JP2022152652A - Separator for lead accumulator battery, and lead accumulator battery including the same - Google Patents

Abstract

To provide a separator for a lead accumulator battery capable of improving a life performance of a lead accumulator battery in a case where charge and discharge are repeated in an idling stop (IS) test including large-current discharge and charge/discharge in a partial state of charge (PSOC).SOLUTION: A separator for a lead accumulator battery contains a polymer material and an oil, and includes at a principal part 105 a central part 110, a first end part 111 and a second end part 112 located at both end parts in a first direction D1, and a third end part 113 and a fourth end part 114 located at both end parts in a second direction D2 perpendicular to the first direction. A ratio of a percentage content of the oil to a percentage content of the polymer material at the first end part Re1 and a ratio of the percentage content of the oil to the percentage content of the polymer material at the central part Rc satisfy Re1≥Rc. A ratio of the percentage content of the oil to the percentage content of the polymer material at least at one of the second, third, and fourth end parts Re and the ratio Rc at the central part satisfy Re<Rc.SELECTED DRAWING: Figure 1

Description

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 in-vehicle use and industrial use. 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.

Patent Document 1 discloses a flooded lead-acid battery that includes a positive electrode plate, a negative electrode plate, a separator that separates the positive electrode plate and the negative electrode plate, and an electrolytic solution that soaks the positive electrode plate, the negative electrode plate, and the separator. and proposes a flooded lead-acid battery characterized in that a porous layer is arranged between an upper portion of the positive electrode plate and an upper portion of the separator.

Patent Document 2 includes a positive electrode plate, a negative electrode plate, a perforated sheet disposed between the positive electrode plate and the negative electrode plate and having through holes formed in the thickness direction, and an electrolytic solution. A lead-acid battery is proposed in which the aperture ratio is different between the upper part and the lower part.

In Patent Document 3, 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.

WO2017/042850 WO2019/225389 JP-A-2001-338631

Lead-acid batteries are sometimes used in an undercharged state called a partial state of charge (PSOC). For example, in idle stop (IS) applications such as idle start stop (ISS) vehicles, lead-acid batteries are used in PSOCs. Repeated charging and discharging of a PSOC tends to cause stratification in which the specific gravity of the electrolyte in the upper part of the battery is low and the specific gravity of the electrolyte in the lower part of the battery is high. Also, in IS applications, the number of times the engine is started is large, and large current discharge is repeated. As a result, charging and discharging reactions are concentrated on the upper portion of the electrode plate, and the softening and falling off of the positive electrode material on the upper portion of the positive electrode plate tend to become noticeable. Conventionally, as in Patent Document 1 or Patent Document 2, attempts have been made to improve the life performance by making the reactivity of the entire electrode plate more uniform by lowering the reactivity of the upper portion of the electrode plate. However, by improving the reactivity of the part with low reactivity, the life performance (hereinafter sometimes referred to as IS life performance) when the charge and discharge are repeated in the IS test including charge and discharge in PSOC and large current discharge ) can be improved.

In addition, the separator may contain oil as a pore-forming agent or the like. When the separator contains oil, the resistance of the separator increases and the reactivity of the electrode plate decreases. By removing the oil from the separator, the resistance of the separator can be reduced, and the decrease in reactivity of the electrode plate can be reduced. However, in this case, the life performance when the lead-acid battery is overcharged at a high temperature (for example, a temperature of 75° C. or higher) (hereinafter sometimes referred to as high-temperature overcharge life performance) deteriorates.

One aspect of the present invention is a lead-acid battery separator,
The separator contains a polymer material and oil, and includes a central portion, first and second ends positioned at both ends in a first direction, and a second separator perpendicular to the first direction. a third end and a fourth end located at both ends in the direction,
A ratio Re1 of the oil content in the first end portion to the polymer material content and a ratio Rc of the oil content in the central portion to the polymer material content satisfy Re1≧Rc. death,
the ratio Re of the oil content to the polymeric material content at at least one of the second end, the third end and the fourth end, and the ratio Rc at the central portion; relates to a lead-acid battery separator that satisfies Re<Rc.

High IS life performance and high high-temperature overcharge life performance can be ensured in lead-acid batteries.

FIG. 3 is a schematic plan view showing a state in which the separator according to one embodiment of the present invention is stacked on the electrode plate. FIG. 2 is a schematic plan view for explaining a portion of the separator of FIG. 1 where samples are taken for measuring the content of oil and polymer material at the central portion and each end of the main portion; 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.

Generally, in an IS test of a lead-acid battery, the electrode plates are unlikely to be in an overcharged state and the electrolyte solution is unlikely to be agitated, so stratification tends to proceed. When stratification occurs, charge-discharge reactions are concentrated in the upper part of the electrode plate and the reactivity is increased, while the reactivity is reduced in the lower part and the side part of the electrode plate. In the upper part of the positive electrode plate where the charge/discharge reaction concentrates, the positive electrode material is likely to deteriorate, soften and fall off. When the positive electrode material falls off, the capacity decreases and the IS life performance decreases. In Patent Document 1 or Patent Document 2, the variation in reactivity in the electrode plate is reduced by lowering the reactivity of the upper portion of the electrode plate. However, it would be ideal if the reactivity variation in the electrode plate could be reduced by increasing the reactivity of the portion of the electrode plate with low reactivity.

When lead-acid batteries are overcharged, stratification and degradation of positive electrode materials are mitigated. However, in addition to the high potential of the positive electrode plate during overcharge, the positive electrode material contains lead dioxide, which has a strong oxidizing power as a positive electrode active material. 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.

The separator may contain oil as a pore former or the like. When the separator contains oil, the oxidative deterioration of the separator (more specifically, the oxidative deterioration of the polymer material constituting the separator) is suppressed, which is advantageous from the viewpoint of ensuring higher high-temperature overcharge life performance. However, since the insulating oil clogs the pores of the separator, the resistance of the separator tends to increase and the reactivity of the electrode plate tends to decrease. Therefore, in a lead-acid battery, it is difficult to ensure high IS life performance while ensuring high high-temperature overcharge life performance.

Also, in IS applications, many thin electrode plates are stacked to form an electrode plate group. In this case, the negative electrode current collector may bend at the edge of the negative electrode plate and penetrate the separator, causing a short circuit. Such a short circuit is particularly likely to occur near the lower end or side end of the negative electrode plate.

