WO2022255443A1

WO2022255443A1 - Separator for lead-acid battery, and lead-acid battery including same

Info

Publication number: WO2022255443A1
Application number: PCT/JP2022/022453
Authority: WO
Inventors: 悦子伊藤; 和成安藤; 創太福田; 敏宏吉田
Original assignee: 株式会社Ｇｓユアサ
Priority date: 2021-06-04
Filing date: 2022-06-02
Publication date: 2022-12-08

Abstract

This separator for a lead-acid battery comprises a porous film. The porous film has a crystalline region and an amorphous region. In an X-ray diffraction spectrum of the porous film, a crystallinity degree represented by 100 × I_c/(I_c + I_a) is greater than or equal to 20%. I_c is the integrated intensity of a diffraction peak having a greatest peak height among diffraction peaks corresponding to the crystalline region. I_a is the integrated intensity of a halo corresponding to the amorphous region.

Description

Separator for lead-acid battery and lead-acid battery including the same

The present invention relates to a lead-acid battery separator and a lead-acid battery including the same.

Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. A lead-acid battery includes a positive plate and a negative plate, a separator interposed therebetween, and an electrolyte. Various performances are required for separators of lead-acid batteries.

In Patent Document 1, a raw material composition comprising a mixture of 20 to 60% by mass of polyolefin resin, 80 to 40% by mass of inorganic powder, and 40 to 240% by mass of mineral oil is heated. After being melted and kneaded, it is molded into a sheet having ribs, then immersed in an immersion tank of an organic solvent capable of dissolving the oil to extract and remove a portion of the oil, followed by heating and drying. A ribbed separator for a lead-acid battery containing 5 to 30% by mass of oil, wherein the difference in oil content between the rib portion and the base portion of the separator is 5% by mass or less. is suggesting.

US Pat. No. 5,300,009 is a separator for lead-acid batteries comprising a polyolefin microporous membrane, said polyolefin microporous membrane comprising polyethylene, preferably ultra-high molecular weight polyethylene, particulate fillers, and treated plasticizers. and wherein the particulate filler is present in an amount of 40% or more by weight, and the polyethylene comprises a shish kebab forming comprising a plurality of extended chain crystals (shish forming) and a plurality of folded chain crystals (kebab forming). wherein the average repetition or period of said kebab formation is between 1 nm and 150 nm, preferably less than 120 nm.

A porous film and a glass mat may be used together as a separator. For example, Patent Document 3 discloses a lead-acid battery comprising a positive electrode plate, a negative electrode plate, an electrolytic solution, and a separator, wherein the separator comprises a porous sheet and a glass mat, and the electrolytic solution contains 0.02 mol/L or more of aluminum ions. A lead-acid battery containing 0.2 mol/L or less and containing 0.02 mol/L or more and 0.2 mol/L or less of lithium ions is proposed.

Patent Document 4 discloses a lead-acid battery in which a separator, which is a laminate of a porous resin thin film and a glass mat, is interposed between a positive electrode plate and a negative electrode plate. , (a) a plurality of ribs are provided on at least one side of the base portion of the synthetic resin thin film, (b) a glass mat is attached between the ribs, and (c) the ribs on both ends are also provided outside the ribs. and (d) when the glass mat is adhered to the base portion of the synthetic resin thin film, the surface of the glass mat on the opposite side of the adhered surface is inclined from the top surface of the rib portion. (e) the separator having the glass mat attached to the synthetic resin thin film is inserted into the electrode plate group and housed in the container of the lead-acid battery, the rib portion is attached to the positive electrode plate. A lead-acid battery is proposed in which the glass mat is pressurized and compressed until it abuts, and the stacking pressure is 10 to 60 kPa.

Patent Document 5 describes "a lead-acid battery separator, the lead-acid battery separator comprising a porous membrane and/or a fibrous mat, and one or more A lead-acid battery separator comprising a conductive element or nucleating additive."

JP-A-2001-338631 Japanese Patent Publication No. 2019-514173 JP 2013-84362 A JP 2016-139455 A Japanese Patent Publication No. 2020-533741

In a lead-acid battery, the positive electrode plate contains lead dioxide, which has a strong oxidizing power, as a positive electrode active material. In an overcharged lead-acid battery, the potential of the positive plate is high. Therefore, the separator facing the positive electrode plate is easily oxidized and deteriorated. Oxidative deterioration of the separator during overcharging is particularly noticeable at high temperatures (for example, temperatures of 75° C. or higher). In a lead-acid battery, when the separator is oxidatively degraded, the flexibility is reduced, cracks are generated, and short circuiting occurs, resulting in the end of the life.

A separator for a lead-acid battery may have ribs on the surface facing the positive electrode plate, or may contain oil as a pore-forming agent. Such a separator can suppress oxidative deterioration to some extent, and is therefore advantageous from the viewpoint of ensuring high high-temperature overcharge life performance. However, with the changes in the use environment and usage patterns of lead-acid batteries, the separators for lead-acid batteries are required to have even higher high-temperature overcharge life performance.

One aspect of the present disclosure is a lead-acid battery separator comprising:
the separator comprises a porous film, the porous film comprising a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the porous film, the degree of crystallinity represented by 100×I _c /(I _c +I _a ) is 20% or more,
I _c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region;
I _a relates to the lead-acid battery separator, which is the integrated intensity of the halo corresponding to the amorphous region.

Provide a separator that can improve high-temperature overcharge life performance in lead-acid batteries.

BRIEF DESCRIPTION OF THE DRAWINGS It is a partially cutaway perspective view which shows the external appearance and internal structure of the lead storage battery which concerns on one Embodiment of this invention. 1 is an X-ray diffraction spectrum of a porous film used for a lead-acid battery separator of an example. 5 is a graph showing the relationship between the total Vt of the volume of the first pores of the porous film used for the separator of each lead-acid battery of Example 2 and the IS life performance. FIG. 2 is a schematic plan view of the lead-acid battery separator of FIG. 1 ; 10 is a graph showing part of the results of Experimental Example 3 of Example 4. FIG. 10 is a graph showing another part of the results of Experimental Example 3 of Example 4. FIG.

　Lead-acid batteries may be used under harsh conditions. One of the typical uses of lead-acid batteries is for automobiles. In recent years, automobiles have been caught in traffic jams and are used constantly like commercial vehicles, increasing the chances that lead-acid batteries are exposed to an overcharged state. Hereinafter, life performance when exposed to an overcharged state at a high temperature (for example, a temperature of 75° C. or higher) may be referred to as high-temperature overcharge life performance. In addition, with global warming, opportunities to use lead-acid batteries in higher temperature environments in summer are increasing. Therefore, in recent years, lead-acid batteries are required to have a higher level of high-temperature overcharge life performance than ever before.

When ribs are provided on the surface of the porous film that constitutes the separator, facing the positive electrode plate, a gap is formed between the separator and the positive electrode plate, which tends to reduce oxidative deterioration of the porous film. However, as the performance of lead-acid batteries has improved, it has become common to accommodate a large number of small-thickness plates in each cell. is insufficient to suppress Even when the porous film contains oil, oxidative deterioration of the porous film can be reduced to some extent. However, since the insulating oil clogs the pores of the porous film, the resistance of the separator tends to increase and the reactivity of the electrode plate tends to decrease. Therefore, it is difficult to increase the content of oil in the porous film in high-performance lead-acid batteries. Thus, with conventional separators, it is difficult to improve the high-temperature overcharge life performance of lead-acid batteries to a high level.

In view of the above, a lead-acid battery separator according to one aspect of the present invention includes a porous film, the porous film including crystalline regions and amorphous regions. In the X-ray diffraction (XRD) spectrum of the porous film, the crystallinity expressed by 100×I _c /(I _c +I _a ) is 20% or more. Here, I _c is the integrated intensity of the diffraction peak having the maximum peak height (hereinafter sometimes referred to as the first diffraction peak) among the diffraction peaks corresponding to the crystalline region. _Ia is the integrated intensity of the halo corresponding to the amorphous region.

Because the crystallinity of the porous film is 20% or more, the oxidation resistance of the porous film can be improved, and the oxidation resistance of the separator itself can be improved. In this case, unlike the case of the conventional oil-containing separator, even if the oxidation resistance is enhanced, there is almost no contradiction such as an increase in resistance. Therefore, even a high-performance lead-acid battery can ensure excellent high-temperature overcharge life performance.

A separator for a lead-acid battery has a relatively large thickness, unlike a separator for a lithium-ion secondary battery. In addition, compared to lithium-ion secondary batteries, lead-acid batteries have a lower positive electrode potential when overcharged, so sufficient oxidation resistance could be ensured by ribs, oil, etc. in conventional usage environments and usage patterns. . In addition, the thicker the separator, the more difficult it becomes to increase the degree of crystallinity, and the higher the degree of crystallinity, the harder and more brittle the separator tends to be. From this point of view, in conventional separators for lead-acid batteries, the crystallinity of the porous film contained in the separator has not been controlled. The crystallinity of porous films included in separators for conventional lead-acid batteries tends to be relatively low, about 18% or less. Contrary to such conventional wisdom, in the lead-acid battery separator of one aspect of the present invention, it has become clear that the high-temperature overcharge life performance can be greatly improved by setting the crystallinity of the porous film to 20% or more. rice field.

The thickness of the porous film is preferably 100 µm or more and 300 µm or less. When the thickness is within such a range, the effect of suppressing oxidative deterioration of the porous film contained in the separator is further enhanced, and the high-temperature overcharge life performance can be further improved.

The crystallinity of the porous film is preferably 40% or less. In this case, it is easy to secure the flexibility of the separator, and in addition, it is easy to manufacture.

The porous film preferably contains oil. In this case, the effect of suppressing oxidative deterioration of the porous film contained in the separator is further enhanced, and higher high-temperature overcharge life performance can be ensured.

The porous film preferably contains polyolefin, and more preferably contains polyolefin containing at least ethylene units. Such a porous film is easily oxidatively deteriorated, but the degree of crystallinity can be increased relatively easily. When the porous film comprises a polyolefin containing at least ethylene units, the first diffraction peak corresponds to the (110) plane due to the crystalline regions.

In the porous film, the total Vt of the volume of pores (first pores) having a pore diameter of 0.005 μm or more and 10 μm or less may be 0.8 cm ³ /g or more. Hereinafter, the total volume Vt of the first pores may be simply referred to as the first pore volume Vt.

In lead-acid batteries, sulfate ions, which have a large specific gravity, descend during charging, and stratification is likely to occur, where a difference in the specific gravity of the electrolyte (that is, the difference in the concentration of sulfuric acid) occurs between the upper and lower parts of the battery case. Stratification becomes noticeable when lead-acid batteries are used in an undercharged state called partial state of charge (PSOC). For example, in IS applications such as idling start-stop (ISS) vehicles or charge control applications, lead-acid batteries are used in PSOCs, so stratification is likely to be noticeable. When the stratification becomes significant, the positive electrode plate deteriorates, and the life performance (also referred to as IS life performance) of the lead-acid battery when used in a PSOC decreases.

