WO2019225389A1 - Lead storage battery - Google Patents

Abstract

A lead storage battery (1) is provided in which durability under repeated charging and discharging is improved. In this embodiment, a lead storage battery (1) is provided that includes: a positive electrode plate (20); a negative electrode plate (30); a perforated sheet (50) disposed between the positive electrode plate (20) and the negative electrode plate (30), through holes being formed in the perforated sheet (5) in the thickness direction; and an electrolytic solution, the porosity of the perforated sheet (50) differing in the upper and lower sections thereof.

Description

Lead acid battery

The present invention relates to a lead storage battery.

Conventionally, a positive electrode plate, a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, an electrolytic solution, and a battery case that accommodates the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution are provided. A lead storage battery is known (for example, Patent Document 1).

In the lead storage battery described in Patent Document 1, a film body is attached to the surface of the negative electrode plate. The film body includes a base material and a hydrophilic film that covers the surface of the base material. A material and a support material, the hydrophilic material includes alumina or silica, the support material is acrylamide, silica sol, or a silane coupling agent, and the porosity (gap ratio) of the substrate is: The upper part of the negative electrode plate is higher than the lower part of the negative electrode plate.

JP 2017-068920 A

In the lead storage battery described in Patent Document 1, durability against repeated charge and discharge may not be good.

This embodiment makes it a subject to provide the lead storage battery with which durability with respect to repeated charging / discharging was improved.

The lead storage battery of the present embodiment includes a positive electrode plate, a negative electrode plate, a perforated sheet disposed between the positive electrode plate and the negative electrode plate and having a through-hole formed in the thickness direction, and an electrolyte solution. The aperture ratio is different between the upper part and the lower part.
With the above configuration, durability against repeated charge and discharge can be improved.

FIG. 1 is a view showing an appearance and a part of the inside of the lead storage battery according to the present embodiment. FIG. 2 is a partial cross-sectional view of the electrode plate group in the lead storage battery according to the present embodiment. FIG. 3 is a schematic view of an example of a perforated sheet viewed from one side in the thickness direction. FIG. 4 is a graph showing the relationship between the discharge time and the electrode plate potential difference in a lead storage battery.

Hereinafter, an embodiment of a lead storage battery according to the present invention will be described with reference to FIGS. 1 to 3. In addition, the name of each component (each component) of this embodiment is a thing in this embodiment, and may differ from the name of each component (each component) in background art.

The lead storage battery 1 of the present embodiment is a lead storage battery that includes an aqueous sulfuric acid solution as an electrolyte, has lead dioxide or lead sulfate as an active material for the positive electrode, and has metallic lead or lead sulfate as the active material for the negative electrode. The lead storage battery 1 supplies electric energy to the outside during discharging and stores the electric energy inside during charging.

As shown in FIG. 1, the lead-acid battery 1 includes a battery case 60 (case), an electrolytic solution housed in the battery case 60 (case), and a plurality of electrode plate groups 10 immersed in the electrolytic solution. ,including. The lead acid battery 1 further includes a positive electrode terminal 70, a negative electrode terminal 80, and a connection member 90 that electrically connects the plurality of electrode plate groups 10 in series. The lead storage battery 1 supplies the electrical energy stored in the plurality of electrode plate groups 10 to the outside via the positive electrode terminal 70 and the negative electrode terminal 80, or stores the electric energy from the outside in the plurality of electrode plate groups 10. Is configured to do. The lead storage battery 1 of this embodiment is a liquid lead storage battery.

The battery case 60 (case) has a rectangular parallelepiped shape having a rectangular bottom surface. The battery case 60 (case) includes a case main body 61 that opens upward, and a lid portion 62 that closes the opening of the case main body 61. The case main body 61 has a plurality of cell chambers formed by partitioning the internal space by partition walls. The plurality of cell chambers are arranged in the same direction (horizontal direction) as the long side direction of the bottom surface. Each cell chamber accommodates an electrolytic solution and one electrode plate group 10. The lid 62 has a liquid port plug 91 that can discharge the gas generated inside the battery to the outside of the battery.

