder (a mixture of lead and lead oxide, where the lead oxide ratio is often around 50 to 80% by weight) with water, dilute sulfuric acid, etc. It is obtained by a step of applying the obtained lead paste to a support such as a grid made of lead or a lead alloy, expanded metal, punched metal, etc., filling it, aging, and drying. In this way, the paste type lead electrode plate has a relatively simple manufacturing method and electrode structure, so it has good discharge characteristics during a small number of charge/discharge cycles, but as the number of charge/discharge cycles progresses, the paste type lead electrode plate becomes retained in the plate. The active material (converted from the above-mentioned lead paste by chemical conversion) becomes noticeably softened and falls off, and the characteristics begin to deteriorate. Therefore, it is already known that it is effective to add a fluororesin to the lead paste in order to improve the softening and shedding of the active substance. According to this method, fine particles of fluororesin firmly adhere to each other and become fibrous due to the mechanical force applied during the kneading process during paste preparation, resulting in the resulting lead paste having rubber-like elasticity. softening of active substances,
It suppresses shedding and has a much longer lifespan compared to additive-free products. However, as mentioned above, lead paste with rubber-like elasticity or extremely high viscosity obtained by adding and kneading fluororesin is difficult to fill into the support of the electrode plate by kneading, and this tendency This problem becomes more pronounced as the amount of fluororesin added increases. In addition, in order to improve the filling properties of the lead paste by kneading it onto the support, the amount of fluororesin added may be reduced, and if the rubber-like elasticity or viscosity of the resulting lead paste is lowered too much, it will become fibrous. However, there were problems such as a decrease in the amount of fluororesin and a decrease in the effectiveness in suppressing the softening and falling off of the active material. Therefore, the present invention provides a method for improving the kneading properties of a lead paste without reducing the amount of fluororesin to be made into fibers in the lead paste. That is, the present invention is characterized by using a lead paste to which calcium silicate is added in addition to lead powder, water, sulfuric acid, and fluorine resin dispersion.
The calcium silicate used here has countless pores inside the calcium silicate fine particles itself in the lead paste, keeping the paste's porosity high, and its high water content keeps the paste's elasticity low. It's useful. In addition, at this time, almost no adverse effect is observed on the fiberization of the fluororesin during paste preparation. In the lead paste, the amount of fluororesin in the fluororesin dispersion suitable for making the fluororesin into fibers is 0.5 to 10% per 1 kg of lead powder.
g, and the appropriate amount of calcium silicate added to improve the kneading properties while maintaining the characteristics of the lead paste containing fluororesin, that is, the elasticity due to the fibrous fluororesin, is 3 to 3. It is in the range of 50g. Within this range, the rubber-like elasticity of the paste provided by the fluororesin will not be impaired.
Due to the high porosity and high water content of calcium silicate, the elasticity of the paste as a whole can be kept low, making it possible to improve the spreadability on the support and improve the discharge characteristics and life of the electrode. Hereinafter, an example in which the present invention is applied to a positive electrode plate of a lead-acid battery for starting an automobile will be described in detail. For 1 kg of lead powder, 200 ml of water, aqueous dispersion of polytetrafluoroethylene (specific gravity 1.6,
2 ml of polytetrafluoroethylene resin (content of 60% by weight), and calcium silicate (content of silicon dioxide and calcium oxide of approximately 40% each)
While kneading 20g (weight%, loss on ignition of approximately 20%) in a kneader, 70ml of sulfuric acid with a specific gravity of 1.40 is added dropwise to form a lead paste. The obtained lead paste is filled into a lead grid using an automatic filling machine, and after being made into a positive electrode plate using a known method, it is combined with a known paste-type negative electrode plate.
An NS40Z type battery was constructed. As Comparative Example 1, a case in which calcium silicate was not added during paste kneading in Examples was investigated. In this case, when filling the lead paste with an automatic filling machine, the rubber-like elasticity of the lead paste resulted in poor filling of the grid, leaving many cracks or small voids. In addition,
The amount of filling in this case is about 5% by weight compared to the example.
There weren't many. As Comparative Example 2, water was added to 1 kg of lead powder compound.
The case where 170 ml of sulfuric acid with a specific gravity of 1.40 and 70 ml of sulfuric acid with a specific gravity of 1.40 was added and no fluororesin dispersion and calcium silicate were added was investigated. Note that the filling amount in this case was almost the same as in the example. When the battery described above is discharged with a current of 150A at a temperature of -15℃, the voltage at the 5th second of discharge and
The discharge time until the voltage reached 6V was as shown in Table 1.

[Table] Table 2 shows the lifespan when charging and discharging at a current of 5A for 5 hours and discharging at 20A for 1 hour.

[Table] As shown above, when a lead paste containing a fluororesin dispersion and calcium silicate is used, it is possible to obtain good filling performance and excellent discharge characteristics and life. In this example, in the present invention, 1.92 g of polytetrafluoroethylene resin (2
ml x specific gravity 1.6 x 60/100), calcium silicate 20g
I gave an example of adding . Next, add 20% calcium silicate.
It was decided to clarify the preferable amount by changing the amount of polytetrafluoroethylene resin while keeping g constant. Table 3 summarizes the amount of polytetrafluoroethylene resin added, the characteristics of the manufacturing method, the voltage at 5 seconds as a battery, the discharge time, and the lifespan.

[Table] From this result, even if a small amount of polytetrafluoroethylene resin is added, there is an effect of improving performance, but 0.5 g or more is appropriate to show a significant performance improving effect. Regarding the upper limit, if too much is added, it will become too fibrous and difficult to fill, and the active substance of the electrode will be covered with the binder, which will reduce the discharge voltage and discharge time, and shorten the lifespan. Rather, it deteriorates. Therefore, 10g or less is appropriate. Of course, this range will be affected slightly depending on the amount of calcium silicate, but it is still within the range of 0.5 to 10.
There is no change in the fact that g is appropriate. Next, the amount of calcium silicate was varied while keeping the amount of polytetrafluoroethylene resin constant.
Table 4 shows the amounts added and the results.

【table】

[Table] In this case as well, adding even a small amount of calcium silicate will have the same effect. However, significant effects appear to occur at doses above 3g. On the other hand, the upper limit is preferably 50 g or less because if too much is added, the active mass will decrease and the voltage characteristics and life will deteriorate. In this case as well, if the amount of polytetrafluoroethylene resin changes, the optimum amount of calcium silicate will be slightly affected, but the range of 3 to 50 g is still suitable. From the above results, it has become clear that the amount of polytetrafluoroethylene resin is preferably 0.5 to 10 g and the amount of calcium silicate is preferably 3 to 50 g per 1 kg of lead powder. Note that the ratio of silicon dioxide and calcium oxide in calcium silicate, the ratio of loss on ignition (most of the loss is water), etc. vary widely, but the present invention will work no matter which ratio is selected. It is possible to obtain the effect of Further, in the embodiment, an example of application to a paste-type lead positive electrode has been described, but the present invention can be applied to a paste-type negative electrode as well as a paste-type lead positive electrode.

Claims (1)

[Claims] 1. A support made of lead powder, sulfuric acid, water, a fluororesin dispersion containing 0.5 to 10 g of fluororesin per 1 kg of the lead powder, and a paste prepared by kneading 3 to 50 g of calcium silicate per 1 kg of the lead powder. A method for producing a paste-type electrode for a lead-acid battery, characterized by applying the paste to the electrode.