JPS63187572A - Sealed lead acid battery - Google Patents

Abstract

PURPOSE:To retard self discharge and decrease in electrolyte and to increase overcharging performance by fabricating a plate group by a cathode plate having a lead-calcium-tin alloy grid in which the content of calcium on the surface is lowered than that in the central part, an anode plate, and a separator. CONSTITUTION:A grid made of lead-calcium tin alloy is treated with strong alkaline solution to dissolve calcium on the surface of the grid and to decrease the concentration of calcium on the surface then that in the central part, then paste is filled in the grid to form a cathode plate. A plate group is fabricated by the cathode plate, a anode plate, and a separator. A decrease in electrolyte caused by overcharge is prevented, overcharge performance is increased without deterioration in the other performance, and a grid having high mechanical strength can be obtained.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applied to sealed lead-acid batteries, which are used in a wide variety of applications for portable equipment, and which are used in power sources for VTRs, for which demand has recently increased rapidly. This is related to the improvement of

Conventional Technology There have been numerous proposals regarding sealed lead-acid batteries. Typically, the amount of electrolyte is equal to or less than the pore volume of the electrode plate group, so that there is no free liquid, and the oxygen gas generated from the anode plate is absorbed by the negative plate at the end of charging. A method is adopted to suppress the decrease. Sealed lead-acid batteries do not have free liquid, so they do not leak even if they are turned over or placed upside down, and they do not require water replenishment, so they are used in a wide variety of applications.

Problems to be Solved by the Invention This type of battery is widely used in trickle applications and cycle applications, but in such cases, there are many chances that the battery will be overcharged. When overcharged, the deterioration of the anode plate during charging, i.e. the formation of a passive layer at the interface between the active material and the lattice,
In addition, a decrease in capacity due to a decrease in group pressure due to deterioration of the separator has been considered a problem. In order to solve the peak during this period, lead-
It is effective to use an antimony-based alloy. However, in that case, the antimony in the anode grid dissolves into the electrolyte and further precipitates on the cathode plate. At that time, since the hydrogen overvoltage of antimony is small, self-discharge is large and the amount of electrolyte decreases significantly.

The present invention solves the above problems. That is, the present invention provides a sealed lead-acid battery with excellent overcharging characteristics while suppressing self-discharge and electrolyte loss.

Means for Solving the Problems The present invention involves treating a grid made of lead, calcium, and tin alloy used for an anode plate in a strongly alkaline solution before filling the grid with an active material paste. The hermetic seal is characterized in that the electrode plate group is composed of an anode plate, a cathode plate, and a separator, each having a lattice body in which calcium on the surface of the lattice body is dissolved and the concentration of calcium on the surface is lower than that in the center. A lead-acid battery is disclosed.

The overcharging characteristics of this battery were superior to conventional ones, and the electrolyte did not decrease due to overcharging. In a battery using the lattice of the present invention for the anode plate, even if overcharged, the anode plate Since a passive layer is not formed on the lattice and the active material interface, and the electrolyte does not decrease, capacity deterioration is unlikely to occur.

Example Examples of the present invention will be described below.

Calcium content is O when tin content is 0.5% by weight
A cast grid having a concentration of 0.1% by weight was prepared, and a sealed lead-acid battery was constructed from an anode plate, a glass mat separator, and a cathode plate using the cast grid. However, the grid for the cathode plate was produced by casting from a lead-calcium alloy (calcium content: 0.1% by weight).

Combining these two cathode plates and one anode plate, 12V
A battery with a 10 hour rate discharge capacity of 1.2 Ah was produced. still,
Sulfuric acid with a specific gravity of 1.34 was used as the electrolytic solution for the battery, and the electrolytic solution was adjusted so that there was no free solution.

The battery was charged at a current rate of 10 hours, discharged at a current rate of 6 hours, and after confirming the initial capacity, was charged at a constant current of 50 m for 3 months. After overcharging, the battery was discharged at a current rate of 5 hours, and the ratio of its capacity to the initial capacity was defined as the capacity remaining rate.

The figure shows the relationship between the calcium content in the anode plate lattice and the capacity residual rate. This figure suggests that the smaller the calcium content, the larger the capacity remaining rate and the better the overcharge characteristics. The lower the calcium content, the better the overcharge characteristics, but as the calcium content decreases, the mechanical strength of the lattice becomes weaker, and the electrode plate (lattice) may become deformed when applying the paste. This increases the probability that the product will become defective. In other words, a lattice body with strong mechanical strength and a low calcium content on the lattice surface in contact with the active material is considered to be most preferable for overcharging characteristics.

From this point of view, in order to reduce the calcium content at the interface between the lattice and the active material, the calcium content is set to 0.
After immersing a grid body weighing 0.05 and 0.1 weight ε in a 1ON sodium hydroxide aqueous solution for 10 minutes, the grid body was filled with an active material to prepare an anode plate.

The overcharging characteristics of these batteries are shown in the figure. This figure suggests that the battery using the lattice body treated as described above has excellent overcharging characteristics. It is presumed that the reason for this effect is that the calcium concentration on the surface of the anode plate and the grid body is lower than that in the center of the grid body, and the overcharge characteristics are improved.

Effects of the Invention As described above, the present invention provides a lattice body that improves overcharging characteristics and has strong mechanical strength without deteriorating other battery characteristics, and its industrial value is extremely high. Chill with a dog.

[BRIEF DESCRIPTION OF THE DRAWINGS] The figure shows the relationship between calcium content and capacity retention rate.

Claims (2)

[Claims] (1) The electrode plate group includes an anode plate having a lattice of lead, calcium, and tin alloy, and the calcium concentration on the surface of the lattice is lower than that in the center of the lattice, a cathode plate, and a separator. A sealed lead-acid battery characterized by: (2) Claim 1, characterized in that, in an anode plate having a lattice body made of lead, calcium, and tin alloy, the lattice body is treated in a strong alkaline solution before filling the lattice body with an active material. Sealed lead acid battery as described.