Each electrode plate group 10 includes a plurality of positive plates 20 (positive electrodes), a plurality of negative plates 30 (negative electrodes), a plurality of separators 40 for physically separating the positive plates 20 and the negative plates 30, and positive plates. 20 includes a positive electrode strap 71 that electrically connects the two electrodes 20 in parallel and a negative electrode strap 81 that electrically connects the negative electrode plates 30 in parallel. As shown in FIG. 2, each electrode plate group 10 further includes a perforated sheet 50 disposed between the positive electrode plate 20 and the negative electrode plate 30 and having a through hole A formed in the thickness direction. In each electrode plate group 10, a plurality of positive electrodes 20, a plurality of separators 40, and a plurality of negative electrodes 30 are stacked in the thickness direction. The thickness direction (stacking direction) of the positive electrode plate 20 and the negative electrode plate 30 of each electrode plate group 10 is the same as the direction in which the plurality of electrode plate groups 10 are arranged in the battery case 60 (case). The separator 40 is disposed between the positive electrode plate 20 and the negative electrode plate 30.

In the lead storage battery 1, among the electrode plate groups 10 adjacent to each other, the positive electrode strap 71 of one electrode plate group 10 and the negative electrode strap 81 of the other electrode plate group 10 are connected by the connection member 90. Thus, the plurality of electrode plate groups 10 are electrically connected in series.

The perforated sheet 50 is disposed between the positive electrode plate 20 and the separator 40 or between the negative electrode plate 30 and the separator 40. The perforated sheet 50 is formed of a porous base material impregnated with an electrolytic solution. As shown in FIG. 3, the perforated sheet 50 is formed with a plurality of through holes A penetrating in the thickness direction. The thickness of the portion of the separator 40 where the through hole A is not formed may be 0.01 mm or more and 2.0 mm or less in a state where the separator 40 is not compressed in the thickness direction.
In the present embodiment, the “through hole” means a hole penetrating from one surface to the other surface in the thickness direction of the perforated sheet 50. The holes are formed substantially parallel to the thickness direction of the perforated sheet 50.

In the present embodiment, the “through hole” is a hole whose outer periphery is surrounded by the base material of the perforated sheet 50 when the perforated sheet 50 is viewed in plan from the thickness direction. Good. In the present embodiment, the “through hole” is a hole in which a part of the outer periphery of the hole is not surrounded by the base material of the perforated sheet 50 when the perforated sheet 50 is viewed in plan from the thickness direction. There may be. “A hole in which a part of the outer periphery of the hole is not surrounded by the base material of the perforated sheet 50” means that when the perforated sheet 50 is viewed in plan from the thickness direction, the end of the perforated sheet 50 is inward. It includes a hole extending in a slit shape. In the present embodiment, the shape of the “through hole” is not particularly limited.

For example, the perforated sheet 50 is provided with a plurality of through holes A having a hole area of 0.5 mm ² or more. Each hole area of the through hole A is preferably 1 mm ² or more, may be 10 mm ² or more. In addition, each hole area of the through hole A may be 600 mm ² or less, or 200 mm ² or less. The sizes of the plurality of through holes A may be the same as or different from each other.
When the hole area of the through-hole A is 1 mm ² or more, the specific gravity difference of the electrolytic solution after repeated charge and discharge can be further reduced. Moreover, when the hole area of the through-hole A is 200 mm < ² > or less, the specific gravity difference of the electrolyte solution after repeated charging / discharging can be made smaller.

The shape of the through hole A (the shape when viewed from one side in the thickness direction) is not particularly limited, and is, for example, a circle, a rectangle, a triangle, or the like. In the perforated sheet 50, a circular through hole A having a hole diameter (diameter) of 1 mm or more and 20 mm or less may be formed. Thereby, the tensile strength of the perforated sheet 50 is ensured more reliably. For example, the perforated sheet 50 is formed with 15 to 15000 through holes A per 100 cm ² .

The aperture ratio in the perforated sheet 50 is different between the upper part and the lower part. In other words, the aperture ratio of the perforated sheet 50 may be higher than the aperture ratio of the lower part. The perforated sheet 50 may have a lower opening ratio than a top opening ratio.
The “upper portion” is a portion from the upper end to the lower side by 30% with respect to the vertical length of the perforated sheet 50 (the vertical length in the region sandwiched between the positive electrode plate 20 and the negative electrode plate 30). On the other hand, the “lower part” is a part up to 30% in length upward from the lower end. In addition, the part sandwiched between the upper part and the lower part is also simply referred to as “middle part” below. Further, in the present embodiment, “upper” and “lower” because “upper” and “lower” means that the direction from the bottom surface of the battery case 60 of the lead storage battery 1 to the opening (the lid 62) is upward, Based on “upper” and “lower” when the opposite direction is the lower direction. The vertical direction corresponds to the direction of gravity when the lead storage battery 1 is placed on an automobile or the like.

