WO2020144732A1 - Separator and lead storage battery - Google Patents

Abstract

This separator 100 for a lead storage battery has a first layer 110a, a second layer 110b, and a third layer 110c, wherein the first layer 110a is disposed on one surface 100a of the separator 100, the second layer 110b is disposed on the other surface 100b of the separator 100, the third layer 110c is disposed between the first layer 110a and the second layer 110b, the first layer 110a and the second layer 110b have average pore sizes that are smaller than the average pore size of the third layer 110c, and the total thickness of the first layer 110a and the second layer 110b is greater than the thickness of the third layer 110c.

Description

Separator and lead acid battery

The present invention relates to a separator that can be used in a lead storage battery, and a lead storage battery.

Currently, maintenance-free valve-regulated lead-acid batteries are used for uninterruptible power supplies and power storage applications. Further, in recent years, the valve-regulated lead-acid battery is also used for cycle applications such as for electric vehicles. For such a cycle application, higher output is required. For higher output, the number of electrodes in the battery case can be increased by reducing the electrode thickness, separator thickness, etc.

A sheet made of glass fiber is used as a separator for control valve type lead-acid batteries, and the separator also holds the sulfuric acid, which is the electrolytic solution, and also supplies the electrolytic solution to the positive and negative electrodes. Thus, since the separator holds the electrolytic solution inside, in the battery manufacturing process, in the discharging step called "Battery formation", lead sulfate easily elutes in the separator, and the thickness of the separator If the thickness is made thin, there is a problem that a short circuit (penetration short circuit) easily occurs due to charge and discharge. Therefore, a relatively thick separator (separator having a thickness of several mm) is currently used for the purpose of preventing permeation short-circuiting, and it is difficult to reduce the thickness of the separator.

In order to solve this problem, Patent Document 1 below proposes a separator that is capable of suppressing permeation short-circuit and achieving a thin film by adding an inorganic filler to the glass fiber. Further, in Patent Document 2 below, a separator is proposed, in which two glass sheets having an inorganic filler unevenly distributed on one side are stuck together with the surfaces having the inorganic filler unevenly distributed.

Japanese Patent Laid-Open No. 11-260335 Japanese Patent Laid-Open No. 2002-151033

However, the method of adding an inorganic filler to the separator as in Patent Documents 1 and 2 has a problem that it becomes difficult to retain the electrolytic solution because the pores in the glass sheet are blocked. Therefore, it is required for the lead-acid battery separator to prevent permeation short-circuiting during battery case formation by another method when the thickness of the separator is reduced.

An object of the present invention is to provide a lead storage battery separator that can prevent a permeation short circuit during battery case formation even if the separator thickness is thin, and a lead storage battery using the same.

A separator according to one aspect of the present invention is a lead-acid battery separator having at least a first layer, a second layer, and a third layer, the first layer being disposed on one surface side of the separator. , The second layer is disposed on the other surface side of the separator, the third layer is disposed between the first layer and the second layer, and the first layer and the second layer The average pore diameter of the layer is smaller than the average pore diameter of the third layer, and the total thickness of the first layer and the second layer is larger than the thickness of the third layer.

A lead storage battery according to another aspect of the present invention includes a positive electrode, a negative electrode, and the separator described above, and the separator is arranged between the positive electrode and the negative electrode.

With these separators and lead-acid batteries, even if the separator thickness is reduced, it is possible to prevent penetration short-circuiting during battery case formation.

According to the present invention, in a lead-acid battery, even if the thickness of the separator is reduced, it is possible to prevent an infiltration short circuit during formation of the battery case.

It is sectional drawing which shows an example of a separator. It is an exploded perspective view showing an example of a lead acid battery. It is a schematic diagram of an electron micrograph for explaining the measuring method of the number average fiber diameter of glass fiber.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

In the present specification, the numerical range indicated by using "to" indicates the range including the numerical values before and after "to" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of a certain stage can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another stage. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. “A or B” may include either one of A and B, or may include both. Unless otherwise specified, the materials exemplified in the present specification can be used alone or in combination of two or more kinds. The content of each component in the composition means the total amount of the plurality of substances present in the composition, unless a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. The terms “film” and “layer” include not only the structure of the shape formed on the entire surface but also the structure of the part formed when observed as a plan view. The term “step” is included in the term as long as the intended action of the step is achieved not only when it is an independent step but also when it cannot be clearly distinguished from other steps. Since the specific gravity changes with temperature, it is defined as the specific gravity converted at 20° C. in this specification.

The separator according to this embodiment is a lead-acid battery separator having at least a first layer, a second layer, and a third layer. In the present embodiment, the first layer is arranged on the one surface side of the separator, the second layer is arranged on the other surface side of the separator, and the third layer is arranged between the first layer and the second layer. Will be placed. The average pore diameter of the first layer and the second layer is smaller than the average pore diameter of the third layer, and the total thickness of the first layer and the second layer is larger than the thickness of the third layer. .. The separator according to the present embodiment has a structure obtained by stacking at least a first layer, a third layer and a second layer in this order.

According to the present embodiment, in a lead storage battery, even if the thickness of the separator is thin (for example, even if the thickness is 1.5 mm or less), it is possible to prevent the permeation short circuit during the formation of the battery case. According to this embodiment, even if the thickness of the separator is reduced, it is possible to prevent the permeation short circuit during the formation of the battery case without using the inorganic filler that blocks the pores.

It is assumed that the factors that prevent the penetration short circuit are as follows. However, the factors are not limited to the following contents.
That is, generally, in a lead storage battery, lead sulfate is generated during discharge during formation of a battery case and the specific gravity (sulfuric acid concentration) of the electrolytic solution is reduced. Then, when lead sulfate is eluted into the electrolytic solution and permeates into the separator, an infiltration short circuit may occur.
In the present embodiment, the average pore diameters of the first layer and the second layer, which are the outer layers, are smaller than the average pore diameter of the third layer, which is the intermediate layer. Electrolyte diffuses slowly. In this case, in the outer layer having a low diffusibility, the electrolytic solution whose specific gravity has decreased due to discharge is difficult to diffuse, whereas in the intermediate layer having a high diffusive property, the electrolytic solution whose specific gravity has decreased due to discharge easily diffuses, and the outer layer The specific gravity of the electrolytic solution tends to be lower than that. As a result, a difference in specific gravity of the electrolytic solution between the outer layer and the intermediate layer is likely to occur, and in the intermediate layer, the electrolytic solution having a small specific gravity comes into contact with (is mixed with) the electrolytic solution having a large specific gravity on the outer layer side, so that the specific gravity is It becomes large and the solubility of lead sulfate decreases, so that lead sulfate precipitates. On the other hand, in the outer layer, lead sulfate is less likely to deposit.
Further, in the present embodiment, the total thickness of the first layer and the second layer that are the outer layers is larger than the thickness of the third layer that is the intermediate layer. In this case, it is easy to suppress the precipitation of lead sulfate in the entire intermediate layer, and it is easy to suppress the precipitation of lead sulfate in the outer layer as well because the electrolytic solution having a low specific gravity permeates into the outer layer.
Due to these, in the present embodiment, it is possible to prevent an infiltration short circuit.