In view of the above, a lead-acid battery separator according to one aspect of the present invention contains a polymer material and oil, and has a central portion and first and second ends located at both ends in the first direction. and a third end and a fourth end located at both ends in a second direction perpendicular to the first direction. The ratio of the oil content at the first end to the polymer material content Re1 (=oil content/polymer material content) and the ratio of the oil content to the polymer material content at the central portion Rc ( = oil content/polymer material content) satisfies Re1≧Rc. the ratio Re of the oil content to the polymeric material content at at least one of the second, third and fourth ends (=oil content/polymeric material content); The ratio Rc in the central portion satisfies Re<Rc. The content of oil and the content of polymer material are based on mass. The ratio Re1, the ratio Re and the ratio Rc correspond to mass ratios.

In this specification, at least one end of the second end, the third end, and the fourth end is defined as "at least one end other than the first end" or "an end other than the first end". may be referred to as a "department". Further, an end portion satisfying Re<Rc among the end portions other than the first end portion may simply be referred to as an “end portion satisfying Re<Rc”.

The lateral separator has a lower ratio Re of oil content to polymeric material content at at least one end portion other than the first end portion as compared to the central portion and the first end portion. When the ratio Re is small, the oil content is relatively low, so the resistance of the separator is low and the diffusibility of the electrolytic solution is improved. Therefore, at least one end portion other than the first end portion has a smaller ratio Re than the central portion and the first end portion. High diffusibility can be secured. Also, the separator has a relatively high ratio of oil content to polymeric material content at the first end and central portion. When such a separator is used in a lead-acid battery, the first end faces the upper end of the electrode plate, and the end that satisfies Re<Rc faces at least one of the side end and the lower end of the electrode plate. can be made The end of the separator that satisfies Re<Rc is opposed to a portion of the electrode plate where the reactivity tends to be low (specifically, at least one of the side end and the bottom end of the electrode plate), thereby increasing the resistance. can be reduced, and the diffusibility of the electrolytic solution can be enhanced. As a result, at least one of the side edge portion and the bottom edge portion of the electrode plate, the charge/discharge reaction proceeds more easily, and the reactivity can be enhanced. In addition, since the polymer content is relatively low in the first end portion and the central portion of the separator compared to the end portion where Re<Rc is satisfied, it tends to be easy to ensure high IS life performance. Therefore, the reactivity of the entire electrode plate can be made more uniform while maintaining high reactivity in the center and upper end portions of the electrode plate. In IS applications, in particular, since high-current discharge is performed, the diffusibility of the electrolytic solution has a large effect on life performance and discharge performance. Stratification is also reduced by improving the diffusibility of the electrolyte at the side edges or bottom edges. Therefore, high IS life performance can be obtained. In addition, at the first end and the central portion of the separator facing the portion of the electrode plate originally having high reactivity, the polymer content is relatively low compared to the end satisfying Re<Rc, but the oil content is relatively low. is relatively large, so high oxidation resistance can be obtained. Therefore, when the lead-acid battery is overcharged at high temperature, high life performance (that is, high temperature overcharge life performance) can be ensured. Further, in IS applications, the lower end portion or side end portion of the negative electrode plate tends to be curved. However, at the ends satisfying Re<Rc, relatively high strength (puncture strength) can be ensured due to the relatively high polymer material content.

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 group of plates 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, and the separator is the lead-acid battery separator described above. The first end of the separator faces the upper ends of both the positive plate and the negative plate.

The third and fourth ends of the separator are located outside both side edges of the central portion, and the ratio Re at least one of the third and fourth ends and the ratio Rc at the central portion are equal to Re <Rc is preferably satisfied. At the third end and the fourth end extending in the direction intersecting with the first end, the ratio Re can be easily adjusted when the separator is manufactured industrially. Therefore, high IS life performance and high high-temperature overcharge life performance can be more easily ensured. Moreover, since the polymer material content is relatively high in at least one of the third end portion and the fourth end portion, high puncture strength can be ensured. By increasing the piercing strength of the third end portion or the fourth end portion facing the side end portion where the negative electrode plate is easily deformed, short circuiting at the third end portion or the fourth end portion can be suppressed.

The difference (Rc-Re) between the ratio Rc and the ratio Re is preferably 0.01 or more and 0.13 or less. In this case, higher IS life performance can be obtained, and high-temperature overcharge life performance can be further improved.

The separator preferably contains inorganic particles. In this case, the wettability of the separator with respect to the electrolytic solution is increased, so that the resistance of the separator can be further reduced. Therefore, higher IS life performance can be obtained.

The separator preferably contains polyolefin. Separators containing polyolefins tend to have low oxidation resistance. However, even in this case, since the oil content is relatively high in the first end portion and the central portion of the separator, high high-temperature overcharge life performance can be ensured.

In lead-acid batteries, the positive plate typically includes a positive current collector and the negative plate typically includes a negative current collector. At least one of the positive electrode current collector and the negative electrode current collector may be formed by expansion processing. A current collector formed by expansion does not have vertically and horizontally extending ribs. Therefore, in the electrode plate including the current collector formed by the expanding process, the current collection path from the tab to the bottom end or the side end is long, so the reactivity at the bottom end or the side end tends to decrease. Even in such a case, by controlling the ratio Re in at least one end portion of the separator other than the first end portion to be smaller than the ratio Rc in the center portion, the reactivity of the entire electrode plate can be made more uniform. It is possible to ensure high IS life performance.

The electrolyte contained in the lead-acid battery may contain at least one of aluminum ions and lithium ions. In this case, since coarsening of lead sulfate generated during discharge is suppressed, charge acceptance is improved, and lead sulfate is easily reduced to lead during charge. Since the effect of suppressing stratification increases, higher IS life performance can be obtained.

The concentration of aluminum ions in the electrolytic solution is preferably 0.02 mol/L or more and 0.2 mol/L or less. Further, the concentration of lithium ions in the electrolytic solution is preferably 0.02 mol/L or more and 0.2 mol/L or less. In these cases, the IS life performance can be further enhanced.

