JPH11144719A - Sealed lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the life performance, without damaging the initial performance of a battery by using a positive electrode plate consisting of an active material obtained by adding a specified quantity of tin or a compound thereof to a Pb-Ca grating, having an effective grid diameter of a specified value or more. SOLUTION: In a grid having an effective diameter of 7 mm or more, 0.2-3 wt.% of a thin compound is added to an active material, whereby the discharge capacity and life performance can be improved. Namely, since the tin compound generates minute PbO2 to increase the surface area of an active material, the discharge capacity is increased. Further, since the PbO2 closely covers the grid surface, a passive state film is hardly generated even in a grating having a long electric path with active material, and the life time performance is thus improved. The effective diameter is shown by 4× (the ratio of the area of one square of the grid to the circumferential length of one square of the grid). Although the performance become disadvantageous when this value is large, the life time performance can be improved without reducing the effective diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a positive electrode plate of a sealed lead-acid battery, and an object thereof is to improve the life performance of the sealed lead-acid battery without impairing the initial performance of the sealed lead-acid battery. is there.

[0002]

2. Description of the Related Art In recent years, as lead storage batteries for cycle services such as EVs, sealed lead storage batteries that do not require any troublesome maintenance such as water refilling are mainly used. Is used.

[0003]

Although this type of battery is superior to a liquid battery in the above respects, it does not adhere to the surface of the positive electrode grid when deep charge / discharge is repeated or overcharged. There is a problem that a working film is formed and the life is easily shortened.

[0004] In order to make it difficult for a passive film to be formed, or to make it easy to be released by charging as soon as it is formed, a grid is formed so that the electric path (distance) between the active material and the current collector is as short as possible. For example, a method of increasing the density of the active material so that the contact between the lattice and the active material is increased, or the density of the active material is reduced (the effective diameter of the lattice is reduced) is adopted.

[0005] These methods are effective if only the life performance is evaluated. However, all of these methods involve an increase in battery weight (increase in lattice weight and increase in the amount of active material). It is a means of improving the life performance at the expense of the initial capacity (energy density) at the expense of the initial capacity.
It was difficult to apply.

[0006]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for producing a grid having an effective diameter of 7 mm or more represented by the formula [4 × (area of one grid) ÷ (perimeter of one grid)]. In a Pb—Ca based lattice of
The present invention is characterized in that a positive electrode plate made of an active material to which 3 wt% is added is used, and the tin compound is stannous sulfate. The effective diameter described here is a coefficient expressing a function required for the grid, such as the outer dimensions of the grid, the thickness, the type of active material to be employed, the volume ratio of the grid to the active material, and the workability. It is calculated by an equation.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of repeated experiments, it was confirmed that both the initial capacity and the life performance could be improved without reducing the effective diameter of the grid as much as possible. In a grid having a large grid, which is considered to be disadvantageous to the life performance due to a long electric path, that is, a grid having a large effective diameter, particularly a grid having an effective diameter of 7 ° or more, a tin compound is added to the active material in an amount of 0.1%. It has been found that the addition of 2 to 3% is effective in improving the discharge capacity and the life performance. This is thought to be because the tin compound generates dense PbO ₂ and increases the surface area of the active material, thereby increasing the discharge capacity.

Further, it is considered that since the dense PbO ₂ densely covers the lattice surface, a passive film is less likely to be formed even in a lattice having a long electric path with the active material, so that the life performance is improved. According to the present invention, it is possible to improve the initial capacity and the life performance without reducing the effective diameter of the lattice and without employing a high-density active material.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

[0010] Stannous sulfate is added to the lead powder obtained by a conventional method.
After thoroughly mixing while adding an aqueous solution in which tin sulfate was dissolved and stirred little by little, the mixture was ground with a predetermined amount of diluted sulfuric acid to prepare a positive electrode paste. These pastes are filled into lattices of Pb-Ca alloys having different effective diameters, and are subjected to aging and drying steps to form unmodified cathode plates A-1, A-2 to E of the same thickness.
-7 and E-8 were obtained. Table 1 shows the amount of tin sulfate added to each positive electrode plate and the effective diameter of the lattice.