The aperture ratio of the perforated sheet 50 is obtained as follows. Specifically, in a state where the perforated sheet 50 is viewed in plan from the thickness direction, the perforated sheet is divided into a square region by dividing the perforated sheet in the vertical direction (vertical direction) and the direction perpendicular to the vertical direction (lateral direction) at intervals of 5 mm. Divide (divide into square grids with sides of 5 mm). In each divided area, the area ratio (%) occupied by the holes in each area is measured. The aperture ratio is obtained by calculating the average value of the area ratio occupied by the holes in each region measured in a plurality of regions. The aperture ratio is obtained for each of the upper part and the lower part.
In other words, the aperture ratio is the aperture ratio in each divided area obtained by dividing the perforated sheet 50 into a square grid area having a side of 5 mm in a state where the perforated sheet 50 is viewed from the thickness direction. A certain area opening ratio is measured, and is an arithmetic average of all the measured area opening ratios.

The measurement of the aperture ratio can also be performed using image processing. As for the method for measuring the aperture ratio in a certain part, the area ratio occupied by the holes may be measured for all of the plurality of regions included in the part, and the aperture ratio may be obtained from the average value. It is not limited. For example, in a certain part, the area ratio occupied by the holes may be measured for a plurality of regions at the same height position (vertical direction position), and the average value may be used as the aperture ratio of the region.

In the present embodiment, a perforated sheet 50 in which a plurality of through holes A are formed is disposed between the positive electrode plate 20 and the negative electrode plate 30. Therefore, while the positive electrode plate 20 and the negative electrode plate 30 are insulated by the perforated sheet 50, the electrolytic solution moves from one surface of the perforated sheet 50 to the other surface via the through hole A, and The electrolyte can move up and down along the other surface.
In the present embodiment, the aperture ratio of the perforated sheet 50 is further different between the upper part and the lower part. Therefore, as will be described in detail below, durability after repeated charge and discharge can be improved.
In the case where the perforated sheet 50 having an opening ratio larger in the upper part than in the lower part is used, the current distribution of the electrode plate can be made closer to uniform during discharge. This is because, during discharge, discharge tends to proceed preferentially in the lower portions of the positive electrode plate 20 and the negative electrode plate 30. By providing the perforated sheet 50 having a lower aperture ratio in the lower part, the current flowing in the vertical direction can be suppressed in the lower part. As a result, it is estimated that the current distribution in the vertical direction can be made more uniform in each of the positive electrode plate 20 and the negative electrode plate 30.
On the other hand, when the perforated sheet 50 having an opening ratio larger at the lower portion than at the upper portion is used, the current distribution of the electrode plate can be made to be uniform in charging. This is because, during charging, charging is likely to proceed preferentially at the top of each of the positive electrode plate 20 and the negative electrode plate 30. By providing the perforated sheet 50 having a lower aperture ratio in the upper part, the current flowing in the vertical direction can be suppressed in the upper part. As a result, it is estimated that the current distribution in the vertical direction can be made more uniform in each of the positive electrode plate 20 and the negative electrode plate 30.
Thus, the durability after repeated charging and discharging can be improved by making the current distribution of the electrode plate both uniform during charging and discharging uniform.

In the perforated sheet 50, the difference between the upper opening ratio (%) and the lower opening ratio (%) is preferably 15 points or more, and more preferably 20 points or more. Further, the difference between the upper opening ratio (%) and the lower opening ratio (%) may be 50 points or less, or 40 points or less. The opening ratio (%) in the middle part may be the same as either the opening ratio (%) in the upper part or the opening ratio (%) in the lower part, or the opening ratio (%) in the upper part and the lower part. It may be a value between the aperture ratio (%).
The difference between the upper aperture ratio (%) and the lower aperture ratio (%) is 15 points or more, so that the current distribution of the electrode plate in charge and discharge can be made more uniform, and durability against repeated charge and discharge. Can be further improved.

In the perforated sheet 50, the aperture ratio (%) may be 30% or more in either the upper part or the lower part where the aperture ratio (%) is higher. When the aperture ratio of either the upper part or the lower part having a higher aperture ratio is 30% or more, the current distribution of the electrode plate in charge / discharge can be made more uniform, and durability against repeated charge / discharge can be further improved. Can be improved. On the other hand, the aperture ratio (%) may be 40% or less in either the upper part or the lower part where the aperture ratio (%) is lower.

