JP2817378B2 - Sealed lead-acid battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery, and more particularly to an improvement in its high-rate discharge performance.

Prior art and its problems The discharge capacity of a sealed lead-acid battery is determined by its electrode group configuration and the amount of sulfuric acid in the battery. In many cases, the larger the amount of sulfuric acid in the battery and the larger the surface of the electrode plate, the larger the discharge capacity. This tendency becomes remarkable especially when high-rate discharge is performed.

Therefore, conventionally, in a battery of the same size, a method of using a highly concentrated electrolytic solution or increasing the number of electrode plates has been adopted to increase the high rate discharge capacity.

However, if the concentration of the electrolyte is too high, the life of the battery is adversely affected. Also, it is recognized that the capacity of the negative electrode plate decreases in an electrolytic solution having a certain concentration or more. For this reason, the electrolyte concentration cannot be increased without limit, and a remarkable increase in capacity cannot be expected by the method of increasing the electrolyte concentration.

On the other hand, a method of increasing the number of electrode plates and reducing the current density on the electrode plates at the same current is effective and widely adopted. However, in this method, the ratio of the separator in the volume of the electrode plate group increases, the positive and negative electrode plates become thinner, and the amount of the active material decreases, which adversely affects the life of the battery. Furthermore, when the number of electrode plates per battery increases, the number of steps required in the electrode plate manufacturing process and battery assembly increases, and there is a problem that the battery manufacturing cost increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not shorten the life of a sealed lead-acid battery and does not complicate the manufacturing process. The purpose is to provide.

That is, a main object of the present invention is to provide a sealed lead-acid battery having a good high-rate discharge capacity within a limited size, and therefore to provide a configuration of an electrode group.

The capacity of the sealed lead-acid battery is such that the current density on one side of the positive electrode plate is 0.1 A.
In the case of a low rate discharge of about / dm ^2, it is mainly determined by the total amount of sulfuric acid in the battery. On the other hand, in the case of high-rate discharge at the same current density of about 10 A / dm ^2, it is determined mainly by the amount of sulfuric acid retained in the fine pores of the positive electrode plate.

Therefore, in order to increase the high-rate discharge capacity without changing the number of electrode plates within the same electrode group size, it is necessary to increase the amount of sulfuric acid retained on the positive electrode plate. For this purpose, it is necessary to increase the porosity of the positive electrode active material and increase the thickness of the positive electrode plate. However, when the thickness of the positive electrode plate is increased, the diffusion of the electrolytic solution is deteriorated. Therefore, the thickness of the positive electrode plate cannot be increased without limitation.

On the other hand, the negative electrode plate is usually designed so as to provide a capacity equal to or greater than that of the positive electrode. The capacity of the negative electrode depends on the diffusion rate of sulfuric acid into the negative electrode plate during high-rate discharge, together with the amount of the metal active material. The diameter of the fine pores of the negative electrode plate is generally larger than that of the positive electrode plate, and the structure is such that sulfuric acid is easily diffused. However, when the current density is increased, the supply of sulfuric acid by diffusion alone becomes insufficient. Therefore, the amount of sulfuric acid held on the negative electrode plate must be set to a certain ratio or more in advance with respect to that of the positive electrode plate.

As described above, the present invention specifies the amount of the electrolyte to be held in the positive electrode plate and the negative electrode plate.

The present invention provides a porous positive electrode plate containing lead dioxide as a main component, a porous negative electrode plate containing metal lead as a main component, and fine glass fibers or fine polymer fibers or fine silica powder as main components. In a sealed lead-acid battery having a structure in which almost all of the electrolyte is held in the electrode group constituted by the separator, the thickness of the electrode group is set to T, and the thickness of the positive electrode plate constituting the electrode group is set to T. When the width is W and the height of the positive electrode plate is H, W × H ×
This is a sealed lead-acid battery in which an electrolyte of a volume corresponding to 20% or more of the volume of the electrode group represented by T is held in the positive electrode plate.

Further, the present invention provides the above sealed lead-acid battery, wherein a volume of the electrolyte corresponding to 75% or more of the volume of the electrolyte held in the positive electrode plate is held in the negative electrode plate.

Further, the present invention provides the above sealed lead-acid battery, wherein the thickness of the positive electrode plate is set to 5.8 mm or less.Example When the dimensions of the electrode plate group are the same, the high-rate discharge capacity of the sealed lead-acid battery is: It is determined by the distribution of the electrolyte in the electrode group and the thickness of the electrode. Hereinafter, examples of the present invention will be described based on three experimental data.