According to the present embodiment, by reducing the thickness of the separator, the capacity of the lead storage battery can be increased by increasing the number of electrodes (electrode plates etc.) used. Therefore, according to the present embodiment, even if the thickness of the separator is reduced, it is possible to prevent the permeation short circuit at the time of forming the battery case and to increase the capacity of the lead storage battery.

The lead storage battery according to the present embodiment includes a positive electrode, a negative electrode, and a separator according to the present embodiment, and the separator is arranged between the positive electrode and the negative electrode. The lead storage battery according to the present embodiment can be used as a control valve type lead storage battery. The lead storage battery according to this embodiment can be used in an electric vehicle. Examples of electric vehicles include micro hybrid vehicles such as ISS (start-stop system vehicles) and power generation control vehicles. The electric vehicle according to the present embodiment includes the lead storage battery according to the present embodiment.

The positive electrode (for example, the positive electrode plate) has a positive electrode current collector and a positive electrode active material filling portion, and the positive electrode active material is filled with the positive electrode current material to form the positive electrode active material filling portion. .. The negative electrode (for example, the negative electrode plate) has a negative electrode current collector and a negative electrode active material filling portion, and the negative electrode active material is filled in the negative electrode current material to form the negative electrode active material filling portion. .. In the present specification, the positive electrode after the chemical conversion and the positive electrode current collector are removed is referred to as a “positive electrode active material”, and the negative electrode after the chemical conversion is removed from the negative electrode current collector is referred to as the “negative electrode active material”.

One of the first layer and the second layer in the separator according to the present embodiment is in contact with the positive electrode, and the other of the first layer and the second layer is in contact with the negative electrode. The separator according to the present embodiment is preferably composed of the first layer, the second layer, and the third layer from the viewpoint of easily preventing a permeation short circuit. The separator according to the present embodiment may have a layer other than the first layer, the second layer, and the third layer between the first layer and the second layer.

In this embodiment, at least a part of the separator is arranged between the positive electrode and the negative electrode. The separator may be bag-shaped. The separator may wrap at least one selected from the group consisting of a positive electrode and a negative electrode. The separator does not have to surround the positive electrode and the negative electrode.

FIG. 1 is a sectional view showing an example of a separator. The separator 100 according to the present embodiment includes a first layer 110a arranged on the one surface 100a side of the separator 100, a second layer 110b arranged on the other surface 100b side of the separator 100, and a first layer 110a. And a third layer 110c disposed between the second layer 110b and the second layer 110b. The separator 100 is composed of a first layer 110a, a second layer 110b and a third layer 110c. The separator 100 is disposed between the positive electrode and the negative electrode. For example, the first layer 110a is in contact with the positive electrode and the second layer 110b is in contact with the negative electrode. One surface of the first layer 110a is in contact with the positive electrode, and the other surface of the first layer 110a is in contact with the third layer 110c. For example, one surface of the second layer 110b is in contact with the negative electrode and the other surface of the second layer 110b is in contact with the third layer 110c. The average pore diameter of the first layer 110a and the second layer 110b is smaller than the average pore diameter of the third layer 110c, and the total thickness of the first layer 110a and the second layer 110b is the third layer 110c. Greater than the thickness of.

FIG. 2 is an exploded perspective view showing an example of a lead storage battery. The lead-acid battery 1 shown in FIG. 2 includes a plurality of positive electrode plates 2, a plurality of negative electrode plates 3, a plurality of separators 4, a hollow battery case 5, and a lid body 6 for sealing the battery case 5. There is. The lid 6 is provided with a control valve 7 that controls the pressure in the battery case 5, a positive electrode terminal 8 that connects the positive electrode plate 2 to the outside, and a negative electrode terminal 9 that connects the negative electrode plate 3 to the outside. ..

The positive electrode plate 2 has a positive electrode current collector and a positive electrode active material filling portion filled in the positive electrode current collector. The negative electrode plate 3 has a negative electrode current collector and a negative electrode active material filling portion filled in the negative electrode current collector. A positive electrode plate 2 and a negative electrode plate 3 are alternately arranged, and a separator 4 is arranged between the positive electrode plate 2 and the negative electrode plate 3 to form an electrode plate group.

The plurality of positive electrode plates 2 are electrically connected to each other by connecting the ears 2a provided on each positive electrode plate 2 via the straps 2b. The plurality of negative electrode plates 3 are electrically connected to each other by connecting the ears 3a provided on each negative electrode plate 3 to each other via the strap 3b. The strap 2b of the positive electrode plate 2 is provided with a positive electrode column 2c for connecting the positive electrode plate 2 to the positive electrode terminal 8. The strap 3b of the negative electrode plate 3 is provided with a negative electrode column 3c for connecting the negative electrode plate 3 to the negative electrode terminal 9.

The separator 4 can be used, for example, as an electrolytic solution holder (retainer) that holds an electrolytic solution. The separator 4 has the above-mentioned first layer, second layer, and third layer. For example, the first layer contacts the positive electrode plate 2 and the second layer contacts the negative electrode plate 3.

The battery case 5 can accommodate the electrode plate group and is not particularly limited as long as it has resistance to an electrolytic solution such as dilute sulfuric acid. The battery case 5 is made of polypropylene, polyethylene, ABS resin or the like. The inside of the battery case 5 may be divided into a plurality of cell chambers. In this case, for example, the electrode plate group is housed in each cell chamber. Then, the lead plate battery is accommodated by connecting the electrode plate group housed in one cell chamber and the electrode plate group housed in the cell chamber adjacent thereto to each other so that straps of opposite polarities are connected to each other. Can be configured.

The battery case 5 contains an electrode plate group and an electrolytic solution. The electrolytic solution contains, for example, sulfuric acid. The electrolytic solution may further contain aluminum ions. The electrolytic solution containing aluminum ions can be obtained, for example, by mixing sulfuric acid and aluminum sulfate.

The lid 6 is made of, for example, the same material as the battery case 5. The lid 6 is attached to the battery case 5 by, for example, heat fusion or adhesion using an adhesive.

The separator according to the present embodiment may not contain an inorganic filler, and may contain an inorganic filler. At least one selected from the group consisting of the first layer, the second layer, and the third layer may not contain an inorganic filler, and may contain an inorganic filler. The content of the inorganic filler may be 0.001% by mass or less, and 0.0001% by mass or less, based on the total mass of the separator, the first layer, the second layer, or the third layer. May be 0.00001% by mass or less.

The separator according to this embodiment can contain glass fiber. At least one selected from the group consisting of the first layer, the second layer, and the third layer can contain glass fiber.

As the glass fiber, commercially available glass fiber that is usually used for a lead storage battery separator can be used. The glass fiber preferably contains an alkali glass from the viewpoint of easily obtaining excellent durability and acid resistance. The glass fiber may include C glass. The glass fiber of the C glass composition has excellent acid resistance. As the glass fibers, one kind or two or more kinds of fibers may be mixed and used for obtaining a glass sheet having a desired pore size.

