JPH07320728A - Positive electrode plate for lead-acid battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a positive electrode plate for a lead-acid battery capable of uniformly conducting charge/discharge ration over the whole electrode plate. CONSTITUTION:Before formation, a specified area including a part most far from a lug 1 of a nonformed active material layer, or electrode plate lower half 2 is immersed in dilute sulfuric acid having a specific gravity of 1.05-1.75 to increase the porosity of the electrode plate lower half 2 than that of electrode plate upper half. The weight ratio of alpha-PbO2/beta-PbO2 in the electrode plate lower half 2 is made smaller than the weight ratio of alpha-PbO2/beta-PbO2 in the electrode plate upper half.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode plate for a lead storage battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a positive electrode plate used in a lead acid battery such as a sealed lead acid battery, a paste type positive electrode plate having an active material layer formed by applying an active material paste on a current collector having an ear is used. In this case, in order to increase the capacity of the lead storage battery and extend the charge / discharge cycle life, it is necessary to make the charge / discharge reaction in the entire positive electrode plate as uniform as possible. If the charge / discharge reaction is made as uniform as possible, the charge / discharge reaction of the active material will be dispersed throughout the electrode plate, and it will be possible to prevent the muddy formation of the active material due to repeated charge / discharge cycles from concentrating on a part of the active material and to improve the active material utilization rate. Can be increased. As a result, the capacity of the lead storage battery can be increased and the charge / discharge cycle life can be extended. However, in a commonly used paste type positive electrode plate, a charge / discharge reaction is more likely to occur as the active material is closer to the edge of the electrode plate. Therefore, there is a problem that the charge / discharge reaction concentrates in the vicinity of the ears and the electrolytic solution causes stratification, which lowers the capacity of the battery and shortens its life.
In particular, in a sealed battery, the movement of the electrolytic solution is limited, so that such a problem has remarkably appeared. Therefore, Japanese Patent Laid-Open No. 4-1
As disclosed in Japanese Patent Publication No. 71666 and Japanese Patent Laid-Open No. 4-366555, the distance between the ear bones of the grid (collector) and the grid bone connecting the ears to each other is shortened to reduce the distance of the current collector. It was studied to make the current collection efficiency as uniform as possible over the entire electrode plate. Further, as disclosed in JP-A-3-127464, in a battery in which a powder holding an electrolytic solution is filled between positive and negative electrode plates, the particle size of the powder located at the lower part of the battery is the same as that of the powder located at the upper part of the battery. It was also studied to make the amount of the electrolytic solution larger in the lower part of the battery than in the upper part of the battery by making the particle size smaller so as to make the charge / discharge reaction in the entire electrode plate as uniform as possible.

[0003]

However, even if the structure of the lattice bone constituting the current collector is changed or the electrolytic solution holder is improved, the charge / discharge reactivity of the active material itself does not change. There was a limit to making the charge / discharge reaction uniform in the whole.

An object of the present invention is to provide a positive electrode plate for a lead storage battery, in which charge and discharge reactions are more uniform in the whole electrode plate, and a method for easily manufacturing the positive electrode plate.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a positive electrode plate for a lead storage battery, which comprises an active material layer formed by applying an active material paste on a current collector having an ear portion. The porosity within a predetermined range (hereinafter referred to as the ear furthest part) including the part farthest from the part is higher than the porosity of other parts (hereinafter referred to as the ear non-farthest part). , constituting the active material layer as _{α-PbO 2 / β-PbO} 2 weight ratio of ear farthest portion is smaller than the _{α-PbO 2 / β-PbO} 2 weight ratio of ears non farthest portion. Note that α-Pb referred to here
The O ₂ / β-PbO ₂ weight ratio is the ratio of the weight of α-PbO _{2 to} the weight of β-PbO ₂ .

In order to manufacture a positive electrode plate for a lead storage battery, the farthest portion of the ear of the unformed active material layer is diluted with diluted sulfuric acid having a specific gravity of 1.05 or more and 1.75 or less before forming the unformed electrode plate in a battery case. It may be immersed for a predetermined time. When immersed in dilute sulfuric acid having a high specific gravity, the ear furthest part is converted to lead sulfate in a short time. The immersion time is determined so that most of the unformed active material in the ear furthest part is converted to lead sulfate. And when the unformed electrode plate is formed into a battery case, the ear furthest part is formed from the state of lead sulfate,
A large amount of β-PbO ₂ is formed, and α-Pb in the farthest part of the ear is formed.
O ₂ / β-PbO ₂ weight ratio is α-Pb in the ear farthest part
It becomes smaller than the O ₂ / β-PbO ₂ weight ratio. Further, in the lead sulfated portion, the chemical conversion reaction is likely to proceed, so that the farthest part of the ear is formed before the farthest part of the ear. Therefore, at the end of chemical formation, the furthest part of the ear becomes hyperplastic and becomes more porous than the non-farthest part of the ear.

