JP2022152915A - lead acid battery - Google Patents

Abstract

To provide a lead acid battery having good cycle characteristic.SOLUTION: A lead acid battery hereof comprises a plurality of positive electrode plates 31 and a plurality of negative electrode plates 32 which are arranged to alternate, separators 40, and an electrolyte solution. The separators include a first separator 41 including a nonwoven fabric configured of organic fibers, and a second separator 42 including a glass fiber mat, which are arranged so that the nonwoven fabric and the glass fiber mat are laminated between one positive electrode plate and the negative electrode plate adjacent to the positive electrode plate. On condition a proportion that a volume of pores Pf in a range of 0.01-3.2 μm in diameter accounts for in a total volume of pores Pf of the nonwoven fabric when measuring all the pores Pf by a mercury penetration method is Vf(%), and a proportion that a volume of pores Pp in a range of 0.01-3.2 μm in diameter accounts for in a total volume of pores Pp of the positive electrode plate when measuring all the pores Pp by the mercury penetration method is Vp(%), and the ratio Vf/Vp is in a range of 0.10-0.50.SELECTED DRAWING: Figure 2

Description

The present invention relates to lead-acid batteries.

Lead-acid batteries are used in a variety of applications, such as in-vehicle use and industrial use. A lead-acid battery includes positive and negative plates and a separator disposed therebetween. Various performances are required for separators of lead-acid batteries. Therefore, lead-acid batteries using various separators have been conventionally proposed.

Patent Document 1 (Japanese Unexamined Patent Application Publication No. 10-40896) discloses "a sealed lead-acid battery characterized by using, as a separator, a mat made of fine glass fibers and a hydrophilized synthetic fiber nonwoven fabric." ing.

Patent Document 2 (International Publication No. 2013/046498) describes "a laminate of an acrylonitrile-based fiber non-woven fabric separator and a glass fiber mat separator, wherein the acrylonitrile-based fiber non-woven fabric separator contains acrylonitrile having a diameter of 0.5 μm to 2.0 μm. A battery separator structure characterized by using at least system fine fibers.".

JP-A-10-40896 WO2013/046498

However, the conventional lead-acid battery described above may not have sufficient cycle characteristics. In particular, the cycle life of the conventional lead-acid battery is remarkably reduced when subjected to charge-discharge cycles accompanied by high-rate discharge.

One aspect of the present invention relates to lead-acid batteries. The lead-acid battery includes a plurality of positive electrode plates and a plurality of negative electrode plates that are alternately arranged, a separator, and an electrolytic solution, wherein the separator includes a nonwoven fabric made of organic fibers. and a second separator comprising a glass fiber mat, wherein the nonwoven fabric and the glass fiber mat are laminated between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate. The pores Pf having a diameter in the range of 0.01 μm to 3.2 μm occupying the volume of all the pores Pf when the pores Pf of the nonwoven fabric are measured by a mercury intrusion method is Vf (%), and when the pores Pp of the positive electrode plate are measured by a mercury intrusion method, the pores Pp having a diameter of 0.01 μm to 3.2 μm account for the volume of all the pores Pp The volume ratio of the pores Pp in the range is Vp (%), and the ratio Vf/Vp is in the range of 0.10 to 0.50.

ADVANTAGE OF THE INVENTION According to this invention, the lead acid battery with a predetermined favorable cycle characteristic is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the structure of the lead storage battery which concerns on one Embodiment of this invention. FIG. 2 is a cross-sectional view schematically showing the configuration of an example of an electrode plate group used in the lead-acid battery shown in FIG. 1; FIG. 3 is a cross-sectional view schematically showing the configuration of another example of the electrode plate group used in the lead-acid battery shown in FIG. 1; 4 is a graph showing characteristics of lead-acid batteries manufactured in Examples.

Hereinafter, embodiments of the present invention will be described with examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present invention can be obtained. In this specification, the range described as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "A or more and B or less".

(lead-acid battery)
A lead-acid battery according to the present embodiment includes a plurality of positive electrode plates and a plurality of negative electrode plates that are alternately arranged, a separator, and an electrolytic solution. The separator includes a first separator containing non-woven fabric made of organic fibers and a second separator containing a glass fiber mat. The nonwoven fabric may be hereinafter referred to as "nonwoven fabric (F)". Between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate, the nonwoven fabric (F) and the glass fiber mat are arranged so as to be laminated. When the pores Pf of the non-woven fabric are measured by the mercury intrusion method, the ratio of the volume of the pores Pf having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pf is Vf (% ). When the pores Pp of the positive electrode plate are measured by a mercury intrusion method, the ratio of the volume of the pores Pp having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pp is Vp ( %). The ratio Vf/Vp is in the range of 0.10-0.50.

"Volume of all pores" is the volume measured by mercury porosimetry and corresponds to the sum of the individual volumes of all pores. “Volume of pores with diameters in the range of 0.01 μm to 3.2 μm” is the volume measured by mercury porosimetry and is the volume of pores determined to have diameters in the range of 0.01 μm to 3.2 μm. It corresponds to the sum of the individual volumes of the pores.

The positive plate includes a positive current collector and a positive electrode material disposed around the positive current collector. The pores of the positive electrode material are measured when the pore size distribution of the positive plate is measured. Therefore, the pores Pp of the positive electrode plate can be read as the pores Pp of the positive electrode material included in the positive electrode plate.

Non-woven fabrics and glass fiber mats are formed by entangling fine fibers. Therefore, a large number of minute voids exist in the nonwoven fabric or the glass fiber mat. Such minute voids can be regarded as pores. That is, nonwovens and fiberglass mats have a porous structure containing a large number of pores of different sizes. Pore size analysis on such nonwovens and fiberglass mats provides information on the distribution of pore diameters.

A glass fiber mat is a mat composed of glass fibers. The glass fiber mat may be referred to as Absorbed Glass Mat (AGM) or Absorbent Glass Mat. Therefore, in this specification, glass fiber mat can be read as absorbent glass mat.

Separators are required to prevent short circuits and to retain electrolyte. The glass fiber mat has a high porosity and a high electrolyte retention capacity. However, the glass fiber mat alone is insufficient to prevent short circuits. Therefore, it has been conventionally proposed to use a combination of a glass fiber mat and a synthetic fiber nonwoven fabric.

