Wet lead-acid battery

Abstract

This liquid type lead-acid battery includes a positive electrode plate, a negative electrode plate, a separator that separates the positive electrode plate and the negative electrode plate, and an electrolyte in which the positive electrode plate, the negative electrode plate and the separator are immersed. Porous layers are provided between the upper portion of the positive electrode plate and the upper portion of the separators and excluded from the lower portion of the positive electrode plate. The configuration described above can prevent the electrode material from softening at and falling off from the upper portion of the positive electrode plate, and can also prevent stratification of the electrolyte. Thus, the life of the liquid type lead-acid battery can be improved, and particularly, the life of the battery for a vehicle with start-stop system can be improved significantly.

Description

Liquid lead-acid battery This invention relates to a liquid lead-acid battery. In a lead-acid battery, as charge and discharge occur, a specific gravity difference is generated between the upper and lower electrolytes in the battery cell, causing stratification. When the electrolyte stratifies, the charge and discharge reactions become local, resulting in a decline in battery performance. Lead-acid batteries are increasingly being used in idle-stop vehicles. In this application, shallow charge and discharge cycles are frequently repeated, and the opportunity for the electrolyte to be stirred by gassing is reduced. As a result, stratification progresses easily, and sulfation at the lower part of the negative electrode plate also progresses easily. Therefore, charge and discharge become more concentrated at the upper part of the electrode plate, and at the upper part of the positive electrode plate, the electrode material is more likely to soften and fall off. Some liquid lead-acid batteries have a glass mat bonded to the entire surface of the separator for the purpose of suppressing the softening and falling off of the positive electrode material. However, if the ion conduction resistance between the electrode plates increases due to the glass mat, the discharge performance, charge acceptance, etc. will decline, and once stratification occurs, it is difficult to eliminate. Therefore, the life performance in idle-stop vehicles does not improve. Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2007-87871) discloses arranging a glass mat in contact with the upper part of the negative electrode plate in a liquid lead-acid battery and arranging a separator only at the lower part of the electrode plate. Japanese Unexamined Patent Application Publication No. 2007-87871 aims to prevent performance degradation due to a decrease in the liquid level of the electrolyte. Even when the liquid level of the electrolyte decreases, the upper part of the negative electrode plate is brought into contact with the electrolyte by the glass mat. This promotes the oxygen absorption reaction at the upper part of the negative electrode plate, generates water, and limits the decrease in the liquid level. Also, even when the liquid level decreases, the upper part of the negative electrode plate is shielded from the air by the electrolyte, preventing oxidation of the negative electrode plate. Japanese Unexamined Patent Application Publication No. 2007-87871 Japanese Unexamined Patent Application Publication No. 2007-87871 does not consider the softening and falling off of the electrode material in the positive electrode plate. In contrast, the inventor studied suppressing the softening and falling off of the positive electrode material by controlling the ionic conductivity between the electrode plates. And by arranging a porous layer between the upper part of the positive electrode plate and the upper part of the separator, it was found that the softening and falling off of the positive electrode material can be suppressed, and the stratification of the electrolyte can also be suppressed, thereby improving the life performance of the liquid lead-acid battery. The basic problem of this invention is to suppress softening and shedding of the electrode material at the upper part of the positive electrode plate. An additional problem of this invention is to greatly improve the life performance when used in an idle stop vehicle. This invention relates to a flooded lead-acid battery having a positive electrode plate, a negative electrode plate, a separator that separates the positive electrode plate and the negative electrode plate, and an electrolytic solution that immerses the positive electrode plate, the negative electrode plate, and the separator, characterized in that a porous layer is disposed between the upper part of the positive electrode plate and the upper part of the separator and excluding the lower part of the positive electrode plate. Hereinafter, the flooded lead-acid battery may be simply referred to as a lead-acid battery or a battery. In the lead-acid battery of this invention, due to the porous layer disposed at the upper part of the positive electrode plate, the ionic conduction resistance at the upper part between the electrode plates increases. Therefore, charging and discharging approaches a state where it occurs uniformly regardless of the top and bottom of the electrode plate, whereby softening and shedding of the electrode material (active material) at the upper part of the positive electrode plate can be suppressed. Also, since discharging approaches a state where it occurs uniformly throughout the electrode plate, stratification of the electrolytic solution can also be suppressed. The porous layer has a thickness of, for example, 2 mm or less, preferably 1 mm or less, and the thickness is measured under a pressure of 19.6 KPa in accordance with the Battery Industry Association Standard SBA S 0406. The porous layer may be, for example, a porous synthetic resin film or the like, but when it is a glass mat, the life performance of the lead-acid battery can be more greatly improved. This is presumably because the glass mat can prevent diffusion of the electrolytic solution and can reduce stratification due to precipitation of sulfuric acid during charging. When the average fiber diameter of the glass fibers in the glass mat is 1.2 μm or more and 25 μm or less, the life performance can be greatly improved while reducing the high-rate discharge performance and the decrease in charge acceptance due to the porous layer. Also, when the average fiber diameter is less than 1.2 μm, the high-rate discharge performance and the charge acceptance tend to decrease, and when the average fiber diameter exceeds 25 μm, the improvement in life performance due to the