Specifically, in the perforated sheet 50, when the upper opening ratio (%) is larger than the lower opening ratio (%), the upper opening ratio (%) is, for example, 30% or more and 80% or less. The opening ratio (%) of the lower part is, for example, 0% or more and 40% or less.
On the other hand, in the perforated sheet 50, when the lower opening ratio (%) is larger than the upper opening ratio (%), the upper opening ratio (%) is, for example, 0% as shown in FIG. The opening ratio (%) of the lower part is, for example, 30% or more and 80% or less.
In the perforated sheet, a plurality of through holes having a hole area of 1 mm ² or more are formed, and the difference between the upper opening ratio (%) and the lower opening ratio (%) is different as described above. The aperture ratio (%) is preferably in the above numerical range.

The portion other than the through hole A in the perforated sheet 50 is porous and can hold the electrolytic solution. The perforated sheet 50 is, for example, a nonwoven fabric in which through holes are formed. The material of the perforated sheet 50 may be polyolefin such as polyethylene or polypropylene, or polyester. Specifically, the perforated sheet 50 may be a polyolefin nonwoven fabric in which the through-holes A are formed. The perforated sheet 50 may be a sheet formed of glass fiber or cellulose fiber.

In this embodiment, the perforated sheet 50 is disposed between the negative electrode plate 30 and the separator 40. By disposing the perforated sheet 50 between the negative electrode plate 30 and the separator 40, the durability against repeated charge / discharge can be further improved as compared with the case where the perforated sheet 50 is disposed between the positive electrode plate 20 and the separator 40. it can. This is because the current bias is more easily caused by the negative electrode plate 30 than by the positive electrode plate 20, and the effect of equalizing the current is obtained by bringing the perforated sheet 50 closer to the negative electrode plate 30. Infer.

The positive electrode plate 20 includes a metal positive electrode current collector 21 and a positive electrode material 22 attached to the positive electrode current collector 21. The positive electrode current collector 21 includes a lattice-shaped lattice portion, an upper frame bone disposed along the upper end portion of the lattice portion, and an ear portion protruding upward from a part of the upper portion of the upper frame bone. The positive electrode plate 20 is formed by filling the lattice portion with the positive electrode material 22. In the positive electrode plate 20, the positive electrode material 22 adheres to almost all of the lattice portions, and the positive electrode material 22 does not adhere to the ear portions. By connecting the ears of the positive electrode plates 20 via the positive electrode strap 71, the plurality of positive electrode plates 20 are electrically connected in parallel.

The positive electrode current collector 21 is formed by, for example, an expanding process.

The ear part of the positive electrode current collector 21 has a flat plate shape and protrudes upward from a part of the upper frame bone. The upper part of the ear part is disposed below the liquid surface of the electrolytic solution.

The positive electrode current collector 21 is made of lead (Pb) or a lead alloy (made of Pb alloy) containing lead (Pb) and a metal other than lead, for example. Specifically, the positive electrode current collector 21 may be made of a Pb—Ca—Sn alloy. The positive electrode current collector 21 may be formed by processing one metal plate. In the positive electrode current collector 21, the material of the lattice portion and the material of the ear portion may be the same.

The positive electrode material 22 includes an active material made of particulate lead dioxide. The positive electrode material 22 may contain elements other than reinforcing fibers and Pb.

The positive electrode material 22 includes particles containing lead dioxide (PbO ₂ ) as an active material. Since a part of lead dioxide changes to lead sulfate along with discharge, the above particles may contain lead sulfate during charging and discharging.

Examples of reinforcing fibers that can be included in the positive electrode material 22 include synthetic resin fibers.

The negative electrode plate 30 has a metal negative electrode current collector 31 and a negative electrode material 32 attached to the negative electrode current collector 31. The structure of the negative electrode current collector 31 is the same as that of the positive electrode current collector 21. For example, the negative electrode material 32 may contain an additive in addition to the active material, and may contain an organic shrinkage agent, a carbon material such as carbon black, and / or barium sulfate as the additive. .

The negative electrode material 32 includes particles containing metallic lead (Pb) as an active material. Since a part of lead changes to lead sulfate with discharge, the above particles may contain lead sulfate during charging and discharging.

The organic shrinkage agent as the additive is, for example, lignin (sulfonic acid), bisphenol formaldehyde condensate or the like. The negative electrode material 32 may contain 0% by mass or more and 1% or less of an organic shrinkage agent.

Examples of the carbon material include graphite such as natural graphite and artificial graphite, carbon black such as ketjen black (registered trademark) and acetylene black, and carbon nanotube.

