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

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 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 percentage content of the oil at the first end part Ce1 and a percentage content of the oil at the central part Cc satisfy Ce1≥Cc. A percentage content of the oil at least at one of the second, third, and fourth end parts Ce and the percentage content of the oil at the central part Cc satisfy Ce<Cc.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separator for a lead-acid battery and a lead-acid battery including the same. [Background technology]

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. Lead-acid batteries include positive and negative electrode plates, a separator interposed between them, and an electrolyte. Separators for lead-acid batteries are required to have various performance characteristics.

[0003] Patent Document 1 proposes a flooded lead-acid battery having a positive electrode plate, a negative electrode plate, a separator separating the positive electrode plate and the negative electrode plate, and an electrolyte in which the positive electrode plate, the negative electrode plate, and the separator are immersed, characterized in that a porous layer is disposed between an upper portion of the positive electrode plate and an upper portion of the separator.

[0004] Patent Document 2 proposes a lead-acid battery including 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 electrolyte, wherein the aperture ratio of the perforated sheet differs between the upper and lower portions.

[0005] Patent Document 3 proposes a ribbed separator for lead-acid batteries containing 5 to 30 mass% of oil, which is obtained by heating and melting a raw material composition consisting of a mixture of 20 to 60 mass% of polyolefin resin, 80 to 40 mass% of inorganic powder, and 40 to 240 mass% of mineral oil relative to the blend, and kneading the mixture while forming it into a ribbed sheet.The separator is then immersed in an immersion bath of an organic solvent that can dissolve the oil to extract and remove some of the oil, and then heated and dried.The separator is characterized in that the difference in oil content between the rib portion and the base portion of the separator is 5 mass% or less. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 042850 [Patent Document 2] International Publication No. 2019 / 225389 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-338631 Summary of the Invention [Problem to be solved by the invention]

[0007] Lead-acid batteries are sometimes used in a partially charged state (PSOC). For example, in idle-stop (IS) applications, such as idle-start-stop (ISS) vehicles, lead-acid batteries are used in PSOC. Repeated charge and discharge in PSOC easily leads to stratification, where the electrolyte density in the upper part of the battery is low and the electrolyte density in the lower part of the battery is high. Furthermore, in IS applications, the engine is started frequently, resulting in repeated high-current discharges. Therefore, charge and discharge reactions tend to concentrate in the upper part of the electrode plate, leading to significant softening and detachment of the positive electrode material in the upper part of the positive plate. Previous attempts have been made to improve life performance by reducing the reactivity of the upper part of the electrode plate to make the reactivity of the entire electrode plate more uniform. However, it would be advantageous to improve the life performance (hereinafter sometimes referred to as IS life performance) during repeated charge and discharge in PSOC and IS tests, including high-current discharge.

[0008] Furthermore, the separator may contain oil as a pore-forming agent. When the separator contains oil, the separator resistance increases and the reactivity of the electrode plates decreases. Removing the oil from the separator can reduce the separator resistance and mitigate the decrease in the reactivity of the electrode plates. However, in this case, the life performance (hereinafter sometimes referred to as high-temperature overcharge life performance) when the lead-acid battery is overcharged at high temperatures (e.g., temperatures of 75°C or higher) decreases. [Means for solving the problem]

[0009] One aspect of the present invention is a separator for a lead-acid battery, wherein the separator contains oil and, in a main part, includes a central part, a first end part and a second end part located at both end parts in a first direction, and a third end part and a fourth end part located at both end parts in a second direction perpendicular to the first direction. The oil content Ce1 at the first end part and the oil content Cc at the central part satisfy Ce1 ≥ Cc, and the oil content Ce at at least one of the second end part, the third end part, and the fourth end part and the oil content Cc at the central part satisfy Ce < Cc. The present invention relates to a separator for a lead-acid battery.

Advantages of the Invention

[0010] In a lead-acid battery, high IS life performance and high high-temperature overcharge life performance can be ensured.