The fiber diameter of the glass fiber (for example, the number average fiber diameter) is not particularly limited, but is preferably within the following range. The fiber diameter is preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, from the viewpoint of easily increasing the pore size of the separator. The fiber diameter is preferably 100 μm or less, more preferably 50 μm or less, still more preferably 20 μm or less, from the viewpoint that the electrolytic solution tends to be easily retained in the separator. From these viewpoints, the fiber diameter is preferably 0.3 μm to 100 μm.

At least one selected from the group consisting of the first layer and the second layer can contain a glass fiber having a fiber diameter (for example, a number average fiber diameter) smaller than that of the glass fiber of the third layer.

At least one selected from the group consisting of the first layer and the second layer preferably contains glass fibers having a fiber diameter (for example, a number average fiber diameter) within the following range. The fiber diameter is preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, from the viewpoint of easily preventing permeation short circuit. The fiber diameter is preferably 5 μm or less, more preferably 2 μm or less, still more preferably 1 μm or less, from the viewpoint of easily preventing permeation short circuit and from the viewpoint of easily holding the electrolytic solution in the separator. From these viewpoints, the fiber diameter is preferably 0.3 to 5 μm.

The third layer preferably contains glass fibers having a fiber diameter (for example, number average fiber diameter) in the following range. The fiber diameter is preferably 1 μm or more, more preferably 1.5 μm or more, still more preferably 2 μm or more, from the viewpoint of easily preventing permeation short circuit and from the viewpoint of easily increasing the pore size. The fiber diameter is preferably 100 μm or less, more preferably 50 μm or less, further preferably 20 μm or less, particularly preferably 10 μm or less, from the viewpoint of easily preventing permeation short-circuiting and from the viewpoint of easily holding the electrolytic solution in the separator. It is preferably 5 μm or less, very preferably 3 μm or less. From these viewpoints, the fiber diameter is preferably 1 to 100 μm, more preferably 1 to 10 μm.

The fiber length (for example, the number average fiber length) of glass fibers is not particularly limited, but is preferably in the following range. The fiber length is preferably 1 μm or more, more preferably 100 μm or more, still more preferably 500 μm or more, from the viewpoint that it tends to be easily adjusted to a uniform pore size. The fiber length is preferably 30 mm or less, from the viewpoint that a separator having a sufficiently high strength (for example, 1 MPa or more) tends to be easily manufactured, and from the viewpoint that good paper-forming property tends to be easily obtained at the time of paper-making described later, 20 mm or less is more preferable, and 10 mm or less is further preferable. From these viewpoints, the fiber length is preferably 1 μm to 30 mm.

In the present embodiment, the fiber diameter (for example, number average fiber diameter) and fiber length (for example, number average fiber length) of glass fibers are determined by dynamic image analysis method and laser scanning method (for example, JIS L 1081 (wool fiber test method)). ), or by direct observation with a scanning electron microscope (SEM) or the like. Specifically, the number average fiber diameter and the number average fiber length can be determined by observing at least about 200 glass fibers using these methods and taking the average value thereof.

The separator according to the present embodiment can contain an organic binder, and may contain glass fiber and an organic binder. At least one selected from the group consisting of the first layer, the second layer, and the third layer can contain an organic binder, and may contain glass fiber and an organic binder.

The organic binder preferably has excellent acid resistance and water resistance, and examples thereof include an olefin resin, an acrylic resin, a urethane resin, and a styrene resin. As the organic binder, a thermoplastic resin introduced with a hydrophilic group such as a sulfo group or a carboxyl group may be used from the viewpoint of easily improving the affinity between the separator and the electrolytic solution. The organic binder preferably contains at least one selected from the group consisting of an olefin resin and a styrene resin from the viewpoint of easily achieving both excellent mechanical strength and liquid retaining property of the electrolytic solution. The organic binder may contain at least one selected from the group consisting of polypropylene and polyethylene from the viewpoint of easily obtaining excellent acid resistance and water resistance, and from the viewpoint of easily obtaining excellent affinity of the separator for sulfuric acid. It is more preferable to include polypropylene. The organic binders may be used alone or in combination of two or more.

The content of the organic binder contained in the separator is preferably in the following range with respect to the total mass of the glass fiber (total mass in the separator). The content of the organic binder contained in at least one selected from the group consisting of the first layer, the second layer and the third layer is such that the total mass of the glass fiber (the first layer, the second layer or the The following range is preferable with respect to the total mass in the layer 3). The content of the organic binder is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, further preferably 3% by mass from the viewpoint that the separator is easily broken because the strength of the separator is easily maintained. % Or more is particularly preferable, 5% by mass or more is extremely preferable, and 6% by mass or more is very preferable. The content of the organic binder is preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, and particularly preferably 9% by mass or less, from the viewpoint of easily retaining the electrolytic solution in the separator. , 7 mass% or less is extremely preferable. From these viewpoints, the content of the organic binder is preferably 0.5 to 20% by mass.

The average pore diameter Da of at least one selected from the group consisting of the first layer and the second layer is preferably in the following range. The average pore diameter Da is preferably 1 μm or more, more preferably 1.5 μm or more, still more preferably 2 μm or more, particularly preferably 2.5 μm or more, particularly preferably 3 μm or more, from the viewpoint of easy diffusion of the electrolytic solution. 5 μm or more is very preferable, and 4 μm or more is even more preferable. The average pore diameter Da is preferably 10 μm or less, more preferably 8 μm or less, further preferably 7 μm or less, particularly preferably 6 μm or less, very preferably 5 μm or less, and very preferably 4.5 μm or less from the viewpoint of easily retaining the electrolytic solution. Is preferred. From these viewpoints, the average pore diameter Da is preferably 1 to 10 μm. The average pore diameters of the first layer and the second layer may be the same or different from each other.

The average pore diameter Db of the third layer is preferably in the following range. The average pore diameter Db is preferably 5 μm or more, more preferably more than 5 μm, further preferably 6 μm or more, particularly preferably 7 μm or more, and particularly preferably 8 μm or more, from the viewpoint of easily holding the electrolytic solution in the separator, 9 μm The above is very preferable, 10 μm or more is further preferable, 10.5 μm or more is further preferable, and 11 μm or more is particularly preferable. The average pore diameter Db is preferably 100 μm or less, more preferably 80 μm or less, further preferably 50 μm or less, particularly preferably 30 μm or less, and most preferably 20 μm or less, from the viewpoint of being able to delay the diffusion of the electrolytic solution, and 18 μm or less. Is more preferable, 15 μm or less is even more preferable, 13 μm or less is further preferable, 12 μm or less is particularly preferable, and 11.5 μm or less is extremely preferable. From these viewpoints, the average pore diameter Db is preferably 5 to 100 μm, more preferably 5 to 20 μm.