In PSOC charging/discharging applications (for example, IS applications), charging and discharging including high-current discharge are repeated, so that reactivity decreases particularly at the lower ends and side ends of the electrode plates. A lead-acid battery including the lead-acid battery separator according to one aspect of the present invention can ensure excellent life performance even in such applications.

(Explanation of terms)
(main part of the separator)
When the separator is interposed between the positive electrode plate and the negative electrode plate, the main portion of the separator includes both the region of the separator where the electrode material of the positive electrode plate is arranged and the region where the electrode material of the negative electrode plate is arranged. means the part opposite to In an electrode plate group including a positive electrode plate and a negative electrode plate, in a separator that faces only each electrode plate positioned at the end of the electrode plate group, the main part is the main surface of each electrode plate on which the electrode material is arranged. It means the part facing the area. The main surfaces of the electrode plate mean each of a pair of surfaces occupying most of the surface of the electrode plate (that is, a pair of surfaces excluding the end surfaces).

(Separator Center, Edges, First and Second Directions, and Edges of Electrode Plates)
The separator, when viewed in a direction perpendicular to the surface of the separator, includes a central portion and four end portions surrounding the central portion on four sides. In the main part of the separator, the four ends are a first end and a second end positioned at both ends in the first direction, and a third end positioned at both ends in a second direction perpendicular to the first direction. and a fourth end. In the main part of the separator, the central part is sandwiched between the first end and the second end. In the main part of the separator, the central part, the first end and the second end are sandwiched between the third end and the fourth end. In other words, in the main part of the separator, the third end and the fourth end are located outside the both ends in the second direction of the central part, the first end and the second end.

In a lead-acid battery, the separator is arranged such that the first end faces the upper end of the plate. Therefore, in a lead-acid battery, the second end of the separator faces the lower end of the plate, and the third and fourth ends face the side ends of the plate.

Note that the upper end portions of the electrode plates (the positive electrode plate and the negative electrode plate) correspond to the ends on the downstream side in the current collecting direction. The plates usually have ears at their upper ends. In the electrode plate, the vertical direction is defined with the side on which the ears are provided as the upper side and the side opposite to the ears as the lower side. The vertical direction of the electrode plate is the same as the vertical direction of the lead-acid battery. In the separator, the side facing the upper side (that is, ear portion side) of the electrode plate is the upper side of the separator, and the side facing the lower side of the electrode plate is the lower side of the separator. In a lead-acid battery, the first direction of the separator is the vertical direction of the lead-acid battery, and the second direction is the horizontal direction of the lead-acid battery.

(Oil content and polymer material content in the central and end portions of the main part)
The main part of the separator is divided into 4 equal parts in the first direction and 4 equal parts in the second direction, for a total of 16 regions. At this time, the oil content rate and the polymer material content rate in the central portion of the main portion are obtained for the central four regions. The oil content and polymeric material content at each of the first and second ends are determined for each of the two regions located outside the central four regions in the first direction. The oil content and polymeric material content at each of the third and fourth ends are determined for each of the two regions located outside the central four regions in the second direction. If the separator has ribs, samples for determining oil content and polymer material content are taken from areas without ribs.

The oil content and polymeric material content are determined for fresh separators or separators taken from lead-acid batteries in early use. When removing the separator from the lead-acid battery, the separator is removed from the lead-acid battery in a fully charged state.

(Fully charged state)
In this specification, the fully charged state of a 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. The numerical value described as the rated capacity is a numerical value whose unit is Ah. The unit of current set based on the numerical value described as the rated capacity is A.

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

In this specification, the term "battery in the early stage of use" means a battery in which not much time has passed since the start of use and which has hardly deteriorated.

(oil)
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.

(polyolefin)
A polyolefin is a polymer containing at least olefinic units (that is, a polymer containing at least monomeric units derived from an olefin). Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefinic units, and copolymers containing olefinic units and copolymerizable monomeric 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.

Hereinafter, lead-acid batteries according to 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)
In the main part facing the electrode material, the separator has a central part, a first end and a second end sandwiching the central part in the first direction, a central part, the first end and the second end. It includes a third end and a fourth end that sandwich in two directions. In the main portion of the separator, the first end is positioned outside the upper end of the central portion and the second end is positioned outside the lower end of the central portion. In the main part of the separator, the third end and the fourth end are located outside the respective side edges of the central part, the first end and the second end.

The separator contains polymeric material and oil. The oil contained in the separator originates, for example, from the pore-forming agent used in the manufacturing process of the separator.

The ratio Re1 of the oil content at the first end to the polymer material content and the ratio Rc of the oil content at the central portion to the polymer material content satisfy Re1≧Rc. Since the first end faces the upper end of the electrode plate, the difference between the ratio Re1 and the ratio Rc (=Re1-Rc) is smaller from the viewpoint of maintaining high reactivity of the upper end of the electrode plate. is preferred. (Re1-Rc) is, for example, 0.1 or less, preferably 0.05 or less. In particular, when (Re1-Rc)=0, the separator can be easily manufactured industrially while maintaining high reactivity of the upper portion of the electrode plate.

The ratio Re of the oil content to the polymer material content at at least one end other than the first end and the ratio Rc of the oil content to the polymer material content at the central portion satisfy Re<Rc . Since the reactivity of the lower end portion of the electrode plate is particularly prone to decrease, the ratio Re at the second end portion may be made smaller than the ratio Rc at the central portion from the viewpoint of increasing the reactivity of this lower end portion. From the viewpoint of facilitating industrial production of the separator, it is preferable that the ratio Re and the ratio Rc at least one of the third end portion and the fourth end portion satisfy Re<Rc. From the viewpoint of enhancing the reactivity at both side ends of the electrode plate and ensuring higher IS life performance, it is preferable that the ratio Re is smaller than the ratio Rc at both the third end and the fourth end. In this case, high piercing strength of the third end portion and the fourth end portion is obtained, so that even if the side end portion of the negative electrode plate is deformed, the effect of suppressing a short circuit is enhanced.

The difference (=Rc-Re) between the ratio Rc and the ratio Re should be greater than zero. (Rc-Re) is preferably 0.03 or more, more preferably 0.04 or more, from the viewpoint of enhancing the effect of making the reactivity of the entire electrode plate more uniform and obtaining higher IS life performance. (Rc-Re) is preferably 0.25 or less, more preferably 0.24 or less. When (Rc-Re) is within such a range, the oxidation resistance of the separator is enhanced, and higher high-temperature overcharge life performance can be ensured.