When the pore volume of the porous film increases, the diffusibility of the electrolytic solution improves, which is advantageous from the viewpoint of suppressing stratification. However, since the contact area with the electrolytic solution increases, oxidation deterioration of the porous film tends to progress. Damage to the separator due to oxidative deterioration of the porous film causes a short circuit and shortens the life of the separator, so the effect of improving the IS life performance is limited.

Here, the lead-acid battery separator of one aspect of the present invention includes a porous film, the porous film includes a crystalline region and an amorphous region, and the crystallinity of the porous film is 20% or more. And when the total Vt of the volume of the first pores in the porous film (first pore volume Vt) is 0.8 cm ³ /g or more, high diffusibility of the electrolytic solution can be obtained and the resistance of the separator can be reduced. can be kept low. Therefore, the effect of suppressing stratification is enhanced, and the charging and discharging reactions can be performed smoothly. However, when the first pore volume Vt is within the above range, the contact area with the electrolytic solution increases, so that the oxidation deterioration of the porous film tends to progress easily. In a lead-acid battery, when the porous film is oxidatively degraded, the flexibility is reduced, cracks are generated, and short circuiting occurs, resulting in the end of the life of the battery. Even if stratification can be reduced, it is difficult to improve IS lifetime performance. On the other hand, in the separator according to the aspect of the present invention, since the crystallinity of the porous film is 20% or more, the oxidation resistance of the porous film itself can be enhanced. Therefore, by reducing oxidation deterioration of the porous film, deterioration of IS life performance due to short circuit is suppressed, and the effect of improving IS life performance by suppressing stratification is sufficiently exhibited. Therefore, excellent IS life performance can be secured.

Note that when the first pore volume Vt is less than 0.8 cm ³ /g, even if the degree of crystallinity is changed, the IS life performance hardly changes. In this case, since the surface area of the porous film is small, the contact with the electrolytic solution is reduced, and oxidative deterioration is suppressed. Therefore, it is considered that increasing the crystallinity of the porous film does not affect the IS life performance. Thus, when the first pore volume Vt is less than 0.8 cm ³ /g and when it is 0.8 cm ³ /g or more, the behavior of the IS life performance when changing the crystallinity of the porous film is completely different. In the lead-acid battery separator of one aspect of the present invention, when the first pore volume Vt is 0.8 cm ³ /g or more, the IS life performance can be greatly improved by setting the crystallinity to 20% or more. It became clear.

The total Vt of the volume of the first pores in the porous film (first pore volume Vt) is the first pores in the porous film obtained by the mercury intrusion method (pore diameter of 0.005 μm or more and 10 μm or less It is the sum of the volume of pores).

The first pore volume Vt is preferably 0.9 cm ³ /g or more. In this case, the effect of improving the IS life performance by setting the degree of crystallinity to 20% or more is particularly remarkable.

The crystallinity of the porous film is preferably 25% or more. In this case, since the oxidation resistance of the porous film is further enhanced, and the oxidation resistance of the separator is further enhanced, the IS life performance can be further improved.

The separator may include a laminate of a porous resin film and a glass fiber mat.

　Lead-acid batteries may be used under harsh conditions. One of the typical uses of lead-acid batteries is for automobiles. In recent years, automobiles have been caught in traffic jams and are used constantly like commercial vehicles, increasing the chances that lead-acid batteries are exposed to an overcharged state. In addition, with global warming, opportunities to use lead-acid batteries in higher temperature environments in summer are increasing. In addition, when exposed to an overcharged state in a high-temperature environment, the softening of the positive electrode material becomes noticeable, and the positive electrode material falls off due to vibration, shortening the life of the separator. As a result, a short circuit occurs and the life of the battery is shortened. Therefore, in recent years, lead-acid batteries are required to have a higher level of high-temperature overcharge life performance than ever before.

In a lead-acid battery, repeated charging and discharging softens the positive electrode material. Providing a glass fiber mat as in

Patent Documents

3 and 4 is advantageous in reducing falling off of the softened positive electrode material. However, since the separator, which is a laminate, has a higher resistance than the case of only the porous film, the cold cranking current (CCA) performance is lowered. Reducing the thickness of the porous film can reduce the deterioration of CCA performance. However, since the thickness of the glass fiber mat is not so large, the dropped positive electrode material or the edge of the current collector easily penetrates the glass fiber mat. If the thickness of the porous film that constitutes the laminate is small, the porous film will be torn and short-circuited, shortening the service life.

In lead-acid batteries, when overcharged, the oxidizing power of the positive electrode active material increases, and oxidation progresses more easily at high temperatures. Therefore, when the battery is overcharged at a high temperature (for example, 75° C. or higher), the porous film is likely to be oxidized, and the life performance is likely to be reduced. When the separator contains an oil such as a pore-forming agent, deterioration of the porous film due to oxidation can be reduced to some extent. However, since the insulating oil clogs the pores of the separator, the resistance of the separator increases, and the cold cranking current (CCA) performance tends to decrease. Therefore, it is difficult to increase the content of oil in the separator in high-performance lead-acid batteries that require high CCA performance. Moreover, when a glass fiber mat is used together with the porous film, the falling off of the positive electrode material can be suppressed to some extent by the glass fiber mat. However, it is difficult to completely prevent the falling off of the positive electrode material. Furthermore, the separator, which is a laminate, has a higher resistance than the porous film alone, so the CCA performance is lowered. Reducing the thickness of the porous film can reduce the deterioration of CCA performance. However, since the thickness of the glass fiber mat is not so great, the dropped positive electrode material may penetrate the glass fiber mat. When the positive electrode material comes into contact with the porous film, the porous film is torn due to oxidative deterioration, causing a short circuit and shortening the service life. Thus, with conventional separators, it is difficult to improve the high-temperature overcharge life performance of lead-acid batteries to a high level.

In view of the above, when the lead-acid battery separator of one aspect of the present invention includes a laminate of a resin porous film and a glass fiber mat, the crystallinity of the porous film is 20% or more. The oxidation resistance of the porous film itself can be improved. Therefore, even if the dropped high-potential positive electrode material penetrates the glass fiber mat and comes into contact with the porous film during high-temperature overcharging, breakage due to oxidative deterioration is suppressed, and the occurrence of a short circuit can be suppressed. As a result, the high temperature overcharge life performance can be improved. Even if the thickness of the porous film is reduced, deterioration of the porous film due to oxidation can be suppressed, so deterioration of the CCA performance can be suppressed. Therefore, it is possible to ensure excellent high-temperature overcharge life performance while ensuring high CCA performance. In other words, when increasing the crystallinity of the porous film, there is almost no contradiction such as increasing the resistance even if the oxidation resistance is increased, as in the case of increasing the oil content of the conventional separator. Therefore, even a high-performance lead-acid battery can ensure excellent high-temperature overcharge life performance.

In addition, the porous film itself may be used as a separator for lead-acid batteries. Porous film separators for lead-acid batteries have a relatively large thickness, unlike separators for lithium-ion secondary batteries and the like. In addition, lead-acid batteries have a lower positive electrode potential when overcharged than lithium-ion secondary batteries, so sufficient oxidation resistance could be secured by oil or the like in conventional usage environments and usage patterns. In addition, as the thickness of the porous film increases, it tends to become more difficult to increase the degree of crystallinity. From this point of view, the degree of crystallinity has not been controlled in conventional separators for lead-acid batteries. The crystallinity of porous films used in separators for conventional lead-acid batteries tends to be relatively low, about 18% or less. Contrary to such conventional wisdom, in the lead-acid battery separator of one aspect of the present invention, the crystallinity of the porous film laminated with the glass fiber mat is 20% or more, thereby reducing the resistance of the porous film. In addition, high oxidation resistance can be secured while suppressing the increase in the resistance of the laminate with the glass fiber mat.

The thickness of the porous film is preferably 100 μm or more. When the thickness is within such a range, the effect of suppressing oxidative deterioration is further enhanced, and higher high-temperature overcharge life performance can be ensured. The thickness of the porous film is preferably 300 μm or less. In this case, it is easy to keep the resistance of the porous film low, so relatively high CCA performance can be easily obtained.

The porous film may have a region not covered with the glass fiber mat at least part of the edge. In such a region, the dropped positive electrode material sticks into the porous film or comes into contact with the porous film and oxidizes and deteriorates, resulting in short circuit and deterioration in high-temperature overcharge life performance. However, even in such a case, since the porous film has a high degree of crystallinity, the oxidation resistance of the porous film can be improved. A decrease in charge life performance can be reduced.

A lead-acid battery separator according to one aspect of the present invention may include a porous film and a carbon material disposed on its surface.

The life of a lead-acid battery is also greatly reduced by uneven concentration of the electrolyte (stratification). In lead-acid batteries, the concentration of the electrolyte at the top of the battery can be lower than the concentration of the electrolyte at the bottom, thereby reducing battery life performance.

When the separator of the present embodiment includes a carbon material disposed on the surface of the porous film, this carbon material contacts the electrode (positive electrode or negative electrode) in the lead-acid battery and is thus electrically connected to the electrode. . As a result, when the lead-acid battery is charged (for example, at the end of charging), water can be electrolyzed on the surface of the carbon material to generate gas. Since the electrolytic solution is stirred by the generated gas, stratification of the electrolytic solution is suppressed.

However, when electrolysis of water occurs on the surface of the separator, it is important to suppress the oxidation of the porous film by the generated oxygen gas. Since the separator of the present embodiment uses a porous film with a high degree of crystallinity, it is possible to suppress oxidation of the porous film.

In addition, lead-acid batteries are being improved in performance by using a large number of thin electrode plates. A lead-acid battery using a large number of thin plates has a high rate of defects during manufacturing due to insufficient strength of the separator. Therefore, increasing the strength of the separator is particularly important for improving the reliability and productivity of high-performance lead-acid batteries.

The inventors of the present application have found that a separator having unexpected strength can be obtained by combining a porous film with a high degree of crystallinity and a carbon material. That is, according to the separator of the present embodiment, it is possible to configure a high-performance lead-acid battery with high life performance and high productivity.