First, Table 1 shows the current three types of electrode plate group structures of the sealed lead-acid batteries A, B, and C, which are composed of a positive electrode plate, a negative electrode plate, and a separator, and have different electrode plate sizes.

Next, without changing the height (H) and width (W) of the electrode group of the batteries A, B, and C, the thickness of the positive electrode, the thickness of the negative electrode plate, the active material external ratio, and the thickness of the separator were changed. Each battery was prototyped.

(Example 1) Using a plurality of batteries in which the configuration of the above-mentioned electrode group was changed, a discharge current was determined for each battery so that the current per unit surface area of the positive electrode plate was constant, and a capacity test was performed. Was performed. However, the configuration of the battery used is such that the ratio of the electrolyte held on the negative electrode plate to the volume of the electrolyte held on the positive electrode plate is 0.
The thickness was set to 8 or more, and the thickness of the positive electrode plate was changed from 3.40 mm to 5.00 mm. Also, considering the life of the battery, the external ratio of the positive electrode active material should be 3.10
To 3.35.

FIG. 1 shows the ratio t of the volume of the electrolyte held by the positive electrode to the volume of the electrode plate group (H × W × T), and the current density i (A / dm ² ).
FIG. 6 is a relationship diagram with a numerical value obtained by dividing the capacity of the battery in FIG. The volume of the electrolyte held in the positive electrode is calculated by dividing the difference between the total weight of the positive electrode plate immediately after disassembly of the battery and the total weight of the positive electrode plate after washing and drying by the electrolyte specific gravity. Was.

In FIG. 1, a curve showing the relationship between the t value and the capacity density at a certain current density i is the t value of a point where the test results of many batteries are plotted on a graph when the t value is in the range of 0.100 to 0.285. Is a quadratic regression curve with 変 数 as a variable.

The standard deviation of the deviation from the quadratic regression calculated based on this curve is 1.2% with respect to the average value of the capacitance density at all the current density i values in the example. Was less than.

In FIG. 1, the slope of the quadratic curve drawn for each value of the current density i shows that the ratio of the slope of the curve changes rapidly around t = 0.20. Second
The figure shows the change in the slope of the regression curve.
The numerical value z represented by the following equation is plotted on the vertical axis, and (t, z) is plotted.

That is, z represents the ratio of the slope of the regression curve in the minute section. As can be seen from FIG. 2, it begins to decrease sharply at z near t = 0.21.

Therefore, when the current density i of the positive electrode plate is 7.85 A / dm ² or more, in the region of t <0.21, the capacity density increases as t increases, and the increase in capacity density decreases near t = 0.20. Or almost disappear.

By the way, in the current sealed lead-acid battery, t is at most 0.175 at most, and for example, the capacity density of the sealed lead-acid battery of the present embodiment in which t = 0.21 is increased by 11 to 14% as compared with the current product. Table 2 shows a comparison of the capacitance density with respect to the t value in the current density.

As is clear from Table 2, when t> 0.20, the capacity density at high rate discharge can be increased.

That is, it is possible to increase the capacity density in high-rate discharge by holding a volume of the electrolytic solution corresponding to 20% or more of the volume (W × H × T) of the electrode plate group in the positive electrode plate. it can.

(Example 2) Next, the influence of the negative electrode plate of the battery is exerted. A sealed lead-acid battery by changing the external ratio of the negative electrode plate active material and the thickness of the negative electrode plate so that the ratio r of the amount of electrolyte solution retained (volume) of the negative electrode plate to the amount of electrolyte solution retained (volume) of the positive electrode plate varies from 0.65 to 1.15 Was prototyped. The positive electrode plate of these prototype batteries and the t value are all the same,
The electrolyte solution was injected into the electrode group of each battery in such an amount that it could be absorbed without excess or deficiency. Table 3 shows the relationship between r and capacity density of each of the three types of batteries A, B, and C. The capacity density was represented by an index with the capacity density of r = 0.90 as 100. An experiment was performed under the conditions of t = 0.215 and i = 11.78.

As is clear from Table 3 and FIG. 3, the r value is from 0.70.
The rate of increase in capacity between 0.80 is not suddenly small, r ≧ 0.
In 85, there is no big change in battery capacity. Conversely, when r <0.70, the battery capacity also decreases with the decrease in r, indicating that the battery capacity is limited by the negative electrode.

