JPS6255273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in positive electrodes in lead-acid batteries,
Even if the positive electrode has a high packing density of pasty active material in the positive electrode lattice, by adding lignin or a lignin derivative to the pasty active material, it is possible to suppress the decrease in the initial capacity without impairing battery performance. purpose.

Conventionally, there has been a tendency for the capacity at the beginning of the cycle to decrease when the paste filling density in the positive electrode grid is increased, and this tendency shows that when the amount of sulfuric acid (H ₂ SO ₄ ) added to the paste is constant, the paste density is approximately
It becomes noticeable when it exceeds 3.7g/cc. When the amount of H ₂ SO ₄ is increased, the initial capacity is relatively large, but the disadvantage is that the life of the electrode plate is shortened. Moreover, if the paste density is high, the rapid discharge characteristics will also deteriorate.

The present inventors conducted several studies using high-density paste in order to maintain a long service life and increase the initial capacity as much as possible. The reason for increasing the paste filling density in the grid is to lengthen the life, especially the overcharge life, and to maintain a high capacity until the life. However, when the paste filling density is increased as described above, the initial capacity and rapid discharge characteristics are not good. These causes are due to the high paste filling density in the positive electrode plate during formation or in the battery state.
Diffusion of H ₂ SO ₄ is _poor , especially to the center of the electrode plate _.
This is thought to be due to the fact that it is difficult to diffuse and react with H ₂ SO ₄ , and furthermore, if the diffusion of H 2 SO 4 into the inside of the electrode plate is delayed, the amount of a-PbO ₂ produced increases during formation. Furthermore, if the diffusion of H ₂ SO ₄ is poor, the supply of H ₂ SO ₄ , which is a reactant, will be delayed, and the discharge characteristics will naturally deteriorate.

Furthermore, batteries that use Pb-Sn-As alloys for the lattice, which have been developed in response to the demand for maintenance-free batteries in recent years, have problems with maintenance issues in the market, such as over-discharging, for reasons that are not yet clear. In order to withstand the control, the application of especially high-density paste tends to be unavoidable, and it is difficult to meet the reliability under such control and the initial capacity requirements at the same time. This is an important key in the industrialization of batteries.

Among the above-mentioned drawbacks, the main purpose of the present invention is to improve the decrease in initial capacity, and the present invention incorporates lignin into the positive electrode paste as an additive that improves the diffusion of H ₂ SO ₄ without deteriorating other battery characteristics. Alternatively, lignin derivatives are added. More preferably, since it becomes difficult to fill the paste into the lattice when the paste viscosity increases, it is preferable that the additive can also improve the filling property by adding the additive.

It has been known to use lignin or lignin derivatives as additives in the negative electrode plates of lead-acid batteries. The purpose of this is to improve the low-temperature rapid discharge characteristics and the life of the negative electrode, and it has not been specifically added to the positive electrode so far. The present inventors focused on this lignin or lignin derivative,
By adding this to the positive electrode paste, the requirements for reliability and initial capacity of the positive electrode can be achieved.

Hereinafter, details of the present invention will be explained according to examples.

Lead (Pb) - tin (Sn) - as positive electrode lattice alloy
Using an arsenic (As) alloy, this grid was filled with the following paste. Paste mixing involves mixing ordinary lead powder with water (H ₂ O) and H ₂ SO ₄ using a kneader or the like. The paste density at this time is 3.3, while the amount of added H ₂ SO ₄ is kept constant, and the paste density during grid filling is 3.3.
It was adjusted to 3.7, 4.1, 4.5, 4.9, 5.3, 5.7 g/cc. Next, the paste composition should be the same as above,
These were mixed with 0.5% by weight of sodium ligninsulfonate based on the active material lead powder. The lignin derivative may be added to either lead powder, H ₂ O, or H ₂ SO ₄ . Next, as a representative example, assume that the paste density is constant at 3.7 g/cc, and the amount of sodium ligninsulfonate added is 0.01, 0.05, 0.1, 0.5, 1.0, 2.0,
The cases of 3.0 and 5.0% by weight were investigated. After filling the grid with such a paste, it was chemically converted by a conventional method to form an electrode plate. Moreover, the negative electrode was produced by a normal method.

Combining these positive and negative electrode plates, we use them as an electrolyte.
Using silica colloid containing H ₂ SO ₄ , a 3Ah battery was fabricated by discharging at a rate of 5 hours, and the capacity after the first charge was confirmed. The capacity was confirmed by discharging at a current rate of 5 hours. Next, charge it for 15 hours at a current rate of 10 hours,
It was then discharged at a current rate of 5 hours. Note that in the third cycle, discharge was performed at a rate of 1 hour.

An example of the results is shown below. First, during paste kneading, when the paste density was the same, the viscosity of the paste decreased as the amount of sodium ligninsulfonate added increased. Next, FIG. 1 shows the discharge capacity in the first cycle. In FIG. 1, curve number 1 shows the capacity of the paste plate without addition of sodium ligninsulfonate. From now on paste filling density 3.7g/
It can be seen that it is difficult to obtain the capacity in the first cycle at cc or more. Curve 2 is the capacity at the first cycle when 0.3% by weight of sodium ligninsulfonate is added to the lead powder. Comparing this with curve 1 clearly shows the effect of adding sodium ligninsulfonate. Curve 3 shows the 1-hour rate discharge characteristic of the electrode plate without the addition of sodium ligninsulfonate. This also shows that when the paste filling density is 3.7 g/cc or more, the discharge capacity is small. Curve 4 shows the 1-hour rate discharge characteristic when 0.3% by weight of sodium ligninsulfonate was added. Moreover, when this sodium ligninsulfonate is added, rapid discharge characteristics can also be improved. Figure 2 shows the results regarding the effect of adding sodium ligninsulfonate. In the figure, curve 5 shows the capacity in the first cycle, and curve 6 shows the hourly rate discharge capacity in the third cycle. From this result, the amount of sodium ligninsulfonate added is preferably 0.05% by weight or more based on the lead powder. Also, if it exceeds 5% by weight, bubbles will occur during charging, and the amount of lead powder will decrease relatively, so the upper limit is 3.0% by weight.
is preferred. The additives shown here are only for sodium ligninsulfonate, but other additives include lignin or lignin derivatives,
For example, almost similar results were obtained for thiolignin. In addition, as an example of the amount of sodium ligninsulfonate added, the paste density is 3.7g/
Only cc is shown, but the density is 3.7g/cc or more 5.3
Similar results were obtained for pastes up to g/cc. Note that it was not possible to fill the lattice at a density higher than 5.3 g/cc.

As mentioned above, the paste filling density is 3.7 to 5.3 g/
When lignin or a lignin derivative is added to the cc paste active material in a range of 0.05 to 3.0% by weight based on the active material powder, the initial capacity of the positive electrode can be improved, and the initial rapid discharge characteristics can also be improved. Furthermore, the addition of this lignin or lignin derivative lowered the viscosity of the paste, which had the advantage of making it easier to fill the paste into the lattice.

[Brief explanation of the drawing]

FIG. 1 shows the discharge capacity characteristics depending on whether or not sodium ligninsulfonate is added, and FIG. 2 is a diagram showing the relationship between the amount of sodium ligninsulfonate added and the discharge capacity.

Claims (1)

[Claims] 1. A lead-acid battery characterized in that a positive electrode grid is filled with a positive electrode paste active material in which lignin or a lignin derivative is added in an amount of 0.05 to 3.0% by weight based on the active material powder at a packing density of 3.7 to 5.3 g/cc.