JPH0533504B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to improvements in lead-acid batteries. [Prior Art and Problems to be Solved by the Invention] A lead-acid battery uses dilute sulfuric acid as an electrolyte, and as is well known, the charge/discharge reaction is expressed by the following equation. PbO ₂ +Pb+2H ₂ SO ₄ 2PbSO ₄ +2H ₂ O In other words, sulfuric acid in the electrolytic solution is consumed during discharging and generated during charging, and the specific gravity of the liquid decreases or increases accordingly. Water produced by discharge rises along the electrode plate surface, and sulfuric acid produced by charging descends, so that the electrolytic solution becomes stratified with low specific gravity in the upper part and high specific gravity in the lower part during charge/discharge cycles. This problem can be solved by overcharging the battery through gassing, but many recent chargers use a constant voltage charging method, and stratification is difficult to eliminate, resulting in problems such as sulfation at the bottom of the electrode plate and a decrease in capacity. There is a point. Furthermore, in the case of sealed lead-acid batteries in which the electrolyte is made into a gel or impregnated and held in a porous body, in other words, the electrolyte is made non-fluid, convection of the liquid due to gassing occurs even if overcharged. Therefore, it was difficult to eliminate stratification. [Means for Solving the Problems] The present invention solves the above-mentioned problems of lead-acid batteries. The gas at the upper end of the cell comes into contact with the electrolyte at the upper part of the cell through the electrolyte impregnated in the porous body disposed at the upper edge of the groove or through the upper space within the cell so as to be in equilibrium with the electrolyte at the upper part of the cell. The gas at the lower end of the groove is in equilibrium with the electrolyte at the lower part of the cell via the electrolyte impregnated in a porous body disposed at the lower edge of the groove or via the lower space within the cell. It's about being in contact with each other. The mechanism of action of the lead-acid battery according to the present invention is as follows. First, inside the cell of a lead-acid battery, there is an air groove that communicates vertically and is filled with gas. By contacting the cell directly or indirectly through a porous body impregnated with the same electrolyte as the surroundings, it contains water vapor as a gas at an equilibrium pressure determined by the concentration and temperature of the electrolyte in the upper part of the cell. become. On the other hand, the gas at the lower end of the groove comes into contact with the electrolytic solution in the lower part of the cell either directly through the lower space inside the cell or indirectly through a porous body impregnated with the same electrolytic solution as the surroundings. As a result, water vapor with an equilibrium pressure determined by the concentration and temperature of the electrolytic solution in the lower part of the cell is contained as a gas. In other words, when stratification occurs, and the electrolyte at the top of the cell has a low specific gravity and the electrolyte at the bottom has a high specific gravity, the water vapor partial pressure of the gas at the top of the vertically communicating air groove is high, and the water vapor partial pressure of the gas at the bottom is high. becomes lower. As a means of reducing the water vapor partial pressure of the gas in the lower part, the temperature of the porous body at the lower end of the cavity may be lowered. In the gas space, differences in concentration depending on location are eliminated relatively quickly due to Brownian motion of the base particles.
Therefore, the water vapor moves in a direction that eliminates the difference in water vapor partial pressure between the upper and lower parts of the air groove, that is, from the upper side to the lower side, and water is condensed in the porous body at the lower end. This movement of water within the groove eliminates the stratification of the electrolyte within the cell. In a typical lead-acid battery using a liquid electrolyte, it is necessary to fill the upper and lower edges with a porous material in order to prevent the electrolyte from flowing into the cavity. In addition, in order to prevent the electrolyte from entering and to discharge water generated at the lower end, a gas generation mechanism, such as a water electrolysis electrode, is grounded in the cavity, and the gas pressure in the cavity is reduced to the pressure in the cell space. It is necessary to keep it slightly higher than that. Stratification can be eliminated by the same mechanism of action in sealed lead-acid batteries in which the electrolyte is in gel form or impregnated into a porous body such as an isolation part, but in this case, the electrolyte in the cell Since it is non-fluidized, the electrolyte does not flow into the cavity. Therefore, there is no need to keep the pressure inside the air groove higher than the pressure inside the cell, and there is no need to install a gas generation mechanism. Further, the upper and lower edges of the hollow groove may or may not be filled with a porous material. This is because the gas at the upper end or lower end of the air gap groove contains water vapor that is in equilibrium with the electrolyte at the upper or lower part of the cell via the space at the upper or lower part of the cell. [Example] The lead-acid battery of the present invention will be described below with reference to the drawings. Figure 1 shows an embodiment of the lead-acid battery of the present invention, in which 1 is a positive electrode plate, 2 is a negative electrode plate, 3 is a separator, 4 is a dilute sulfuric acid electrolyte, 5 is a container, and 6 is a container. 7 is a lid, 8 is an exhaust part, 9 is a positive terminal, and 10 is a negative terminal. Also, 11 is a plastic tube,
Porous bodies 12, 12' are attached to the upper and lower edges thereof. Further, 13 is a space formed by the plastic tube 11 and the porous bodies 12, 12', and is a hollow groove that communicates with the upper and lower parts of the cell, and 14 is a water electrolysis electrode. The empty groove 13 is filled with gas,
The gas at the upper end is in contact with the electrolyte impregnated in the porous body 12 at the upper edge, and the gas at the lower end is in contact with the porous body 1 at the lower edge.
2' is in contact with the electrolyte impregnated. In the embodiment of the present invention having such a structure, the electrolyte 4
When the electrolyte is stratified, the water vapor evaporated from the low specific gravity electrolyte impregnated in the porous body 12 at the upper edge fills the air groove 13, and the high specific gravity electrolyte impregnated in the porous body 12' at the lower edge is filled. It is absorbed by the electrolyte, eliminating stratification. The water electrolysis electrode 14 is used to generate gas and push back the electrolyte when the electrolyte enters the space 13. In FIG. 2, a cooler 15 cools the porous body 12' at the lower edge. In this case, water vapor impregnated into the porous body 12 at the upper edge and evaporated from the high-temperature dilute sulfuric acid fills the air groove 13, and condenses in the low-temperature porous body 12' at the lower edge to form water. Become. In the above example, the cavity was shown as being placed below the surface of a normal electrolyte, but it is also possible to use a gel-like electrolyte or a porous plate impregnated and held in the electrolyte. It can also be applied to fluidized sealed lead-acid batteries. Next, using a lead-calcium alloy lattice,
Capacity: Approximately 30Ah using positive and negative electrode plates with a height of approximately 100mm
The results of an experiment on eliminating stratification using a prototype battery are shown below. Plastic pipes with an inner diameter of approximately 25 mm and a length of 100 mm, with regular lead-acid battery separators attached to the upper and lower edges, were placed vertically on the side of the electrode plate group. In the case of a liquid type battery, the tips of two coated lead wires of 1 mm in diameter were placed about 2 mm above the separator at the bottom end with only 5 mm exposed, and the wires were passed through the plastic pipe and battery lid and pulled out of the battery. . In addition, a 2 mm thick copper plate covered with a thin plastic film was placed in contact with the lower surface of the separator at the lower end of the plastic pipe, and this copper plate was covered with foamed plastic and insulated except for the area in contact with the separator. In this way, we prototyped a liquid battery and a gel battery using a mixture of colloidal silica and dilute sulfuric acid. At this time, the liquid density below the center of the electrode plate is approximately
1.30, dilute sulfuric acid of about 1.20 was filled above the center, and after being left at about 25°C for one week, electrolytic solution was collected from the upper and lower edges of the electrode plate, and the concentration was determined by titration and converted to specific gravity. Note that during this standing period, 3.0 V was applied between the two lead wires to the liquid battery according to the present invention. The results are summarized in Table 1.