The average pore diameter of the first layer and the second layer is smaller than the average pore diameter of the third layer. That is, the ratio of the average pore diameter of the first layer and the second layer to the average pore diameter of the third layer (average pore diameter of the first layer and the second layer/average pore diameter of the third layer) Is less than 1 from the viewpoint of preventing permeation short circuit. The average pore diameter of each layer can be increased by increasing the fiber diameter of the glass fiber.

The ratio Da/Db of the average pore diameter Da of at least one selected from the group consisting of the first layer and the second layer to the average pore diameter Db of the third layer is preferably in the following range. The ratio Da/Db is preferably 0.1 or more, more preferably 0.2 or more, further preferably 0.25 or more, particularly preferably 0.3 or more, and 0.35 or more, from the viewpoint of easily preventing permeation short circuit. Is highly preferred. The ratio Da/Db is preferably 0.9 or less, more preferably 0.8 or less, still more preferably 0.7 or less, particularly preferably 0.6 or less, and 0.5 or less, from the viewpoint of easily preventing a permeation short circuit. Is extremely preferable, 0.45 or less is very preferable, and 0.4 or less is even more preferable. From these viewpoints, the ratio Da/Db is preferably 0.1 or more and less than 1.

The total thickness (film thickness) T of the separator according to this embodiment is preferably in the following range. The total thickness T of the separator is preferably 0.1 mm or more, more preferably 0.3 mm or more, and more preferably 0.1 mm or more from the viewpoint of easily manufacturing the separator by a general papermaking method and easily holding a necessary amount of the electrolytic solution. 4 mm or more is more preferable, 0.5 mm or more is particularly preferable, 0.6 mm or more is extremely preferable, and 0.7 mm or more is very preferable. The total thickness T of the separator is preferably 1.5 mm or less, more preferably 1.2 mm or less, and more preferably 1.0 mm or less from the viewpoint that the number of electrodes (electrode plates etc.) used can be increased and the capacity of the lead storage battery can be easily increased. Is more preferable, and 0.8 mm or less is particularly preferable. From these viewpoints, the total thickness T of the separator is preferably 0.1 to 1.5 mm. The total thickness T of the separator may exceed 1.5 mm.

The ratio Ta/T of at least one thickness Ta selected from the group consisting of the first layer and the second layer to the total thickness T of the separator is preferably in the following range. The ratio Ta/T is preferably 0.6 or less, more preferably 0.5 or less, still more preferably 0.45 or less, particularly preferably 0.4 or less, and 0.375 or less from the viewpoint of easily preventing a permeation short circuit. Is highly preferred. The ratio Ta/T is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.25 or more, particularly preferably 0.3 or more, and more preferably 1/3 or more, from the viewpoint of easily preventing a permeation short circuit. Is extremely preferable, and 0.35 or more is very preferable. From these viewpoints, the ratio Ta/T is preferably 0.1 to 0.6.

The thickness Ta of at least one selected from the group consisting of the first layer and the second layer is preferably in the following range. The thickness Ta is preferably 0.01 mm or more, more preferably 0.05 mm or more, further preferably 0.1 mm or more, particularly preferably 0.2 mm or more, and more preferably 0.25 mm or more, from the viewpoint of easily preventing a permeation short circuit. Very preferable, and 0.3 mm or more is very preferable. The thickness Ta is preferably 1 mm or less, more preferably 0.8 mm or less, further preferably 0.6 mm or less, particularly preferably 0.4 mm or less, and particularly preferably 0.35 mm or less, from the viewpoint of easily preventing a permeation short circuit. .. From these viewpoints, the thickness Ta is preferably 0.01 to 1 mm. The thicknesses of the first layer and the second layer may be the same or different from each other.

The ratio Tb/T of the thickness Tb of the third layer to the total thickness T of the separator is preferably in the following range. The ratio Tb/T is preferably 0.1 or more, more preferably 0.15 or more, further preferably 0.2 or more, and particularly preferably 0.25 or more, from the viewpoint of easily preventing a permeation short circuit. The ratio Tb/T is preferably 0.9 or less, more preferably 0.7 or less, still more preferably 0.5 or less, particularly preferably 0.4 or less, and more preferably 1/3 or less from the viewpoint of easily preventing a permeation short circuit. Is extremely preferable, and 0.3 or less is very preferable. From these viewpoints, the ratio Tb/T is preferably 0.1 to 0.9.

The thickness Tb of the third layer is preferably in the following range. The thickness Tb is preferably 0.02 mm or more, more preferably 0.05 mm or more, further preferably 0.1 mm or more, particularly preferably 0.15 mm or more, and particularly preferably 0.2 mm or more, from the viewpoint of easily preventing a permeation short circuit. Highly preferred. The thickness Tb is preferably 2 mm or less, more preferably 1.5 mm or less, further preferably 1 mm or less, particularly preferably 0.8 mm or less, and particularly preferably 0.6 mm or less, from the viewpoint of easily preventing a permeation short circuit. Very preferably 0.5 mm or less, more preferably 0.45 mm or less, even more preferably 0.4 mm or less, particularly preferably 0.3 mm or less. From these viewpoints, the thickness Tb is preferably 0.02 to 2 mm.

The ratio Ta/Tb of the thickness Ta of at least one selected from the group consisting of the first layer and the second layer to the thickness Tb of the third layer is preferably in the following range. The ratio Ta/Tb is preferably 0.1 or more, more preferably 0.3 or more, further preferably 0.5 or more, particularly preferably 0.7 or more, and 0.9 or more, from the viewpoint of easily preventing a permeation short circuit. Is extremely preferable, 1 or more is very preferable, more than 1 is even more preferable, 1.25 or more is further preferable, and 1.5 or more is particularly preferable. The ratio Ta/Tb is preferably 3 or less, more preferably 2.5 or less, further preferably 2 or less, particularly preferably 1.75 or less, and most preferably 1.5 or less, from the viewpoint of easily preventing a permeation short circuit. From these viewpoints, the ratio Ta/Tb is preferably 0.1 to 3.

The total thickness Tt of the first layer and the second layer is larger than the thickness Tb of the third layer. That is, the ratio Tt/Tb of the total Tt of the thicknesses of the first layer and the second layer to the thickness Tb of the third layer is more than 1 from the viewpoint of preventing permeation short circuit. The ratio Tt/Tb is preferably 1.2 or more, more preferably 1.5 or more, further preferably 1.75 or more, particularly preferably 2 or more, and particularly preferably 2.5 or more, from the viewpoint of easily preventing a permeation short circuit. Preferably, 2.75 or more is very preferable, and 3 or more is even more preferable. The ratio Tt/Tb is preferably 10 or less, more preferably 8 or less, further preferably 6 or less, particularly preferably 5 or less, very preferably 4 or less, and very preferably 3 or less, from the viewpoint of easily preventing a permeation short circuit. .. From these viewpoints, the ratio Tt/Tb is preferably more than 1 and 10 or less.

The pore size and thickness of each layer constituting the separator can be measured by the method described in the examples.