The present invention also includes a lead-acid battery containing the lead-acid battery separator described above. A lead-acid battery includes at least one cell that includes a plate assembly and an electrolyte, and the plate assembly includes a positive plate, a negative plate, and the above separator interposed between the positive plate and the negative plate. By including the above separator, the high-temperature overcharge life performance of the lead-acid battery can be significantly improved.
When the separator includes a laminate of a resin porous film and a glass fiber mat, the glass fiber mat may be in contact with the positive electrode plate. By using the laminate, the resistance of the separator can be kept low, and high CCA performance can be ensured. By obtaining high oxidation resistance of the porous film, it is possible to suppress the tearing of the porous film due to the dropped positive electrode material, and the occurrence of short circuit is suppressed, so that excellent high-temperature overcharge life performance is secured. can be done.
When the separator includes a porous film and a carbon material disposed on its surface, the carbon material may be disposed on both of the two main surfaces of the porous film, or on the positive electrode plate side or the negative electrode plate side. It may be arranged on the main surface of the side. For example, the carbon material of the separator may be arranged on one of the two main surfaces of the porous film, which faces the negative electrode plate. When electrolysis of water occurs during charging, oxygen gas is generated on the positive electrode side. By arranging the carbon material on the negative electrode plate side, it is possible to suppress the oxidation of the porous film due to the generation of oxygen gas in the separator.

The lead-acid battery may be a valve-regulated battery, but a liquid battery (vented battery) is preferable. Valve-regulated lead-acid batteries are sometimes called VRLA (Valve Regulated Lead-Acid Battery).

In this specification, the vertical direction of a lead-acid battery or components of a lead-acid battery (electrode plate, container, separator, etc.) means the vertical direction of the lead-acid battery when the lead-acid battery is used. Each of the positive electrode plate and the negative electrode plate has an ear portion for connection with an external terminal. there is

　Hereinafter, the separator and the lead-acid battery according to the embodiments of the present invention will be described more specifically with reference to the drawings. However, the present invention is not limited to the following embodiments.

(separator)
A separator includes a porous film. The porous film may be made of resin. The separator may be a laminate of a resin porous film and a glass fiber mat. The separator may have a carbon material on at least one surface of the porous film.

(porous film)
The porous film includes crystalline regions in which the molecules of the constituent material of the porous film are arranged relatively regularly (ie, highly ordered) and amorphous regions in which the molecules are poorly arranged. Therefore, in the XRD spectrum of the porous film, a diffraction peak due to the crystalline region is observed, and scattered light due to the amorphous region is observed as a halo. Excellent high-temperature overcharge life performance is obtained when the degree of crystallinity represented by 100×I _c /(I _c +I _a ) is 20% or more in the XRD spectrum of the porous film. Here, _Ic is the integrated intensity of the diffraction peak (first diffraction peak) having the maximum peak height among the diffraction peaks corresponding to the crystalline region, and _Ia is the halo corresponding to the amorphous region. is the integrated intensity of

For example, in the XRD spectrum of a porous film containing a polyolefin containing ethylene units, a diffraction peak corresponding to the (110) plane of the crystalline region is observed in the range of 2θ from 20 ° to 22.5 °, and the crystalline A diffraction peak corresponding to the (200) plane of the region is observed in the range of 2θ from 23° to 24.5°. A halo in the amorphous region is observed in the range of 2θ from 17° to 27°. Among the diffraction peaks due to the crystalline region, the diffraction peak corresponding to the (110) plane has the highest peak height and corresponds to the first diffraction peak.

The crystallinity of the porous film is 20% or more, and may be 22% or more, 23% or more, or 25% or more from the viewpoint of ensuring higher high-temperature overcharge life performance. When the first pore volume Vt in the separator is 0.8 cm ³ /g or more, the degree of crystallinity may be 23% or more or 25% or more from the viewpoint of ensuring higher IS life performance. The degree of crystallinity may be 40% or less, 37% or less, 35% or less, or 30% or less. When the degree of crystallinity is within such a range, it is easy to ensure the flexibility of the separator, and the production is easy. The crystallinity of the porous film can be at least any of the above lower limits and at most any of the above upper limits.

The crystallinity of the porous film is 20% or more (or 22% or more) and 40% or less, 20% or more (or 22% or more) and 37% or less, 20% or more (or 22% or more) and 35% or less, 23%. It may be 40% or more (or 37% or less), or 23% or more and 35% or less.

The integrated intensities of the diffraction peaks and halos are obtained by fitting the diffraction peaks due to the crystalline regions and the halos due to the amorphous regions in the XRD spectrum of the porous film. Using the obtained integrated intensity _Ic of the first diffraction peak and the obtained integrated intensity _Ia of the halo, the degree of crystallinity is obtained from the above formula.

The first pore volume Vt in the porous film is preferably 0.8 cm ³ /g or more. By setting the first pore volume Vt within such a range, high diffusibility of the electrolytic solution can be obtained, and the resistance of the separator can be kept low. Therefore, excellent IS life performance is obtained. Also, high CCA (cold cranking current) performance can be ensured. From the viewpoint of ensuring higher IS life performance, the first pore volume Vt is more preferably 0.9 cm ³ /g or more, and even more preferably 1.05 cm ³ /g or more. The first pore volume Vt may be, for example, 2.2 cm ³ /g or less. The first pore volume Vt is preferably 2.0 cm ³ /g or less, more preferably 1.9 cm ³ /g or less, from the viewpoint that the effect of improving the IS life performance by increasing the degree of crystallinity is more likely to be exhibited. . The first pore volume Vt in the porous film can be any lower limit or more and any upper limit or less.

The first pore volume Vt is 0.8 cm ³ /g or more and 2.2 cm ³ /g or less (or 2.0 cm ³ /g or less), 0.9 cm ³ /g or more and 2.2 cm ³ /g or less (or 2 .0 cm ³ /g or less), 1.05 cm ³ /g or more and 2.2 cm ³ /g or less (or 2.0 cm ³ /g or less), 0.8 cm ³ /g or more (or 0.9 cm ³ /g or more) It may be 1.9 cm ³ /g or less, or 1.05 cm ³ /g or more and 1.9 cm ³ /g or less.

A porous film includes, for example, a polymer material (hereinafter also referred to as a base polymer). Since the porous film contains crystalline regions, the base polymer usually contains a crystalline polymer. Porous films include, for example, polyolefins. A polyolefin is a polymer containing at least olefinic units (that is, a polymer containing at least monomeric units derived from an olefin).

A polyolefin and another base polymer may be used in combination as the base polymer. The ratio of polyolefin to the entire base polymer contained in the porous film is, for example, 50% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. The proportion of polyolefin is, for example, 100% by mass or less. The base polymer may consist of polyolefin only. When the ratio of polyolefin is high like this, the porous film tends to be easily deteriorated by oxidation. , high high temperature overcharge life performance can be ensured.

Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefin units, and copolymers containing olefin units and copolymerizable monomer units. A copolymer containing olefin units and copolymerizable monomer units may contain one or more olefin units. Further, the copolymer containing olefin units and copolymerizable monomer units may contain one or more copolymerizable monomer units. A copolymerizable monomer unit is a monomer unit derived from a polymerizable monomer other than an olefin and copolymerizable with an olefin.

Polyolefins include, for example, polymers containing at least C _2-3 olefins as monomer units. The C _2-3 olefin includes at least one selected from the group consisting of ethylene and propylene. More preferred polyolefins are, for example, polyethylene, polypropylene, and copolymers containing C _2-3 olefins as monomer units (eg, ethylene-propylene copolymers). Among polyolefins, it is preferable to use polyolefins containing at least ethylene units (polyethylene, ethylene-propylene copolymer, etc.). Polyolefins containing ethylene units (polyethylene, ethylene-propylene copolymers, etc.) may be used in combination with other polyolefins.

The porous film preferably contains oil. When the porous film contains oil, the effect of suppressing oxidative deterioration of the porous film can be further enhanced, so higher high-temperature overcharge life performance can be ensured. Oil refers to a hydrophobic substance that is liquid at room temperature (20° C. or higher and 35° C. or lower) and separates from water. Oils include naturally derived oils, mineral oils, and synthetic oils. Mineral oil, synthetic oil and the like are preferable as the oil. Examples of oils include paraffin oil and silicone oil. The porous film may contain one type of oil or a combination of two or more types.

The oil content in the porous film may be 11% by mass or more or 12% by mass or more. The oil content is preferably 18% by mass or less. When the oil content is within this range, the effect of suppressing oxidative deterioration of the porous film is further enhanced. Also, the resistance of the separator can be kept relatively low.

The porous film may be sheet-like. Alternatively, a sheet-like porous film may be used as a separator by folding in a bellows shape. The porous film may be formed into a bag shape. Either one of the positive electrode plate and the negative electrode plate may be housed in a bag-like porous film.

The porous film may or may not have ribs. A porous film having ribs includes, for example, a base portion and ribs erected from the surface of the base portion. The ribs may be provided only on one surface of the porous film or each base portion, or may be provided on both surfaces. The base portion of the porous film is a portion excluding projections such as ribs among constituent portions of the porous film, and refers to a sheet-like portion that defines the outer shape of the porous film.

The thickness of the porous film is, for example, 90 μm or more. From the viewpoint of obtaining higher high-temperature overcharge life performance, the thickness is preferably 100 μm or more or 150 μm or more. The thickness of the porous film is, for example, 300 μm or less. From the viewpoint of keeping the resistance of the separator low, the thickness of the porous film may be 250 μm or less, 200 μm or less, or 150 μm or less. Even with such a small thickness of the porous film, sufficient oxidation resistance can be obtained, and high high-temperature overcharge life performance can be ensured. . The thickness of the porous film means the average thickness of the portion of the porous film facing the electrode material. When the porous film has a base portion and ribs erected from at least one surface of the base portion, the thickness of the porous film is the average thickness of the base portion.

The thickness of the porous film is 90 μm or more and 300 μm or less (or 250 μm or less), 90 μm or more and 200 μm or less, 100 μm or more (or 150 μm or more) and 300 μm or less, 100 μm or more (or 150 μm or more) and 250 μm or less, or 100 μm or more (or 150 μm or more). ) may be 200 μm or less.

When the porous film has ribs, the rib height may be 0.05 mm or more. Also, the rib height may be 1.2 mm or less. The height of the rib is the height of the portion that protrudes from the surface of the base portion (protrusion height).

The height of the ribs provided in the region facing the positive electrode plate of the porous film may be 0.4 mm or more. The height of the rib provided in the region of the porous film facing the positive electrode plate may be 1.2 mm or less.

When the separator is a laminate of a porous film and a glass fiber mat, the ribs of the porous film may be provided on the surface of the negative electrode plate. In this case, the ribs are preferably provided on the portion of the porous film facing the negative electrode material. Providing ribs on the negative electrode plate side facilitates the diffusion of the electrolytic solution. The height of the ribs provided on the negative electrode plate side is, for example, 50 μm or more. The rib height may be, for example, 400 μm or less or 300 μm or less.

When the separator is a laminate of a porous film and a glass fiber mat, and ribs are provided on the positive electrode plate side of the porous film, they may be provided in areas not covered with the glass fiber mat. When ribs are provided in the portion facing the positive electrode material, a glass fiber mat may be arranged between adjacent ribs as in Patent Document 2. However, considering the ease of lamination with the glass fiber mat, it is not necessary to provide ribs on the positive electrode plate side of the porous film.