Further, only the porosity may be changed between the farthest portion of the ear and the farthest portion of the ear, and the porosity of the farthest portion of the ear may be made higher than the porosity of the farthest portion of the ear. . In addition, α-PbO
Only the ₂ / β-PbO ₂ weight ratio is changed between the ear furthest part and the ear non-farthest part, and α-PbO ₂ / β-P of the ear furthest part is changed.
bO ₂ weight ratio is α-PbO ₂ / β-P in the ear farthest part
It may be smaller than the bO ₂ weight ratio. In any of these cases, it is possible to promote the homogenization of the charge / discharge reaction in the entire electrode plate as compared with the conventional case.

[0008]

When the porosity in the ear furthest part is higher than that in the ear non-farthest part as in the present invention, the diffusion rate of the electrolytic solution into the active material layer is increased in the ear furthest part. Since it becomes faster, the charge / discharge reactivity becomes higher. Β-PbO ₂ is α-
Since the charge-discharge reaction is easier than that of PbO ₂ , as in the present invention, the α-PbO ₂ / β-PbO ₂ weight ratio in the farthest part of the ear is the α-PbO ₂ / β-in the farthest part of the ear. If it is smaller than the PbO ₂ weight ratio, the charge / discharge reactivity in the farthest part of the ear becomes high. As a result, the charge / discharge reaction is promoted in the ear furthest part where the charge / discharge reaction is unlikely to occur, and the charge / discharge reaction of the battery can be made more uniform over the entire electrode plate. According to the present invention, even when a grid body (current collector) in which a longitudinal mid bone and a transverse mid bone are arranged orthogonally in a commonly used frame bone is used, the battery is charged more than in the conventional case. There is an advantage that the discharge reaction can be made more uniform over the entire electrode plate.

[0009]

【Example】

(Example 1) The positive electrode plate for a lead storage battery of this example was manufactured as follows. First, 80% by weight of lead powder and 20% by weight of dilute sulfuric acid having a concentration of 50% were kneaded to prepare an active material paste.
Next, 40 g of this active material paste was filled in a grid body (current collector) made of a Pb-Ca-Sn alloy having a size of 70 mm x 70 mm x 5 mm to prepare an undried electrode plate. In addition, as the lattice body, one in which the longitudinal mid bone and the transverse mid bone were arranged orthogonally in the frame bone was used. Then, the undried electrode plate was left to stand in an atmosphere having a temperature of 30 ° C. and a humidity of 98% for 48 hours to be matured, and then left to stand in an atmosphere having a temperature of 80 ° C. for 16 hours to be dried to prepare an unformed electrode plate. Next, as shown by the hatched portion in FIG. 1, the farthest ear portion (lower half portion of the electrode plate) 2, which is a predetermined range including a portion farthest from the ear portion 1 of this unformed positive electrode plate, has a specific gravity of 1. Thirty
The lower half 2 of the electrode plate was converted to lead sulfate by immersing it in dilute sulfuric acid for 30 minutes. The concentration of dilute sulfuric acid must be higher than 1.05 and not higher than 1.75. The specific gravity is less than 1.05,
If it exceeds 1.75, the solubility of lead sulfate in sulfuric acid becomes high as shown in FIG. 2, and lead sulfate cannot be formed. The immersion time is preferably 10 to 50 minutes. Next, one unformed positive electrode plate in which the lower half of the electrode plate was immersed in dilute sulfuric acid was combined with two known unformed negative electrode plates to form an electrode plate group, and this electrode plate group was diluted with diluted sulfuric acid having a specific gravity of 1.250. The electrolysis solution consisting of was used to form a battery case to complete a formation electrode plate incorporated in a battery. As can be seen from Table 1 below, in the active material layer of the positive electrode plate of this example, the lower half of the electrode plate (farthest away from the ear) is more porous than the upper half of the electrode (non-farthest from the ear). Is 10% higher, α-PbO ₂ / β
-PbO ₂ weight ratio of 25% smaller. The lower half of the electrode plate has a porosity of 5 to 15% higher than that of the upper half of the electrode plate, and α-PbO ₂ /
It is preferable that the weight ratio of β-PbO ₂ is smaller by 20 to 25%.