In the lead-acid batteries described in Patent Documents 1 and 2, a synthetic fiber nonwoven fabric and a glass fiber mat are used as separators. Comparing the synthetic fiber nonwoven fabric and the glass fiber mat, the glass fiber mat generally has a higher affinity with the electrolytic solution. Therefore, when a synthetic fiber nonwoven fabric and a glass fiber mat are laminated and used, a large amount of electrolyte is retained in the glass fiber mat, while the amount of electrolyte retained in the synthetic fiber nonwoven fabric tends to decrease. Such unevenness of the electrolyte solution causes various characteristic deterioration such as an increase in internal resistance and a decrease in cycle life of the lead-acid battery. In order to suppress the bias of the electrolyte, in the lead-acid batteries described in Patent Documents 1 and 2, acrylonitrile-based fiber nonwoven fabric and synthetic fiber nonwoven fabric that has been hydrophilized are used as the synthetic fiber nonwoven fabric that has a high affinity with the electrolyte. used.

The idea disclosed in Patent Documents 1 and 2 is to improve the hydrophilicity of the synthetic fiber nonwoven fabric by changing the material of the nonwoven fabric. However, such a method may not be able to fully meet the current requirements for lead-acid batteries. For example, in the method of improving the hydrophilicity of the synthetic fiber nonwoven fabric by changing the material of the nonwoven fabric, the expected effect cannot be obtained when the electrolyte decreases due to the use of a lead-acid battery and the electrolyte is unevenly distributed. There is Under these circumstances, as a result of investigation, the inventors of the present application have found a technique for improving the characteristics of lead-acid batteries by an approach completely different from the conventional one. The present invention is based on this new finding.

When a conventional separator containing a synthetic fiber nonwoven fabric and a glass fiber mat is used, cycle characteristics may be insufficient. Expansion and contraction of the synthetic fiber nonwoven fabric and generation of gas from the electrodes during charge/discharge cycles tend to reduce the electrolytic solution in the synthetic fiber nonwoven fabric. As a result of investigation, the inventors of the present application have found that the reduction of the electrolyte in the synthetic fiber nonwoven fabric is affected by the structure of the positive electrode plate.

Furthermore, the inventors of the present application focused on the ratio of fine pores, and the ratio Vf/Vp of the ratio Vf of fine pores in the nonwoven fabric (F) and the ratio Vp of fine pores in the positive electrode plate was It has been found that the charge-discharge cycle characteristics can be improved by making it higher than that of the lead-acid battery. Specifically, the inventors have found that by setting the ratio Vf/Vp in the range of 0.10 to 0.50, the characteristics (cycle life, etc.) of the lead-acid battery can be significantly improved. Although the reason for this is not clear at present, it can be considered as follows.

It is considered that the smaller the pores are, the lower the fluidity of the electrolytic solution filled in the fine pores. Therefore, the electrolytic solution filled in the fine pores is less likely to move from the filled portion and is less likely to be absorbed by the pores in the positive electrode plate. As a result, the amount of electrolytic solution in the nonwoven fabric (F) is maintained, and deterioration of the performance of the lead-acid battery can be suppressed. For example, an increase in internal resistance can be suppressed by maintaining the amount of electrolyte in the nonwoven fabric (F). By suppressing an increase in internal resistance, an increase in IR drop during high-rate discharge is suppressed, and the discharge capacity during high-rate discharge is maintained. Therefore, suppression of an increase in internal resistance is particularly effective in improving cycle characteristics associated with high-rate discharge.

The ratio Vf/Vp is 0.10 or greater, and may be 0.12 or greater, 0.15 or greater, 0.17 or greater, or 0.20 or greater. Cycle life with high rate discharge can be improved by increasing the ratio Vf/Vp. The ratio Vf/Vp is 0.50 or less, and may be 0.33 or less, 0.27 or less, 0.20 or less, or 0.17 or less. By lowering the ratio Vf/Vp, the production of the first separator containing the nonwoven fabric (F) is facilitated, and the production cost can be reduced. These lower and upper limits can be arbitrarily combined as long as there is no contradiction. For example, the ratio Vf/Vp is in the range 0.10-0.50, 0.12-0.50, 0.15-0.50, 0.17-0.50, or 0 It may be in the range of 0.20 to 0.50. In these ranges, the upper limit may be replaced by 0.33, 0.27, 0.20, or 0.17, so long as the upper limit is not less than or equal to the lower limit.

The ratio Vf/Vp is preferably in the range of 0.12-0.33, more preferably in the range of 0.17-0.33. According to these configurations, it is possible to particularly improve the life characteristics in charge-discharge cycles involving high-rate discharge.

The ratio Vf/Vp can be changed by changing Vf and/or Vp. The ratio Vf may be changed by changing the diameter of the organic fibers forming the nonwoven fabric (F) and/or the areal density (mass per unit area) of the nonwoven fabric (F). Vf can be increased by decreasing the diameter of the organic fibers, and Vf can be decreased by increasing the diameter of the organic fibers. Further, Vf can be increased by increasing the areal density of the nonwoven fabric (F), and Vf can be decreased by decreasing the areal density.

The ratio Vp can be changed according to the manufacturing conditions of the positive electrode plate. For example, Vp can be changed by changing the manufacturing conditions of the positive electrode paste used for manufacturing the positive electrode plate, the conditions of applying and drying the positive electrode paste, and the like. For example, the proportion of liquid in the positive electrode paste may be varied. The liquid in the positive paste is removed during the formation of the positive plate. Therefore, Vp can be increased by increasing the proportion of liquid in the positive electrode paste. Alternatively, it is also possible to change Vp by changing the particle size of the material (for example, lead) used in the positive electrode paste. In general, increasing the particle size of the material used for the positive electrode paste tends to decrease Vp.

Vf (%) of the nonwoven fabric (F) may be 8.3% or more, 9.0% or more, 11.0% or more, 14.0% or more, or 16.0% or more. Vf may be 30.0% or less, 26.0% or less, or 22.0% or less. These lower and upper limits may be combined arbitrarily as long as there is no contradiction. For example, Vf may be in the range of 8.3-30.0%. The lower and/or upper limits of this range may be replaced with the above lower and/or upper limits.