When the separator is a laminate of a porous film and a glass fiber mat, the porous film may have a region not covered with the glass fiber mat at least part of the edge. In the state of high-temperature overcharge, when the dropped high-potential positive electrode material comes into contact with this region, the porous film is oxidized and deteriorated, or the positive electrode material bites into the porous film, causing the porous film to break. A short circuit occurs, and it is easy to reach the end of life. However, in the aspect of the present invention, even in such a case, oxidation deterioration and breakage of the porous film are suppressed by increasing the oxidation resistance of the porous film, and the occurrence of short circuits can be suppressed. A porous film is roughly square and usually has four edges: top and bottom edges and both side edges. At one end, the width of the region of the porous film not covered with the glass fiber mat (for example, w _p in FIG. 4 described below) is, for example, 1 mm or more, and may be 2 mm or more. The width of this region is, for example, 5 mm or less, and may be 4.5 mm or less or 4 mm or less. The porous film may have areas on the side edges (preferably on both side edges) that are not covered with the glass fiber mat. When the bag-like porous film and the glass fiber mat are laminated, a predetermined region of the side end including the bag-like crimped portion is exposed outside the glass fiber mat.

The width of the above region may be 1 mm or more (or 2 mm or more) and 5 mm or less, 1 mm or more (or 2 mm or more) and 4.5 mm or less, or 1 mm or more (or 2 mm or more) and 4 mm or less.

A porous film is produced by, for example, extruding a resin composition containing a base polymer, a pore-forming agent, and a penetrating agent (surfactant) into a sheet, stretching the film, and removing at least part of the pore-forming agent. obtained by removing Removal of at least a portion of the pore-forming agent forms micropores in the matrix of the base polymer. The porous film (or the resin composition used for producing the porous film) may contain inorganic particles. When a carbon material is placed on the surface of the porous film, the inorganic particles do not contain the carbon material. After removing the pore-forming agent, the sheet-like porous film is dried if necessary. For example, the degree of crystallinity is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion, the draw ratio during stretching, and the temperature during drying. . For example, the degree of crystallinity tends to increase when the sheet is quenched during extrusion molding, the draw ratio is increased, or the temperature during drying is decreased. The stretching treatment may be carried out by biaxial stretching, but is usually carried out by uniaxial stretching. The sheet-like porous film may be folded into a bellows shape or processed into a bag shape, if necessary.

The pore structure and the first pore volume Vt in the separator control the affinity between the base polymer and the pore-forming agent and/or the penetrating agent, control the dispersibility of the pore-forming agent, and determine the type of inorganic particles. and/or select the particle size, select the type of penetrant, adjust the amount of the inorganic particles, the amount of the pore-forming agent, and/or the amount of the penetrant, and/or the surface of the inorganic particles can be adjusted by adjusting the amount of functional groups and/or atoms present in .

In the porous film having ribs, the ribs may be formed into a sheet when extruding the resin composition. Alternatively, the ribs may be formed by pressing the sheet with a roller having grooves corresponding to the ribs after molding the resin composition into a sheet or after removing the pore-forming agent.

Pore-forming agents include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent preferably contains at least oil. By using oil, an oil-containing porous film is obtained, and the effect of suppressing oxidative deterioration is further enhanced. The pore-forming agents may be used singly or in combination of two or more. Oil and other pore-forming agents may be used in combination. A liquid pore-forming agent and a solid pore-forming agent may be used in combination. At room temperature (20° C. or higher and 35° C. or lower), a liquid pore-forming agent is classified as a liquid pore-forming agent, and a solid pore-forming agent as a solid pore-forming agent.

The above-mentioned oil is preferable as the liquid pore-forming agent. Solid pore formers include, for example, polymer powders.

　The amount of pore-forming agent in the porous film may vary depending on the type. The amount of the pore-forming agent in the porous film is, for example, 30 parts by weight or more per 100 parts by weight of the base polymer. The amount of the pore-forming agent is, for example, 60 parts by weight or less per 100 parts by weight of the base polymer.

For example, a porous film containing oil is formed by extracting and removing part of the oil from a sheet formed using oil as a pore-forming agent using a solvent. A solvent is selected, for example, according to the type of oil. For example, the oil content in the porous film can be adjusted by adjusting the type and composition of the solvent, extraction conditions (extraction time, extraction temperature, speed of supplying the solvent, etc.).

The surfactant as a penetrant may be, for example, either an ionic surfactant or a nonionic surfactant. Surfactants may be used alone or in combination of two or more.

The content of the penetrant in the porous film is, for example, 0.01% by mass or more, and may be 0.1% by mass or more. The content of the penetrant in the porous film may be 10% by mass or less.

As the inorganic particles, for example, ceramic particles are preferable. Ceramics constituting the ceramic particles include, for example, at least one selected from the group consisting of silica, alumina, and titania.

The content of inorganic particles in the separator may be, for example, 40% by mass or more. The content of inorganic particles is, for example, 80% by mass or less, and may be 70% by mass or less.

(glass fiber mat)
The glass fiber mat may be laminated on the surface of the porous film facing the positive electrode plate. For example, a bag-shaped porous film may have a glass fiber mat laminated to both outer surfaces of the bag. For example, when the electrode plate at the end of the electrode plate group is the negative electrode plate, the bag-shaped porous film containing this negative electrode plate has a glass fiber mat laminated on the surface of the side facing the positive electrode plate, and the positive electrode plate is formed. The porous film may be exposed on the surface that does not face the plate.

A glass fiber mat is a mat (or non-woven fabric) made of glass fiber. The glass fiber mat may be a material called Absorbed Glass Mat (AGM).

The glass fiber mat may be entirely made of glass fiber. The glass fiber mat may contain glass fibers as a main component. The glass fiber content in the glass fiber mat may be 90% by mass or more or 95% by mass or more. The content of glass fibers in the glass fiber mat is 100% by mass or less. The glass fiber mat may contain components other than glass fibers, such as organic fibers, acid-resistant inorganic powders, and polymers as binders, but their content is usually 10% by mass or less or 5% by mass. % by mass or less.

The average fiber diameter of the glass fiber is, for example, 0.1 μm or more, and may be 0.5 μm or more. When the average fiber diameter of the glass fibers is within such a range, the effect of suppressing falling off of the softened positive electrode material is enhanced. The average fiber diameter of the glass fibers is, for example, 30 μm or less, and may be 10 μm or less. In this case, an excessive increase in the internal resistance of the battery can be suppressed. In addition, it is possible to secure relatively high flexibility of the glass fiber mat, and it is easy to hold a relatively large amount of electrolytic solution.

The average fiber diameter of the glass fiber may be 0.1 μm or more (or 0.5 μm or more) and 30 μm or less, or 0.1 μm or more (or 0.5 μm or more) and 10 μm or less.

The surface density of the glass fiber mat is, for example, 100 g/m ² or more. The surface density of the glass fiber mat may be 250 g/m ² or less, or 200 g/m ² or less.

A separator that is a laminate of a porous film and a glass fiber mat is obtained, for example, by laminating a porous film and a glass fiber mat. More specifically, the separator may be formed by laminating a glass fiber mat on the surface of the porous film facing the positive electrode plate. The porous film and the glass fiber mat may be simply placed on top of each other, or may be laminated (or fixed) using an adhesive. Alternatively, the porous film and the glass fiber mat may be laminated (or fixed) using welding (heat sealing, etc.) or mechanical adhesion methods (gear sealing, etc.). Examples of adhesives include silicone-based adhesives, epoxy-based adhesives, and polyolefin-based adhesives. It is preferable that the amount of the adhesive applied is small so as not to increase the resistance of the separator. For example, it is preferable to apply the adhesive to a portion of the porous film or fiberglass mat rather than to the entire surface to be adhered.

(carbon material)
A conductive carbon material can be used as the carbon material. Examples of conductive carbon materials include graphite, activated carbon, conductive carbon black, carbon fibers, carbon nanotubes, and the like. Examples of conductive carbon black include acetylene black, ketjen black, high surface area carbon black, and the like. From the viewpoint of productivity, it is preferable to use carbon black, and for example, it is preferable to use acetylene black, high surface area carbon black, and ketjen black. The carbon material may be at least one selected from the group consisting of conductive carbon black and conductive carbon fiber. The carbon material may be layered on the surface of the porous film. A method of arranging the carbon material will be described later.

Of the two main surfaces of the porous film, the carbon material may be arranged only on one main surface (the main surface on the positive electrode plate side or the main surface on the negative electrode plate side), or may be arranged on both main surfaces. may In other words, the carbon material is present on at least one surface of the separator. In one preferred example, the carbon material is arranged only on one major surface of the porous film. As will be described later, the carbon material may be arranged only on the main surface of the porous film on the negative electrode plate side.

The carbon material may be arranged in layers so as to cover the main surface of the porous film, or may be arranged in a non-layered form. Examples of non-layered morphologies include morphologies arranged in discrete islands. The thickness of the layer of carbon material may be in the range of 5 μm to 30 μm (eg in the range of 10 μm to 20 μm). The thickness of the carbon material layer can be measured in the same manner as the thickness of the separator.

The content of the carbon material (the carbon material placed on the surface of the porous film) in the separator may be 2% by mass or more, preferably 3% by mass or more. By setting the content to 2% by mass or more, it is possible to particularly improve the oxidation resistance and strength of the separator. The content may be 40% by mass or less, or 30% by mass or less.

There is no particular limitation on the method of arranging the carbon material on the surface of the porous film. For example, the carbon material may be formed by applying a carbon material, a composition containing the carbon material, or a dispersion containing the carbon material to the surface of the porous film. The coating method is not particularly limited, and a doctor blade method, roller coating method, spray coating method, dipping method, vapor deposition method, other printing methods, and the like may be used. Examples of dispersions containing carbon materials include dispersions in which carbon materials are dispersed in a dispersion medium (water and/or organic solvent). The amount and thickness of the carbon material placed on the surface of the porous film can be adjusted by controlling the amount of the applied carbon material.

(analysis or size measurement of porous films and fiberglass mats)
(Preparation of separator)
For the analysis or size measurement of the porous film or glass fiber mat, an unused separator or a separator taken from a fully charged lead-acid battery at the beginning of use is used. Separators removed from lead-acid batteries are washed and dried prior to analysis or measurement. The measurement of the XRD spectrum of the porous film is performed using a porous film on which nothing is placed on the surface if the porous film is available before the glass fiber mat or carbon material is placed on the surface. may Further, the measurement of the XRD spectrum of the porous film having the glass fiber mat or the carbon material arranged only on one side may be performed using the surface on which the glass fiber mat or the carbon material is not arranged.

　The separator removed from the lead-acid battery is washed and dried according to the following procedure. The separator taken out from the lead-acid battery is immersed in pure water for 1 hour to remove the sulfuric acid in the separator. Next, the separator is taken out from the liquid in which it was immersed, left to stand in an environment of 25° C.±5° C. for 16 hours or longer, and dried.