(Example 2) In the positive electrode plate of this example, the porosity is changed by changing the amount of water contained in the active material paste and changing the porosity only between the earmost part and the ear farthest part. This is a positive electrode plate in which the porosity of the far part is higher than the porosity of the non-farthest part of the ear part, and was manufactured as follows. First, 80% by weight of lead powder and 20% by weight of dilute sulfuric acid having a concentration of 50% were kneaded, and then 5% by weight of water was added and further kneaded to prepare a high-moisture active material paste. Further, 80% by weight of lead powder and 20% by weight of dilute sulfuric acid having a concentration of 50% were kneaded to prepare a low water content active material paste. Next, 20 g of the above-mentioned multi-moisture active material paste was applied to the lower half of the current collector similar to that used in Example 1, and 20 g of the above-mentioned low-moisture active material paste was applied to the upper half of the current collector. I made a wet plate. The lower half of the current collector is a portion corresponding to the hatched portion of the electrode plate shown in FIG. Next, this undried electrode plate was aged and dried under the same conditions as in Example 1 to prepare an unformed electrode plate. Then, the unformed electrode plate was formed in a battery case under the same conditions as in Example 1 to complete the formed electrode plate in the battery.

(Embodiment 3) In the positive electrode plate of the present embodiment, only the α-PbO ₂ / β-PbO ₂ weight ratio was changed by lead tin in the ear farthest part and the ear non-farthest part to obtain the ear part. Α-P in the farthest part
bO ₂ / β-PbO ₂ ears non farthest part by weight alpha-P
The positive electrode plate was made smaller than the bO ₂ / β-PbO ₂ weight ratio, and was manufactured as follows. First, lead powder 70% by weight
And 10% by weight of red lead and 20% by weight of dilute sulfuric acid having a concentration of 50% were kneaded to prepare a lead-containing active material paste. Also lead powder 80
A non-lead active material paste was prepared by mixing 20% by weight of dilute sulfuric acid having a concentration of 50% with 50% by weight. Next, 20 g of the lead-containing active material paste described above was applied to the lower half of the current collector similar to that used in Example 1, and 20 g of the non-lead active material paste described above was applied to the upper half of the current collector. Was applied to prepare an undried electrode plate. The lower half of the current collector is a portion corresponding to the hatched portion of the electrode plate shown in FIG. Next, this undried electrode plate was aged and dried under the same conditions as in Example 1 to prepare an unformed electrode plate. Then, the unformed electrode plate was formed in a battery case under the same conditions as in Example 1 to complete the formed electrode plate in the battery.

Comparative Example 1 The positive electrode plate of this comparative example was manufactured in the same manner as in Example 1 except that it was not immersed in dilute sulfuric acid before forming the unformed electrode plate.

(Comparative Example 2) In the positive electrode plate of this comparative example, as shown in FIG. 3, the distance between the portion farthest from the ears 11 and the lattice bones 3 connecting the ears 11 becomes short as a current collector. As described above, a lattice body in which the lattice bones 3 ... Are radially arranged is used, and the others are manufactured in the same manner as in Comparative Example 1.

Table 1 shows the porosity and α-PbO ₂ / β of the active material layers in the upper and lower halves of each of the positive and negative electrode plates of the above Examples and Comparative Examples.
Shows the results of measurement of -PbO ₂ weight ratio.

[0015]

[Table 1] Next, each lead-acid battery incorporating each positive electrode plate of the above-mentioned examples and comparative examples was discharged at 1.25 A to a final voltage of 1.7 V and then charged and discharged at 1.5 A (2.45 V limit) for 20 hours. The cycle life characteristics of each battery were examined repeatedly.
FIG. 4 shows the measurement result. From this figure, Examples 1 to 1
It can be seen that the battery using the positive electrode plate of No. 3 has a longer life and a higher capacity than the batteries using the positive electrode plate of Comparative Examples 1 and 2.
In particular, it can be seen that the battery using the positive electrode plate of Example 1 in which both the porosity and the α-PbO ₂ / β-PbO ₂ weight ratio are changed has the longest life and high capacity.