Vp (%) of the positive electrode plate may be 60.0% or more, or 70.0% or more. Vp may be 99.0% or less, or 92.0% or less. These lower and upper limits may be combined arbitrarily as long as there is no contradiction. For example, Vp ranges from 60.0 to 99.0%, ranges from 60.0 to 92.0%, ranges from 70.0 to 99.0%, or ranges from 70.0 to 92.0%. may be in

The nonwoven fabric (F) may have an average thickness in the range of 0.05 mm to 0.5 mm (for example in the range of 0.1 mm to 0.3 mm). By setting the average thickness of the nonwoven fabric (F) to 0.1 mm or more, the effect of preventing a short circuit can be enhanced. Internal resistance can be reduced by setting the average thickness of the nonwoven fabric (F) to 0.3 mm or less.

Each of the plurality of positive electrode plates may include a positive electrode current collector including an expanded grid portion (first expanded grid portion), and each of the plurality of negative electrode plates includes an expanded grid portion (second expanded grid portion). It may also contain a negative electrode current collector. Each of the first expanded grid portion and the second expanded grid portion may be a grid body without surrounding frame ribs. Since the expanded grid is prone to bending, short circuit prevention is particularly important. In particular, in a lattice body having no frame ribs around it, short circuits are likely to occur around the positive electrode plate and the negative electrode plate due to expansion of the electrode material. Therefore, when using a current collector including an expanded grid portion, it is preferable to store the positive electrode plate and/or the negative electrode plate in a bag made of the nonwoven fabric (F).

Organic fibers may include split fibers, including acrylic fibers. Using split fibers facilitates increasing the ratio Vf/Vp. Liquid retention can be enhanced by using acrylic fibers.

Acrylic fibers are fibers (acrylonitrile fibers) formed using a polymer containing acrylonitrile units (acrylonitrile polymers). The acrylonitrile-based polymer may contain only acrylonitrile units as structural units. Alternatively, the acrylonitrile-based polymer may be a copolymer containing acrylonitrile units and other monomeric units. The other monomer units may be one kind, or two or more kinds. The proportion of acrylonitrile units in the polymer may be, for example, 50% by mass or more, 70% by mass or more, 80% by mass or more, or 85% by mass or more. Examples of other monomers copolymerized with acrylonitrile include acrylic acid, methacrylic acid, derivatives thereof, olefinic monomers (vinyl acetate, vinyl chloride, vinylidene chloride, etc.) and the like. Acrylic fibers include acrylic fibers.

Split fibers containing acrylic fibers may be commercially available split fibers, or may be synthesized by a known method. Split fibers containing acrylic fibers may be formed, for example, by spinning composite fibers containing portions of acrylic fibers and portions of other fibers. Known polymers (polyethylene, polypropylene, and other polymers) may be used as the polymer that constitutes the other fibers of the composite fiber. The nonwoven fabric (F) may be formed as follows. First, a sheet is obtained by making paper from fibers including composite fibers. Next, a high-pressure jet of water is jetted onto the sheet to entangle the fibers and at the same time split the conjugate fibers. Thus, a nonwoven fabric (F) containing split fibers (for example, split fibers of acrylic fibers) is obtained.

The organic fibers constituting the non-woven fabric (F) may include organic fibers formed by detaching components in the electrolytic solution from fibers containing the components that are detached in the electrolytic solution. By using such organic fibers, it becomes easy to increase the ratio Vf. The nonwoven fabric (F) used for manufacturing the lead-acid battery may contain the organic fiber containing the component, or may be composed only of the organic fiber containing the component. When such a nonwoven fabric (F) is used to produce a lead-acid battery, the component desorbs from the organic fibers over time. By desorbing the component, it is possible to increase the ratio of fine pores. The component detached into the electrolytic solution may be a component eluted during electrolysis, or a component decomposed in the electrolytic solution and detached from the organic fibers. Examples of such ingredients include acetate and the like. Commercially available fibers may be used as the organic fibers containing such components, or they may be synthesized by known methods.

The first separator may comprise a plurality of bags made of non-woven fabric (F). In that case, one electrode plate selected from the plurality of positive electrode plates and the plurality of negative electrode plates may be accommodated in the bag. A bag made of nonwoven fabric (F) is, for example, a bag with three sides closed and one side open. The bag may be formed, for example, by stacking nonwoven fabrics (F) and heat-sealing them at predetermined locations. A positive plate and/or a negative plate can be inserted from one open side of the bag.

The second separator may include a plurality of cross-sectional U-shaped mats composed of fiberglass mats. Further, the bag containing each of the one electrode plates may be arranged inside the mat having a U-shaped cross section. Alternatively, each of the other electrode plates, which is not the one electrode plate, may be arranged inside the cross-sectionally U-shaped mat. The cross-sectionally U-shaped mat may hereinafter be simply referred to as "U-shaped mat". From another point of view, the cross-sectionally U-shaped mat is a mat folded in two.

The nonwoven fabric (F) may be arranged adjacent to the positive electrode plate. For example, the positive electrode plate may be adjacent to the nonwoven fabric (F) by being housed in a bag made of the nonwoven fabric (F). When the non-woven fabric (F) is adjacent to the positive electrode plate, the amount of electrolyte retained in the non-woven fabric (F) is particularly affected by the positive electrode plate. Therefore, the configuration of the present invention is particularly advantageous when the nonwoven fabric (F) is adjacent to the positive electrode plate without the glass fiber mat interposed therebetween.

The lead-acid battery of the present embodiment may be a valve-regulated lead-acid battery, or may be another lead-acid battery (such as a liquid lead-acid battery). The controlled valve type has the advantage of not requiring water replenishment. On the other hand, repeated charging and discharging tends to cause a problem that the electrolyte gradually decreases and the internal resistance increases. In general, when a separator in which a synthetic fiber nonwoven fabric and a glass fiber mat are laminated is used, the amount of electrolyte in the synthetic fiber nonwoven fabric tends to decrease significantly due to the reduction of the electrolyte. Therefore, the configuration of this embodiment is particularly preferable in the case of a valve-regulated lead-acid battery.