The method for manufacturing a separator according to the present embodiment is a method for manufacturing a lead-acid battery separator having at least the above-mentioned first layer, second layer and third layer. According to the separator manufacturing method of the present embodiment, the separator of the present embodiment can be obtained.

The separator manufacturing method according to the present embodiment includes a separator manufacturing step of manufacturing a separator having at least the above-mentioned first layer, second layer, and third layer. The separator producing step includes, for example, a first layer producing step of obtaining a first layer, a second layer producing step of obtaining a second layer, and a third layer producing step of obtaining a third layer. You may have. In the first layer preparation step (or the second layer preparation step, the third layer preparation step), the first layer (or the first layer (or the first layer preparation step) is performed by performing papermaking using a slurry containing glass fiber and an organic binder. The step of obtaining the second layer and the third layer). In this case, the glass fiber can have a fiber diameter in the above-described preferable range (for example, a number average fiber diameter). The first layer, the second layer and/or the third layer by adjusting the fiber diameter of the glass fiber used in the first layer producing step, the second layer producing step and/or the third layer producing step. The pore size of the can be adjusted. By adjusting the amounts of the glass fiber and the organic binder used in the first layer forming step, the second layer forming step and/or the third layer forming step, the first layer, the second layer and/or the The thickness of the three layers can be adjusted. The separator manufacturing step includes a stacking step of stacking the first layer, the second layer, and the third layer on each other to obtain a stack having the first layer, the second layer, and the third layer. You may have.

The method of manufacturing the separator according to the present embodiment is not particularly limited, and includes wet papermaking, dry papermaking and the like. Among these, it is preferable to adopt a papermaking method based on a wet method (wet papermaking). This manufacturing method is a glass fiber, a slurry preparation step of preparing a slurry containing an organic binder, a papermaking body manufacturing step of making a papermaking body by making a slurry, and a papermaking body in a thickness direction using a pressing machine. The method includes a compressed body producing step of producing a compressed body by compression, and a heat treatment step of heat treating the compressed body at a temperature equal to or higher than the softening point of the resin (organic binder), if necessary. By this method, a low cost and thin lead acid battery separator can be easily manufactured. Here, the paper product obtained by paper-making the slurry is a sheet-shaped or mat-shaped molded product in which glass fibers are bonded with an organic binder, and may be referred to as a “glass sheet” hereinafter. The compressed body is obtained by compressing this glass sheet in the thickness direction. The number of glass sheets used for producing the compressed body may be one, or a plurality of glass sheets may be stacked in the thickness direction.

In the slurry preparation process, glass fiber and organic binder are dispersed in a prescribed dispersion medium. The slurry can be prepared by, for example, a mixer, a ball mill, a pulper, or the like. Water can be used as the dispersion medium. The content of each raw material component in the slurry can be adjusted, for example, so that the content of each raw material component in the obtained lead storage battery separator falls within the above range.

The blending amount of the organic binder in the slurry preparation step is preferably within the following range with respect to the total mass of the glass fiber. The amount of the organic binder is preferably 0.75 mass% or more, more preferably 1.5 mass% or more, still more preferably 3 mass% or more, from the viewpoint of easily obtaining a separator that is not easily broken because strength is easily maintained. 4.5% by mass or more is particularly preferable, 7.5% by mass or more is extremely preferable, and 9% by mass or more is very preferable. The blending amount of the organic binder is preferably 30% by mass or less, more preferably 22.5% by mass or less, further preferably 15% by mass or less, from the viewpoint of easily obtaining a separator that easily retains the electrolytic solution. A mass% or less is particularly preferable, and 10.5 mass% or less is extremely preferable. From these viewpoints, the compounding amount of the organic binder is preferably 0.75 to 30% by mass.

The slurry may contain a surfactant. When the slurry contains the surfactant, the raw material components are easily dispersed when the lead storage battery separator is manufactured. The surfactant may be decomposed in a subsequent heat treatment. The surfactant may be any of a silane coupling agent, a cationic surfactant, an anionic surfactant, a nonionic surfactant and the like. The content of the surfactant is preferably 0.01 to 5 mass% based on the total mass of the slurry.

It is preferable to use an alkyl ammonium salt as the cationic surfactant. Examples of the cationic surfactant include dioctyldimethylammonium chloride, didecyldimethylammonium chloride, dicocodimethylammonium chloride, coco (rectification) benzyldimethylammonium chloride, octadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, and dihexadecyl chloride. Dimethylammonium, Di(hydrogenated tallow) dimethylammonium, Di(hydrogenated tallow) benzylmethylammonium, Chloride (hydrogenated tallow) benzyldimethylammonium, Dioleyldimethylammonium chloride, Di(ethylenehexadecanecarboxylate) dimethylammonium , Diallyldimethylammonium chloride, N-octadecyl-N-dimethyl-N'-trimethyl-propylene-diammonium chloride, poly(dioctyldimethylammonium chloride), poly(didecyldimethylammonium chloride), poly(dicocodimethylammonium chloride) ), poly(cocobenzyldimethylammonium chloride), poly(octadecyltrimethylammonium chloride), poly(dioctadecyldimethylammonium chloride), poly(dihexadecyldimethylammonium chloride), poly(dioleyldimethylammonium chloride), poly(chloride) Di (ethylene hexadecane carboxylate) dimethyl ammonium), poly (diallyl dimethyl ammonium chloride), etc. are mentioned.

Examples of the anionic surfactant include carboxylates, N-acyl sarcosinates, alkane sulfonates, straight chain and branched chain alkyl aryl sulfonates, dialkyl sulfosuccinates, aryl sulfonates, naphthalene sulfonates, N -Acyl-N-alkyl laurates, 2-sulfoethyl esters of fatty acids, olefin sulfonates, alkyl sulphates, sulphated natural oils, sulphated alkylphenol alkoxylates, alkanols, phenols and alkylphenols Phosphate esters of alkoxylates, alkyl (aryl) sulfonates, sulfate esters, phosphate esters, alkyl (aryl) phosphates, alkyl (aryl) phosphonates, polyoxyethylene alkyl ether phosphates, carboxylated alkyl ethoxy Examples thereof include rates, carboxylated dodecylbenzene sulfonates, ammonium polyoxyethylene alkyl ether sulfates and the like.

Examples of nonionic surfactants include polyoxyalkylene dialkyl esters, polyoxyalkylene alkyl esters, polyoxyalkylene alkyl ethers, sorbitan alkyl esters, and the like.

The slurry may contain a flocculant. When the slurry contains the aggregating agent, the yield of the manufactured separator can be improved. The flocculant may be any of inorganic flocculants (aluminum sulfate, polyaluminum chloride, polyferric sulfate, ferric chloride, etc.), cationic polymer flocculants, anionic polymer flocculants, etc. Good. As the aggregating agent, one type may be used alone, or two or more types may be used in combination. The content of the aggregating agent is preferably 0.01 to 10 mass% based on the total amount of the solid content of the slurry. The content of the aggregating agent is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, still more preferably 3 to 6% by mass, based on the total mass of the glass fiber.