porous layer becomes slight. Preferably, the height of the porous layer is 20% or more and 60% or less of the height of the positive electrode plate, and particularly preferably 30% or more and 55% or less. By selecting the height of the porous layer, it is possible to reduce the decrease in the initial performance of the storage battery due to the porous layer, more effectively suppress the softening and falling off of the electrode material at the upper part of the positive electrode, and further improve the life performance. When comparing the case where the separator wraps the positive electrode plate and the case where it wraps the negative electrode plate, the life performance is improved when wrapping the negative electrode plate. In addition, whether wrapping the positive electrode plate or the negative electrode plate, it is preferable that the separator wraps the electrode plate from the lower part to the upper part of the electrode plate. The application of the lead storage battery is arbitrary, but when it is used for an idle stop vehicle where the stratification of the electrolytic solution is rarely eliminated by gassing, sulfation is likely to occur at the lower part of the negative electrode plate, and the charge and discharge reaction concentrates on the upper part of the electrode plate, the life performance is greatly improved. Vertical cross-sectional view of the main part of the liquid-type lead storage battery (Type B) of the example, Vertical cross-sectional view of the main part of the liquid-type lead storage battery (Type C) of the second example, Vertical cross-sectional view of the main part of the liquid-type lead storage battery (Type D) of the comparative example, Vertical cross-sectional view of the main part of the liquid-type lead storage battery (Type E) of the second comparative example, Diagram for explaining the arrangement of the porous layer with respect to the positive electrode plate, Vertical cross-sectional view of the main part of the liquid-type lead storage battery of the third example, Enlarged vertical cross-sectional view showing the main part of FIG. 6 The optimal examples of the present invention are shown below. When implementing the present invention, those skilled in the art can appropriately modify the examples according to common knowledge and the disclosure of the prior art. With reference to FIGS. 1 to 7, the structure of the lead storage battery of the example will be described, and its characteristics are shown in Table 1. FIGS. 1 and 2 show the lead storage batteries (Types B and C) of the example, and FIGS. 3 and 4 show the lead storage batteries (Types D and E) of the comparative example. In each figure, 2 is the positive electrode plate, which is composed of a positive electrode grid (not shown) and a positive electrode electrode material, and 4 is the negative electrode plate, which is composed of a negative electrode grid (not shown) and a negative electrode electrode material. Hereinafter, the electrode material will be simply referred to as the active material. The type of the grid is arbitrary, and a casting grid, a punched grid, an expanded grid, etc. can be used. The positive electrode active material is composed of lead dioxide and additives such as synthetic fiber reinforcing agents, and the negative electrode active material is composed of spongy lead and additives such as shrinkage preventives such as barium sulfate and lignin, carbon such as carbon black, and synthetic fiber reinforcing agents. The positive and negative plates 2 and 4 are arranged in the vertical direction, and ear portions 6 are provided at their upper parts. A porous layer 8 made of a glass mat is arranged so as to contact the upper part of the positive plate 2. The thickness of the porous layer 8 is, for example, 0.3 mm or more and 2 mm or less, preferably 0.4 mm or more and 1 mm or less, and here it is set to 0.5 mm. The average fiber diameter of the glass fibers constituting the glass mat 8 is, for example, 0.3 μm or more and 30 μm or less, and as shown in Table 1, 1.2 μm or more and 25 μm or less is preferable. The average fiber diameter of the glass fibers can be measured by observing the surface of the glass mat with an electron microscope or the like and averaging the diameters of three or more fibers. Examples of using a microporous polyethylene film as the porous layer are shown in FIGS. 6 and 7, which will be described later. 10 is a bag-shaped separator made of polyethylene, which is made of a microporous synthetic resin film. Polyethylene is an example thereof, and ribs are provided on the base polyethylene film. The separator 10 may wrap either the positive plate 2 or the negative plate 4, but it is preferable to wrap the negative plate 4 in terms of life performance. Then, a sulfuric acid electrolyte (not shown) is arranged so as to immerse the entire positive and negative plates 2 and 4, the porous layer 8, and the separator 10, and these are housed in an electrolytic cell. Also, the porous layer 8 is in contact with the positive plate 2 and the separator 10. The porous layer 8 is attached to the positive plate 2 or the separator 10 so as not to fall off, but it may be positioned by the pressure applied between the positive and negative plates 2 and 4. The difference between the examples (FIGS. 1 and 2) and the comparative examples (FIGS. 3 and 4) is that in the examples, the porous layer 8 is between the upper part of the positive plate 2 and the upper part of the separator 10, and in the comparative examples, the porous layer 8 is between the upper part of the negative plate 4 and the upper part of the separator 10. In the examples, the porous layer 8 is in contact with the positive plate 2 and the separator 10. The cases where the separator 10 wraps the negative plate 4 are the B-type example (FIG. 1) and the D-type comparative example (FIG. 3), and the cases where the separator 10 wraps the positive plate 2 are the C-type example (FIG. 2) and the E-type comparative example (FIG. 4). Referring to FIG. 5, the meaning of the area S1 where the porous layer 8 contacts the positive electrode plate 2 will be described. If the area of the positive electrode plate 2 excluding the ear part 6 is S2, then S1 / S2 is important, and this ratio is preferably 0.2 or more and 0.6 or less, particularly preferably 0.3 or more and 0.55 or less. When the width of the porous layer 8 is equal to or greater than the width of the positive electrode plate 2, for example, when their widths are equal, the area ratio S1 / S2 is the ratio of the height of the porous layer 8 to the positive electrode plate 2. Note that the porous layer 8 only needs to be above the positive electrode plate 2. For example, when S1 / S2 is 1 / 3, 1 / 4, 1 / 5, etc., it is not excluded that the upper end of the porous layer 8 is slightly lower than the upper end of the positive electrode plate 2. Also, the porous layer 8 is, for example, rectangular, but is not limited to this shape. FIGS. 6 and 7 show an example in which a porous layer 12 made of the same material and having the same film thickness as the polyethylene separator 10 is arranged to contact the upper part of the positive electrode plate 2. FIG. 6 shows the entire electrode plates 2 and 4, and FIG. 7 shows the upper part thereof. 