A plurality of positive plates, a plurality of negative plates, and a separator constitute a plate group. The plurality of positive plates and the plurality of negative plates are alternately arranged as negative plates/positive plates/negative plates/positive plates. That is, the positive electrode plate and the negative electrode plate are usually alternately arranged one by one. The number of positive plates and the number of negative plates may be different. Typically, one of the positive and negative plates is one more than the other. For example, the number of positive plates may be one more than the number of negative plates. Alternatively, the number of negative plates may be one more than the number of positive plates. In those cases, the more plates can be arranged at both ends of the plate group. There is no limit to the number of positive plates and negative plates. The number of positive plates and the number of negative plates may each independently range from 2 to 20 (eg, from 3 to 16).

Between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate, the nonwoven fabric (F) and the glass fiber mat are arranged so as to be laminated. These may be arranged in the order positive plate/non-woven fabric (F)/glass fiber mat/negative plate. Alternatively, they may be arranged in the order positive plate/glass fiber mat/non-woven fabric (F)/negative plate.

In a preferred example, a first separator containing a plurality of nonwoven fabric (F) bags and a second separator containing a plurality of U-shaped mats are used. First to fourth examples of separator arrangement in this case will be described below. In a first example, the positive electrode plate is housed in a non-woven fabric (F) bag, and the bag is placed inside the U-shaped mat. The negative electrode plate is not placed inside the nonwoven fabric (F) bag and inside the U-shaped mat. In a second example, the negative electrode plate is housed in a non-woven fabric (F) bag, and the bag is placed inside the U-shaped mat. The positive plate is not placed inside the nonwoven fabric (F) bag and inside the U-shaped mat. In a third example, the positive plate is housed in a non-woven fabric (F) bag, and the negative plate is placed inside the U-shaped mat. In a fourth example, the negative plate is housed in a non-woven fabric (F) bag, and the positive plate is placed inside the U-shaped mat.

As long as the nonwoven fabric (F) and the glass fiber mat are laminated between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate, the structure of the electrode plate group is not limited to the above structure. The form of the nonwoven fabric (F) and the form of the glass fiber mat may each independently be a sheet, a bag, or a body having a U-shaped cross section.

(Evaluation of ratio Vf/Vp)
The Vf (%) of the non-woven fabric (F) and the Vp (%) of the positive electrode plate are measured by pore analysis using mercury porosimetry. A ratio Vf/Vp can be obtained from the measured Vf and Vp. The volumes Vf and Vp may be measured using an unused first separator and positive plate. Alternatively, Vf and Vp may be measured using the first separator and positive electrode plate removed from the lead-acid battery.

When the separator and positive plate are taken out of the lead-acid battery and measured, they are taken out of the lead-acid battery in a fully charged state. Separators and positive plates removed from lead-acid batteries are washed and dried prior to measurement. Cleaning and drying of the separator are performed in the following procedure. First, the separator taken out from the lead-acid battery is immersed in pure water (cleaning liquid) for 1 hour, thereby removing the sulfuric acid in the separator. Next, the separator is taken out from the cleaning liquid and left to stand in an environment of 25° C. for 16 hours or more to dry. The separator thus obtained is measured. Cleaning of the positive electrode plate is performed in the same manner as cleaning of the separator. Next, the positive electrode plate after washing is dried by leaving it in an environment of 90° C. for 6 hours or longer.

Specifically, Vf of the nonwoven fabric (F) is measured as follows. First, a part of the non-woven fabric (F) constituting the first separator (for example, the vicinity of the central part where welding is not performed) is cut into a size of 100 mm×100 mm to obtain a sample. The pore size distribution of the obtained sample is measured using a mercury porosimeter (manufactured by Shimadzu Corporation, Autopore IV9510). Vf is determined from the measured pore size distribution. The pressure range for measurement is from 0.5 psia (3447 Pa) to about 60,000 psia (about 419 MPa). 0.5 psia (3447 Pa) corresponds to a 360 μm diameter pore. About 60,000 psia (about 419 MPa) corresponds to a 0.003 μm diameter pore. Therefore, the above pressure range corresponds to a pore diameter range of 0.003 μm to 360 μm.

Specifically, the Vp of the positive electrode plate is measured as follows. First, 1 g of positive electrode material is obtained as a sample from a portion of the positive electrode plate (for example, near the central portion of the positive electrode plate). The pore distribution of the sample is measured under the same conditions as the measurement of the pore distribution of the nonwoven fabric (F), except that the sample is used. Vp is determined from the measured pore size distribution.

(Average thickness of nonwoven fabric (F))
For the average thickness of the nonwoven fabric (F), the average value of 10 arbitrarily selected equally spaced points is used. The thickness of each point is measured using, for example, an outer micrometer (0 to 25 mm) specified in JIS B7502:2016 (micrometer).

The fully charged state of a flooded lead-acid battery is defined by JIS D 5301:2019. More specifically, in a water tank at 25 ° C ± 2 ° C, at a current (A) that is 0.2 times the value described as the rated capacity (value in units of Ah), measured every 15 minutes During charging The state in which the lead-acid battery is charged until the terminal voltage (V) or the electrolyte density converted to temperature at 20° C. shows a constant value with three significant digits three times consecutively is defined as a fully charged state. In the case of a valve-regulated lead-acid battery, a fully charged state is defined as a current (0.2 times the rated capacity value (unit: Ah) in an air tank at 25°C ± 2°C). In A), constant current constant voltage charging is performed at 2.23 V / cell, and the charging current during constant voltage charging is a value (A) that is 0.005 times the value (value in Ah) described in the rated capacity. The charging is finished when it becomes .

A fully-charged lead-acid battery refers to a fully-charged chemical lead-acid battery. The lead-acid battery may be fully charged immediately after the formation as long as it is after the formation, or after some time has passed since the formation. may be used).

An example of the configuration of the lead-acid battery of the present invention will be described below. In addition, you may use the structural member mentioned above for the structural member demonstrated below. You may apply a well-known structural member to structural members other than the structural member characteristic of this invention.

(separator)
The separator includes a first separator including a nonwoven fabric (F) made of organic fibers and a second separator including a glass fiber mat. The first separator may be mostly (for example, 80% by mass or more) composed of the nonwoven fabric (F), or may be composed only of the nonwoven fabric (F). The second separator may be mostly (for example, 80% by mass or more) composed of a glass fiber mat, or may be composed only of a glass fiber mat.