For example, in the paper making process, after making a paper product (glass sheet) by making a slurry with a general paper machine in the paper making process, in the compression product making process, the paper making body is applied in the thickness direction using a pressure machine. A compression body (separator for a lead storage battery) is produced by compression. In order to obtain a desired compact, it is preferable to compress the paper product at 1 to 30 MPa for 1 to 5 minutes. As the paper product (glass sheet) used for producing the compressed body, one sheet may be used alone, or a plurality of sheets may be stacked in the thickness direction and used.

The heat treatment step is not necessarily performed, but can be performed as necessary according to the material composition of the separator. By heat-treating the compressed body at a temperature equal to or higher than the softening point of the resin (organic binder) in the heat treatment step, the organic binder is softened and glass fibers, clay minerals and the like can be reliably bound to each other. By coating a part or all of the surface of glass fiber, clay mineral, etc. with a resin (organic binder), flexibility can be imparted to the separator. Further, the resin (organic binder) is partially decomposed to function as a template, and the holding power of the electrolytic solution can be improved. The treatment temperature is not necessarily limited because it depends on the softening point of the resin (organic binder), but is preferably 100 to 200°C. When the treatment temperature is 100° C. or higher, glass fibers, clay minerals, etc. tend to be easily bound to each other. When the processing temperature is 200° C. or lower, the manufacturing process can be simplified easily. The heat treatment step may be performed under appropriate pressure depending on the constituent material of the lead storage battery separator.

The positive electrode active material may include β-PbO ₂ as a Pb component. The positive electrode active material may include alpha-PbO _2, it may not include the alpha-PbO _2. The positive electrode active material may contain a Pb component other than PbO ₂ (for example, PbSO ₄ ) and an additive described below, if necessary.

The positive electrode active material is obtained by obtaining an unformed positive electrode active material by aging and drying a paste positive electrode active material (positive electrode active material paste) containing a raw material of the positive electrode active material, and then forming the unformed positive electrode active material. Can be obtained at For the positive electrode, the unformed positive electrode active material is obtained by aging and drying the pasty positive electrode active material filled in the positive electrode current collector (casting grid body, expanded lattice body, etc.). It can be obtained by forming. The unformed positive electrode active material may contain tribasic lead sulfate as a main component. Examples of the raw material for the positive electrode active material include lead powder and red lead (Pb ₃ O ₄ ).

The positive electrode current collector serves as a conductive path for a current from the positive electrode active material and holds the positive electrode active material. The positive electrode current collector has, for example, a lattice shape. Examples of the composition of the positive electrode current collector include lead alloys such as lead-calcium-tin alloys and lead-antimony-arsenic alloys. Selenium, silver, bismuth, etc. may be added to the positive electrode current collector depending on the application. A positive electrode current collector can be obtained by forming these lead alloys in a grid shape by a gravity casting method, an expanding method, a punching method or the like.

Examples of additives that can be included in the positive electrode active material include carbon materials (excluding carbon fibers) and reinforcing short fibers. Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and Ketjen black. Examples of the reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

The negative electrode active material may include Pb as a Pb component. The negative electrode active material can contain a Pb component other than Pb (for example, PbSO ₄ ) and an additive described later, if necessary. The negative electrode active material may include porous spongy lead.

The negative electrode active material is obtained by aging and drying a pasty negative electrode active material (negative electrode active material paste) containing a raw material of the negative electrode active material to obtain an unformed negative electrode active material and then forming the unformed negative electrode active material. Can be obtained at For the negative electrode, the unformed negative electrode active material is obtained by aging and drying the paste-like negative electrode active material filled in the negative electrode current collector (cast grid, expanded grid, etc.). It can be obtained by forming. The unformed negative electrode active material may contain tribasic lead sulfate as a main component. Examples of the raw material for the negative electrode active material include lead powder.

The negative electrode current collector serves as a conductive path for a current from the negative electrode active material and holds the negative electrode active material. The negative electrode current collector may be the same as or different from the positive electrode current collector described above.

Examples of additives that can be contained in the negative electrode active material include resins having a sulfo group and/or a sulfonate group, barium sulfate, carbon materials (excluding carbon fibers), and reinforcing short fibers. Examples of the resin having a sulfo group and/or a sulfonate group include, for example, lignin sulfonic acid, lignin sulfonate, and a condensate of phenols, aminoaryl sulfonic acid, and formaldehyde (for example, bisphenol, aminobenzene sulfonic acid, and (Condensation product with formaldehyde). Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and Ketjen black. Examples of the reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

The pasty positive electrode active material and/or the pasty negative electrode active material may contain a solvent and/or sulfuric acid. Examples of the solvent include water (for example, ion-exchanged water) and an organic solvent.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Example 1>
(Number average fiber diameter measurement)
The number average fiber diameter of the glass fibers described below was measured in advance by the following procedure. After glass fiber was cast with epoxy resin, it was sliced with a diamond cutter to a thickness of 4 mm. After slicing, the cross section of the glass fiber (cross section perpendicular to the length direction of the glass fiber) was polished with diamond abrasive grains having a diameter of 9 μm. Further, a measurement sample was prepared by polishing with diamond abrasive grains having a diameter of 5 μm and then polishing with diamond abrasive grains having a diameter of 1 μm. After depositing platinum on the measurement sample by ion sputtering (manufactured by Hitachi High Technologies Co., Ltd., trade name: E-1030), a cross section of the glass fiber was formed using SEM (manufactured by Hitachi High Technologies Co., Ltd., trade name: S-8020). I observed. The fiber diameter of a total of 200 glass fibers was measured, and the average value was obtained as the number average fiber diameter. At this time, if the cross section of the glass fiber is a perfect circle, the diameter of the perfect circle is acquired as the fiber diameter, and if the cross section of the glass fiber is an elliptical shape, the minor axis is acquired as the fiber diameter (FIG. 3). See the reference numerals A and B represent fiber diameters). The cross section parallel to the length direction of the glass fiber was excluded from the measurement of the fiber diameter.

(Preparation of separator)
210 g of glass fibers A (water content: 5% by mass, manufactured by Lauscha, trade name: C-08-R) having a number average fiber diameter of 0.8 μm were adjusted to 20 kg by adding water, and then a surfactant (dispersant) was used. Manufactured by Meisei Chemical Industry Co., Ltd., trade name: PASCOR HA-52, “PASCOR” is a registered trademark) 20 g was added to obtain a mixed solution A. After this mixed solution A was put into a 20 L pulper (manufactured by Kumagai Riki Kogyo Co., Ltd.), the mixed solution A was stirred for 10 minutes. With respect to the glass fiber B having a number average fiber diameter of 4.1 μm, a mixed solution (mixed solution B) was prepared by the same procedure and then stirred. After stirring, 4.5 kg was taken from the mixed solution A containing the glass fibers A, 0.5 kg was taken from the mixed solution B containing the glass fibers B, and these were mixed to obtain a mixed solution C. That is, this mixed liquid C contained 90% by mass of glass fibers having a number average fiber diameter of 0.8 μm and 10% by mass of glass fibers having a number average fiber diameter of 4.1 μm, based on the total mass of the glass fibers. ..