The separator 40 is porous and holds the electrolytic solution therein. The separator 40 is an insulating member. The separator 40 prevents a short circuit between the positive electrode plate 20 and the negative electrode plate 30 while holding the electrolytic solution. For example, the separator 40 may be formed in a bag shape and may be disposed in the electrode plate group 10 in a state of wrapping either the positive electrode plate 20 or the negative electrode plate 30.

The separator 40 is, for example, a microporous film, a woven fabric, or a non-woven fabric. Examples of the material of the separator 40 include a polymer compound, glass, and ceramic. Examples of the polymer compound include polyolefin (PO) such as polypropylene (PP) and polyethylene (PE). The separator 40 may include an inorganic filler, carbon particles, and the like.

The electrolytic solution is an aqueous solution of sulfuric acid. The density of the electrolyte in a fully charged state (20 ° C.) ^may be 1.20g / cm 3 ~ 1.35g / cm 3. The electrolytic solution contains at least sulfuric acid. The electrolytic solution may further contain aluminum ions, sodium ions, and the like.

Next, an example of a method for manufacturing the lead storage battery 1 of the above embodiment will be described.

In the manufacturing method of the lead storage battery 1, first, the positive electrode plate 20 is produced by filling the positive electrode current collector 21 with a positive electrode paste containing lead powder. Moreover, the negative electrode plate 30 is produced by filling the negative electrode current collector 31 with a negative electrode paste containing lead powder. Moreover, the perforated sheet | seat 50 is produced, for example by forming the some through-hole A in a nonwoven fabric. Next, the positive electrode plate 20, the separator 40, the perforated sheet 50, and the negative electrode plate 30 are laminated to form the electrode plate group 10. Subsequently, the lead storage battery 1 is assembled by placing the plurality of electrode plate groups 10 in the case body 61 of the battery case 60, closing the opening of the case body 61 with the lid portion 62, and putting the electrolytic solution in the battery case 60. Finally, chemical conversion is performed on the assembled lead-acid battery 1.

In the production of the positive electrode plate 20, the grid portion of the positive electrode current collector 21 is filled with a positive electrode paste containing lead powder. The positive electrode paste at the time of filling is prepared by kneading lead powder and additives with dilute sulfuric acid. The mass of the positive electrode material 22 can be adjusted by changing the filling amount of the positive electrode paste into the lattice portion of the positive electrode current collector 21. As a method for filling the positive electrode paste, a general method is adopted. After filling, an aging process is performed, and a drying process is further performed.

In the production of the negative electrode plate 30, the negative electrode plate 30 is produced in the same manner as the production of the positive electrode plate 20 described above. In addition, as the separator 40, what is marketed can be used.

In the production of the perforated sheet 50, for example, through holes A are formed in the thickness direction in a non-woven fabric made of polyolefin by punching. By appropriately adjusting the size and number of the through holes A, the perforated sheet 50 is produced so that the upper and lower portions have predetermined opening ratios.

In the formation of the electrode plate group 10, the plurality of positive electrode plates 20 are arranged so that the positive electrode plates 20 and the negative electrode plates 30 are alternately arranged in one direction and the separators 40 are sandwiched between the positive electrode plates 20 and the negative electrode plates 30. And a plurality of separators 40 and a plurality of negative electrode plates 30 are laminated to form a laminate. At this time, for example, the perforated sheet 50 is disposed between the separator 40 and the negative electrode plate 30. The positive electrode straps 71 electrically connect the positive electrode plates 20 in parallel. The negative electrode straps 81 electrically connect the plurality of negative electrode plates 30 in parallel.

The electrolytic solution is prepared, for example, by adding sulfuric acid to water and mixing. By changing the amount of sulfuric acid to be added, the density of the electrolyte can be adjusted.

In assembling the lead storage battery 1, a plurality of electrode plate groups 10 are placed in the case body 61 of the battery case 60. The electrode plate group 10 is accommodated in each cell chamber of the case body 61 partitioned by the partition walls. The plurality of electrode plate groups 10 are electrically connected in series by the connecting member 90. The electrolytic solution is put into the case main body 61.

In the chemical conversion treatment, a predetermined amount of electricity is applied to the assembled lead storage battery 1.

The lead storage battery 1 manufactured as described above is used, for example, as a battery for automobiles, forklifts, and the like. The use and size of the lead storage battery 1 are not particularly limited.

In addition, the lead acid battery of this invention is not limited to the said embodiment, Of course, various changes can be added within the range which does not deviate from the summary of this invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment. Furthermore, a part of the configuration of an embodiment can be deleted.