In this specification, the fully charged state of a liquid lead-acid battery is defined by the definition of JIS D 5301:2019. More specifically, the terminal voltage (V ) or the fully charged state is the state in which the electrolyte solution density converted to temperature at 20° C. is charged three times consecutively until it shows a constant value with three significant digits. 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 . The numerical value described as the rated capacity is a numerical value whose unit is Ah (ampere hour). The unit of current set based on the numerical value described as the rated capacity is A (ampere).

A fully charged lead-acid battery is a fully-charged lead-acid battery that has already been chemically formed. 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).

In this specification, the term "battery in the early stage of use" means a battery that has not undergone much deterioration since the start of use and has not deteriorated.

(XRD spectrum)
The XRD spectrum of the porous film is measured by irradiating X-rays in the direction perpendicular to the surface of the porous film facing the positive electrode plate in the separator. When the separator is composed only of a porous film, a sample for measurement is produced by processing the portion of the separator facing the electrode material into a strip shape. When the separator is a laminate of a porous film and a glass fiber mat, the sample for measurement is obtained by peeling off the glass fiber mat from the porous film and processing the area where the adhesive is not applied into strips. It is made by For separators or porous films that have ribs on the surface facing the positive plate, the sample is processed so that it does not contain ribs. For separators having carbon material on both sides, the carbon material is removed by polishing, and then the XRD spectrum is measured. Measurement and fitting of the XRD spectrum are performed under the following conditions.
(Measurement condition)
Measuring device: RINT-TTR2, manufactured by Rigaku Fitting: FT (step scan) method Measuring angle range: 15-35°
Step width: 0.02°
Measurement speed: 5°/min
XRD data processing: using XRD pattern analysis software (PDXL2, manufactured by Rigaku).

(First pore volume Vt)
A sample (hereinafter referred to as sample A) is prepared by processing the portion of the porous film facing the electrode material into a strip of 20 mm×5 mm. For the porous film having ribs, Sample A is produced by processing the base into strips so as not to include ribs. When the separator is a laminate of the porous film and the glass fiber mat, the porous film and the glass fiber mat are separated, and in the area where the adhesive is not applied, the part of the separator facing the electrode material is 20 mm × 5 mm. to produce a sample (hereinafter referred to as sample A). For sample A, the pore size distribution is determined using a mercury porosimeter under the following conditions, and Vt is determined by totaling the volumes of the first pores.
Mercury porosimeter: Autopore IV9510, manufactured by Shimadzu Corporation Pressure range for measurement: 4 psia (≈27.6 kPa) to 60,000 psia (≈414 MPa) Pore distribution: 0.01 μm to 50 μm

(Porous film thickness and rib height)
The thickness of the porous film is obtained by measuring the thickness of the porous film portion at five arbitrarily selected points in the cross-sectional photograph of the separator and averaging the measured thicknesses. When the carbon material is provided in layers, the thickness of the layer of the carbon material is obtained in a similar manner.

The height of the rib is obtained by averaging the heights from one surface of the base portion of the rib measured at 10 arbitrarily selected locations of the rib in the cross-sectional photograph of the separator.

(Oil content in porous film)
When the separator is a laminate of a porous film and a glass fiber mat, the glass fiber mat is peeled off from the porous film in the separator. A sample (hereinafter referred to as sample B) is prepared by processing the portion of the separator facing the electrode material into a strip shape in the region where the adhesive is not applied. If the separator has a carbon material on the surface of the porous film, the carbon material is removed by polishing, and the portion of the separator facing the electrode material is processed into a strip shape to prepare Sample B. . When the porous film has ribs, it is processed to produce sample B so as not to include ribs.

About 0.5 g of sample B is taken and weighed accurately to determine the initial sample mass (m0). Place the weighed sample B in an appropriately sized glass beaker and add 50 mL of n-hexane. Next, ultrasonic waves are applied to each beaker for about 30 minutes to elute the oil contained in sample B into n-hexane. Next, a sample is removed from n-hexane, dried in the air at room temperature (20° C. or higher and 35° C. or lower), and weighed to determine the mass (m1) of the sample after oil removal. Then, the oil content is calculated by the following formula. The oil content is determined for 10 samples B, and the average value is calculated. Let the average value obtained be the content rate of the oil in a porous film.
Oil content (% by mass) = (m0-m1)/m0 x 100

(Content of inorganic particles in porous film)
A portion of sample B prepared in the same manner as described above is sampled, accurately weighed, placed in a platinum crucible, and heated with a Bunsen burner until white smoke is no longer emitted. Next, the resulting sample is heated in an electric furnace (550° C.±10° C. in an oxygen stream) for about 1 hour to be ashed, and the ashed matter is weighed. The ratio (percentage) of the mass of the ash to the mass of the sample B is calculated and defined as the inorganic particle content (% by mass). The content of inorganic particles is determined for 10 samples B, and the average value is calculated. Let the obtained average value be the content rate of the inorganic particle in a porous film.

(Content of penetrant in porous film)
A portion of sample B prepared in the same manner as described above is sampled, weighed accurately, and dried at room temperature (20° C. or higher and 35° C. or lower) under a reduced pressure environment lower than atmospheric pressure for 12 hours or more. The dried material is placed in a platinum cell, set in a thermogravimetry device, and heated from room temperature to 800° C.±1° C. at a temperature elevation rate of 10 K/min. The amount of weight loss when the temperature is raised from room temperature to 250°C ± 1°C is taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of sample B is calculated, and the content of the above penetrant. (% by mass). As a thermogravimetry device, T.I. A. Q5000IR manufactured by Instruments is used. The penetrant content is determined for 10 samples B, and the average value is calculated. The obtained average value is defined as the penetrant content in the porous film.

(Average fiber diameter of glass fiber mat)
The average fiber diameter of glass fibers is determined by averaging the maximum diameters of arbitrary cross sections perpendicular to the longitudinal direction of arbitrary 100 fibers taken out from the glass fiber mat portion of the separator.

(Area density of glass fiber mat)
Cut the part facing the electrode material of the separator, collect the part where the adhesive is not applied, weigh it, and measure the vertical and horizontal size of the glass fiber mat part (in other words, the vertical and horizontal size of the cut part) size). The glass fiber mat is peeled off from the cut portion and the mass of the porous film is measured. Subtract the mass of the porous film from the mass of the cut portion to obtain the mass of the glass fiber mat portion. The area is calculated from the vertical and horizontal sizes of the glass fiber mat portion, and the mass (g) of the glass fiber mat portion per 1 m ² is obtained as the areal density.

(Positive plate)
A paste-type positive plate is used as the positive plate. The pasted positive plate comprises a positive current collector and a positive electrode material. 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. In addition, members such as mats and pasting paper may be attached to the electrode plates. Such a member (also referred to as a sticking member) is included in the electrode plate because it is used integrally with the electrode plate. When the positive electrode plate includes the sticking member, the positive electrode material is the portion of the positive electrode plate excluding the positive current collector and the sticking member.

The positive electrode current collector contained in the positive electrode plate may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Processing methods include, for example, expanding processing and punching processing. It is preferable to use a grid-like current collector as the positive electrode current collector because it facilitates carrying the positive electrode material.

Pb--Ca-based alloys and Pb--Ca--Sn-based 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 the alloy layer may be a single layer or a plurality of layers.

The positive electrode material contained in the positive plate contains 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 (such as reinforcing materials) as necessary.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers, etc.). Examples of resins (or polymers) constituting organic fibers include acrylic resins, polyolefin resins (polypropylene resins, polyethylene resins, etc.), polyester resins (including polyalkylene arylates (polyethylene terephthalate, etc.)). , and celluloses (cellulose, cellulose derivatives (cellulose ether, cellulose ester, etc.)). Celluloses also include rayon.

The content of the reinforcing material in the positive electrode material is, for example, 0.03% by mass or more. Moreover, the content of the reinforcing material in the positive electrode material is, for example, 0.5% by mass or less.

An unformed paste-type positive electrode plate is obtained by filling a positive current collector with positive electrode paste, aging and drying. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and optionally other additives (reinforcing material, etc.) and kneading them.

A positive electrode plate can be obtained by chemically forming an unformed positive electrode plate. Formation can be performed by charging the electrode plate group including the unformed positive electrode plate while immersing the electrode plate group in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. However, formation may be performed before assembly of the lead-acid battery or the electrode plate assembly.

(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. In some cases, the above-described attachment member is attached to the negative electrode plate. In this case, the attachment member is included in the negative electrode plate. When the negative plate includes the sticking member, the negative electrode material is the portion of the negative plate excluding the negative current collector and the sticking member.

The negative electrode current collector can be formed in the same manner as the positive electrode current collector. At least one of the positive electrode current collector and the negative electrode current collector may be a current collector formed by an expanding process. In the electrode plate using the current collector formed by expanding, the corners of the electrode plate may be deformed due to interference with the manufacturing equipment during the manufacturing process of the electrode plate. When a lead-acid battery is manufactured using such electrode plates, the corners of the electrode plates are likely to break through the separator at the initial stage, resulting in a short circuit. Since the separator in which the carbon material is arranged on the surface of the porous film has high strength, even when it is combined with the electrode plate using the expanded lattice, it is possible to suppress the initial short circuit due to the deformation of the electrode plate. At least one of the positive plate and the negative plate may contain an expanded lattice.

The lead alloy used for the negative electrode current collector may be any of Pb--Sb-based alloy, Pb--Ca-based alloy, and Pb--Ca--Sn-based alloy. These lead or lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element. The negative electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

The negative electrode material contained in the negative plate contains a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction, and may contain an organic shrinkage agent, carbonaceous material, barium sulfate, and the like. The negative electrode material may contain other additives (such as reinforcing materials) as necessary.

Examples of organic shrink-proofing agents include lignin, lignin sulfonic acid, and synthetic organic shrink-proofing agents (formaldehyde condensates of phenol compounds, etc.). The negative electrode material may contain one kind or two or more kinds of organic expanders.

The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more. The content of the organic shrink-proofing agent is, for example, 1% by mass or less.

Examples of carbonaceous materials in negative electrode materials include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, and soft carbon. The negative electrode material may contain one type of carbonaceous material, or may contain two or more types.

The content of the carbonaceous material in the negative electrode material is, for example, 0.1% by mass or more. The content of the carbonaceous material may be, for example, 3% by mass or less.

The content of barium sulfate in the negative electrode material is, for example, 0.1% by mass or more. The content of barium sulfate is, for example, 3% by mass or less.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers (such as organic fibers made of resin as described for reinforcing materials for positive electrode materials), etc.).

The content of the reinforcing material in the negative electrode material is, for example, 0.03% by mass or more. Moreover, the content of the reinforcing material in the negative electrode material is, for example, 0.5% by mass or less.