(Nonwoven fabric (F))
The nonwoven fabric (F) is composed of organic fibers. 70% by weight or more (eg, 80% by weight, 90% by weight or more, or 95% by weight or more) of the first separator is organic fibers. The first separator may consist only of organic fibers. Examples of organic fibers include synthetic fibers (polyolefin fibers, acrylic fibers, polyester fibers, etc.), fibers containing naturally derived components, and the like. Examples of polyolefin fibers include polyethylene fibers and polypropylene fibers. Examples of polyester fibers include polyethylene terephthalate fibers and the like. Examples of fibers containing naturally derived components include pulp fibers (eg, cellulose fibers). The first separator may contain components other than organic fibers, such as acid-resistant inorganic powder and a polymer as a binder.

In order to increase the permeability of the electrolyte into the fine pores and the retention of the electrolyte in the pores, the hydrophilicity of the organic fibers is preferably high. From that point of view, it is preferable to use organic fibers having higher hydrophilicity than polyolefin fibers that are not hydrophilized. For example, a polymer (for example, a copolymer) using a monomer containing a hydrophilic group (such as a hydroxyl group or a carboxyl group) may be used, or an organic fiber subjected to hydrophilization treatment may be used. A known hydrophilization treatment may be used for the hydrophilization treatment. Examples of organic fibers that are more hydrophilic than non-hydrophilized polyolefin fibers include acrylic fibers and polyethylene terephthalate fibers (PET fibers). A preferred example of organic fibers is a copolymer synthesized using a monomer containing a hydrophilic group and acrylonitrile.

The organic fibers may be split fibers. By using split fibers, it becomes easier to increase the ratio Vf.

Among the organic fibers constituting the nonwoven fabric (F), split fibers may have an average fiber diameter in the range of 0.01 μm to 1.0 μm (for example, in the range of 0.01 μm to 0.75 μm). The average fiber diameter of the organic fibers forming the nonwoven fabric (F) may be in the range of 0.5 μm to 15 μm (for example, in the range of 0.5 μm to 10 μm). By setting the average fiber diameter to 9 μm or less, it becomes easier to increase the ratio Vf. The average fiber diameter of the organic fibers can be determined as the average value of the 100 numerical values obtained by determining the maximum diameter of any cross section perpendicular to the longitudinal direction of any 100 fibers. As for split fibers, each split fiber is treated as one fiber. For example, 10 divided fibers are treated as 10 fibers.

The nonwoven fabric (F) may have an areal density in the range of 40 g/m ² to 90 g/m ² (for example in the range of 50 g/m ² to 80 g/m ² ). By setting the average fiber diameter of the organic fibers constituting the nonwoven fabric (F) in the range of 0.5 μm to 15 μm and the surface density of the nonwoven fabric (F) in the range of 40 g/m ² to 90 g/m ² , the ratio Vf Easier to make big.

(glass fiber mat)
A glass fiber mat is, for example, a sheet (eg, non-woven fabric) formed using glass fibers. The entire glass fiber mat may be made of glass fiber. Alternatively, the glass fiber mat may contain glass fibers as a major component. The glass fiber content in the second separator may be 90% by mass or more or 95% by mass or more. The second separator may contain components other than glass fibers, such as organic fibers, acid-resistant inorganic powder, and polymers as binders, but their content is usually 20% by mass or less ( For example, 10% by mass or less or 5% by mass or less).

The average fiber diameter of the glass fibers may be in the range of 0.1 μm to 30 μm, or in the range of 0.5 μm to 15 μm. The average fiber diameter of glass fibers can be obtained by obtaining the maximum diameter of any cross section perpendicular to the longitudinal direction of arbitrary 100 fibers and averaging 100 numerical values.

The areal density of the fiberglass mat may be in the range of 100 g/m ² to 250 g/m ² (eg in the range of 100 g/m ² to 200 g/m ² ).

(Positive plate)
The positive plate includes a positive current collector and a positive electrode material disposed on the positive current collector. A positive electrode material is held by a positive current collector. The positive electrode material is a portion of the positive electrode plate excluding the positive current collector. The positive electrode current collector can be formed by casting lead or a lead alloy or processing a lead or lead alloy sheet. Examples of processing methods include expanding processing and punching processing.

Pb--Ca alloys and Pb--Ca--Sn alloys are preferable as the lead alloy used for the positive electrode current collector in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, and may have a plurality of alloy layers. It is preferable to use a Pb--Ca-based alloy or a Pb--Sb-based alloy for the core bar.

The positive electrode material includes a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed.

A positive electrode plate may be produced by the following method. First, a positive electrode current collector is filled with a positive electrode paste, aged and dried to prepare an unformed positive electrode plate. A positive electrode plate is obtained by chemically forming this unformed positive electrode plate. Positive electrode paste is prepared by mixing materials including lead powder, additives, water, sulfuric acid, and the like.

The liquid content in the positive electrode paste may be in the range of 10 to 40% by mass (eg, in the range of 10 to 30% by mass).

(negative plate)
A negative electrode plate of a lead-acid battery is composed of a negative current collector and a negative electrode material. The negative electrode material is a portion of the negative electrode plate excluding the negative electrode current collector.

The negative electrode current collector may be formed by casting lead or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of processing methods include expanding processing and punching processing.

The lead alloy used for the negative electrode current collector may be any one of a Pb--Sb-based alloy, a Pb--Ca-based alloy, and a Pb--Ca--Sn-based alloy. These lead or lead alloys may further contain other additive elements, and may contain at least one element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, and Cu.

The negative electrode material includes a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction. The negative electrode material may also include shrink-proofing agents, carbonaceous materials (such as carbon black), barium sulfate, and the like. The negative electrode agent amount may contain other additives as needed.

The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually made using lead powder.

A negative electrode plate may be produced by the following method. First, a negative electrode current collector is filled with a negative electrode paste, aged and dried to prepare an unformed negative electrode plate. A negative electrode plate is obtained by chemically forming this unformed negative electrode plate. The negative electrode paste can be prepared, for example, by adding water and sulfuric acid to a material containing lead powder, an organic anti-shrunk agent, and optionally various additives, and kneading the mixture. In the aging step, the unformed negative electrode plate is preferably aged in an environment of higher temperature and higher humidity than room temperature.