For example, in the above-described embodiment, the so-called paste-type positive electrode plate 20 has been described in detail, but in the present invention, the positive electrode may be of a clad type.

A lead-acid battery was manufactured as shown below.

(Test Example 1)
(1) Preparation of positive electrode (positive electrode plate) Lead powder and dilute sulfuric acid were mixed to prepare a positive electrode paste. The prepared positive electrode paste was filled in the grid portion of the current collector and aged. Further, a plurality of positive electrode plates were produced by drying.

(2) Production of negative electrode (negative electrode plate) Lead powder, sodium lignin sulfonate (organic anti-shrinkage agent), carbon black, barium sulfate, and dilute sulfuric acid were mixed to prepare a negative electrode paste. 0.3 parts by mass of sodium lignin sulfonate, 0.4 parts by mass of carbon black (conductive agent), and 0.5 parts by mass of barium sulfate were used with respect to 100 parts by mass of lead powder. The prepared negative electrode paste was filled in the grid portion of the current collector and aged. Further, a plurality of negative electrode plates were produced by drying.

(3) Separator A PE microporous film with a thickness of 1 mm was used as a separator.

(4) Production of perforated sheet A PP non-woven fabric having a thickness of 0.1 mm was used as the raw sheet of the perforated sheet. A plurality of through-holes (circular, diameter: about 3.6 mm, hole area: 10 mm ² ) were formed by punching so as to achieve the aperture ratio shown in Table 1.

(5) Preparation of Electrolytic Solution As an electrolytic solution, an aqueous sulfuric acid solution having a density (20 ° C.) of 1.280 g / cm ³ was prepared.

(6) Arrangement of electrode plate group in case The positive electrode plate (six pieces), the negative electrode plate (seven pieces), the electrolytic solution, the separator, the perforated sheet, and the battery case (case) ) Was used to assemble a liquid lead-acid battery according to a conventional method.
First, an electrode plate group was prepared in which a plurality of separators were disposed between the positive electrode plate and the negative electrode plate and stacked. At this time, the perforated sheet was disposed between the negative electrode plate and the separator. Next, one electrode plate group was accommodated in each cell chamber of the case body partitioned by the partition walls. A plurality of electrode plate groups were connected in series, and the opening of the case body was closed with a lid, and then the electrolyte was put into the battery case to assemble the battery.

(7) Chemical conversion treatment Chemical conversion treatment was applied to the assembled battery to produce a 35 Ah lead acid battery.

(Test Examples 2 to 7)
As shown in Table 1, a battery was manufactured in the same manner as in Test Example 1 except that the aperture ratio of the perforated sheet was changed or the perforated sheet was not used.

(Test Examples 8 to 14)
As shown in Table 2, a battery was manufactured in the same manner as in Test Example 1 except that the aperture ratio of the perforated sheet was changed or the perforated sheet was not used.

<Durability evaluation test for repeated charge / discharge (cycle durability test)>
The durability against repeated charge and discharge was evaluated using the lead storage battery of each test example. The test in Table 1 was performed with cycle pattern I (discharge 1.25I ₅ , 2h, charge 1.25I ₅ 5h, maximum voltage 2.7V / cell). When the battery voltage at the time of discharge became 10.2 V, it was determined as the life, and the number of charge / discharge cycles until the end of the life was determined as the durability against repeated charge / discharge. On the other hand, the test in Table 2 was performed with cycle pattern II (discharge 0.5I ₅ , 2h, charge 0.5I ₅ 5h, maximum voltage 2.4V / cell). When the battery voltage at the time of discharge became 10.2 V, it was determined as the life, and the number of charge / discharge cycles until the end of the life was determined as the durability against repeated charge / discharge.
Tables 1 and 2 show the results of durability evaluation tests for repeated charge and discharge.

<Evaluation test of current distribution uniformity>
Using the lead storage battery of each test example, the degree of current distribution uniformity was evaluated. Specifically, in a state where the electrode plate group is immersed in the electrolytic solution, a lead wire is connected to the lower ends of the positive electrode plate and the negative electrode plate, and the voltage between the terminals having the same polarity as the above lead wire is measured. Uniformity was evaluated. If the measured potential difference is always constant during charging and discharging, the current distribution is considered to be substantially uniform. On the other hand, when the voltage difference fluctuates, the current distribution is not uniform. For a lead storage battery having no perforated sheet, the battery of the test example in which the change width of the electrode plate potential difference is reduced by 20% or more with respect to the change width of the electrode plate potential difference of such a battery is A, less than 20% and The battery of the test example that decreased by 10% or more was determined as B, and the battery of the test example that decreased by less than 10% was determined as C. Such a determination was based on the average value of the change width of the electrode plate potential difference through the entire charge / discharge cycle.
Tables 1 and 2 show the results of the evaluation test of the uniformity of the current distribution. FIG. 4 shows a graph showing an example of the measurement result of the potential difference over time in such an evaluation test.