14 is a film-like base with a uniform thickness, and the thickness is, for example, 0.2 mm or more and 0.3 mm or less (in the example, the thickness is 0.25 mm), and from this, ribs 15 with a thickness of, for example, 0.2 mm or more and 0.5 mm or less (in the example, the height of the ribs is 0.3 mm) protrude. Since the porous layer 12 is made of the same material and has the same thickness as the separator 10, folding the separator 10 from the negative electrode plate 4 to the positive electrode plate 2 side and doubling the separator 10 above the electrode plates 2 and 4 will result in a substantially same structure, which is also included in the examples. A lead-acid battery was manufactured according to a conventional method except that the porous layers 8 and 12 were provided. Additives were added to the lead powder to obtain electrode materials (active materials) for the positive and negative electrodes, which were pasted and filled into the positive and negative grids, followed by drying and aging. Then, for example, by tank formation, a lead-acid battery for a liquid-type idling stop vehicle with an output of 12 V was obtained. However, the application of the lead-acid battery is arbitrary. For the lead-acid battery, the initial performance was evaluated by measuring the low-temperature high-rate discharge performance and charge acceptance in accordance with JIS D 5301, and the life performance was evaluated by conducting an idling stop life test in accordance with the Battery Industry Association Standard SBA S 0101. However, in the idling stop life test, the charging voltage was changed from 14V to 14.4V, and the charge and discharge current was changed according to the battery size. The results are shown in Table 1. Battery A1 is a conventional example without a porous layer. As the position of the porous layer, it shows whether it is in contact with the positive electrode plate 2 or the negative electrode plate 4, and the ratio of the area S1 covered by the porous layer to the total area S2 of the electrode plate. Low-temperature HR represents the low-temperature high-rate discharge performance, and life is the idling stop life. The results are shown as relative values with the conventional battery A1 as 100%. The dropout rate of the active material at the upper part of the positive electrode was determined by disassembling the battery after 36,000 cycles, cutting the positive electrode plate along the line at half of its height, and measuring the ratio of the active material that dropped off during the life test. By covering only the upper part of the positive electrode plate 2 with the porous layers 8 and 12, the idling stop life was improved, and the decrease in the low-temperature high-rate discharge performance and charge acceptance could be limited within an acceptable range. The improvement in the idling stop life is considered to be due to the fact that the porous layers 8 and 12 made the entire positive electrode plate 2 approach a state of uniformly participating in charge and discharge, reducing the softening and dropout of the active material at the upper part of the positive electrode plate 2, being able to suppress the stratification of the electrolyte, and being able to suppress the sulfation at the lower part of the negative electrode plate 4. Also, in the case of the porous layer 8 made of a glass mat, it is considered to have contributed to restricting the precipitation of sulfuric acid generated during charging to the lower part and suppressing the stratification. In battery B1 where the porous layer 8 covers the entire surface of the positive electrode plate 2, the dropout of the positive electrode active material could be suppressed, but no improvement in performance was observed. In battery B2 where the porous layer 8 covers 2 / 3 of the positive electrode plate 2 and a part of the lower part of the positive electrode plate 2 is covered by the porous layer 8, no improvement in performance was observed either. These are considered to be the results of restricting the charge and discharge at the lower part of the positive electrode plate 2 by the porous layer 8. On the other hand, in batteries B3 and B4 where the porous layer 8 covers the upper 1 / 2 or 1 / 3 of the positive electrode plate 2, both showed a significant improvement in life performance and had little impact on the initial performance (charge and discharge performance). When comparing the batteries with the porous layer 8 (Battery B7, C3) and the batteries with the porous layer 12 (Battery B10, C6) that have similar initial performance, better performance was obtained for the porous layer 8 of the glass mat. This indicates that even though the ionic conduction resistance of the electrolyte is the same, the porous layer 8 of the glass mat that can prevent the diffusion of the electrolyte is more advantageous in terms of suppressing stratification and preventing softening and shedding of the positive electrode active material. Regarding the effect of the average fiber diameter of the glass fiber, when the fiber diameter is 30 μm, the pore diameter is large, so the influence on the initial performance is small, but it was found that the improvement in life does not increase significantly. Also, when the fiber diameter is 0.8 μm, the pore diameter is too small, and it was found that the decrease in initial performance is large. And in the range where the average fiber diameter is 1.2 μm or more and 25 μm or less, the idling stop life performance could be greatly extended while keeping the decrease in initial performance within an acceptable range. In the B-type battery where the separator 10 is in contact with the negative electrode plate 4, higher life performance was obtained than in the C-type battery where the separator 10 is in contact with the positive electrode plate 2. This suggests that when the separator 10 wraps the positive electrode plate 2, the gas generated during charging tends to accumulate in the porous layer 8 in the separator 10, reducing the reaction area of the positive electrode plate 2. 2 Positive electrode plate 4 Negative electrode plate 6 Ear 8, 12 Porous layer 10 Polyethylene separator 14 Base 15 Rib