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

The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying to prepare an unformed negative electrode plate, and then forming the unformed negative electrode plate. The negative electrode paste is prepared by adding water and sulfuric acid to lead powder, an organic anti-shrinking agent, and optionally various additives, and kneading the mixture. In the aging step, the unformed negative electrode plate is preferably aged at a temperature and humidity higher than room temperature.

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

There is no particular limitation on the number of positive electrode plates and negative electrode plates included in one cell. However, a separator in which a carbon material is arranged on the surface of a porous film is particularly preferably used for a lead-acid battery in which one cell accommodates a large number of positive plates and negative plates, specifically 12 or more sheets in total. . This is because the tensile strength of the separator is particularly important when a total of 12 or more positive electrode plates and negative electrode plates are accommodated in one cell.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid. The electrolytic solution may be gelled if necessary.

The electrolyte may further contain at least one metal ion selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

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

The method for evaluating each characteristic will be described below.
(1) High-temperature overcharge life performance High-temperature overcharge life performance of a lead-acid battery is evaluated based on the life of the lead-acid battery at this time by performing a high-temperature overcharge endurance test in the following procedure.
(a) Place the accumulator in an air bath at 75°C ± 3°C throughout the entire test period.
(b) Connect the storage battery to the life test device and continuously repeat the following discharge and charge cycles. The cycle of this discharge and charge is defined as one lifetime (one cycle).
Discharge: Discharge current 25.0 A ± 0.1 A for 60 seconds ± 1 second Charge: Charge voltage 14.80 V ± 0.03 V (limit current 25.0 A ± 0.1 A) for 600 seconds ± 1 second (c) Under test , and left for 56 hours every 480 cycles, then continuously discharged at a rated cold cranking current of 390 A for 30 seconds, and the voltage at 30 seconds is recorded. After that, charging of (b) is performed. Note that these discharges and charges are also added to the number of lifespans (number of cycles).
(d) The 30th second voltage measured in the test of (c) is 7.2 V or less, and the test is terminated when it is confirmed that it does not rise again. ) is used as an indicator of life performance.
The rated cold cranking current is a measure of engine starting performance, and is the discharge current determined so that the voltage at the 30th second is 7.2 V or more after discharging at a temperature of -18°C ± 1°C. is.

(2) IS life performance The IS life performance of a lead-acid battery is evaluated based on the life of the lead-acid battery at this time by carrying out an IS life test according to the following procedure based on SBA S 0101:2014.
a) Place the accumulator in the gas phase at 25±2° C. throughout the entire test period. The wind velocity in the vicinity of the storage battery shall be 2.0 m/s or less.
b) Connect the storage battery to the life test equipment and perform the following discharges (Discharge 1 and Discharge 2) and charge. This discharge and charge is one cycle of discharge and charge. The cycle of discharge and charge is then repeated continuously.
Discharge: Discharge 1 Discharge current I _D ± 1 A for 59.0 ± 0.2 seconds (where I _D is calculated using the following conversion formula and rounded to the first decimal place. I _D = 18 .3 x _I20 )
Discharge 2 Discharge current 300±1A for 1.0±0.2 seconds Charge: Charge voltage 14.00±0.03V (limit current 100.0±0.5A) for 60.0±0.3 seconds Cycle 3600 After 40-48 hours of rest each time, the cycle is started again. Water retention does not occur until 30,000 cycles.
The final discharge voltage (terminal voltage) of discharge 2 is measured, and the number of cycles until it reaches 7.2 V is obtained, which is used as an index of IS life performance.
_I20 means 20 hour rate current (A).

(3) CCA performance In accordance with JIS D 5301:2006, the startability of a lead-acid battery is evaluated according to the current value at which the terminal voltage becomes 7.2 V or higher 30 seconds after the start of discharge, according to the following procedure. A higher current value means a higher startability and a lower resistance of the separator.
(a) Place the storage battery in a cooling room at -18°C ± 1°C for at least 16 hours after full charge is complete.
(b) After confirming that the temperature of the electrolyte in one of the cells in the center is -18°C ± 1°C, discharge with CCA390A for 30 seconds.
(c) Record the terminal voltage 30 seconds after the start of discharge.

(4) Tensile Strength of Separator The tensile strength of the separator is measured by the following procedure. First, a test piece is obtained by cutting a separator into a size of 10 mm×40 mm. Using a precision universal testing machine (Shimadzu Corporation, product name: AGS-X), this test piece was subjected to a tensile test under the conditions of 20 mm chuck distance, 5 mm/min tensile speed, and 25°C. Tensile strength.

An example of the lead-acid battery according to the present embodiment will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example lead-acid battery described below. Also, the components of the example lead-acid battery described below can be modified based on the above description. Also, the matters described below may be applied to the above embodiments. Further, in the embodiments described below, components that are not essential to the lead-acid battery according to the present embodiment may be omitted.

FIG. 1 shows the appearance of an example of a lead-acid battery according to an embodiment of the present invention.
A lead-acid battery 1 includes a battery case 12 that accommodates an electrode plate group 11 and an electrolytic solution (not shown). The interior of the container 12 is partitioned into a plurality of cell chambers 14 by partition walls 13 . Each cell chamber 14 accommodates one electrode plate group 11 . The opening of the container 12 is closed with a lid 15 having a negative terminal 16 and a positive terminal 17 . The lid 15 is provided with a liquid port plug 18 for each cell chamber. When rehydrating, the rehydration liquid is replenished by removing the liquid port plug 18. - 特許庁The liquid port plug 18 may have a function of discharging the gas generated inside the cell chamber 14 to the outside of the battery.

The electrode plate group 11 is configured by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 interposed therebetween. Here, a bag-shaped separator 4 for housing the negative electrode plate 2 is shown, but the shape of the separator is not particularly limited. When a separator in which a glass fiber mat or a carbon material is arranged only on one main surface of a porous film is processed into a bag shape, the glass fiber mat or the carbon material is arranged on either the inner surface or the outer surface of the bag. be. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf portion 6 connecting a plurality of negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode shelf portion connecting a plurality of positive electrode plates 3 in parallel. 5 is connected to the positive pole 7 . The positive pole 7 is connected to a positive terminal 17 outside the lid 15 . In the cell chamber 14 located at the other end of the battery case 12 , the negative electrode column 9 is connected to the negative electrode shelf 6 , and the through connector 8 is connected to the positive electrode shelf 5 . The negative electrode column 9 is connected to a negative electrode terminal 16 outside the lid 15 . Each through-connector 8 passes through a through-hole provided in the partition wall 13 and connects the electrode plate groups 11 of adjacent cell chambers 14 in series.

The matters described in this specification can be combined arbitrarily.

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

<Example 1>
<<Lead-acid batteries E1-1 to E1-10 and C1-1>>
Each lead-acid battery was produced in the following procedure.
(1) Preparation of Separator A resin composition containing 100 parts by mass of polyethylene, 160 parts by mass of silica particles, 80 parts by mass of paraffin oil as a pore-forming agent, and 2 parts by mass of a penetrating agent is extruded into a sheet. After molding and stretching, a part of the pore-forming agent was removed to produce a microporous membrane (porous film) having ribs on one side. At this time, the cooling rate and stretching ratio of the extruded sheet were adjusted so that the crystallinity of the porous film determined by the above-described procedure was the value shown in Tables 1 and 2. In addition, in Example 1, only the porous film was used as the separator.

The oil content of the separator obtained by the above procedure was 11 to 18% by mass, and the silica particle content was 60% by mass. The rib height determined by the procedure described above was 0.6 mm. Tables 1 and 2 show the thickness of the separator (thickness of the base portion) obtained by the above procedure.

Next, the sheet-like microporous membrane was folded in two so that ribs were arranged on the outer surface to form a bag, and the overlapped ends were crimped to obtain a bag-like separator.

The crystallinity of the porous film, the oil content, the silica particle content, the thickness of the base portion, and the height of the rib are the values obtained for the separator before production of the lead-acid battery. It is almost the same as the value measured by the procedure described above for the separator taken out from the lead-acid battery.

(2) Production of positive electrode plate A positive electrode paste was prepared by mixing lead oxide, reinforcing material (synthetic resin fiber), water and sulfuric acid. The positive electrode paste was filled in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 100 mm, a height of 110 mm, and a thickness of 1.6 mm. A positive plate was obtained.

(3) Preparation of Negative Electrode Plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate, lignin, reinforcing material (synthetic resin fiber), water and sulfuric acid. The negative electrode paste was filled in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 100 mm, a height of 110 mm, and a thickness of 1.3 mm. A negative plate was obtained. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used were such that the content of each component in the negative electrode plate taken out from a fully charged lead-acid battery was 0.3% by mass, 2.1% by mass and 0.3% by mass, respectively. It was adjusted to be 1% by mass and 0.1% by mass.

(4) Preparation of lead-acid battery An unchemically formed negative electrode plate was placed in a bag-like separator and laminated with a positive electrode plate to form an electrode plate group with seven unchemically formed negative electrode plates and six unchemically formed positive electrode plates. .

The lugs of the positive electrode plate and the lugs of the negative electrode plate were welded to the positive shelf and the negative shelf by a cast-on-strap (COS) method, respectively. The electrode plate group is inserted into a polypropylene battery case, the electrolyte is injected, and chemical conversion is performed in the battery case so that the rated voltage is 12 V and the rated capacity is 30 Ah (5 hour rate capacity (Ah described in the rated capacity). A liquid lead-acid battery with a capacity when discharged at a current (A) that is 1/5 of the value of )) was assembled. Six electrode plate groups are connected in series in the container.

A sulfuric acid aqueous solution was used as the electrolyte. The specific gravity at 20° C. of the electrolytic solution after chemical conversion was 1.285.

(5) Evaluation FIG. 2 shows the XRD spectrum of separator E1-1 measured by the procedure described above. As shown in FIG. 2, a diffraction peak corresponding to the (110) plane of the crystalline region of polyethylene was observed in the range of 2θ = 21.5° to 22.5°, and the diffraction peak corresponding to the (200) plane was observed. A peak was observed in the range 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the high-temperature overcharge life performance was evaluated according to the procedure described above. The high-temperature overcharge life performance was evaluated by the ratio of the number of cycles of each lead-acid battery to 100 cycles of the lead-acid battery C1-1.

The evaluation results are shown in Tables 1 and 2. E1-1 to E1-10 are examples. C1-1 is a comparative example.

As shown in Table 1, when the crystallinity of the separator was 20% or more, the high-temperature overcharge life performance was significantly improved compared to when the crystallinity was 18%, which corresponds to the conventional technology. It is considered that this is because the oxidation resistance was improved by increasing the crystallinity of the separator.

As shown in Table 2, when the thickness of the separator is 100 μm or more and 300 μm or less, higher high-temperature overcharge life performance can be ensured.