(Rc-Re) is greater than 0 and 0.25 or less (or 0.24 or less), 0.03 or more and 0.25 or less (or 0.24 or less), or 0.04 or more and 0.25 or less (or 0 .24 or less).

The separator has a portion that does not face the electrode material outside the main portion. More specifically, it has upper and lower ends and both side ends of the separator outside the main portion of the separator. The ratio of oil content to polymeric material content in these portions is not particularly limited. In view of the ease of adjusting the ratio of oil content to polymeric material content at each end of the separator body, the ratio of oil content to polymer material content in the outer portion of the separator body is , may be the same as the ratio at the ends of adjacent features. For example, the upper end of the separator may be adjacent to the first end of the feature, and the ratio of oil content to polymeric material content at the upper end of the separator may be the same as at the first end. . Both side edges of the separator are adjacent to the third and fourth ends of the feature, respectively, and the ratio of the oil content to the polymer material content at each side edge of the separator is the third and fourth edges of the separator. It may be the same as the ratio at each of the fourth ends.

The average oil content in the separator is, for example, 5% by mass or more. From the viewpoint of further increasing the effect of suppressing oxidation deterioration of the separator, the average oil content in the separator is preferably 10% by mass or more, more preferably 12% by mass or more or 12.5% by mass or more, and 13% by mass. or more. The average oil content in the separator is, for example, 20% by mass or less, preferably 18% by mass or less. In this case, the resistance of the separator can be further reduced.

The average oil content of the separator is 5% by mass or more and 20% by mass or less (or 18% by mass or less), 10% by mass or more and 20% by mass or less (or 18% by mass or less), 12% by mass or more and 20% by mass or less ( or 18% by mass or less), 12.5% by mass or more and 20% by mass or less (or 18% by mass or less), or 13% by mass or more and 20% by mass or less (or 18% by mass or less).

The separator may be sheet-like. Also, a sheet that is bent into a bellows shape may be used as the separator. The separator may be formed in the shape of a bag, and either one of the positive electrode plate and the negative electrode plate may be wrapped in the bag-shaped separator. In any form, when the separator is placed on a flat surface, the surface (specifically, the upper surface) of the separator is viewed from the direction perpendicular to this surface, and the central part and each end of the main part are part is determined.

The separator may or may not have ribs. A separator 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 separator or each base portion, or may be provided on both surfaces. In addition, the base portion of the separator is a portion excluding projections such as ribs among constituent portions of the separator, and refers to a sheet-like portion that defines the outer shape of the separator.

The separator is formed by, for example, extruding a resin composition containing a polymer material (hereinafter also referred to as a base polymer), a pore-forming agent containing at least oil, and a penetrant (surfactant) into a sheet, and then forming the separator. Obtained by removing the pore agent. Removal of at least a portion of the pore-forming agent forms micropores in the matrix of the base polymer. By adjusting at least one selected from the group consisting of the blending ratio of the constituent components of the resin composition and the amount of oil removed in each of the central portion and each end of the main portion of the separator, the central portion and each end The ratio of oil content to polymeric material content at the ends can be adjusted. For example, by removing a greater amount of oil and containing less oil at at least one end other than the first end than at the first end and the central portion, the ratio Re is reduced to the ratio Rc and the ratio Rc It may be smaller than Re1. The sheet-like separator may be bent into a bellows shape or processed into a bag shape, if necessary.

In separators having ribs, the ribs may be formed into the sheet during extrusion of 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.

The base polymer contained in the separator is not particularly limited as long as it is a base polymer used in lead-acid battery separators. Polyolefins are often used as base polymers. 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 separator 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. Such high proportions of polyolefin tend to result in low oxidation resistance, but even in such cases, the first end and center of the separator will contain some oil, which can lead to high temperature overheating. Charging life performance can be ensured.

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 average content of the polymer material (base polymer) in the separator is, for example, 20% by mass or more, and may be 25% by mass or more or 30% by mass or more. When the average polymer material content is within this range, the separator tends to have high strength. The average content of the polymer material (base polymer) in the separator is, for example, 60% by mass or less, and may be 50% by mass or less. When the average content of the polymer material is within such a range, lowering of the wettability of the separator to the electrolytic solution is suppressed, so that higher IS life performance can be easily secured.

Pore-forming agents include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent contains at least oil. By using oil, the effect of suppressing oxidation deterioration of the separator is further enhanced, and high IS life performance can be obtained. 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.

Mineral oil, synthetic oil and the like are preferable as the liquid pore-forming agent. Examples of liquid pore-forming agents include paraffin oil and silicone oil. Solid pore formers include, for example, polymer powders.

The amount of pore-forming agent in the separator may vary depending on the type. The amount of the pore-forming agent in the separator 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.

Surfactants as penetrants may be, for example, ionic surfactants or nonionic surfactants. Surfactants may be used alone or in combination of two or more.

The content of the penetrant in the separator is, for example, 0.01% by mass or more, and may be 0.1% by mass or more. The penetrant content in the separator may be 10% by mass or less or 5% by mass or less.

The content of the penetrant in the separator is 0.01% by mass or more (or 0.1% by mass or more) and 10% by mass or less, or 0.01% by mass or more (or 0.1% by mass or more) and 5% by mass or less. may be

The separator (or the resin composition used for producing the separator) may contain inorganic particles. If the separator contains inorganic particles, the IS life performance can be further improved.

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 the inorganic particles in the separator is, for example, 40% by mass or more, and may be 50% by mass or more. When the inorganic particle content is within this range, higher IS life performance can be obtained. The content of the inorganic particles is, for example, 80% by mass or less, and may be 75% by mass or less or 70% by mass or less.

The content of inorganic particles in the separator is 40% by mass or more (or 50% by mass or more) and 80% by mass or less, 40% by mass or more (or 50% by mass or more) and 75% by mass or less, or 40% by mass or more (or 50% by mass or more). mass % or more) may be 70 mass % or less.

