JPH0554881A - Lead-acid battery positive electrode plate and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve lead-acid battery characteristics by causing a paste, obtained by rubbing out a dilute sulfuric acid and a mixture prepared by dripping a sulfate having a specified amount of tin onto a lead powder, to be filled into a grating consisting of a lead/calcium alloy containing no antimony. CONSTITUTION:A water solution of SnSO4 dissolved to a specified concentration is mixed into a lead powder while the solution is being added bit by bit to the lead powder in anatomized condition until the tin content has a specified concentration with the lead powder being used as a reference. A paste obtained by rubbing out the resulting mixture and a dilute sulfuric acid is filled into a grating formed of cast Pb-Ca-Sn alloy containing to antimony. The resulting grating is aged and dried to obtain a non-formed positive electrode plate. Repetition of charging/discharging cycle per specified length of time would make the variation in the charge capacity proportion small. Dispersion of the tin portion into the lead powder through the mentioned addition and mixing enables uniform distribution of the former in the latter, whereby it is possible to improve the battery characteristics while making the variation in the charging capacity small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a maintenance-free lead-acid battery composed of a paste-type electrode plate, and more particularly to a positive electrode plate for improving the discharge capacity of a sealed lead-acid battery without variations and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in a maintenance-free lead-acid battery composed of a paste type electrode plate, in particular, a sealed lead-acid battery, the positive electrode plate is made of a Pb-Ca-based alloy containing substantially no Sb or only a small amount of Sb. A cast grid or expanded metal grid was filled with a paste obtained by kneading lead powder as the main component and dilute sulfuric acid, and aged and dried to produce an unformed positive electrode plate. In addition, the unformed negative plate also
Usually, a lead storage battery, which is manufactured by a similar manufacturing method using a grid made of a Pb-Ca alloy containing substantially no Sb and is assembled by an unformed positive and negative electrode plate, is first charged by battery formation or the like to obtain a battery. Was completed. A lead storage battery using a grid made of a Pb-Ca-based alloy for a positive electrode plate has very little decrease in the amount of electrolytic solution due to charge and discharge, and has excellent maintenance-free characteristics. This is an indispensable technology for absorption-type sealed lead-acid batteries. However, there is a problem that the active material of the positive electrode plate is softened by repeated charging / discharging accompanied by deep discharge, and finally the active material of the positive electrode plate is deteriorated such as falling off, resulting in a rapid decrease in battery capacity.

As a measure for improving such a problem, much research has been conducted on a lead alloy composition for a lattice, a method for producing a lattice, an additive to a positive electrode active material and the like.

For example, as shown in JP-A-61-277158, by using a positive electrode plate filled with a paste obtained by kneading a mixture of lead powder and tin oxide powder and dilute sulfuric acid, Proposals have been made to suppress such a rapid capacity decrease.

[0005]

As described above, Pb
By using a positive electrode plate filled with a paste obtained by kneading lead powder to which tin oxide is added and dilute sulfuric acid in a lattice made of a Pb-Ca-based alloy such as -Ca-Sn alloy, deep discharge is generated. A rapid decrease in capacity during charge / discharge cycles is suppressed. Such a suppressing effect is due to the tin content of the tin oxide added to the lead powder that becomes the positive electrode active material. That is, a dense PbSO ₄ layer that forms a passivation phenomenon is formed at the interface between the lattice and the active material, which is closely related to the charge acceptance characteristics in constant voltage charging that is widely used for charging lead acid batteries. It is considered that the tin content hinders the formation. However, if the tin content in the paste is not uniform, the above-mentioned effects may vary, and battery characteristics may not be substantially improved.

[0006]

The present invention eliminates the above-mentioned drawbacks by a simple and effective means. Specifically, as in the prior art, a small amount of solid tin oxide powder is added to lead powder. Addition,
Use a paste that is harmless to the battery without mixing, and is added in small amounts in the form of a water-soluble tin sulphate aqueous solution that is added dropwise or sprayed, and then mixed with diluted sulfuric acid. The purpose was achieved by doing.

[0007]

The addition of tin to lead powder is effective at about 0.2% or more as the tin content in the positive electrode active material. It was necessary to preliminarily mix the lead powder and the tin oxide powder for a long time. This is because tin oxide is a solid and the addition amount is relatively small. Therefore, in the present invention, the additive in the form of a water-soluble tin sulfate aqueous solution, which is harmless to the battery, is dropped or sprayed and mixed and dispersed little by little to the lead powder. Even when mixed, the distribution of tin content is uniform, and the effect is very small.
It greatly contributes to the improvement of battery characteristics.

[0008]

EXAMPLES Examples of the present invention will be described below.

0.02 mol / l was added to lead powder obtained by a conventional method.
The SnSO ₄ aqueous solution dissolved in the above concentration was sprayed to an amount corresponding to 1 mol% of tin content based on the lead content in the lead powder, and mixed little by little, and then mixed with a predetermined amount of dilute sulfuric acid. The paste obtained by kneading with Pb-Ca-S
An n-alloy cast grid is filled, aged and dried to obtain an unformed positive electrode plate.