4% by mass of aluminum sulfate (coagulant, manufactured by Nippon Light Metal Co., Ltd.) with respect to the total mass of the glass fiber was added to the mixed solution C, and then stirred with a stirrer for 10 minutes. Then, as an organic binder, polypropylene emulsion (manufactured by Unitika Ltd., trade name: TC-4010, an aqueous dispersion obtained by amine-neutralizing a propylene-acrylic acid copolymer) was used as a resin component based on the total mass of the glass fiber. Was added to the mixed solution C so that the content of the mixture was 9% by mass, and the mixture was stirred for 2 minutes to prepare a slurry A.

Similarly, a slurry B was prepared by the same procedure when only the glass fibers C having a number average fiber diameter of 2.4 μm were used.

140 g of slurry A was poured into a φ160 mm round sheet machine (made by Kumagai Riki Kogyo Co., Ltd.) equipped with an 80 mesh wire mesh while pouring water. Water was injected until the amount of water in the sheet machine became about 80% (7 L), and then the mixture was stirred several times with a stirring rod. Then, water was drained and papermaking was performed to obtain a glass sheet A1. By repeating the same operation, a glass sheet A2 similar to the glass sheet A1 was obtained. Next, 100 g of the slurry B was similarly paper-made to obtain a glass sheet B.

After covering the glass sheet A1 with a first filter paper (26-WA, manufactured by Advantech Co., Ltd.) and thoroughly dehydrating it with a couching roll, the glass sheet A1 is peeled off together with the first filter paper from the above-mentioned 80 mesh wire mesh. I took it. Next, the glass sheet A1 and the glass sheet B were brought into contact with each other, and then the first filter paper was covered with the second filter paper (26-WA, manufactured by Advantech Co., Ltd.) and thoroughly dehydrated with a cooling roll. Then, the first filter paper and the second filter paper were peeled off to obtain a laminate. Then, the glass sheet A2 was superposed on the glass sheet B in the above-mentioned laminate. Further, the glass sheet A1 was covered with a third filter paper (26-WA, manufactured by Advantech Co., Ltd.) and thoroughly dehydrated with a couching roll. Subsequently, the third filter paper was peeled off to prepare a glass sheet having a three-layer structure.

This glass sheet was pressed at 410 kPa for 5 minutes with a press (made by Kumagai Riki Kogyo Co., Ltd.) and then dehydrated. After dehydration, it was heated and dried with a rotary dryer (Kumagaya Riki Kogyo Co., Ltd.) at 120° C. for 4 minutes, and further sufficiently dried in a constant temperature bath at 105° C. to obtain a lead storage battery separator.

(Thickness measurement)
Using a Shopper type thickness meter (manufactured by Yasuda Seiki Co., Ltd.), the thickness was measured at 6 points under pressure of 20 kgf/cm ² (1.96 MPa), and the average value was obtained as the thickness of the lead storage battery separator. .. Regarding the thickness of each layer of the multi-layer separator, a separator was prepared using only each layer, and the thickness was obtained as the thickness of each layer.

(Pore size analysis)
Using a fully automatic pore size distribution analyzer (Poro Master 60-GT, Quanta Chrome Co.), 0.05 g of the separator was added to a small cell (diameter: 10 mm×30 mm) to measure the average pore size of the separator. Regarding the mercury parameters, the mercury contact angle was set to 140 degrees and the mercury surface tension was set to 480 dyn/cm. The measurement range of the pore size was set to the range of 0.0036 to 1000 μm, and each value was calculated to obtain the median pore size as the average pore size of the separator. Regarding the pore size of each layer of the multi-layer separator, a separator was prepared using only each layer, and the pore size was obtained as the pore size of each layer.

(Measurement of binder amount)
The amount of binder in the separator (reference: total mass of glass fiber) was measured by the following procedure. First, 3 g of the separator was completely dried in a thermostat at 105°C. Next, after cooling to room temperature in a desiccator, the mass of the separator before heating was measured. After the measurement, the separator was put in a crucible and dried by heating at about 500° C. for 30 minutes or more. Next, after cooling to room temperature in a desiccator, the mass of the separator after heating was measured. The amount of binder was obtained from the mass difference before and after heating.

(Production of electrode plate)
Lead powder and red lead (Pb ₃ O ₄ ) were used as raw materials for the positive electrode active material (lead powder:lead red=96:4 (mass ratio)). A raw material for the positive electrode active material, 0.07 mass% of reinforcing short fibers (acrylic fibers) based on the total mass of the raw material for the positive electrode active material, and water were mixed and kneaded. Subsequently, a paste-like positive electrode active material was prepared by kneading while adding dilute sulfuric acid (specific gravity 1.280) little by little.
Lead powder was used as a raw material of the negative electrode active material. 0.2% by mass of lignin-based resin (lignin sulfonate) (as solid content), 0.1% by mass of reinforcing short fibers (acrylic fiber), 1.0% by mass of barium sulfate, carbon material (furnace black) ) Was added to the lead powder and then dry mixed (the compounding amount is the compounding amount based on the total mass of the raw materials of the negative electrode active material). Next, after adding water, the mixture was kneaded. Subsequently, diluted sulfuric acid (specific gravity: 1.280) was added little by little and kneaded to prepare a pasty negative electrode active material.
The electrode plate so that the ratio (N/P) of the total mass (N) of the negative electrode active material and the total mass (P) of the positive electrode active material in the control valve type lead storage battery in a fully charged state is 0.7. The positive electrode current collector was filled with the paste positive electrode active material, and the electrode plate (negative electrode current collector) was filled with the paste negative electrode active material. A cast grid body made of a lead alloy was used as the electrode plate.

Using the electrode plate filled with the paste-like positive electrode active material, an unformed positive electrode plate was produced by going through the aging process of the following aging conditions 1 to 3 and the drying process of the following drying conditions.
Aging condition 1 "Temperature: 80°C, Humidity: 98%, Time: 10 hours"
Aging condition 2 "Temperature: 65°C, Humidity: 75%, Time: 13 hours"
Aging condition 3 "Temperature: 40°C, Humidity: 65%, Time: 40 hours"
Drying condition "Temperature: 60℃, Time: 24 hours"

Using an electrode plate filled with a paste-like negative electrode active material, an aging step under aging conditions "temperature: 40°C, humidity: 98%, time: 40 hours" and a drying condition "temperature: 60°C, time: 24 hours". An unformed negative electrode plate was produced by going through the drying step of “.

(Preparation of lead acid battery)
While one surface of the separator is in contact with the unformed negative electrode plate and the other surface of the separator is in contact with the unformed positive electrode plate, three unformed positive electrode plates and four unformed negative electrode plates are attached. An electrode plate group was produced by alternately laminating the above separators. After inserting the electrode plate group into the battery case, the positive electrode terminal and the negative electrode terminal were welded to the electrode plate group, and the battery case was sealed. Next, a total of three lead acid batteries were produced by injecting an electrolytic solution containing diluted sulfuric acid as a main component with a specific gravity of 1.28 into the battery case through an exhaust plug and then attaching a control valve.