The thickness of the main part of the separator is, for example, 0.15 mm or more. From the viewpoint of keeping the resistance of the separator low, the thickness of the separator is preferably 0.25 mm or less, more preferably 0.20 mm or less. The thickness of the main portion of the separator means the average thickness of the main portion. When the separator has a base portion and ribs erected from at least one surface of the base portion in the main portion, the thickness of the main portion of the separator is the average thickness of the base portion. When a sticking member (mat, pasting paper, etc.) is stuck to the separator, the thickness of the sticking member is not included in the thickness of the separator.

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

(separator analysis or size measurement)
An unused separator or a separator removed from a fully charged lead-acid battery in the initial stage of use is used for analysis or size measurement of the separator. Separators removed from lead-acid batteries are washed and dried prior to analysis or measurement.

The cleaning and drying of the separator removed from the lead-acid battery are performed according to the following procedures. 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.

(Oil content in separator)
The main part of the separator is divided into 16 regions as described above. A sample for measuring the oil content of the central portion is prepared by cutting a portion of the four central regions into strips. Sections of the upper two regions of the central four regions are cut into strips to produce samples for measuring the oil content of the first end. Sections of the two lower regions of the central four regions are cut into strips to prepare samples for measuring the oil content of the second ends. A portion of each of the two regions located outside the four central regions in the second direction was cut into strips to prepare samples for measuring the oil content of each of the third and fourth ends. do. For separators with ribs, each sample is cut without ribs.

For each sample, approximately 0.5 g is taken and weighed accurately to determine the initial sample mass (m0). A weighed sample is placed in an appropriately sized glass beaker and 50 mL of n-hexane is added. Next, ultrasonic waves are applied to each beaker for about 30 minutes to elute the oil contained in the sample 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. For each sample, the oil content is determined a total of 10 times, and the average value is calculated. The average value obtained is taken as the oil content at the center or at each end.
Oil content (% by mass) = (m0-m1)/m0 x 100

The average oil content in the separator is obtained from samples obtained by cutting four regions in the second row from the top into strips among the 16 regions obtained by dividing the main part of the separator. The oil content is determined a total of 10 times in the same manner as for the oil content at the center or each end, except that such a sample is used, and the average value is calculated. The average value obtained is taken as the average oil content in the separator.

(Content of polymer material in separator)
Samples are prepared for measuring the content of polymeric material in the center and at each end of the main part of the separator in the same manner as the samples for measuring the oil content.

A portion of each sample is collected, 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 is calculated and defined as the inorganic content (mass%) in the separator. For each sample, the inorganic content is determined a total of 10 times, and the average value is calculated. The obtained average value is defined as the content of inorganic matter in the central portion or each end portion of the main portion of the separator. The value (% by mass) obtained by subtracting the oil content and the inorganic content in the central portion or each end from 100% by mass is defined as the polymer content in the central portion or each end.

The average content of the polymer material in the separator is obtained from samples obtained by cutting four regions in the second row from the top into strips, out of the 16 regions obtained by dividing the main part of the separator. Except for using such a sample, the content of oil and the content of inorganic matter were determined a total of 10 times in the same manner as the content of polymer material at the center or each end, and the average value of each was calculated. calculate. The value (% by mass) obtained by subtracting the obtained average value from 100% by mass is taken as the average content of the polymer material in the separator.

(Content of inorganic particles in separator)
A sample (hereinafter referred to as sample A) is prepared by cutting the main part of the separator into strips. For a separator having ribs, sample A is made by cutting the base into strips so that the main part of the separator does not contain ribs.

A portion of sample A is collected, accurately weighed, placed in a platinum crucible, and heated with a Bunsen burner until white smoke is no longer produced. 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 A is calculated and defined as the content (% by mass) of the inorganic particles in the separator. The content of the inorganic particles is determined 10 times in total, and the average value is calculated. Let the obtained average value be the content rate of the inorganic particle in a separator.

(Content of penetrant in separator)
A portion of sample A prepared in the same manner as described above is sampled, accurately weighed, 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 longer. 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 the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of sample A is calculated, and the content of the penetrant in the separator. rate (% by mass). As a thermogravimetry device, T.I. A. Q5000IR manufactured by Instruments is used. The penetrant content is determined a total of 10 times, and the average value is calculated. The obtained average value is taken as the penetrant content in the separator.

(Separator thickness and rib height)
The thickness of the separator is obtained by measuring the thickness at five arbitrarily selected points on the base portion of the main part in a cross-sectional photograph of the separator and averaging the thicknesses.

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.

FIG. 1 is a schematic plan view showing a state in which a separator according to one embodiment of the present invention is stacked on an electrode plate. A main portion 105 of the separator 104 faces the portion of the electrode plate 102 where the electrode material is present. Separator 104 includes polymeric material and oil. In the main portion 105, the separator 104 has a central portion 110, a first end portion 111 and a second end portion 112 positioned at both end portions in the _first direction D1, and second end portions 111 and 112 positioned at both end portions in the _second direction D2. It includes a third end 113 and a fourth end 114 . The _first direction D1 is parallel to the vertical direction of the electrode plate. The _second direction D2 is perpendicular to the _first direction D1 and parallel to the horizontal direction of the plates in the lead-acid battery. The first end portion 111 and the second end portion 112 are located outside the upper and lower ends of the central portion 110 . The third end portion 113 and the fourth end portion 114 are positioned outside both side ends of the central portion 110 , the first end portion 111 and the second end portion 112 . Separator 104 overlaps electrode plate 102 such that first end 111 faces the upper end of electrode plate 102 . The ratio Re1 of the oil content in the first end portion 111 to the polymer material content and the ratio Rc of the oil content to the polymer material content in the central portion 110 satisfy Re1≧Rc. The ratio Re of the oil content to the polymeric material content at at least one of the second end 112, the third end 113 and the fourth end 114 and the ratio Rc satisfy Re<Rc . By controlling the ratio of oil content to polymer material content in this manner, high IS life performance and high high-temperature overcharge life performance can be ensured in lead-acid batteries.