Brief Description of the Drawings

[0011] [Figure 1] It is a plan schematic view showing a state where a separator according to an embodiment of the present invention is stacked on a plate electrode. [Figure 2] It is a plan schematic view for explaining a part where a sample for measuring the oil content at the central part and each end part of the main part is taken for the separator of FIG. 1. [Figure 3] It is a partially cut-away perspective view showing the appearance and internal structure of a lead-acid battery according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0012] Generally, in IS tests for lead-acid batteries, stratification easily progresses because the plates are less likely to be overcharged and the electrolyte is less likely to be agitated. When stratification occurs, charge / discharge reactions concentrate at the top of the plate, increasing reactivity, while reactivity decreases at the bottom and sides of the plate. At the top of the positive plate, where charge / discharge reactions concentrate, the positive electrode material is more likely to deteriorate, soften, and fall off. Falling off of the positive electrode material reduces capacity and reduces IS life performance. Patent Documents 1 and 2 reduce reactivity variation in the plate by reducing the reactivity of the top of the plate. However, it would be ideal to reduce reactivity variation in the plate by increasing the reactivity of the less reactive portions of the plate.

[0013] When a lead-acid battery is overcharged, stratification and deterioration of the positive electrode material are reduced. However, the potential of the positive plate is high during overcharge, and the positive electrode material contains lead dioxide, a highly oxidizing positive electrode active material. Therefore, the separator facing the positive plate is prone to oxidative deterioration. Oxidative deterioration of the separator during overcharge is particularly pronounced at high temperatures (e.g., temperatures above 75°C). In lead-acid batteries, oxidative deterioration of the separator reduces its flexibility, causing cracks and short circuits, ultimately terminating the battery's life.

[0014] Separators sometimes contain oil as a pore-forming agent. This is advantageous in terms of ensuring a higher high-temperature overcharge life because it suppresses oxidative degradation of the separator. However, the insulating oil tends to clog the separator's pores, increasing the separator's resistance and reducing the reactivity of the electrode plates. Therefore, it is difficult to ensure a high IS life while maintaining a high high-temperature overcharge life in lead-acid batteries.

[0015] In view of the above, the separator for a lead-acid battery according to one aspect of the present invention contains oil, and in the main part, includes a central part, a first end part and a second end part located at both end parts in the first direction, and a third end part and a fourth end part located at both end parts in a second direction perpendicular to the first direction. The oil content rate Ce1 at the first end part and the oil content rate Cc at the central part satisfy Ce1 ≧ Cc. The oil content rate Ce at at least one of the second end part, the third end part, and the fourth end part and the oil content rate Cc of the oil at the central part satisfy Ce < Cc.

[0016] In this specification, at least one of the second end part, the third end part, and the fourth end part may be referred to as "at least one end part other than the first end part" or "end part other than the first end part". Further, an end part that satisfies Ce < Cc among the end parts other than the first end part may be simply referred to as "end part that satisfies Ce < Cc".

[0017] The separator on the side surface is reduced in resistance and can ensure high diffusibility of the electrolytic solution because, at at least one end other than the first end, the oil content is lower than that in the central portion and the first end. Further, the separator holds a relatively large amount of oil in the first end and the central portion. When such a separator is used in a lead storage battery, the first end can be opposed to the upper end of the electrode plate, and the end satisfying Ce < Cc can be opposed to at least one of the side end and the lower end of the electrode plate. By opposing the end of the separator satisfying Ce < Cc to a portion where the reactivity of the electrode plate tends to be low (specifically, at least one of the side end and the lower end of the electrode plate), the resistance can be reduced and the diffusibility of the electrolytic solution can be increased. As a result, the charge-discharge reaction easily proceeds at least one of the side end and the lower end of the electrode plate, and the reactivity can be enhanced. Thereby, the reactivity of the entire electrode plate can be made more uniform while maintaining high reactivity at the central portion and the upper end of the electrode plate. In particular, in the case of an IS application, since large-current discharge is performed, the influence of the diffusibility of the electrolytic solution on the life performance and the discharge performance is great. By improving the diffusibility of the electrolytic solution at the side end or the lower end, stratification is also reduced. Therefore, high IS life performance can be obtained. Further, the first end and the central portion of the separator opposed to the portion where the reactivity of the electrode plate is originally high contain more oil than the end satisfying Ce < Cc, so high oxidation resistance can be obtained. Therefore, when the lead storage battery is overcharged at a high temperature, high life performance (that is, high-temperature overcharge life performance) can be ensured.

[0018] The present invention also includes a lead storage battery including the above-described separator for a lead storage battery. The lead storage battery includes at least one cell including an electrode plate group and an electrolytic solution. 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 above-described separator for a lead storage battery. The first end of the separator faces the upper ends of both the positive electrode plate and the negative electrode plate.