In this embodiment, a positive electrode plate was manufactured in which the lower half of the electrode plate was the farthest part from the ear. However, as shown in FIG. The half part 12 may be the farthest part of the ear. Further, as shown in FIG. 5B, the left-right half 22 including the portion farthest from the ear 1 may be the farthest ear.

The structure of some of the inventions described in the specification will be described below.

(1) An active material formed by applying an active material paste on a current collector in which a longitudinal bone and a transverse bone are arranged orthogonally in the frame bone and the frame bone has an ear portion. In the positive electrode plate for a lead-acid battery comprising a layer, the active material layer has a porosity of 5 to 15% higher in a farthest ear portion than in a non-farthest ear portion.
A positive electrode plate for a lead storage battery, characterized in that the weight ratio of -PbO ₂ / β-PbO ₂ is smaller by 20 to 25%.

(2) A step of kneading lead powder and dilute sulfuric acid to prepare an active material paste, and a longitudinal bone and a transverse bone are arranged in the frame bone at right angles, and the frame bone is provided with an ear portion. A step of applying the active material paste on the current collector, and then aging and drying to form an unformed electrode plate; and a specific gravity of the farthest ear portion of the unformed electrode plate is higher than 1.05 and is 1.75. 10 to 50 in the following dilute sulfuric acid
A method of manufacturing a positive electrode plate for a lead storage battery, which comprises a step of immersing for a minute and a step of forming the unformed electrode plate in which the farthest part of the ear is immersed in dilute sulfuric acid in a battery case.

[0020]

According to the present invention, the porosity in the farthest part of the ear is set higher than the porosity in the farthest part of the ear, and the α-PbO ₂ / β-PbO ₂ weight ratio in the farthest part of the ear is increased. Is smaller than the α-PbO ₂ / β-PbO ₂ weight ratio in the ear farthest part, the charge / discharge reaction is promoted in the ear farthest part where the charge / discharge reaction is difficult to occur, and the charge / discharge reaction of the battery is promoted. Can be made more uniform over the entire electrode plate. Therefore, the life of the lead acid battery can be extended and the capacity can be increased.

[Brief description of drawings]

FIG. 1 is a view showing a farthest portion of an ear portion of a positive electrode plate of this embodiment.

FIG. 2 is a diagram showing a relationship between specific gravity of sulfuric acid and solubility of lead sulfate.

FIG. 3 is a plan view of a grid body (current collector) used for a pole plate of a comparative example.

FIG. 4 is a diagram showing cycle life characteristics of a battery used in a test.

5 (A) and 5 (B) are diagrams showing the ear furthest part of the positive electrode plate of another embodiment of the present invention.

[Explanation of symbols]

1,11 Ear part 2,12,22 Predetermined range including the part farthest from the ear part (farthest part of the ear part)

Claims (4)

[Claims] 1. A positive electrode plate for a lead storage battery comprising an active material layer formed by applying an active material paste on a current collector having an ear portion, wherein the active material layer is farthest from the ear portion. Within a predetermined range including a portion having a higher porosity than other portions, α- within the predetermined range including a portion farthest from the ear
The weight ratio of PbO ₂ / β-PbO ₂ is α-P in the other portion.
A positive electrode plate for a lead storage battery, which has a smaller bO ₂ / β-PbO ₂ weight ratio. 2. A method for producing a positive electrode plate for a lead storage battery by applying an active material paste on a current collector having ears to form an unformed electrode plate having an unformed active material layer formed thereon, Before forming the chemical conversion electrode plate, a predetermined range including a portion farthest from the ears of the unformed active material layer is immersed in dilute sulfuric acid having a specific gravity of 1.05 or more and 1.75 or less. Manufacturing method of positive electrode plate for lead acid battery. 3. A positive electrode plate for a lead storage battery comprising an active material layer formed by applying an active material paste on a current collector having an ear portion, wherein the active material layer is farthest from the ear portion. A positive electrode plate for a lead-acid battery, wherein the porosity within a predetermined range including the open portion is higher than the porosities of other portions. 4. A lead acid battery positive electrode plate comprising an active material layer formed by applying an active material paste on a current collector having an ear portion, wherein the active material layer is farthest from the ear portion. _{α-PbO 2 / β-PbO} 2 weight ratio other parts of the _{α-PbO 2 / β-PbO} 2 weight ratio positive plate for a lead storage battery, characterized in that less than of a predetermined range including portions.