FIG. 2 is a schematic plan view for explaining a portion of the separator of FIG. 1 where samples are taken to determine the oil content and the polymer material content at the central portion and each end of the main portion. _Let L1 be the length of the main portion 105 of the separator 104 in the _first direction D1, and _L2 be the length in the _second direction D2. As indicated by dotted lines in FIG. 2, the main portion 105 is divided into four equal parts in the _first direction D1 and divided into four equal parts in the _second direction D2, for a total of 16 regions. The oil content and polymeric material content in central portion 110 are determined for samples taken from four regions 110 a , 110 b , 110 c and 110 d near the center of feature 105 . The oil content and polymeric material content at the first end 111 are determined for samples taken from the two regions 111 a and 111 b located at the upper end of the feature 105 . The oil content and polymeric material content at the second end 112 are determined for samples taken from the two regions 112 a and 112 b located at the lower end of the feature 105 . The oil content and polymeric material content at the third end 113 are 110a and 110c out of the four regions 110a-110d sampled at the side ends of the body 105 (specifically, the central portion 110). for samples taken from the two regions 113a and 113b located outside the . The oil content and polymeric material content at the fourth end 114 are 110b and 110d out of the four regions 110a-110d sampled at the side ends of the main portion 105 (specifically, the central portion 110). for samples taken from the two regions 114a and 114b located outside the . Both the average oil content and the average polymer material content in the separator 104 are obtained for samples taken from the four regions 113a, 110a, 110b and 114a in the second row from the top.

(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 included 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 alloys and Pb--Ca--Sn alloys are preferable as the lead alloy used for the positive electrode current collector in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives (such as reinforcing materials) as necessary.

Examples of reinforcing materials for additives 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 amount of reinforcing material in the positive electrode material is, for example, 0.03% by mass or more. Moreover, the amount of the reinforcing material in the positive electrode material is, for example, 0.5% by mass or less.

The amount of reinforcing material in the positive electrode material can be determined by the following procedure. The analysis of the reinforcing material is performed using the positive electrode material collected from the positive electrode plate taken out from the lead-acid battery in the fully charged state.

The positive electrode material is recovered from the positive plate by the following procedure. First, a fully charged lead-acid battery is disassembled, and the obtained positive electrode plate is washed with water for 3 to 4 hours to remove the electrolyte in the positive electrode plate. The washed positive electrode plate is dried in a constant temperature bath at 60° C.±5° C. for 5 hours or longer. After drying, if the positive electrode plate contains the sticking member, the sticking member is removed from the positive electrode plate by peeling. A positive electrode material for analysis (hereinafter referred to as sample B) is obtained by sampling the positive electrode material from near the center of the upper, lower, left, and right sides of the positive plate when viewed from the front. Sample B is pulverized as necessary and used for analysis.

A ground sample B is taken and weighed accurately. Next, sample B was added to a mixed solution of an aqueous nitric acid solution (concentration: 25% by mass) and an aqueous tartaric acid solution (concentration: 500 g/L) (mixing ratio (volume ratio) of the nitric acid aqueous solution and the tartaric acid aqueous solution = 7:2). , dissolve the soluble matter while stirring under heating. The resulting mixture is filtered using a membrane filter (average pore size: 0.45 μm or less). Thereby, the reinforcing material contained in the positive electrode material is obtained as a solid matter on the filter paper. The solid obtained is washed with water and dried. Measure the mass of the dry matter. The ratio (percentage) of the mass of the dried product to the mass of sample B is determined. This ratio corresponds to the amount of reinforcing material in the positive electrode material.

An unformed paste-type positive electrode plate is obtained by filling a positive electrode current collector with a positive electrode paste, followed by 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 is 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. An electrode plate using a current collector formed by expanding tends to have a large variation in reactivity. can be made more uniform in reactivity.

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, a 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, ligninsulfonic acid, synthetic organic shrink-proofing agents (formaldehyde condensates of phenolic compounds, etc.), and the like. The negative electrode material may contain one kind or two or more kinds of organic expanders.

The content of the organic anti-shrinking agent 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 include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, and the like. 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.

The reinforcing material includes, for example, fibers (inorganic fibers, organic fibers (eg, organic fibers made of a resin described for the reinforcing material of the positive electrode material), etc.).

The amount of reinforcing material in the negative electrode material is, for example, 0.03% by mass or more. Moreover, the amount 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 the electrode plate group is immersed 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. Formation produces spongy lead.

(Analysis of Negative Electrode Material or its Constituents)
Methods for quantifying the organic shrinkage agent, carbonaceous material, barium sulfate, and reinforcing material in the negative electrode material are described below. Quantitative analysis of the components of the negative electrode material is performed using the negative electrode material collected from the negative electrode plate removed from the lead-acid battery in a fully charged state.

The negative electrode material is recovered from the negative plate by the following procedure. First, a fully charged lead-acid battery is disassembled to obtain a negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. Washing with water is performed by pressing a pH test paper against the surface of the washed negative electrode plate until it is confirmed that the color of the test paper does not change. However, the time for washing with water shall be within 2 hours. The washed negative electrode plate is dried at 60±5° C. for about 6 hours under reduced pressure. After drying, if the negative plate contains the sticking member, the sticking member is removed from the negative plate by peeling. Next, a sample (hereinafter referred to as sample C) is obtained by separating the negative electrode material from the negative plate. Sample C is pulverized as necessary and subjected to analysis.

《Determination of organic shrinkage agents》
The pulverized sample C is immersed in a 1 mol/L NaOH aqueous solution to extract the organic shrink-proofing agent. An insoluble component is removed by filtration from the extracted NaOH aqueous solution containing the organic expander, and a filtrate (hereinafter also referred to as filtrate D) is recovered.

A predetermined amount of the filtrate D is measured, desalted, concentrated and dried to obtain a powder of the organic shrink-proofing agent (hereinafter also referred to as sample E). Desalting is carried out by using a desalting column, by passing the filtrate D through an ion exchange membrane, or by placing the filtrate D in a dialysis tube and immersing it in distilled water.

The infrared spectrum of sample E, the UV-visible absorption spectrum of a solution obtained by dissolving sample E in distilled water, etc., the NMR spectrum of a solution obtained by dissolving sample E in a solvent such as heavy water, or the substance By combining the information obtained from pyrolysis GC-MS, etc., which can obtain information on individual compounds that are present, the organic expanders are identified.

An ultraviolet-visible absorption spectrum of the filtrate D is measured. From the spectral intensity, the calibration curve prepared in advance, the measured amount of filtrate D, and the mass of sample C, the content of the organic shrinkage agent in the negative electrode material is quantified. If the structural formula of the organic prepressant to be analyzed cannot be strictly specified and the calibration curve for the same organic prepressant cannot be used, the UV-visible absorption spectrum, infrared spectroscopy spectrum, and A calibration curve is generated using available organic preservatives, such as NMR spectra.