[Table] As is clear from the results in the table, among liquid batteries, battery No. 2 according to the present invention has a smaller difference in the specific gravity of the upper and lower liquids after being left as compared to battery No. 1. Further, among gel type batteries, batteries No. 4 and No. 5 according to the present invention have a smaller specific gravity difference than No. 3, and have a remarkable effect on eliminating stratification. [Effects of the Invention] As described above, the present invention solves the stratification of the electrolyte of lead-acid batteries that occurs during charge/discharge cycles with little overcharging, and prevents sulfation and capacity reduction at the bottom of the electrode plate. This has the effect of allowing lead-acid batteries to maintain stable performance for a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of the main parts showing the schematic structure of one embodiment of the lead-acid battery of the present invention, and Fig. 2 shows other embodiments of the mechanism for generating water in the lower part or bottom of the battery case used in the lead-acid battery of the present invention. FIG. 3 is a vertical cross-sectional view of a main part showing an example. 1... Positive electrode plate, 2... Negative electrode plate, 3... Separator, 4... Dilute sulfuric acid electrolyte, 5... Battery container, 11...
Plastic tube, 12, 12'...Porous body, 13
...Empty groove, 14, 14'...Water electrolysis electrode, 15
……Cooler.

Claims (1)

[Claims] 1. An air space that connects the top and bottom and is filled with gas.
A groove is provided in the cell, and the gas at the upper end of the groove flows through the electrolytic solution impregnated in the porous body disposed at the upper edge of the groove or through the upper space within the cell. It is in equilibrium contact with the liquid,
The gas at the lower end of the groove is brought into equilibrium with the electrolyte at the lower part of the cell via the electrolyte impregnated in a porous body disposed at the lower edge of the groove or via the lower space within the cell. A lead-acid battery characterized by contact.