For comparison, a lead powder and a SnO powder obtained on the same scale as the present invention with the tin content of the lead powder, the same kneader and the same mixing and kneading conditions were used. A conventional positive electrode plate filled with a paste of the mixture was also prepared. Using the positive electrode plates according to the examples of the present invention and the conventional example, 50 individual cells each having a nominal capacity of 20 Ah at a 20-hour rate were manufactured.
In order to understand the characteristics of the positive electrode plate, the prototype battery has a larger negative electrode capacity than ordinary products so that the discharge capacity of the battery is regulated by the positive electrode capacity. It was used. After being charged for the first time by battery case formation, it was discharged to 1.75 V at a constant current of 5 hours, 2.
A cycle test was performed in which charging was repeated at a constant voltage of 45 V for 8 hours. The frequency distribution of the discharge capacity ratio with respect to the nominal capacities of the both in the 5th cycle is shown in FIGS. 1 and 2. The discharge capacity ratio of the battery of the conventional example shown in FIG. 1 varies from 102 to 112%, and the statistical dispersion spreads to the range of 5.69, while the embodiment of the present invention shown in FIG. In the battery, the discharge capacity ratio was as small as 105 to 109% and the statistical dispersion was 0.76, which was 4.93 higher than that of the battery according to the conventional example. From the above results, it is clear that the batteries according to the examples of the present invention have less variation in the effect of tin content than the batteries according to the conventional example. Although the results are not shown, the SnO of the conventional example
Instead of the above, a paste obtained by crushing SnSO ₄ crystals, adding and mixing to lead powder, and then kneading with dilute sulfuric acid was also examined. The discharge capacity ratios of the batteries according to the example of the present invention and the conventional example and The statistical variance was at an intermediate level.
Therefore, the dispersion due to the addition and mixing of the tin content to the lead powder is Sn
It can be understood that the use of the SO ₄ aqueous solution is effective for the uniformity of distribution. In the examples, SnSO _{4 as} the first salt was shown, but Sn (SO ₄ ) _{2 as} the second salt was used.
There was no difference in the effect. Addition amount of tin is 1mo
I showed about 1%, but the range of 0.1-3.0mol% is effective, less than 0.1mol% is not effective, and 3.0mol%
If it exceeds%, the characteristics will rather deteriorate. The tin sulfate can be previously dissolved in dilute sulfuric acid depending on the addition amount. In this case, it is not necessary to add tin sulfate in the form of an aqueous solution to lead powder in advance, and a paste obtained by directly kneading lead powder and dilute sulfuric acid in which tin sulfate is previously dissolved has the same effect. Is played. Further, in the example, the grid was filled with the paste, and immediately aged and dried to obtain an unformed positive electrode plate,
Depending on the paste formulation, even if the paste is filled and then subjected to an immersing treatment, followed by aging and drying, it does not depart from the gist of the present invention. Furthermore, in the examples, a cast lattice made of a Pb-Ca-Sn alloy containing substantially no Sb has been described, but an expanded metal lattice made of the same alloy and, for example, Pb-Ca alloy, Pb-Ca-Sn.
Pb-Ca alloy plate such as alloy, Pb on both sides or one side
A similar effect can be obtained in the case of a lattice in which Sb is slightly scattered on the lattice surface, such as an expanded metal lattice using a clad plate in which a Pb alloy foil containing Sb such as -Sn-Sb alloy is rolled and integrated. ..

[0011]

As described in detail above, the lead powder is mixed with a predetermined amount of tin sulfate in the form of an aqueous solution or a dilute sulfuric acid solution, and the distribution of tin content in the paste containing lead powder as the main component is adjusted. By uniforming the discharge capacity in a short time, it is possible to obtain a maintenance-free lead acid battery, in particular, a sealed lead acid battery, which can improve the discharge capacity while reducing the variation.

[Brief description of drawings]

FIG. 1 is a frequency distribution diagram of a discharge capacity ratio with respect to a nominal capacity according to a conventional example.

FIG. 2 is a frequency distribution diagram of a discharge capacity ratio with respect to a nominal capacity according to an embodiment of the present invention.

Claims (5)

[Claims] 1. A grid of a lead-calcium alloy containing substantially no antimony or only a small amount of antimony, and a predetermined amount of a tin sulfate aqueous solution is added dropwise or atomized to lead powder to form a small amount. A positive electrode plate for a lead storage battery filled with a paste obtained by mixing and dispersing while adding and kneading these mixtures and dilute sulfuric acid, and a method for producing the same. 2. A lattice made of a lead-calcium alloy containing substantially no antimony or little antimony and lead powder and diluted sulfuric acid prepared by dissolving a predetermined amount of tin sulfate in advance. A positive electrode plate for a lead storage battery filled with the paste obtained by the combination and a method for producing the same. 3. The lead-acid battery according to claim 1, wherein the tin content of the tin sulfate to be added is in the range of 0.1 to 3.0 mol% based on the lead content in the lead powder. Positive electrode plate and manufacturing method thereof. 4. The lead storage battery according to claim 1, wherein the grid made of a lead-calcium alloy is a lead-calcium-tin alloy and is a cast grid or an expanded metal grid containing substantially no antimony. Positive plate. 5. A lead-calcium alloy lattice is provided on both or one side of a lead-calcium alloy plate such as a lead-calcium alloy or a lead-calcium-tin alloy, and antimony such as a lead-tin-antimony alloy. The positive electrode plate for a lead storage battery according to claim 1, which is an expanded metal grid using a clad plate obtained by rolling and integrating a lead alloy foil containing a.