<<Determination of Carbonaceous Material, Barium Sulfate, and Reinforcement>>
50 mL of nitric acid having a concentration of 20% by mass is added to 10 g of the pulverized sample C and heated for about 20 minutes to dissolve the lead component as lead ions. The resulting solution is then filtered to remove solids such as carbonaceous materials and barium sulfate.

After dispersing the obtained solid content in water to form a dispersion, the reinforcing material is recovered from the dispersion using a sieve. The reinforcement is washed with water, dried and weighed. The ratio (percentage) of the mass of the dried product to the mass of sample C is determined. This ratio corresponds to the content of the reinforcing material in the negative electrode material.

After the reinforcing material has been removed, the dispersion is subjected to suction filtration using a membrane filter whose mass has been measured in advance, and the membrane filter is dried together with the filtered sample in a drier at 110°C ± 5°C. The obtained sample is a mixed sample of carbonaceous material and barium sulfate (hereinafter also referred to as sample F). The mass of the sample F (M _m ) is measured by subtracting the mass of the membrane filter from the total mass of the dried sample F and the membrane filter. Thereafter, the sample F after drying is placed in a crucible together with a membrane filter, and is ignited and incinerated at 1300° C. or higher. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate to obtain the mass of barium sulfate (M _B ). The mass of the carbonaceous material is calculated by subtracting the mass M _B from the mass M _m . The ratio (percentage) of the mass of the obtained barium sulfate and the mass of the carbonaceous material to the mass of the sample C is determined. In this way, the content of barium sulfate and the content of carbonaceous material in the negative electrode material are obtained.

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

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

When the electrolytic solution contains at least one of Al ions and Li ions, charge acceptance is improved, and thus higher IS life performance can be ensured.

The concentration of Al ions in the electrolytic solution is preferably 0.02 mol/L or higher, and may be 0.05 mol/L or higher. When the concentration of Al ions is within such a range, higher charge acceptance can be obtained. The concentration of Al ions in the electrolytic solution is, for example, 0.2 mol/L or less, and may be 0.15 mol/L or less. Even when the concentration of Al ions is within this range, a sufficient charge acceptance improvement effect can be obtained, and a high IS life performance can be ensured.

The Al ion concentration in the electrolytic solution is 0.02 mol/L or more (or 0.05 mol/L or more) and 0.2 mol/L or less, or 0.02 mol/L or more (or 0.05 mol/L or more). It may be 15 mol/L or less.

The concentration of Li ions in the electrolytic solution is preferably 0.02 mol/L or higher, and may be 0.05 mol/L or higher. When the concentration of Li ions is within this range, higher charge acceptance can be obtained. The concentration of Li ions in the electrolytic solution is, for example, 0.2 mol/L or less, and may be 0.15 mol/L or less. Even when the concentration of Li ions is within this range, a sufficient charge acceptance improvement effect can be obtained, and a high IS life performance can be ensured.

The concentration of Li ions in the electrolytic solution is 0.02 mol/L or more (or 0.05 mol/L or more) and 0.2 mol/L or less, or 0.02 mol/L or more (or 0.05 mol/L or more). It may be 15 mol/L or less.

The concentration of metal ions in the electrolyte is determined by high-frequency inductively coupled plasma (ICP) emission spectroscopy of the electrolyte taken out from a fully charged lead-acid battery. More specifically, an ICP emission spectrometer is used to identify the types of metal ions in the electrolytic solution and measure the luminescence intensity of the metal ions. The concentration of metal ions contained in the electrolytic solution is obtained from the measured value of the luminescence intensity and a calibration curve prepared in advance. As the ICP emission spectrometer, ICPS-8000 manufactured by Shimadzu Corporation is used.

The specific gravity of the electrolytic solution 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 matters described in this specification can be combined arbitrarily.

FIG. 3 shows an 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. 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 method for evaluating each characteristic will be described below.

(1) IS life performance In the following procedure, the number of cycles until the terminal voltage reaches 7.2 V is used as an indicator of IS life performance. The minute current discharge of (e) simulates the dark current discharge when the engine is stopped.
(a) After the battery is fully charged, place it in a cooling room at 0°C ± 1°C for at least 16 hours, and then check that the electrolyte temperature in any of the cells in the center is 0°C ± 1°C. do.
(b) Discharge the storage battery at a discharge current of 300 A for 1.0 second.
(c) discharge the storage battery at a discharge current of 25 A for 25 seconds;
(d) Charge the battery with a voltage of 14.0V for 30 seconds.
(e) Repeating the above (b) to (d) discharging and charging as one cycle. At this time, a minute current (20 mA) is discharged for 6 hours every 30 cycles.
(f) Calculate the number of cycles when the terminal voltage becomes less than 7.2 V in (b) above.

(2) High-temperature overcharge life performance A high-temperature overcharge endurance test is performed in the following procedure to measure the life of the lead-acid battery.
(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 these discharges and charges 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 this discharge and charge are also added to the number of lifespans (number of cycles).
(d) When the 30th second voltage measured in the test of (c) becomes 7.2 V or less and confirms that it does not rise again, the test is terminated, and the total number of cycles at this time is used as an index 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.

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

<<Lead-acid batteries E1 to E6 and C1 to C4>>
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 that, a part of the pore-forming agent was removed to prepare a microporous membrane. The amount of the pore-forming agent removed at the third and fourth ends of the main portion of the separator was adjusted. In this way, the ratio of the polymer material content to the oil content at the center and each end determined by the procedure described above was adjusted to the values shown in Table 1. The ratio Re1 of the oil content to the polymer material content at the first end, the ratio Re2 of the oil content to the polymer material content at the second end, the polymer material content of the oil content at the third end The ratio Re3 to the oil content and the ratio Re4 of the oil content at the fourth end to the content of the polymeric material are shown in Table 1. Table 1 also shows the average oil content of the separator obtained by the procedure described above.

Next, the sheet-like microporous membrane was folded in two to form a bag, and the overlapped ends were welded to obtain a bag-like separator. The bag-shaped separator was provided with protruding ribs (outer ribs) on the outer surface. The height of the outer ribs was 0.6 mm and the thickness of the base was 0.2 mm.

