JP3468492B2 - Plate for lead-acid battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved lead-acid battery electrode plate, and more particularly to a long-life lead-acid battery excellent in high-power charge / discharge characteristics.

[0002]

2. Description of the Related Art Lead-acid batteries are relatively inexpensive and have stable performance as secondary batteries, and have been widely used in automobiles as well as in recent years as power sources for portable devices and computer backups. It was Furthermore, recently, new functions have been reviewed not only as a main power source for electric vehicles, but also as a starting power source and for recovering regenerative current. In these applications, it is an important issue to achieve both high output and stable life.

The high rate discharge characteristics are largely controlled by the supply of the electrolytic solution to the active material. In a lead-acid battery, the active material of both the positive electrode and the negative electrode changes to lead sulfate (PbSO ₄ ) due to the discharge reaction. When lead and lead dioxide are converted to lead sulfate, the volume increases about twice. Therefore, as the discharge reaction proceeds, the holes in the electrode plate are blocked by the precipitated lead sulfate,
The diffusion function of sulfate ions is reduced. Conversely, this lead sulfate changes to lead dioxide at the positive electrode and lead at the negative electrode during charging, but if the electrolyte supply capacity into the electrode is poor, this reaction does not proceed smoothly and charging efficiency decreases. To do. In particular, the higher the current density and the higher the charge / discharge, the greater this effect.
As a measure to solve these problems, conventionally, by adjusting the amount of water or sulfuric acid added to the lead powder that is the base of the active material, the packing density of the active material is reduced, and the electrolyte solution in the electrode plate is reduced. A technique of forming a large number of voids capable of holding or diffusing has been put into practical use.

[0004]

However, in the above method, although the high rate discharge characteristic is initially improved,
At present, the cycle life is significantly reduced, and an appropriate balance cannot be achieved. It is an object of the present invention to provide an electrode plate that provides a well-balanced and truly high performance lead storage battery while improving the high rate discharge characteristics and suppressing the decrease in the life due to the high porosity.

[0005]

The present invention is intended to solve the above problems by optimizing the pore structure of the electrode plate. That is, in the lead-acid battery electrode plate of the present invention, the pore distribution of the active material in the charged state is 0.
Pore area A in the range of 8 to 10 μm and pore diameter of 0.01 to
Has its own maximum at pore region B ranging from 0.2 [mu] m, have a clearly separated pore structure distribution in at least two, having a pore diameter of from 0.2μm~0.8μm fine
The hole area C has a minimum value, and the minimum value is the maximum value of the area A.
Of 30% or less .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention goes beyond the conventional concept of simply perforating an electrode plate to form electrode plates having various pore distributions, and after repeated experiments, the service life and high rate discharge characteristics were improved. It is based on the finding of a well-balanced pore distribution. Here, the pores in the region A increase the utilization rate during high-rate discharge, and the pores in the region B determine the limit of discharge capacity including low-rate discharge. The reason why a lead battery having a well-balanced life and high rate discharge characteristics can be obtained by the present invention is considered as follows, although it is not clear. The lead ions in the region B generated by the discharge diffuse into the larger pore region, react with the sulfate ions diffused from the outside, and are deposited as lead sulfate. At this time, if there is an intermediate pore region C continuous with the region A in the region B, precipitation of lead sulfate occurs at that portion, which hinders the diffusion of any ions. Area C
If the content is reduced, lead sulfate will be deposited in the region A having a large pore diameter, and the diffusion obstacle at the time of high rate discharge will be reduced.
Further, it is considered that the state in which the structure having a small number of regions C is formed is the state in which the interparticle bond of the active material is strong. The above-described structure of the present invention is difficult to form from a paste obtained by kneading lead powder having a wide particle size distribution with water and sulfuric acid as in the conventional case, and the application of lead powder having a uniform particle size within a range of ± 10 μm, It can be obtained by a combined method with a means for mixing a water-soluble salt such as sodium sulfate or barium sulfate.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, in the production of the electrode plate, as a raw material for the positive electrode and the negative electrode, a lead powder having a weight ratio of 25% metallic lead and 75% lead monoxide and an oxidation degree of 75% was classified into a particle size range of 30 ± 10 μm. 2 wt% of sodium sulfate powder was added to the product. For the negative electrode, in addition to this, 2% by weight of barium sulfate and 1%
Carbon powder and 0.5% lignin were added to prepare an active material mixture. To this mixture, 10% by weight of water and 15% by weight of dilute sulfuric acid were added and kneaded to form a paste.

The above-mentioned paste was filled in a casting grid made of a lead-calcium alloy and aged in a high temperature and high humidity according to a conventional method.
Then, chemical conversion was performed to prepare a positive electrode plate and a negative electrode plate. For comparison, an electrode plate using a paste obtained by mixing water and sulfuric acid in the same manner as conventional lead powder having an indiscriminate particle size (Comparative Example 1).
Configured. Further, an electrode plate (Comparative Example 2) obtained by increasing the amount of water by 15 wt% was manufactured. FIG. 1 shows the pore distribution of the active material layers of the positive electrode plates in Examples and Comparative Examples. The distribution form of the pores of the active material layer in the electrode plate according to this example is
It is divided into two parts. On the contrary,
In Comparative Example 1, there is a large maximum value in the region of 0.1 to 0.8 μm, that is, in the region C of the present embodiment. Further, in Comparative Example 2, the pores are formed in a wide range including the region C of the present example. In addition, the measurement of the pore distribution is performed by a mercury porosimeter, and the pore diameter is 0.0
Those having a size of 03 μm or more were measured. Next, each of the above-mentioned two positive electrode plates and three negative electrode plates are combined with a mat-shaped separator made of glass fiber interposed therebetween and impregnated with dilute sulfuric acid as an electrolytic solution to regulate the positive electrode capacity of 2Ah, 2V.
The battery of was produced.