Formation may be performed by charging the electrode plate group including the unformed negative electrode plate while immersing the electrode plate group in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. Formation may be performed before assembling the lead-acid battery or before assembling the electrode plate group. Formation produces spongy lead.

(Electrolyte)
The electrolytic solution is an aqueous solution containing sulfuric acid, and may contain at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions. The electrolytic solution may be gelled if necessary.

The specific gravity of the electrolytic solution at 20° C. is, for example, 1.10 g/cm ³ or more. The specific gravity of the electrolyte at 20° C. may be 1.35 g/cm ³ or less. It should be noted that these specific gravities are the values for the electrolytic solution of a chemically formed and fully charged lead-acid battery.

(Exterior body)
A lead-acid battery includes an exterior body. The exterior body may include a battery container that houses the electrode plate group and the electrolytic solution, and a lid portion that covers an opening of the battery container. The battery case may include multiple cell compartments. One electrode plate group may be arranged in one cell chamber. If the lead-acid battery is a valve regulated lead-acid battery (VRLA battery), the enclosure includes a control valve. A control valve is usually located in the lid. The control valve opens when the internal pressure of the exterior body rises (for example, when it exceeds a predetermined value), and releases the gas inside the exterior body to the outside. A known control valve that is used in a lead-acid battery can be used as the control valve.

Examples of embodiments according to the invention are described below with reference to the drawings. The components described above can be applied to the components of the example described below. Also, the examples described below can be modified based on the above description. Also, the matters described below may be applied to the above embodiments. In addition, in the embodiments described below, components that are not essential to the lead-acid battery of the present invention may be omitted.

FIG. 1 is a cross-sectional view schematically showing part of the structure of an example of a valve-regulated lead-acid battery. A lead-acid battery 1 shown in FIG. 1 includes an electrode plate group 30, an electrolytic solution (not shown), and an exterior body (container 10 and lid 12). The battery case 10 contains the electrode plate group 30 and an electrolytic solution. An upper opening of the container 10 is closed with a lid 12 .

The container 10 is divided into a plurality of (three in the example of FIG. 1) independent cell chambers 10R. One electrode plate group 30 is housed in each cell chamber 10R. The lid 12 has an independent exhaust valve (control valve) 13 for each cell chamber 10R. When the internal pressure of the cell chamber 10R exceeds a predetermined upper limit value, the exhaust valve 13 opens and part of the gas within the cell chamber 10R is released to the outside. When the internal pressure of the cell chamber 10R is equal to or lower than the upper limit, the exhaust valve 13 is closed, and the oxygen generated in the positive electrode plate 31 is reduced by the negative electrode plate 32 in the same cell chamber 10R to produce water.

The structure of the valve-regulated lead-acid battery is not limited to the above. FIG. 1 shows an example in which an exhaust valve 13 is arranged in each cell chamber 10R. However, the valve-regulated lead-acid battery may have a structure in which the number of exhaust valves 13 is less than the number of cell chambers 10R. In that case, the lid of the valve-regulated lead-acid battery may have a collective exhaust chamber communicating with each cell chamber. A smaller number (for example, one) of exhaust valves than the number of cell chambers may be arranged in the collective exhaust chamber.

A cross-sectional view of an example of the electrode plate group 30 is shown in FIG. In the following figures, illustration of a positive electrode current collector and a negative electrode current collector is omitted. Electrode plate group 30 in FIG. 2 includes positive electrode plate 31 , negative electrode plate 32 , and separator 40 . The separator 40 includes a first separator 41 containing nonwoven fabric (F) and a second separator 42 containing a glass fiber mat. The nonwoven fabric (F) forming the first separator 41 has the characteristics described above.

The first separator 41 includes a plurality of bags 41a made of nonwoven fabric (F). Each bag 41a accommodates one positive electrode plate 31 . The bag 41a may be formed by folding a non-woven fabric (F) having a size about twice the size of the positive electrode plate 31 at its center and adhering the overlapped two side portions. Bonding of the two sides may be performed by, for example, welding by heating.

The second separator 42 includes a plurality of U-shaped mats (cross-sectional U-shaped mats) 42a made of glass fiber mats. Inside each U-shaped mat 42a, a bag 41a and a positive electrode plate 31 accommodated therein are arranged.

The U-shaped mat 42a is formed by folding one mat at the folding portion 42b. The U-shaped mat 42a has a U-shaped predetermined cross section (the cross section shown in FIG. 1). The predetermined cross section is a cross section perpendicular to the direction in which the bent portion 42b extends. From another point of view, the U-shaped mat 42a is a mat that is folded and overlapped at the folding portion 42b. The inner side of the U-shaped mat 42a means the space between two sheet-like portions connected via the bent portion 42b.

An upper portion of each of the plurality of negative electrode plates 32 is provided with a current-collecting ear (not shown) projecting upward. Each upper portion of the plurality of positive electrode plates 31 is also provided with a current collecting ear (not shown) projecting upward. The ears of the negative electrode plate 32 are connected to each other by a negative electrode strap (not shown). Similarly, the ears of the positive electrode plate 31 are also connected and integrated by a positive electrode strap (not shown). The negative electrode strap is connected to a negative electrode column (not shown) that serves as an external terminal. The positive electrode strap is connected to a positive electrode column (not shown) that serves as an external terminal.

The electrode plate group 30 is configured by alternately arranging the positive electrode plates 31 and the negative electrode plates 32 accommodated in the bag 41a and the U-shaped mat 42a. As a result, between the positive electrode plate 31 and the negative electrode plate 32 adjacent to the positive electrode plate 31, the nonwoven fabric (F) and the glass fiber mat are arranged so as to be laminated. FIG. 2 shows an electrode plate group 30 including five positive plates 31 and six negative plates 32 . The number of negative plates 32 is one more than the number of positive plates 31 . The negative electrode plates 32 are arranged at both ends of the electrode plate group 30 . As described above, the number of positive plates 31 and the number of negative plates 32 may vary. Furthermore, the positions of the positive electrode plate 31 and the negative electrode plate 32 may be interchanged. That is, the negative electrode plate 32 may be accommodated in the bag 41a and the U-shaped mat 42a.