Based on the results shown in Tables 1 and 2, the following considerations were made.
In general, in a liquid lead-acid battery, when charging or discharging at a deep discharge depth is performed, each reaction of discharging or charging occurs unevenly in either the upper part or the lower part of the electrode plate, and in the vertical direction of the electrode plate. Proceeds unevenly. That is, the current distribution in the electrode plate becomes non-uniform. And deterioration of an electrode plate may arise. In addition, the non-uniformity of the current distribution in the charge / discharge reaction is considered to occur due to the stratification of the electrolytic solution, the current collecting performance of the lattice, and the like.
On the other hand, by using a perforated sheet (for example, a non-woven fabric) in which a plurality of through-holes are formed and having different opening ratios between the upper part and the lower part, the current distribution in charge and discharge is made closer to uniform. I found out that
Since the nonwoven fabric is porous and can be impregnated with an electrolytic solution, even if the nonwoven fabric is disposed between the positive electrode plate and the negative electrode plate, the charge / discharge reaction between the positive electrode plate and the negative electrode plate proceeds without being suppressed so much. In other words, the charge / discharge reaction between the positive electrode plate and the negative electrode plate proceeds even through a portion where a hole is not formed (non-penetrating portion). Moreover, it is considered that the charge / discharge reaction proceeds more sufficiently through the through-hole by forming the through-hole.
In charging / discharging, generally, the current flowing between the positive electrode plate and the negative electrode plate does not necessarily flow between the same height portions of the electrode plates, but also flows between different height portions. Specifically, in the initial stage of discharge, the current tends to concentrate toward the upper part of the negative electrode, and in the initial stage of charging, the current tends to flow toward the lower part of the negative electrode. Therefore, the charge / discharge current flows in a biased direction either upward or downward. Therefore, by using a perforated sheet having through holes with different opening ratios at the top and bottom, the flow of current between the plates in the vertical direction, that is, the movement of ions in the electrolyte in the vertical direction, It can be limited on the lower side than the higher side. Charging / discharging by placing the one with a lower aperture ratio of the perforated sheet (either the upper part or the lower part of the perforated sheet) on the one where charge / discharge reaction is likely to occur (for example, either the upper part or the lower part of the electrolyte) The current bias can be made uniform. Thereby, it is thought that the charging / discharging reaction in the path | route of the same height part in a positive electrode plate and a negative electrode plate can occur easily.
On the other hand, when a perforated sheet having through-holes with the same opening ratio at the upper and lower portions is used, the vertical movement of ions in the electrolyte solution is not necessarily restricted between the upper and lower portions, so that the current distribution is uneven. It is thought that this cannot be resolved.

For example, when the aperture ratio of the perforated sheet is high at the top and low at the bottom, the movement of ions in the electrolyte in the vertical direction is restricted at the bottom rather than the top. As a result, when the current concentrates toward the upper part of the negative electrode plate (for example, during discharge), the current flowing from the lower part of the positive electrode plate to the upper part of the negative electrode plate can be suppressed. Therefore, it is considered that the current distribution can be made close to uniform.
On the other hand, for example, when the aperture ratio of the perforated sheet is high at the lower part and low at the upper part, the movement of ions in the electrolytic solution in the upper and lower direction is restricted above the lower part. As a result, when the current concentrates toward the lower part of the negative electrode plate (for example, during charging), the current flowing from the upper part of the positive electrode plate to the lower part of the negative electrode plate can be suppressed. Therefore, it is considered that the current distribution can be made close to uniform.
In addition to this, it is considered that the charge / discharge reaction between the positive electrode active material and the negative electrode active material facing each other through the non-penetrating portion of the nonwoven fabric easily proceeds by way of the through hole. Specifically, even if the active material of one electrode plate and the active material of the other electrode plate are at the same height position and there is a non-penetrating part between these active materials, The reaction proceeds with the active material through a through hole, for example, in a detour path. In addition, when there is a through hole between one active material and the other active material at different height positions, the reaction proceeds through a through hole, for example, along a path inclined upward and downward. Thus, it is considered that the presence / absence of the through-hole facilitates the charge / discharge reaction between the positive electrode plate and the negative electrode plate not only in the path between the same height but also in the path between the different heights. Therefore, it is considered that the current distribution in the vertical direction, which tends to be non-uniform, can be made closer to uniform and cycle durability is improved.