Claims

Revised March 4, 2019. No claims. -------------------------------------------------------------------------- Page 1 of 2 pages. Claims:

1. A wet lead-acid battery with a positive and negative electrode plates and a separator separating the positive and negative electrode plates and an electrolyte solution immersed in the positive and negative electrode plates and the separator, which is characterized by a porous layer placed between the top of the said positive electrode plate and the top of the said separator.

2. A wet lead-acid battery as described in Claims 1, which is characterized by such porous layer being a glass liner.

3. A wet lead-acid battery as described in Claims 1, which is characterized by such porous layer being a polyethylene film.

4. A wet lead-acid battery as described in Claims 2, which is characterized by such glass liner consisting of glass fibers with an average fiber diameter of 1.2 micrometers or more and not exceeding 25 micrometers.

5. A wet lead-acid battery as described in Claims 2, which is characterized by such glass liner consisting of glass fibers with an average fiber diameter of 1.2 micrometers or more and not exceeding 4 micrometers.

6. Wet lead-acid batteries specified in claim 2, which are characterized by a glass plate made of glass fibers with an average fiber diameter of 4 micrometers or more and not exceeding 25 micrometers.

7. Wet lead-acid batteries specified in any one of claims 1-6, which are characterized by a pore height of 20 percent or more and not exceeding 60 percent of the height of the anode plate.

8. Wet lead-acid batteries specified in any one of claims 1-6, which are characterized by a pore height of 20 percent or more and not exceeding 55 percent of the height of the anode plate.

9. Wet lead-acid batteries specified in any one of claims 1-6, which are characterized by a pore height of 30 percent or more and not exceeding 60 percent of the height of the anode plate. Page 2 of 2, page 10.

10. Wet lead-acid batteries specified in any of the claims 1-6, which are characterized by the pore layer height being 30 percent or more and not exceeding 55 percent of the height of the positive plate; 11. Wet lead-acid batteries specified in any of the claims 1-10, which are characterized by the pore layer thickness being 0.3 mm or more and not exceeding 2 mm; 12. Wet lead-acid batteries specified in any of the claims 1-10, which are characterized by the pore layer thickness being 0.4 mm or more and not exceeding 1 mm; 13. Wet lead-acid batteries specified in any of the claims 1-12, which are characterized by the pore layer being attached to the positive plate or separator; 14. Wet lead-acid batteries specified in any of the claims 1-13, which are characterized by the separator enclosing the negative plate; 15. A wet lead-acid battery as specified in any of the claims 1-13, which is characterized by such an insulator enclosing the positive plate.16.Any of the wet lead-acid batteries specified in claims 1-15, which have the specific characteristic 15, are for use with idle-stop vehicles;