A cross-sectional view of another example of the electrode plate group 30 is shown in FIG. The electrode plate group 30 shown in FIG. 3 is different from the electrode plate group 30 shown in FIG. 2 only in the arrangement of the positive electrode plate 31, the negative electrode plate 32, and the separator 40, and redundant description will be omitted.

In the electrode plate group 30 shown in FIG. 3, the positive electrode plate 31 is arranged inside the U-shaped mat 42a, and the negative electrode plate 32 is accommodated in the bag 41a. The positive electrode plates 31 accommodated in the U-shaped mat 42a and the negative electrode plates 32 accommodated in the bag 41a are alternately arranged. The number of negative plates 32 is one more than the number of positive plates 31 . The negative electrode plates 32 are arranged at both ends of the electrode plate group 30 . As described above, the number of positive plates 31 and the number of negative plates 32 may vary. Also, the positive electrode plate 31 and the negative electrode plate 32 may be exchanged. That is, the negative electrode plate 32 may be arranged inside the U-shaped mat 42a, and the positive electrode plate 31 may be accommodated in the bag 41a.

In the electrode plate group 30, on a straight line connecting the positive electrode material of an arbitrary positive electrode plate 31 and the negative electrode material of the negative electrode plate 32 adjacent to the positive electrode plate 31, a nonwoven fabric (F) and a glass fiber mat are laminated. body exists.

The lead-acid battery according to the present invention will be collectively described below.

(1) a plurality of positive plates and a plurality of negative plates arranged alternately;
a separator;
A lead-acid battery comprising an electrolyte,
The separator includes a first separator containing a nonwoven fabric made of organic fibers and a second separator containing a glass fiber mat,
Between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate, the nonwoven fabric and the glass fiber mat are arranged so as to be laminated,
When the pores Pf of the nonwoven fabric are measured by a mercury intrusion method, the ratio of the volume of the pores Pf having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pf is Vf (%),
When the pores Pp of the positive electrode plate are measured by a mercury intrusion method, the ratio of the volume of the pores Pp having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pp is Vp (%),
A lead-acid battery having a ratio Vf/Vp in the range of 0.10 to 0.50.

(2) The lead-acid battery according to (1) above, wherein the ratio Vf/Vp is in the range of 0.12 to 0.33.

(3) The lead-acid battery according to (1) above, wherein the ratio Vf/Vp is in the range of 0.17 to 0.33.

(4) The lead-acid battery according to any one of (1) to (3) above, wherein the average thickness of the nonwoven fabric is in the range of 0.1 mm to 0.3 mm.

(5) Each of the plurality of positive plates includes a positive current collector including a first expanded grid portion, and each of the plurality of negative plates includes a negative current collector including a second expanded grid portion. , the lead-acid battery according to any one of the above (1) to (4).

(6) The lead-acid battery according to any one of (1) to (5) above, wherein the organic fibers include split fibers including acrylic fibers.

(7) The above (1) to (6), wherein the organic fiber includes an organic fiber formed by desorption of the component in the electrolytic solution from a fiber containing the component that is desorbed in the electrolytic solution. A lead-acid battery according to any one of the above.

(8) The first separator includes a plurality of bags made of the nonwoven fabric, and one electrode plate selected from the plurality of positive electrode plates and the plurality of negative electrode plates is accommodated in each of the bags. The lead-acid battery according to any one of (1) to (7) above.

(9) The second separator includes a plurality of mats having a U-shaped cross section made of the glass fiber mats, and the bag containing each of the one electrode plates includes the mat having a U-shaped cross section. The lead-acid battery according to (8) above, which is arranged inside.

(10) The second separator includes a plurality of mats having a U-shaped cross section made of the glass fiber mat, and each of the other electrode plates, which is not the one electrode plate, has a U-shaped cross section. The lead-acid battery according to (8) above, which is arranged inside.

(11) The lead-acid battery according to any one of (1) to (10) above, wherein the nonwoven fabric is arranged adjacent to the positive electrode plate.

(12) The lead-acid battery according to any one of (1) to (11) above, which is a valve-regulated lead-acid battery.

[Example]
EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

(Production of lead-acid batteries A1 to A13 and C1 to C3)
Lead-acid batteries A1 to A13 and C1 to C3 were produced by the following method.
(a) Preparation of Negative Electrode Plate Raw material lead powder, lignin as an organic shrinkage agent, barium sulfate, and carbon black were mixed with an appropriate amount of aqueous sulfuric acid solution to obtain a negative electrode paste. The respective materials were mixed so that the content of the organic shrink-proofing agent was 0.1% by mass, the content of barium sulfate was 0.4% by mass, and the content of carbon black was 0.2% by mass. Next, the negative electrode paste was filled in the mesh portion of the expanded lattice made of the Pb--Ca--Sn alloy, and then aged and dried to obtain an unformed negative electrode plate.

(b) Fabrication of Positive Electrode Plate A positive electrode paste was obtained by mixing raw material lead powder and an aqueous sulfuric acid solution. An unformed positive electrode plate was obtained by filling the positive electrode paste into the mesh portion of the expanded lattice made of the Pb--Ca--Sn alloy, followed by aging and drying. In this example, the value of the ratio Vp was changed by changing the content of the sulfuric acid aqueous solution in the positive electrode paste. Specifically, in the manufacture of the lead-acid battery shown in Table 1, the content of the sulfuric acid aqueous solution in the positive electrode paste was varied within the range of 10 to 40% by mass. When increasing Vp, the content of the sulfuric acid aqueous solution was increased.

(c) Preparation of Separator As separators, a bag-shaped separator (bag-shaped separator) formed using a nonwoven fabric of organic fibers containing acrylic fibers and a U-shaped mat formed using a glass fiber mat were prepared. . In this example, the Vf of the nonwoven fabric was varied by changing the proportion and type of split fibers in the total fibers that make up the nonwoven fabric. Specifically, when increasing Vf, the number of split fibers is increased compared to single fibers and/or the ratio of acetate contained in split fibers is set to 3% by mass or more. In the manufacture of the lead-acid batteries shown in Table 1, the average fiber diameter of the organic fibers used in the nonwoven fabric was changed within the range of 0.5 to 15 μm. Also, the surface density of the nonwoven fabric was varied in the range of 40 to 90 g/m ² .