<Example 2>
<<Lead-acid batteries E2-1 to E2-108 and C2-1 to C2-48>>
Each lead-acid battery was produced in the following procedure.
(1) Preparation of Separator A resin composition containing 100 parts by mass of polyethylene, about 160 parts by mass of silica particles, about 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrating agent was prepared into a sheet. A microporous membrane (porous film) having ribs on one side was produced by extruding the membrane into a single layer, stretching the membrane, and partially removing the pore-forming agent. At this time, the cooling rate and stretching ratio of the extruded sheet were adjusted so that the crystallinity of the porous film determined by the above-described procedure was the value shown in Tables 3 to 5. In addition, the amounts of silica particles and pore-forming agent to polyethylene are adjusted so that the first pore volume Vt and the oil content obtained by the above-described procedure are the values shown in Tables 3 to 5, and the pore-forming The amount of agent removed was adjusted. In addition, in Example 2, only the porous film was used as the separator. The E2-1 separator is the same as the E1-1 separator produced in Example 1.

The content of silica particles obtained by the procedure described above was 60% by mass. The rib height determined by the procedure described above was 0.6 mm. The thickness of the separator (thickness of the base portion) determined by the above procedure was 0.2 mm.

The crystallinity of the porous film, the first pore volume Vt, the oil content, the silica particle content, the thickness of the base portion, and the height of the ribs were determined for the separator before the lead-acid battery was produced. The value is almost the same as the value measured by the above-described procedure for the separator taken out from the manufactured lead-acid battery.

(5) Evaluation For the porous film used for the E2-1 separator, the XRD spectrum measured by the procedure described above is in good agreement with the XRD spectrum of the porous film used for the E-1 separator shown in FIG. showed that. As shown in FIG. 2, a diffraction peak corresponding to the (110) plane of the crystalline region of polyethylene was observed in the range of 2θ = 21.5° to 22.5°, and the diffraction peak corresponding to the (200) plane was observed. A peak was observed in the range 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the IS life performance was evaluated according to the procedure described above. CCA performance was also evaluated using some lead-acid batteries. The IS life performance was evaluated by the ratio (%) of the number of cycles of each lead-acid battery when the number of cycles of the lead-acid battery C2-1 was taken as 100 (%). The CCA performance was evaluated by the ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery when the terminal voltage at 30 seconds of lead-acid battery C2-17 was taken as 100.

Tables 3 to 5 show the evaluation results of IS life performance. Table 6 shows the evaluation results of CCA performance. E2-1 to E2-108 in the table indicate battery numbers and are examples. C2-1 to C2-48 indicate battery numbers and are comparative examples. In Tables 3 to 5, the numerical value at the bottom of the battery number is the IS life performance (%).

As shown in Tables 3 to 5, when the crystallinity of the separator is less than 20%, the first pore volume Vt is 0.8 cm ³ /g compared to when it is less than 0.8 cm ³ /g. The IS life is improved at 0.8 cm ³ /g or more, but the IS life performance decreases (comparison between C2-1 and C2-2 to 2-13, C2-17 and C2-18 to C2 -29, C2-33 and C2-34 to C2-45). Further, when the first pore volume Vt is less than 0.8 cm ³ /g, the IS life performance does not change even if the degree of crystallinity is changed. On the other hand, when the first pore volume Vt is 0.8 cm ³ /g or more, the IS life performance is greatly improved by making the degree of crystallinity 20% or more (Example). This is also clear from FIG. 3, which shows the relationship between the first pore volume Vt and the IS life performance when the oil content is 15% by mass. FIG. 3 is a graph plotting the IS life performance results of C2-17 to C2-32 and E2-37 to E2-72 in Table 4 for each crystallinity. The excellent IS life performance was obtained in the examples because the first pore volume Vt of 0.8 cm ³ /g or more increased the diffusibility of the electrolytic solution and reduced the resistance of the separator. In addition, it is believed that the increase in the degree of crystallinity suppresses oxidation deterioration of the separator, and the effect of suppressing stratification and the effect of improving reactivity due to the increase in the first pore volume Vt are sufficiently exhibited. be done.

As shown in Table 6, when the first pore volume Vt is 0.8 cm ³ /g or more, high CCA performance can be ensured regardless of the degree of crystallinity. From the results in Tables 3 to 6, it can be seen that the examples provide excellent IS life performance while ensuring high CCA performance.

<Example 3>
<<Lead-acid batteries E3-1 to E3-16 and R3-1 to R3-12>>
Each lead-acid battery was produced in the following procedure.
(1) Preparation of Separator A resin composition containing 100 parts by mass of polyethylene, 160 parts by mass of silica particles, 80 parts by mass of paraffin oil as a pore-forming agent, and 2 parts by mass of a penetrating agent is extruded into a sheet. A microporous membrane having ribs on one side was produced by removing part of the pore-forming agent after molding and stretching. At this time, the cooling rate and stretching ratio of the extruded sheet were adjusted so that the crystallinity of the porous film determined by the above-described procedure was the value shown in Tables 7 and 8. The porous film of E3-7 is the same as the separator of E1-1 produced in Example 1 and the separator of E2-1 produced in Example 2.

The oil content of the separator obtained by the above procedure was 11 to 18% by mass, and the silica particle content was 60% by mass. The rib height determined by the procedure described above was 0.2 mm. Tables 7 and 8 show the thickness of the porous film (thickness of the base portion) determined by the procedure described above.

Next, the sheet-like porous film is folded in half so that the ribs are arranged on the inner surface to form a bag, and the overlapped both ends are crimped to form a bag-like porous film (in a flat state). size: length 117 mm x width 152 mm). The crimped portion had a width of 3 mm inside a position 2 mm from the side edge of the porous film. In reference examples R3-1 to R3-8, ribs were formed on the outer surface, and a bag-shaped porous film formed in the same manner as described above was used as a separator, except that the rib height was 0.6 mm. used as

A glass fiber mat (size under atmospheric pressure: 117 mm long x 143 mm wide, average fiber diameter: 17 μm, surface density: 60 g/m ² ) is adhered to both outer surfaces of the bag-like porous film as shown in FIG. pasted with glue. The width of the porous film was greater than the width of the glass fiber mat, and regions with a width of 4.5 mm where the glass fiber mat did not overlap were formed on both side ends of the porous film.

The crystallinity, oil content, silica particle content, base thickness, rib height, glass fiber mat size, average fiber diameter, and surface density of the porous film were measured before the lead-acid battery was manufactured. This is the value obtained for the porous film or glass fiber mat of , which is almost the same as the value measured by the above-described procedure for the porous film or glass fiber mat taken out from the lead-acid battery after production.

(2) Production of positive electrode plate A positive electrode paste was prepared by mixing lead oxide, reinforcing material (synthetic resin fiber), water and sulfuric acid. The positive electrode paste was filled in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 137 mm, a height of 110 mm, and a thickness of 1.6 mm. A positive plate was obtained.

(3) Preparation of Negative Electrode Plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate, lignin, reinforcing material (synthetic resin fiber), water and sulfuric acid. The negative electrode paste was filled in the mesh part of an expanded grid made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 137 mm, a height of 110 mm, and a thickness of 1.3 mm. A negative plate was obtained. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used were such that the content of each component in the negative electrode plate taken out from a fully charged lead-acid battery was 0.3% by mass, 2.1% by mass and 0.3% by mass, respectively. It was adjusted to be 1% by mass and 0.1% by mass.

(4) Preparation of lead-acid battery An unformed negative electrode plate was accommodated in a bag-like porous film of a separator. The negative electrode plate and the positive electrode plate were laminated via a separator so that the glass fiber mats attached to both outer surfaces of the bag were in contact with the positive electrode plate. In R3-1 to R3-8, a negative electrode plate and a positive electrode plate housed in a bag-shaped porous film were laminated. In this manner, an electrode plate assembly was formed of seven unformed negative electrode plates and six unformed positive electrode plates.

The lugs of the positive electrode plate and the lugs of the negative electrode plate were welded to the positive shelf and the negative shelf using the cast-on-strap method, respectively. The electrode plate group is inserted into a polypropylene battery case, the electrolyte is injected, and chemical conversion is performed in the battery case so that the rated voltage is 12 V and the rated capacity is 30 Ah (5 hour rate capacity (Ah described in the rated capacity). A liquid lead-acid battery with a capacity when discharged at a current (A) that is 1/5 of the value of )) was assembled. Six electrode plate groups are connected in series in the container.

(5) Evaluation For the porous film of the separator of lead-acid battery E3-7, the XRD spectrum measured by the procedure described above agrees well with the XRD spectrum of the porous film used for the separator of E-1 shown in FIG. showed that. As shown in FIG. 2, the first diffraction peak corresponding to the (110) plane of the crystalline region of polyethylene was observed in the range of 2θ = 21.5 ° to 22.5 °, corresponding to the (200) plane. A second diffraction peak was observed in the range of 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the CCA performance and high-temperature overcharge life performance of the lead-acid battery were evaluated according to the procedure described above. CCA performance was evaluated by the ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery when the terminal voltage at 30 seconds of lead-acid battery R3-4 was taken as 100. The high-temperature overcharge life performance was evaluated by the ratio (%) of the number of cycles of each lead-acid battery to 100 cycles of the lead-acid battery R3-4.

The evaluation results are shown in Tables 7 and 8. E3-1 to E3-16 are examples. R3-1 to R3-12 are reference examples.

As shown in Table 7, the CCA performance of the separator without the glass fiber mat is affected by the thickness of the separator, and the smaller the thickness, the higher the CCA performance (R3-1 to R3-4). However, the smaller the thickness of the separator, the lower the high temperature overcharge life performance tends to be (R3-1 to R3-4). This is presumably because if the thickness of the separator is small, the separator is likely to break when it comes into contact with the positive electrode material, and short-circuiting is more likely to occur. Without the glass fiber mat, even if the crystallinity of the porous film is increased, there is no change in the CCA performance, but the high temperature overcharge life performance is also improved to some extent (R3-1 to R3-4 and R3-5 ~Comparison with R3-8). For example, even with a very thin porous film thickness of 100 μm, the high temperature overcharge life performance is improved by 15% from 89% to 104% (compare R3-1 and R3-5). Even when the thickness of the porous film is large, the results do not change much, and the effect of increasing the crystallinity is around 10-12%.

When the porous film is laminated with the glass fiber mat, the falling off of the softened positive electrode material is suppressed, so it is expected that the high-temperature overcharge life performance will be improved to some extent. However, when the crystallinity of the porous film is less than 20% and the thickness is 100 μm, even if it is laminated with the glass fiber mat, the improvement effect is small, with only a 9% improvement from 89% cycle to 98%. (Comparison of R3-1 and R3-9). Even when the thickness of the porous film is large, the results do not change much, and the effect of improving the high temperature overcharge life performance by laminating with the glass fiber mat is about 7 to 10% (R3-2 to R3-4 and R3-10 to R3-12). On the other hand, as the thickness of the porous film increases, the CCA performance tends to decrease because the resistance increases.