[0011]

[Table 1] Using these positive plates, a capacity of about 15 Ah (3 hR) -2
A V-type sealed lead-acid storage battery was manufactured according to a normal manufacturing method. In addition, the same thing was used for the negative electrode plate, the specific gravity of the electrolytic solution, and the like. In addition, a lattice having an effective diameter of less than 4 mm significantly increases the mass (weight) of the lattice and reduces the amount of active material. Was excluded from the study because it was not suitable for mass production.

First, the 3hR discharge capacity of these batteries was examined. FIG. 1 shows the relationship between the amount of tin sulfate added and the discharge capacity. Batteries with an effective grid diameter of 7 mm or more (C-series, D-
Series, E-series), the amount of tin sulfate added was 0.1%.
The effect of increasing the discharge capacity appears in the region of 2 wt% or more, and it becomes maximum when 3 wt% is added, and is 10 to 20%.
The discharge capacity has increased. In the region where the amount of addition exceeds 3 wt%, only the same effect as in the case of adding 3 wt% was obtained.

For batteries (A-series, B-series) having an effective lattice diameter of less than 7 °, the effect of increasing the discharge capacity by the addition of tin sulfate was obtained in almost the same addition region as described above. However, reducing the effective diameter inevitably increases the lattice mass (weight) and reduces the amount of active material, so that the effect was small.

Next, batteries (A-6, B-6, C-6, D-6, E-6) to which 2 wt% of tin sulfate is added as a representative
And batteries not containing tin sulfate (A-1, B-1, C
-1, D-1, E-1) were subjected to a cycle life test at a DOD (depth of discharge) of 80%. FIG. 2 shows the transition of the capacity of the battery of each effective diameter when the initial discharge capacity of the battery without tin sulfate was 100%. 7mm effective grating diameter
Thus, the battery (C-
6, D-6, and E-6) maintain the initial discharge capacity for a long period of time, and do not include tin sulfate-free batteries (C-1, D-1, and E-1).
As shown in FIG.

In particular, the battery E-6 (effective diameter 9 mm) having the largest effective diameter among the positive electrode plates manufactured this time is about 60
The zero cycle life performance was shown. The effect of tin sulfate addition was greater as the effective diameter of the lattice was larger. This is because the addition of tin sulfate produces dense PbO ₂ , increasing the initial discharge capacity, and also increasing the dense PbO 2.
_This is probably because the electrode ₂ covered the grid densely, so that the original performance of the electrode plate was exhibited without any discharge trouble such as generation of a passive film.

On the other hand, when the effective diameter of the lattice is smaller than 7 °, the initial capacity increase due to the addition of tin sulfate cannot be expected so much, and the life performance is slightly improved compared to the battery without tin sulfate.

In this case, the upper limit of the effective diameter is set to 9 ° because of the positive electrode grid which can be easily mass-produced. However, it is actually possible to manufacture a battery using a grid having an effective diameter larger than this. Since the same effect can be expected by adding a tin compound, it is considered that there is no upper limit of the effective diameter.

[0018]

As described above, the sealed lead-acid battery according to the present invention is excellent in both initial performance and life performance, and has great industrial value.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the effect of the amount of tin sulfate added to a positive electrode active material and the effective diameter of a positive electrode grid on discharge capacity.

FIG. 2 is a characteristic diagram showing a comparison of charge / discharge cycle characteristics.

Claims (2)

[Claims] In a sealed lead-acid battery, a Pb—Ca-based positive electrode in which the effective diameter of a lattice represented by the formula [4 × (area of one lattice) ÷ (perimeter of one lattice)] is 7 ° or more. 0.2 to 3% by weight (wt)% of tin or tin compound in the lattice
A sealed lead-acid battery using a positive electrode plate made of an added active material. 2. The sealed lead-acid battery according to claim 1, wherein said tin compound is stannous sulfate.