JPH04179063A - Sealed type lead-acid battery - Google Patents

Abstract

PURPOSE:To provide a sealed lead acid battery in thin form by adding Ce sulfate having large dissolutiveness and a high specific electric conductivity to electrolytic solution, CONSTITUTION:Pb-Ca-Sn alloy or Pb-Ca-Sn-Al-alloy is used to a lattice of a pos. electrode plate, while 2-200g/l Ce sulfate is included in electrolytic solution. That is, a larger quantity of Ce sulfate can be dissolved than the quantities of conventional additives, which suppresses Pb ion production in the electrolytic solution having become water at the time of overdischarge, to provide prevention of internal shortcircuiting. This permits to use a thin separator, which should make the resultant cell still thinner in structure.

Description

[Detailed description of the invention] Industrial applications The present invention relates to improvements in sealed lead-acid batteries.

Conventional technology and its issues Sealed lead-acid batteries are widely used as a power source for portable home appliances because the electrolyte is held in a mat-like separator made of glass fiber, so the liquid does not leak outside and does not require additional water replenishment. ing.

Sealed lead-acid batteries are sealed by significantly limiting the amount of electrolyte compared to open lead-acid batteries, but the characteristic of this extremely small amount of electrolyte is that when deep discharge is performed, sulfuric acid in the electrolyte As the electrolyte is consumed, hydrogen ions and sulfate ions disappear, and it becomes just water, resulting in high resistance, which reduces charge recovery.Furthermore, if the electrolyte becomes water after discharge, as shown in Table 1, f! The solubility of acid lead increases extremely, and the dissolved lead sulfate dissociates a large amount of lead ions, which precipitates as needle-shaped lead on the negative electrode plate during charging, penetrates the separator and comes into contact with the positive electrode plate, causing an internal short circuit. Live. This phenomenon is particularly likely to occur in thinner batteries because the separators are thinner, and has been an obstacle in making the batteries thinner.

Table 1 It has been proposed to add soluble sulfates such as sodium vA acid, magnesium sulfate, and ammonium sulfate to the electrolytic solution in order to eliminate these problems. The action of these sulfates is that even when sulfuric acid is exhausted due to deep discharge, the sulfates that do not participate in the battery reaction dissociate into ions, imparting conductivity to the water electrolyte, and due to the common ion effect on lead ions. , suppresses the increase in its concentration and prevents the precipitation of needle-like buttons during charging.

However, since ammonium sulfate has a high solubility, it is expected to be highly effective, whereas ammonium ion (NH4)
) is a polyatomic molecule, it has poor chemical stability and is easily oxidized and decomposed at the positive electrode, disappearing and quickly losing its effectiveness. Magnesium sulfate is superior to sodium sulfate in that it has a slightly higher solubility, but it is inferior in conductivity, and sodium sulfate is currently the most widely used. but,
Sodium sulfate has no effect if the amount added is small, and even if you want to significantly increase the amount added, there is a limit due to low solubility, and the expected effect is not obtained. Therefore, in batteries using thin separators, repeated deep discharges It had the disadvantage of causing an internal short circuit in a short period of time.

Means for Solving the Problems The present invention solves the above drawbacks by adding FiX'#cesium, which has high solubility and high specific conductivity, to the electrolyte, and makes it possible to create thinner sealed lead-acid batteries. It is what makes it possible.

EXAMPLE Table 2 shows the characteristics of cesium sulfate used in the battery of the present invention in comparison with conventional additives.

Table 2 Example 1 Various additives were added to the electrolytic solution as shown in Table 3, and a 5Ah battery was used to conduct the following experiment.

Experiment 1 Discharge with a 20HR current while the voltage between the terminals becomes 0■, then short-circuit the terminals and leave it for 150 hours, then charge with a constant voltage of 2.25V/cell, and after 30 minutes Check the current and the current at the 5th hour.

Experiment 2 After fully charging with constant current, discharge with 2OHRt current until the voltage between the terminals becomes 0■, then short-circuit the terminals and store at 40℃ for 6 months and 12 months. 1
Charge to 200% of the rated capacity using 0HR1 flow and examine the capacity recovery rate. The results are shown in Table 3.

Table 3 From the results of Experiment 1, it can be seen that under the storage conditions shown in the experimental method, the addition of cesium sulfate to the electrolytic solution improves the charging performance compared to the conventional method. The results of Experiment 2 show that the presence of cesium sulfate is effective under the conditions and charging conditions shown in the experimental method. In addition, no internal short circuit was observed in any of the cells to which these were added during charging after being left unused.

Example 2 Two batteries with a thickness of 3 mm (separator thickness 0.811)
0 pieces, divide it into two equal parts, and pour equal amounts of an electrolyte solution in which 150 g of cesium sulfate and 1 are dissolved in sulfuric acid with a specific gravity of 1.300 into one part, a saturated solution of sodium sulfate, and the other part. After initial charging, we conducted an over-discharge test as specified by JIS.As a result, internal short circuits occurred in 8 batteries with the addition of sodium sulfate, but none with the addition of cesium sulfate. Ta. In addition, the battery using cesium sulfate had good current reception during charging after overdischarging. The amount of cesium sulfate added to the electrolyte is 2Q/
f;! Below, the effect is the same as the conventional one, while 20
If the electrolytic solution exceeds 0 Q/A, the reduction in the conductivity of the electrolytic solution itself will greatly affect the reduction in the discharge voltage of the battery, so it is necessary to limit the amount added.

Effects of the invention Since Fii & cesium oxide can be dissolved in larger quantities than conventional additives, it is extremely effective in suppressing lead ion formation in the electrolyte that becomes water during overdischarge and preventing internal short circuits. demonstrate. Therefore, a thinner separator can be used than in the past, and the battery can be made even thinner. Furthermore, since the conductivity is superior to conventional ones, the charge recovery property after being left overdischarged is also good, and its industrial value is great.

Claims (1)

[Claims] 1. A sealed lead-acid battery in which a lead-calcium-tin alloy or a lead-calcium-tin-aluminum alloy is used for the grid of the positive electrode plate, and the electrolyte contains 2 to 200 g/l of cesium sulfate.