Considering the above results, it is expected that even if the crystallinity of the porous film is increased from 18% to 25% and laminated with a glass fiber mat, the high temperature overcharge life performance will be improved by 14 to 22%. be done. However, in fact, E3-1 to E3-4 have improved high temperature overcharge life performance by 36 to 41% compared to R3-1 to R3-4, and a high value of 130 to 138% is obtained. It is Moreover, in E3-1 to E3-4, the deterioration of CCA performance is suppressed to a low level. A similar tendency is observed when the thickness of the porous film is 300 μm or less. From the viewpoint of obtaining excellent high-temperature overcharge life performance and further improving CCA performance, the thickness of the porous film may be 250 μm or less or 200 μm or less.

As shown in Table 8, when the crystallinity of the porous film is 20% or more, lamination with the glass fiber mat ensures excellent high-temperature overcharge life performance while ensuring high CCA performance. (E3-5 to E3-16). High temperature overcharge life performance as high as 115% or more can be obtained even with a very small porous film thickness of 100 μm.

In the examples, lead-acid batteries were produced and evaluated using the porous films and the electrode plates having the sizes described above. can get.

<Example 4>
(Experimental example 1)
In Experimental Example 1, a plurality of separators and a plurality of lead-acid batteries were produced by the following procedure.

(1) Production and Evaluation of Separator A resin composition containing 100 parts by mass of polyethylene, 160 parts by mass of silica particles, 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrating agent was prepared into a sheet. A porous film having ribs on one side was produced by extruding the film, stretching the film, and partially removing the pore-forming agent. At this time, the cooling rate and stretching ratio of the extruded sheet were adjusted so that the crystallinity of the porous film obtained by the procedure described above was the value shown in Table 9.

Next, a carbon material was placed on one main surface (main surface on the negative electrode plate side) of each of the formed porous films by the following procedure. First, a mixture of silica and carbon material was deposited on the separator, and then a pure carbon layer was deposited thereon by roller coating method or spray coating method. Thus, the carbon material was arranged. The thickness of the carbon material was the same for each porous film. Specifically, it was set to 10 μm. Through the above procedure, a plurality of separators having porous films with different degrees of crystallinity were produced.

The oil content of the separator obtained by the above procedure was 11 to 18% by mass, and the silica particle content was 60% by mass. The rib height determined by the procedure described above was 0.6 mm. Table 9 shows the thickness of the separator (thickness of the base portion) obtained by the procedure described above.

The sheet-like separator obtained by the above procedure was folded in two so that ribs were arranged on the outer surface to form a bag. Next, a bag-like separator was obtained by crimping the overlapped ends. The inner surface of the bag-like separator is the surface on which the carbon material is arranged.

The crystallinity of the porous film, the oil content, the silica particle content, the thickness of the separator, and the height of the ribs in the separator are the values obtained for the separator before production of the lead-acid battery. These values are almost the same as the values measured by the above-described procedure for the separator taken out from the manufactured lead-acid battery.

The lugs of the positive electrode plate and the lugs of the negative electrode plate were welded to the positive shelf and the negative shelf by a cast-on-strap (COS) method, respectively. The electrode plate group is inserted into a polypropylene battery case, the electrolyte is injected, and chemical conversion is performed in the battery case so that the rated voltage is 12 V and the rated capacity is 30 Ah (5 hour rate capacity (Ah described in the rated capacity). A liquid lead-acid battery with a capacity when discharged at a current (A) that is 1/5 of the value of )) was assembled. Six electrode plate groups are connected in series in the container. The porous films of the separators used in Battery A1 were the E1-1 separator used in Example 1, the E2-1 separator used in Example 2, and the E3-7 separator used in Example 3. is the same as the porous film of

Regarding the porous film used for the separator of battery A1, the XRD spectrum measured by the procedure described above showed good agreement with the XRD spectrum of the E-1 separator shown in FIG. As shown in FIG. 2, a diffraction peak corresponding to the (110) plane of the crystalline region of polyethylene was observed in the range of 2θ = 21.5° to 22.5°, and the diffraction peak corresponding to the (200) plane was observed. A peak was observed in the range 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the high-temperature overcharge life performance (number of cycles N) was evaluated according to the procedure described above. The high-temperature overcharge life performance was evaluated by the relative value of the cycle number N of each lead-acid battery. The relative value of the cycle number N is a value when the cycle number N of the battery CA1 is 90. Table 9 shows the evaluation results. Batteries A1 to A4 are batteries of invention examples, and battery CA1 is a battery of comparative examples.

As shown in Table 9, when the crystallinity of the porous film was 20% or more, the life performance was significantly improved compared to the crystallinity of 18% corresponding to the conventional technology. This is probably because the oxidation resistance of the separator was improved due to the high crystallinity of the porous film.

(Experimental example 2)
In Experimental Example 2, a lead-acid battery was produced and evaluated in the same manner as in Experimental Example 1, except that the separator was changed. Specifically, a plurality of separators were produced in the same manner as in Experimental Example 1, except that the production conditions for changing the separator thickness and the crystallinity of the porous film were changed. The carbon material was placed under the same conditions as the separator of Experimental Example 1.

The manufactured separator and lead-acid battery were evaluated in the same manner as in Experimental Example 1. Table 10 shows the evaluation results. Batteries B1 to B12 are invention examples, and batteries CB1 to CB4 are comparative examples. The high-temperature overcharge life performance (number of cycles N) in Table 10 is a relative value when the number of cycles N of battery B1 is 100.

As shown in Table 10, by setting the thickness of the separator to 100 μm or more, the high-temperature overcharge life performance could be significantly improved. If the separator is thin (if the porous film is thin), the resin does not flow well into the mold during resin molding to form the porous film. Separator tears) may occur partially. On the other hand, when the thickness of the separator is 100 μm or more (the thickness of the porous film is 90 μm or more), the surroundings of the resin are improved and a homogeneous porous film can be obtained. In addition, placing the carbon material on the surface of the porous film significantly improves the tensile strength of the separator, as will be described later. Therefore, it is considered that the high-temperature overcharge life characteristics were greatly improved.

(Experimental example 3)
In Experimental Example 3, a plurality of separators were produced under different production conditions. Specifically, the same method as in Experimental Example 1 was used, except that the manufacturing conditions for changing the crystallinity of the porous film and the thickness of the separator, and the presence or absence of the arrangement of the carbon material were changed. , a plurality of separators were produced. The produced separator was evaluated in the same manner as in Experimental Example 1.

Furthermore, the tensile strength of the manufactured separator was measured by the method described above. Tables 11 and 12 show the evaluation results of the separator. Separators S1 to S10 are invention example separators, and separators CS1 to CS12 are comparative example separators. The tensile strength is a relative value when the tensile strength of the separator CS1 is set to 100.

The results of Table 11 are shown in FIG. 5, and the results of Table 12 are shown in FIG. As shown in Table 11 and FIG. 5, by disposing the carbon material on the surface and setting the crystallinity of the porous film to 20% or more, the tensile strength of the separator could be significantly increased. As shown in Table 12 and FIG. 6, by disposing the carbon material on the surface and setting the thickness to 100 μm or more, the tensile strength of the separator could be significantly increased.

As shown in FIG. 5, in the separator in which the carbon material was arranged, the effect of increasing the tensile strength by increasing the degree of crystallinity was higher than in the separator in which the carbon material was not arranged. As shown in FIG. 6, in the separator with the carbon material, the effect of increasing the tensile strength by increasing the thickness of the separator was higher than in the separator without the carbon material. Although the reasons for these are not clear, it is believed that placing the carbon material on the surface of the porous film has some kind of synergistic effect.

The lead-acid battery separator according to the above aspect of the present invention is suitable, for example, for IS applications (lead-acid batteries for ISS vehicles, etc.), starting power sources for various vehicles (automobiles, motorcycles, etc.). In addition, the lead-acid battery separator can be suitably used as a power source for industrial power storage devices such as electric vehicles (forklifts, etc.). It should be noted that these uses are merely exemplary. Applications of the lead-acid battery separator and the lead-acid battery according to the above aspects of the present invention are not limited to these.

1: lead-acid battery, 2: negative electrode plate, 3: positive electrode plate, 4: separator, 4a: porous film, 4b: glass fiber mat, 5: positive electrode shelf, 6: negative electrode shelf, 7: positive electrode column, 8: Penetration connector, 9: negative electrode column, 11: electrode plate group, 12: container, 13: partition wall, 14: cell chamber, 15: lid, 16: negative electrode terminal, 17: positive electrode terminal, 18: liquid spout plug, 20 : crimping part, 21: area not covered with the glass fiber mat of the porous film

Claims

A lead-acid battery separator,
the separator comprises a porous film, the porous film comprising a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the porous film, the degree of crystallinity represented by 100×I c /(I c +I a ) is 20% or more,
I c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region;
A lead-acid battery separator, wherein Ia is the integrated intensity of the halo corresponding to the amorphous region.
The lead-acid battery separator according to claim 1, wherein the porous film has a thickness of 100 µm or more and 300 µm or less.
The lead-acid battery separator according to claim 1 or 2, wherein the degree of crystallinity is 40% or less.
The lead-acid battery separator according to any one of claims 1 to 3, wherein the porous film contains oil.
The lead-acid battery separator according to any one of claims 1 to 4, wherein the porous film contains polyolefin.
The polyolefin contains at least ethylene units,
6. The lead-acid battery separator according to claim 5, wherein said diffraction peak with said maximum peak height corresponds to the (110) plane of said crystalline region.
The lead-acid battery according to any one of claims 1 to 6, wherein the total volume Vt of pores having a pore diameter of 0.005 µm or more and 10 µm or less in the porous film is 0.8 cm 3 /g or more. separator for
The lead-acid battery separator according to any one of claims 1 to 7, wherein the degree of crystallinity is 25% or more.
8. The lead-acid battery separator according to claim 7, wherein the total volume Vt is 0.9 cm <3> /g or more.
The lead-acid battery separator according to any one of claims 1 to 9, wherein the separator includes a laminate of the porous film made of resin and a glass fiber mat.
11. The lead-acid battery separator according to claim 10, wherein said porous film has a region not covered with said glass fiber mat on at least a part of its edge.
The lead-acid battery separator according to any one of claims 1 to 11, wherein the separator further includes a carbon material arranged on the surface of the porous film.
The lead-acid battery separator according to claim 12, wherein said carbon material is at least one selected from the group consisting of conductive carbon black and conductive carbon fiber.
A lead-acid battery,
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
A lead-acid battery, wherein the separator is the lead-acid battery separator according to any one of claims 1 to 13.
A lead-acid battery,
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
The separator is the lead-acid battery separator according to claim 10 or 11,
A lead-acid battery, wherein the glass fiber mat is in contact with the positive plate.
A lead-acid battery,
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
The separator is the lead-acid battery separator according to claim 12 or 13,
The lead-acid battery, wherein the carbon material is arranged on one of the two main surfaces of the porous film, which faces the negative electrode plate.