Further, as understood from Table 1 and Table 2, the difference between the opening ratio (%) of the upper part of the perforated sheet and the opening ratio (%) of the lower part is 15 points or more, so that the opening ratio of the upper part is When it is high, the charge / discharge distribution can be made uniform even in the discharge (Table 1). On the other hand, when the opening ratio at the lower part is high, the charge / discharge distribution can be made uniform even in charging (Table 2).

(Test Examples 15 to 17)
As shown in Table 3, the battery was fabricated in the same manner as in Test Example 1 except that the hole area (per one) of the through holes of the perforated sheet was changed or the perforated sheet was not used. Manufactured.

<Evaluation test of difference in specific gravity of electrolyte after repeated charge and discharge>
After 20 charge / discharge cycles were performed under the conditions of cycle pattern I, samples were taken from the upper and lower portions of the electrolytic solution, and the specific gravity of the electrolytic solution was measured. As a method for measuring the specific gravity of the electrolytic solution, a known method such as an optical hydrometer can be used.

As can be seen from Table 3, the electrolyte solution is stratified by arranging a perforated sheet in which through holes are formed and the opening ratios are different between the upper part and the lower part between the positive electrode plate and the negative electrode plate. (In particular, Test Example 16).
Specifically, it is considered that the current distribution can be made closer to uniform as described above by using perforated sheets having different opening ratios at the upper part and the lower part. Thereby, the concentration difference in the vertical direction of the electrolytic solution can be suppressed, and it is considered that stratification can be suppressed. It is considered that durability against repeated charge / discharge can be improved by suppressing stratification.
Moreover, it can suppress more that the gas generate | occur | produced with charging / discharging reaction obstruct | occludes a hole because the magnitude | size of the through-hole of a perforated sheet | seat is 10 mm < ² > or more. Therefore, the electrical path | route in charging / discharging reaction is securable. Even if stratification has already occurred, it is easy to generate charging gas in the lower part of the electrode plate, and it is promoted to eliminate stratification. On the other hand, when the size of the through hole is smaller than 200 mm ² , the difference in charge / discharge characteristics at the same height can be further reduced, and deterioration of the life performance can be suppressed.

Table 4 below shows the results of evaluating the durability against repeated charge and discharge in the same manner as described above using the lead storage battery in which the arrangement of the perforated sheet of Test Example 1 was changed (Test Example 1 ′). Specifically, when the perforated sheets arranged on the positive electrode plate and the negative electrode plate are arranged on the negative electrode plate side with respect to the separator (negative electrode side), and on the positive electrode plate side with respect to the separator (positive electrode side) Table 4 shows the results.
As can be seen from Table 4, by disposing the perforated sheet on the negative electrode side, durability against repeated charge / discharge can be further improved.

1: lead acid battery,
10: Electrode plate group,
20: positive electrode plate (positive electrode), 21: positive electrode current collector, 22: positive electrode material,
30: Negative electrode plate (negative electrode), 31: Negative electrode current collector, 32: Negative electrode material,
40: Separator, 50: Perforated sheet, A: Through hole,
60: Battery case (case), 61: Case body, 62: Cover part,
70: positive electrode terminal, 71: strap for positive electrode,
80: negative electrode terminal, 81: strap for negative electrode,
90: connecting member, 91: liquid spout.

Claims (6)

A positive electrode plate, a negative electrode plate, a perforated sheet disposed between the positive electrode plate and the negative electrode plate and having a through-hole formed in a thickness direction, and an electrolyte solution,
The lead storage battery in which the aperture ratio in the perforated sheet is different between the upper part and the lower part. The lead storage battery according to claim 1, wherein the through hole having a hole area of 1 mm ² or more is formed in the perforated sheet. The lead acid battery according to claim 1 or 2, wherein a difference between the opening ratio (%) of the upper portion and the opening ratio (%) of the lower portion is 15 points or more. The lead acid battery according to any one of claims 1 to 3, further comprising a separator disposed between the positive electrode plate and the negative electrode plate. The lead storage battery according to any one of claims 1 to 4, wherein the perforated sheet has an upper opening ratio (%) higher than a lower opening ratio (%). The lead storage battery according to any one of claims 1 to 4, wherein the perforated sheet has a lower opening ratio (%) than an upper opening ratio (%).

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