[0019] The third and fourth ends of the separator are located outside both side ends of the central portion, and it is preferable that the oil content Ce in at least one of the third and fourth ends and the oil content Cc in the central portion satisfy Ce < Cc. In the third and fourth ends extending in a direction intersecting the first end, when the separator is industrially manufactured, the oil content can be easily adjusted. Therefore, high IS life performance and high high-temperature overcharge life performance can be more easily ensured.

[0020] The ratio Ce / Cc of the oil content Ce to the oil content Cc is preferably 0.50 or more and 0.95 or less. In this case, higher IS life performance can be obtained, and the high-temperature overcharge life performance can be further enhanced.

[0021] The separator preferably contains inorganic particles. In this case, since the wettability of the separator with respect to the electrolytic solution is increased, the resistance of the separator can be further reduced. Therefore, higher IS life performance can be obtained.

[0022] The separator preferably contains polyolefin. In a separator containing polyolefin, the oxidation resistance tends to be low. However, even in this case, since the first end and the central portion of the separator contain a relatively large amount of oil, high high-temperature overcharge life performance can be ensured.

[0023] In lead-acid batteries, the positive electrode plate typically includes a positive electrode current collector, and the negative electrode plate typically includes a negative electrode current collector. At least one of the positive electrode current collector and the negative electrode current collector may be formed by expanding. A current collector formed by expanding does not have vertically or horizontally extending bones. Therefore, in a plate including a current collector formed by expanding, the current collection path from the edge to the bottom or side end is long, which tends to reduce reactivity at the bottom or side end. Even in such a case, by controlling the oil content Ce at at least one end of the separator other than the first end to be smaller than the oil content Cc at the center, reactivity can be made more uniform throughout the plate, ensuring high IS life performance.

[0024] The electrolyte in the lead-acid battery may contain at least one of aluminum ions and lithium ions. In this case, the coarsening of lead sulfate particles generated during discharge is suppressed, improving charge acceptance and facilitating reduction of lead sulfate to lead during charge. The enhanced suppression of stratification results in a longer IS life.

[0025] The concentration of aluminum ions in the electrolyte is preferably 0.02 mol / L or more and 0.2 mol / L or less, and the concentration of lithium ions in the electrolyte 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 improved.

[0026] In applications where charging and discharging is performed at PSOC (for example, IS applications), repeated charging and discharging, including high-current discharge, results in a significant decrease in reactivity, particularly at the bottom and side edges of the electrode plates. A lead-acid battery including a lead-acid battery separator according to one aspect of the present invention can ensure excellent life performance even in such applications.

[0027] (Terminology explanation) (Main part of the separator) When the separator is interposed between a positive electrode plate and a negative electrode plate, the term "main portion of the separator" refers to the portion of the separator that faces both the region of the positive electrode plate where the electrode material is disposed and the region of the negative electrode plate where the electrode material is disposed. In an electrode plate assembly including a positive electrode plate and a negative electrode plate, in a separator that faces only each electrode plate located at the end of the electrode plate assembly, the term "main portion" refers to the portion of the main surface of each electrode plate that faces the region of the electrode material disposed. Note that the term "main surface of the electrode plate" refers to each of a pair of surfaces that occupy most of the surface of the electrode plate (i.e., a pair of surfaces excluding the end faces).

[0028] (Separator center, edges, first and second directions, and electrode plate edges) When viewed from a direction perpendicular to the surface of the separator, the separator includes, in its main part, a central portion and four end portions surrounding the central portion on all four sides. In the separator's main part, the four end portions are composed of a first end portion and a second end portion located at both ends in a first direction, and a third end portion and a fourth end portion located at both ends in a second direction perpendicular to the first direction. In the separator's main part, the central portion is sandwiched between the first end portion and the second end portion. In the separator's main part, the central portion, the first end portion, and the second end portion are sandwiched between the third end portion and the fourth end portion. In other words, in the separator's main part, the third end portion and the fourth end portion are located outside the both ends in the second direction of the central portion, the first end portion, and the second end portion.

[0029] In a lead-acid battery, the separator is arranged so that its first end faces the upper end of the electrode plate, so that its second end faces the lower end of the electrode plate, and its third and fourth ends face the side ends of the electrode plate.