Therefore, in the high rate discharge, it is understood that the capacity of the positive electrode cannot be fully utilized unless the ratio of the amount of electrolyte held in the negative electrode plate to the amount of electrolyte held in the positive electrode plate is about 0.75 or more.

From the above Examples 1 and 2, in order to improve the capacity density at the time of high-rate discharge, an electrolyte solution having a volume corresponding to 20% or more of the volume of the electrode plate group was held in the positive electrode plate, It became clear that a volume of the electrolytic solution corresponding to 75% or more of the volume of the electrolytic solution held in the plate had to be used as an electrode group having a structure held in the negative electrode plate.

(Example 3) In general, in a sealed lead-acid battery, the active material in the electrode plate is supplied with sulfate and proton in the electrolytic solution to sustain the discharge. Therefore, if the diffusion of these materials is insufficient, the capacity of the battery is limited. Become. The supply of the electrolyte component becomes gentler as the location of the discharge reaction becomes farther from the surface of the electrode plate. Therefore, even if the thickness of the positive electrode plate is doubled, the capacity does not double. In order to grasp the influence quantitatively, based on the current sealed lead-acid battery A, the thickness of the positive electrode plate and other electrode plate group components was changed without changing the t value and the r value. A battery was manufactured as a prototype, and the relationship between the positive electrode plate thickness and the capacity density was examined. Table 4 shows the results.

As is evident from Table 4, the capacity density certainly decreases as the thickness of the positive electrode plate increases.
The battery density varies between 5.80 mm, and the capacity density of the battery using a positive electrode plate of 5.80 mm or more suddenly decreases. These results indicate that the thickness of the positive electrode plate should not be 5.8 mm or more.

On the other hand, if an attempt is made to reduce the thickness of the electrode plate, there is a limit in the current production technology, and there is a possibility that the life of the battery is shortened. However, these problems are not due to the electrolytic solution distribution of the battery, but are problems to be solved by future production technology or improvement of the alloy of the lattice body, and the lower limit of the thickness of the positive electrode plate is not set in the present invention. .

As described above, in order to summarize the first to third embodiments, the sealed lead-acid battery A is improved according to the present invention with an improved product A ₁ ,
Its positive electrode plate 5.8mm or more thickness and the cell A _3, cell A ₄ in which the r value of 0.75 or less prototype, respectively, were measured capacitance density as the current article A ₂ and Comparative Example. The results are shown in Tables 5 and 6.

As is clear from Tables 5 and 6, the sealed lead-acid battery according to the present invention has a capacity per unit volume of the electrode plate group at the time of high rate discharge increased by about 20% compared with the current product, and ,
The tendency becomes more remarkable as the current density increases.

Effect of the Invention As described above, the sealed lead-acid battery according to the present invention is:
Compared to conventional batteries, the dimensions (H, W,
In T), an external ratio that increases the high-rate discharge capacity by 11% or more without increasing the number of electrode plates and without increasing the concentration of the electrolyte and shortens the life due to softening of the active material. The above advantage can be obtained without using a positive electrode plate active material having a small value. In these respects, the sealed lead-acid battery according to the present invention is superior to conventional batteries, and has a great industrial value.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the ratio t of the volume of the electrolyte held in the positive electrode to the volume of the electrode plate group and the capacity density of the battery at each current density i. FIG. 2 shows the change in the slope of the regression curve. FIG.

Continuation of the front page (56) References JP-A-60-91572 (JP, A) JP-A-2-102661 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 10 / 06-10/12

Claims (3)

(57) [Claims] A porous positive electrode plate containing lead dioxide as a main component, a porous negative electrode plate containing metal lead as a main component, and fine glass fibers or fine polymer fibers or fine silica powder. In a sealed lead-acid battery having a structure in which almost all of the electrolyte is held in an electrode group composed of separators as components, the thickness of the electrode group is T, and the positive electrode plate constituting the electrode group Where W is the width and H is the height of the positive electrode plate, W × H ×
A sealed lead-acid battery in which an electrolyte of a volume corresponding to 20% or more of the volume of the electrode group represented by T is held in the positive electrode plate. 2. 75% of the volume of the electrolyte held in the positive electrode plate
2. The sealed lead-acid battery according to claim 1, wherein an electrolytic solution having a volume corresponding to the above is held in the negative electrode plate. 3. The sealed lead-acid battery according to claim 1, wherein the thickness of the positive electrode plate is 5.8 mm or less.