(Evaluation of penetration short circuit)
As a permeation short-circuit evaluation, the above-mentioned 3 lead acid batteries were formed in a water tank under the conditions of "water temperature: 35°C, applied amount: 250% of theoretical formation amount of positive electrode active material, time: 60 hours". When the open-circuit voltage after forming the battery case was 2 V or more, it was judged as "no penetration short circuit". The case where all of the three lead acid batteries did not undergo an osmotic short circuit was evaluated as "A", the case where one lead acid battery did an osmotic short circuit was evaluated as "B", and the case where two lead acid batteries did an osmotic short circuit. It was evaluated as “C”, and the case where all lead acid batteries were permeated and short-circuited was evaluated as “D”.

<Example 2>
Similar to Example 1 except that the polypropylene emulsion was added to the mixed solution C such that the resin content was 15% by mass with respect to the total mass of the glass fibers, and then the slurry A was prepared by stirring for 2 minutes. Each evaluation was performed by carrying out.

<Example 3>
When glass sheets A1 and A2 were produced, glass fibers having a number average fiber diameter of 2.4 μm were used in addition to glass fibers A and B, so that the number average fiber diameter was 0.8 μm based on the total mass of the glass fibers. Example 1 except that 70% by mass of the glass fibers, 7% by mass of the glass fibers having a number average fiber diameter of 4.1 μm, and 23% by mass of the glass fibers having a number average fiber diameter of 2.4 μm were prepared. Each evaluation was performed by performing in the same manner as.

<Example 4>
When glass sheets A1 and A2 were produced, glass fibers having a number average fiber diameter of 2.4 μm were used in addition to glass fibers A and B, so that the number average fiber diameter was 0.8 μm based on the total mass of the glass fibers. Example 1 except that a mixed solution C containing 55% by mass of glass fibers, 10% by mass of glass fibers having a number average fiber diameter of 4.1 μm, and 35% by mass of glass fibers having a number average fiber diameter of 2.4 μm was prepared. Each evaluation was performed by performing in the same manner as.

<Example 5>
By using glass fibers having a number average fiber diameter of 5.5 μm in place of the glass fibers B in the production of the glass sheets A1 and A2, a glass having a number average fiber diameter of 0.8 μm based on the total mass of the glass fibers. Same as Example 1 except that a mixed solution C containing 90% by mass of fibers and 10% by mass of glass fibers having a number average fiber diameter of 5.5 μm was prepared and the amount of the slurry A used was changed to 90 g. Each evaluation was performed by performing.

<Example 6>
By using glass fibers C having a number average fiber diameter of 0.8 μm in addition to the glass fibers C in the production of the glass sheet B, the glass fibers 70 having a number average fiber diameter of 2.4 μm based on the total mass of the glass fibers 70. Each evaluation was performed in the same manner as in Example 3 except that a mixed solution C containing 30% by mass of glass fiber and 0.8% by mass of glass fiber was prepared.

<Comparative Example 1>
Same as Example 1 except that the amount of the slurry A used in producing the glass sheets A1 and A2 was changed to 90 g, and the amount of the slurry B used in producing the glass sheet B was changed to 160 g. Each evaluation was performed by performing.

<Comparative example 2>
A separator having a two-layer structure of a glass sheet A1 (negative electrode side layer) and a glass sheet B (positive electrode side layer) is used without producing the glass sheet A2, and the amount of the slurry A used is 250 g when producing the glass sheet A1. Each evaluation was performed in the same manner as in Example 1 except that the above was changed.

<Comparative example 3>
Each evaluation was performed in the same manner as in Comparative Example 2 except for the following matters. That is, the amount of the slurry B used when producing the glass sheet B was changed to 125 g. By using glass fibers having a number average fiber diameter of 5.5 μm in place of the glass fibers B in the production of the glass sheet A1, the glass fibers 90 having a number average fiber diameter of 0.8 μm based on the total mass of the glass fibers 90. A mixed liquid C containing 10% by mass of glass fiber having a mass average of 5.5 μm and a number average fiber diameter of 5.5 μm was prepared, and the amount of the slurry A used was changed to 125 g. Due to these, a separator having a two-layer structure of the glass sheet A1 (negative electrode side layer) and the glass sheet B (positive electrode side layer) was used.

<Comparative example 4>
Each evaluation was performed in the same manner as in Comparative Example 3 except that the glass sheet A1 of the separator was placed on the positive electrode side and the glass sheet B was placed on the negative electrode side.

<Comparative Example 5>
Each evaluation was performed in the same manner as in Example 1 except that a glass sheet obtained by changing the amount of the slurry A used to 250 g was used as the separator having a single-layer structure.

Table 1 shows the pore diameter and thickness of each layer of the separator, the total thickness of the separator and the amount of binder, and the results of the permeation short circuit evaluation.

DESCRIPTION OF SYMBOLS 1... Lead acid battery, 2... Positive electrode plate (positive electrode), 3... Negative electrode plate (negative electrode), 4,100... Separator, 100a... One surface, 100b... Other surface, 110a... 1st layer, 110b... 2nd layer , 110c... Third layer.

Claims (11)

1. A lead storage battery separator having at least a first layer, a second layer and a third layer,
   The first layer is disposed on one side of the separator,
   The second layer is disposed on the other surface side of the separator,
   The third layer is disposed between the first layer and the second layer,
   The average pore diameter of the first layer and the second layer is smaller than the average pore diameter of the third layer,
   A separator, wherein the sum of the thicknesses of the first layer and the second layer is greater than the thickness of the third layer.
2. The separator according to claim 1, wherein the total thickness of the separator is 1.5 mm or less.
3. The separator according to claim 1 or 2, wherein the average pore diameter of at least one selected from the group consisting of the first layer and the second layer is 1 to 10 µm.
4. The separator according to any one of claims 1 to 3, wherein the average pore diameter of the third layer is 5 to 20 µm.
5. The ratio Ta/Tb of the thickness Ta of at least one selected from the group consisting of the first layer and the second layer to the thickness Tb of the third layer is 0.1 to 3. The separator according to any one of to 4.
6. The separator according to any one of claims 1 to 5, wherein the thickness of at least one selected from the group consisting of the first layer and the second layer is 0.01 to 1 mm.
7. The separator according to any one of claims 1 to 6, wherein the thickness of the third layer is 0.02 to 2 mm.
8. The separator according to any one of claims 1 to 7, wherein the separator contains glass fiber and an organic binder.
9. The separator according to claim 8, wherein the organic binder includes polypropylene.
10. The separator according to any one of claims 1 to 9, wherein the separator comprises the first layer, the second layer and the third layer.
11. A positive electrode, a negative electrode, and the separator according to any one of claims 1 to 10,
    A lead storage battery, wherein the separator is disposed between the positive electrode and the negative electrode.

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