The ratio of the oil content at the center and each end of the separator to the content of the polymer material, the average oil content, the thickness of the base portion, and the height of the ribs are based on the separator before fabrication of the lead-acid battery. The obtained 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.

(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 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 100 mm, a height of 110 mm, and a thickness of 1.3 m. A negative plate was obtained. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used are 0.3 mass% and 2 .1% by weight, 0.1% by weight and 0.1% by weight.

(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 ears of the positive electrode plate and the ears of the negative electrode plate were welded to the shelf of the positive electrode and the shelf of the negative electrode 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.

As the electrolytic solution, an aqueous sulfuric acid solution or an aqueous sulfuric acid solution in which aluminum sulfate was dissolved was used. The specific gravity at 20° C. of the electrolytic solution after chemical conversion was 1.285. Table 1 shows the concentration of aluminum ions in the electrolytic solution obtained by the procedure described above.

(5) Evaluation Using the obtained lead-acid battery, the IS life performance and the high-temperature overcharge life performance were evaluated by the procedure described above. The IS life performance and the high-temperature overcharge life performance were evaluated by the ratio (%) of the number of cycles of each lead-acid battery to 100 cycles of the lead-acid battery C1.

Also, using the same separator as the separator used for the lead-acid battery, the puncture strength was measured according to the following procedure.
In accordance with JIS Z 1707: 2019 7.5 "Puncture strength test", fix the test piece including the edge of the separator with a jig, pierce the edge with the needle of the tester, until the needle penetrates Measure the maximum force (N) of Five test pieces are measured in the same manner, and the average value is determined as the puncture strength. A test piece is made by cutting the separator to a size of 50 mm long by 50 mm wide to include the edges. As a testing machine, AGS-X, 10N-10kN manufactured by Shimadzu Corporation is used. A needle with a diameter of 1.0 mm and a semicircular tip (radius of 0.5 mm) is used, and the test speed is 50±5 mm/min. The jig used for fixing the test piece has an upper surface diameter of 10 mm and a lower diameter of 20 mm.

Table 1 shows the evaluation results. E1 to E6 are examples. C1 to C4 are comparative examples.

As shown in Table 1, when the ratio of oil content to polymer material content in the bulk of the separator is uniform, lower average oil content improves IS life performance while increasing high temperature overheating performance. The charge life performance is greatly reduced (C1 to C4).

On the other hand, when Re1≧Rc is satisfied and Re3 and Re4 at the third end and the fourth end are smaller than Rc, high IS life performance is maintained while high high-temperature overcharge life performance is maintained. (E1-E6) are obtained. Even higher IS life performance is obtained when an electrolyte containing Al ions is used (compare E1 and E6). In E1 to E6, high puncture strength can be ensured.

In the example, the case where the ratio Re (Re3 and Re4 in Table 1) at both the third end and the fourth end is smaller than the ratio Rc was shown, but the third end is not limited to this case. When the ratio Re at one of the portion and the fourth end portion is smaller than the ratio Rc, the same effects as described above can be obtained. Further, even when the ratio Re at the second end is smaller than the ratio Rc, an effect similar to the above can be obtained.

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.

102: electrode plate, 104: separator, 105: main part of separator, 110: central part of main part of separator, 111: first end of main part of separator, 112: second end of main part of separator, 113: third end of main part of separator, 114: fourth end of main part of separator, D1: _first direction, D2: _second direction, 110a, 110b, 110c, 110d: oil in central part Areas for taking samples for measuring the content and content of polymeric material, 111a, 111b: Area for taking samples for measuring the oil content and the content of polymeric material at the first end, 112a; 112b: area for taking samples for measuring oil content and polymeric material content at the second end; 113a, 113b: for measuring oil content and polymeric material content at the third end; Sampling Areas 114a, 114b: Sampling Areas for Measuring Oil Content and Polymer Material Content at the Fourth End 1: Lead Acid Battery 2: Negative Plate 3: Positive Plate 4: separator, 5: positive electrode shelf, 6: negative electrode shelf, 7: positive electrode column, 8: through connector, 9: negative electrode column, 11: electrode plate group, 12: battery case, 13: partition wall, 14: cell chamber, 15: lid, 16: negative electrode terminal, 17: positive electrode terminal, 18: liquid port plug

Claims (10)

A lead-acid battery separator,
The separator contains a polymer material and oil, and includes a central portion, first and second ends positioned at both ends in a first direction, and a second separator perpendicular to the first direction. a third end and a fourth end located at both ends in the direction,
A ratio Re1 of the oil content in the first end portion to the polymer material content and a ratio Rc of the oil content in the central portion to the polymer material content satisfy Re1≧Rc. death,
the ratio Re of the oil content to the polymeric material content at at least one of the second end, the third end and the fourth end, and the ratio Rc at the central portion; is a lead-acid battery separator that satisfies Re<Rc. The third end and the fourth end are located outside both side ends of the central portion,
2. The lead-acid battery separator according to claim 1, wherein said ratio Re and said ratio Rc at at least one of said third end and said fourth end satisfy Re<Rc. 3. The lead-acid battery separator according to claim 1, wherein a difference (Rc-Re) between said ratio Rc and said ratio Re is 0.03 or more and 0.25 or less. The lead-acid battery separator according to any one of claims 1 to 3, wherein said polymer material comprises polyolefin. The lead-acid battery separator according to any one of claims 1 to 4, comprising inorganic particles. 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 any one of claims 1 to 5,
A lead-acid battery, wherein the first end faces upper ends of both the positive plate and the negative plate. The positive plate includes a positive current collector,
The negative plate includes a negative current collector,
7. The lead-acid battery according to claim 6, wherein at least one of said positive electrode current collector and said negative electrode current collector is formed by an expanding process. 8. The lead-acid battery according to claim 6, wherein said electrolyte contains at least one of aluminum ions and lithium ions. the concentration of the aluminum ions in the electrolytic solution is 0.02 mol/L or more and 0.2 mol/L or less;
9. The lead-acid battery according to claim 8, wherein the concentration of said lithium ions in said electrolytic solution is 0.02 mol/L or more and 0.2 mol/L or less. The lead-acid battery according to any one of claims 6 to 9, which is charged and discharged in a partially charged state.

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