The stated capacity is calculated by calculating the number of moles of lead atoms contained in the filled paste, and all of them are 2
The theoretical capacity when assuming that an electronic reaction was performed was used.
Table 1 shows the discharge capacities obtained by discharging the battery of this example and the batteries of Comparative Examples 1 and 2 with a constant current of 1 C, which is a relatively high rate. In addition, each battery is charged with a quasi-constant voltage of 2.25V (maximum current 1C) for 2 hours, and the charging / discharging is repeated until the final voltage is 1.3V at 1C, and the discharge capacity decreases to 50% of the initial discharge capacity. Table 1 shows the comparison of the cycle lives up to.

[0010]

[Table 1]

As is clear from Table 1, the battery using the electrode plate according to the present example is significantly superior to Comparative Example 1 in high rate discharge characteristics, as in Comparative Example 2. On the other hand, regarding the cycle life, the battery using the electrode plate according to the present example is superior to the comparative example 2 as in the comparative example 1. From these facts, it was proved that by applying the present invention, a lead storage battery having both excellent high rate discharge characteristics and long life can be constructed.

Next, in the pore distribution of the active material layer, the cycle life when the total pore volume is kept constant and the ratio of the minimum value in the region C to the maximum value in the region A is changed is shown in FIG. It was shown to. As is clear from the figure, there was a difference in life even with the same total pore volume. As described above, it is preferable that the maximum volume exists in the region A and the region B, and at the same time, the pore volume of the region C is limited so that the regions are clearly separated. Further, as shown in FIG. 1, the discharge capacity is measured by changing the ratio of the pore volume of each area while keeping the total volume of the pores constant while having the pore distribution that separates into two areas A and B. did. The results are shown in Fig. 3. This result shows that the effect of the present invention is diminished when the above ratio exceeds 25 % in the high rate discharge capacity.

[0013] shows the results of examining the relationship between the discharge capacity at the pore volume of the realm A and longevity and 1C in FIG. It can be seen from FIG. 4 that the discharge capacity remarkably deteriorates when the total pore volume of the region A is 0.07 cc / g or less, and the cycle characteristics deteriorate when the total pore volume is 0.14 cc / g or more. From this result, in order to obtain a high-performance lead-acid battery in which high rate discharge characteristics and life performance are well balanced, the total pore volume of the region A is 0.07.
It is preferably in the range of cc / g to 0.14 cc / g.

In the above embodiments, sodium sulfate was used as the additive for the positive electrode, but lead compounds such as red lead, basic lead sulfate and lead dioxide can be used in addition to this.
Further, although a cast grid is used as the current collector in the embodiment, an expanded grid may be used. Furthermore, the electrode plate of the present invention,
It is possible to form lead powders of various particle sizes in combination with a solvent-based binder, for example, a kneaded product using polyvinylidene fluoride and N-methylpyrrolidone or a sulfuric acid-free kneaded product. In this case, a thin electrode plate is used. There is an advantage that the pores can be designed. Further, in the above examples, the effect on the positive electrode was described, but when the effect of the pore design was investigated for the negative electrode by the same method, similar results to those for the positive electrode were obtained, and the present invention was applied to the negative electrode. It was confirmed that it was also effective. Also,
Although two pore regions are described in the examples, forming another maximum value in a larger region or a smaller region does not prevent the effect of the present invention.

[0015]

As described above, according to the present invention, it is possible to obtain a lead acid battery having both excellent high rate discharge characteristics and cycle life.

[Brief description of drawings]

FIG. 1 is a diagram showing a pore distribution in a charged state of a positive electrode plate according to an example of the present invention.

FIG. 2 is a diagram showing the relationship between the ratio of the minimum value of the region C to the maximum value of the region A and the cycle life.

FIG. 3 is a diagram showing a relationship between a ratio of a total pore volume of a region B to a total pore volume of a region A and a 1C discharge capacity.

FIG. 4 is a diagram showing a relationship between a total pore volume in a region A, a discharge capacity and a cycle life.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-82159 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/14

Claims (2)

(57) [Claims] 1. The active material is lead or lead dioxide,
The pore size distribution of the active material layer in the charged state is 0.8.
Pore area A in the range of 10 μm and pore diameter of 0.01 to
Each includes a maximum value at the pore region B ranging from 0.2 [mu] m, have a clearly separated pore structure distribution in at least two, having a pore diameter of from 0.2μm~0.8μm fine
The hole area C has a minimum value, and the minimum value is the maximum value of the area A.
30% or less of the lead-acid battery electrode plate. 2. In the charged state, the integrated value of the pore volume of the region A is 0.07 cc / g to 0.14 cc / g, and the integrated value of the pore volume of the region B is 25% of the integrated value of the region A. The electrode plate for a lead storage battery according to claim 1, which is as follows .