JPH08298133A - Sealed lead acid battery - Google Patents

Abstract

PURPOSE: To improve life performance of a sealed lead acid battery by adding phosphoric acid to an electrolyte, and adding a bismuth compound to a positive electrode active material. CONSTITUTION: In a sealed lead acid battery, a gel battery of gelling an electrolyte fixed by colloidal silica, retainer battery of holding an electrolyte to a separator consisting of fine glass fiber and a granular silica battery of holding an electrolyte to granular silica, with which the periphery of a plate group is charged, are provided. In these lead acid batteries, phosphoric acid is added to the electrolyte, simultaneously with adding a bismuth compound of metal bismuth, bismuth oxide, bismuth sulfate, etc., to a positive electrode active material. Preferably, an adding amount of phosphoric acid is 0.25 to 1.5% per an electrolytic amount with an adding amount of bismuth 0.001 to 0.1% per a positive electrode active material. Thus, softening the positive electrode active material of the sealed lead acid battery is prevented, and the life performance of the battery can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of the life performance of a sealed lead-acid battery, and in particular, addition of phosphoric acid to the electrolytic solution and a bismuth compound to the positive electrode active material prevents deterioration of the positive electrode active material and seals it. The purpose is to improve and stabilize the life performance of lead-acid batteries.

[0002]

2. Description of the Related Art Sealed lead-acid batteries include a gel type battery in which an electrolytic solution is gelled and fixed by adding colloidal silica to the electrolytic solution, and a fine glass mat separator which is most widely used at present. Positive and negative, a retainer type battery in contact with the negative electrode plate, and development in recent years,
There is a granular silica battery in which granular silica is filled between the electrode plates and around the electrode plate group.

It is known that each of these sealed batteries has a considerably shorter cycle life than that of a conventional liquid battery using an Sb alloy grid for the positive electrode. One of the causes is deterioration (softening) of the positive electrode active material. In batteries with gelled electrolyte, phosphoric acid has been added to the electrolyte for a long time to delay the softening of the positive electrode active material.However, if the amount of phosphoric acid added is large, the initial capacity will rather decrease. To do.
In addition, in a retainer type battery or a granular silica type battery, addition of phosphoric acid not only lowers the initial capacity but also shortens the life performance.Therefore, adding phosphoric acid alone can prevent deterioration of the positive electrode active material and improve the life performance. Was considered difficult.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the softening of the positive electrode active material of a sealed lead acid battery and to improve the life performance of the battery. As a result of various tests, we have found that by adding phosphoric acid to the electrolytic solution and at the same time adding a bismuth compound to the positive electrode active material, the life of the battery can be extended. The results are shown below using a retainer battery.

[0005]

[Example] When the positive electrode paste was plastered, metal bismuth powder was added in an amount of 0.001% (C), 0.01% (D), based on the weight of the active material,
A 2.4 mm-thick positive electrode plate added with 0.1% (E) and 1% (F) was produced, and 10 positive electrode plates, 11 negative electrode plates of 1.7 mm thickness and a fine glass mat separator were manufactured. From the above, a retainer type sealed battery of about 63 Ah (3hR) -12V was manufactured according to a normal manufacturing method. Conventional positive electrode plates (A, B) in which bismuth is not added to the positive electrode active material
A battery using was also manufactured. A predetermined amount of phosphoric acid [0.25%, 0.5%, 0.75%, 1%, 1.
25%, 1.5% (per weight of electrolytic solution)] The diluted sulfuric acid added was injected, and predetermined charging was performed, and the test was carried out as follows. A battery (A) containing no bismuth in the positive electrode plate and no phosphoric acid added thereto was manufactured and tested at the same time.

These batteries were first measured for 1/3 CA discharge capacity. The results are shown in FIG. 1. In the battery in which phosphoric acid was added to the electrolytic solution, the capacity significantly decreased as the amount of phosphoric acid added increased. However, at the same time, in the battery in which bismuth was added to the positive electrode active material in an amount of 0.001% or more, there was no great difference in the capacity as compared with the battery without addition (A). That is, it was found that bismuth has a function of improving the initial capacity of the battery (utilization rate of the positive electrode active material).

After the initial capacity test, charging / discharging was repeated in a pattern in which the discharge depth was 80% and 110% of the discharge amount was constant current, and the life performance of the battery was examined. The results are shown in Figure 2. As can be seen from the figure, 0.001% of bismuth is added to the positive electrode active material.
Add 0.1% or less, and add 0.25% phosphoric acid to the electrolyte.
In the case of adding not less than 1.5%, no added battery (A)
It had a longer life than The battery (B) containing only bismuth and the battery containing 1% of bismuth had worse life performance.

After the test, these batteries were disassembled,
In the additive-free battery (A), the softening of the positive electrode active material was remarkable. In the battery containing only phosphoric acid, the positive electrode plate was hard and firm, but had low porosity. This seems to be the reason why the performance is difficult. In the battery containing only bismuth, the positive electrode plate softened more than ever, but in the battery containing phosphoric acid, the positive electrode plate was moderately hard. This is probably the reason why the life performance was good.

From the above results, it was found that phosphoric acid hardens the positive electrode active material and bismuth, on the contrary, has a softening effect. It is a new discovery that the life performance is improved as compared with the conventional non-added battery by adding the appropriate amounts of two kinds of additives having adverse effects at the same time.

Although metal bismuth powder was used as bismuth, it goes without saying that the same effect can be obtained with compounds such as bismuth oxide and bismuth sulfate.

In this embodiment, the retainer type battery was tested, but the same effect can be obtained by using the gel type or granular silica type battery.

[0012]

As described above, the present invention improves the life performance of a sealed lead acid battery by adding bismuth to the positive electrode active material and phosphoric acid to the electrolytic solution. From the standpoint of practical application, its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the addition amount of phosphoric acid and bismuth and the initial capacity.

FIG. 2 is a characteristic diagram showing the relationship between the addition amount of phosphoric acid and bismuth and life performance.

Claims (2)

[Claims] 1. A gel type in which an electrolytic solution is gelled and fixed by colloidal silica, a so-called retainer type in which the electrolytic solution is held in a separator made of fine glass fibers, or granules in which the electrolytic solution is filled around the electrode plate group. A sealed lead-acid battery of granular silica type retained on silica, characterized by adding bismuth compounds such as metal bismuth, bismuth oxide, and bismuth sulfate to the positive electrode active material at the same time as phosphoric acid was added to the electrolytic solution. Type lead acid battery. 2. The amount of phosphoric acid added is 0.25 per amount of electrolytic solution.
% Or more and 1.5% or less, and the amount of bismuth added is 0.001% or more and 0.1% or less based on the amount of the positive electrode active material, The sealed lead acid battery according to claim 1.