(d) Production of lead-acid battery The lead-acid battery was produced so as to have a rated voltage of 12 V and a rated 3-hour rate capacity of 60 Ah. One plate group of a lead-acid battery includes 11 positive plates and 12 negative plates. Each positive electrode plate was accommodated in a bag-shaped separator, and further they were arranged inside a U-shaped mat. Next, a group of electrode plates was formed by alternately stacking negative electrode plates and positive electrode plates housed in separators. The electrode plate group was housed in a polypropylene battery case together with an electrolytic solution (sulfuric acid aqueous solution), and chemical conversion was performed in the battery case. In this manner, valve-regulated lead-acid batteries (batteries A1 to A13 and C1 to C3) were produced. The specific gravity at 20° C. of the electrolyte in the fully charged lead-acid battery was 1.28.

(Evaluation of ratio Vf/Vp of manufactured lead-acid battery)
The separator and the positive electrode plate were taken out from the fully charged lead-acid battery thus produced, and Vf and Vp were measured by the method described above. Then, the ratio Vf/Vp was calculated.

(Evaluation of cycle life of manufactured lead-acid battery)
The produced lead-acid battery was subjected to charge-discharge cycles including high-rate discharge, and the cycle life at high-rate discharge was evaluated. In the charge-discharge cycle, discharge was performed at a discharge current of 150 A for 13 minutes. Charging was performed by a five-stage constant current charging method. Specifically, charging was performed by the following method. First, constant current charging was performed at 0.2 CA, and when the charging voltage reached the switching voltage, the charging current was reduced to 0.1 CA. Although the charging voltage decreased due to the reduction of the charging current, the charging current was reduced to 0.05 CA when the charging voltage reached the switching voltage again. Once the charging voltage reached the switching voltage again, the charging current was reduced to 0.025 CA. When the charging voltage reached the switching voltage again, charging was continued for 2.5 hours while maintaining the charging current at 0.025 CA. In this manner, five stages of charging were performed. The switching voltage was set to 14.4V. In addition, 1C means the electric current (A) of the numerical value (Ah) described as rated capacity.

The discharge capacity was measured when the battery was discharged at a discharge current of 150 A to a battery voltage of 8.4 V at the initial stage of the charge/discharge cycle and every 25 cycles. The cycle number at which the discharge capacity reached 80% of the initial discharge charge was defined as the life cycle number. Taking the number of life cycles of battery C3 as 100%, the number of life cycles of the other batteries was relatively evaluated.

Table 1 shows the evaluation results of the lead-acid battery. The batteries C1 to C3 lead-acid batteries are conventional lead-acid batteries.

The data in Table 1 are shown in FIG. As shown in Table 1 and FIG. 4, when the ratio Vf/Vp was in the range of 0.1 to 0.5 (for example, in the range of 0.12 to 0.33), the cycle life was remarkably improved. The ratio Vf/Vp is preferably in the range of 0.12 to 0.33, more preferably in the range of 0.17 to 0.33 (for example, 0.20 to 0.33 range).

INDUSTRIAL APPLICABILITY The present invention can be used for lead-acid batteries, for example, for valve-regulated lead-acid batteries. The valve-regulated lead-acid battery of the present invention may be used as a stationary valve-regulated lead-acid battery such as an uninterruptible power supply (UPS), but its application is not particularly limited.

Reference Signs List 1: lead-acid battery 10: container 10R: cell chamber 12: lid 13: exhaust valve 30: electrode plate group 31: positive electrode plate 32: negative electrode plate 40: separator 41: first separator 41a: bag 42: second separator 42a: U-shaped mat 42b: bent portion

Claims (12)

a plurality of positive plates and a plurality of negative plates arranged alternately;
a separator;
A lead-acid battery comprising an electrolyte,
The separator includes a first separator containing a nonwoven fabric made of organic fibers and a second separator containing a glass fiber mat,
Between the positive electrode plate and the negative electrode plate adjacent to the positive electrode plate, the nonwoven fabric and the glass fiber mat are arranged so as to be laminated,
When the pores Pf of the nonwoven fabric are measured by a mercury intrusion method, the ratio of the volume of the pores Pf having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pf is Vf (%),
When the pores Pp of the positive electrode plate are measured by a mercury intrusion method, the ratio of the volume of the pores Pp having a diameter in the range of 0.01 μm to 3.2 μm to the volume of all the pores Pp is Vp (%),
A lead-acid battery having a ratio Vf/Vp in the range of 0.10 to 0.50. 2. The lead-acid battery according to claim 1, wherein said ratio Vf/Vp is in the range of 0.12 to 0.33. 2. The lead-acid battery according to claim 1, wherein said ratio Vf/Vp is in the range of 0.17 to 0.33. The lead-acid battery according to any one of claims 1 to 3, wherein the average thickness of said non-woven fabric is in the range of 0.1 mm to 0.3 mm. each of the plurality of positive plates includes a positive electrode current collector including a first expanded grid portion;
The lead-acid battery according to any one of claims 1 to 4, wherein each of the plurality of negative plates includes a negative current collector including a second expanded lattice portion. The lead-acid battery according to any one of claims 1 to 5, wherein the organic fibers include split fibers including acrylic fibers. 7. The organic fiber according to any one of claims 1 to 6, wherein the organic fiber includes an organic fiber formed by detaching the component in the electrolytic solution from a fiber containing the component detached in the electrolytic solution. lead-acid battery. The first separator includes a plurality of bags made of the nonwoven fabric,
8. The lead-acid battery according to claim 1, wherein one electrode plate selected from said plurality of positive electrode plates and said plurality of negative electrode plates is accommodated in said bag. The second separator includes a plurality of U-shaped cross-sectional mats made of the glass fiber mat,
9. The lead-acid battery according to claim 8, wherein said bag accommodating each of said one electrode plates is arranged inside said cross-sectionally U-shaped mat. The second separator includes a plurality of U-shaped cross-sectional mats made of the glass fiber mat,
9. The lead-acid battery according to claim 8, wherein each of the other electrode plates, which is not the one electrode plate, is arranged inside the U-shaped cross-sectional mat. The lead-acid battery according to any one of claims 1 to 10, wherein said nonwoven fabric is arranged adjacent to said positive electrode plate. The lead-acid battery according to any one of claims 1 to 11, which is a valve-regulated lead-acid battery.

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