[0030] The upper ends of the plates (positive and negative plates) correspond to the downstream ends in the current collection direction. Plates usually have lugs at their upper ends. The up-down direction of a plate is defined by the side where the lugs are provided being the upper side and the side opposite the lugs being the lower side. The up-down direction of the plate is the same as the up-down direction in the vertical direction of a lead-acid battery. In a separator, the side opposite the upper side of the plate (i.e., the lug side) is the upper side of the separator, and the side opposite the lower side of the plate is the lower side of the separator. In a lead-acid battery, the first direction of the separator is the up-down direction in the vertical direction of the lead-acid battery, and the second direction is the horizontal direction of the lead-acid battery.

[0031] (oil content in the center and edges of key parts) The separator's main portion is divided into four equal parts in the first direction and four equal parts in the second direction, for a total of 16 regions. The oil content Cc in the center of the main portion is determined for the four central regions. The oil content at each of the first and second ends is determined for two regions located outside the four central regions in the first direction. The oil content at each of the third and fourth ends is determined for two regions located outside the four central regions in the second direction. If the separator has ribs, the sample for determining the oil content is taken from a region without ribs.

[0032] The oil content is determined on a separator that is either unused or removed from a lead-acid battery that is in its early stages of use. If the separator is removed from a lead-acid battery, the separator is removed from a fully charged lead-acid battery.

[0033] (fully charged) In this specification, the fully charged state of a lead-acid battery is defined by JIS D 5301:2019. More specifically, the fully charged state is defined as a state in which a lead-acid battery is charged in a water tank at 25°C ± 2°C at a current (A) that is 1 / 10 of the value listed as the rated capacity, until the terminal voltage (V) during charging or the electrolyte density converted to a temperature of 20°C, measured every 15 minutes, shows a constant value to three significant digits three times in a row. The value listed as the rated capacity is in Ah. The unit of current set based on the value listed as the rated capacity is A.

[0034] A fully charged lead-acid battery is a lead-acid battery that has already been chemically formed and is fully charged. The lead-acid battery may be fully charged immediately after chemical formation, or after a certain period of time has passed since chemical formation (for example, a lead-acid battery that is in use (preferably in the early stages of use) after chemical formation may be fully charged).

[0035] In this specification, a battery in its early stages of use refers to a battery that has not been in use for a long time and has not deteriorated much.

[0036] (oil) Oil refers to a hydrophobic substance that is liquid at room temperature (a temperature between 20°C and 35°C) and separates from water. Oil includes naturally occurring oils, mineral oils, and synthetic oils.

[0037] (Polyolefin) Polyolefins are polymers containing at least olefin units (i.e., polymers containing at least monomer units derived from olefins). Polyolefins include, for example, olefin homopolymers, 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 types of olefin units. Furthermore, a copolymer containing olefin units and copolymerizable monomer units may contain one or more types of 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.

[0038] Hereinafter, lead-acid batteries according to embodiments of the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0039] (separator) The separator includes a central portion facing the electrode material, a first end portion and a second end portion sandwiching the central portion in a first direction, and a third end portion and a fourth end portion sandwiching the central portion, the first end portion, and the second end portion in a second direction. In the separator's main portion, the first end portion is located outside the upper end of the central portion, and the second end portion is located outside the lower end of the central portion. In the separator's main portion, the third end portion and the fourth end portion are located outside the respective side ends of the central portion, the first end portion, and the second end portion.

[0040] The separator contains oil, which is derived from, for example, a pore-forming agent used in the manufacturing process of the separator.

[0041] The oil content Ce1 at the first end and the oil content Cc at the central part satisfy Ce1 ≥ Cc. Since the first end is opposed to the upper end of the electrode plate, from the viewpoint of easily maintaining the high reactivity of the upper end of the electrode plate, the ratio Ce1 / Cc of the oil content Ce1 to the oil content Cc is preferably close to 1. The ratio Ce1 / Cc is, for example, 1.1 or less, and preferably 1.05 or less. In particular, when the ratio Ce1 / Cc = 1, the separator can be industrially easily manufactured while maintaining the high reactivity of the upper part of the electrode plate.

[0042] The oil content Ce at at least one end other than the first end and the oil content Cc at the central part satisfy Ce < Cc. Since the lower end of the electrode plate is particularly likely to have a reduced reactivity, from the viewpoint of increasing the reactivity of this lower end, the oil content Ce of the second end may be made less than Cc. From the viewpoint of easy industrial production of the separator, it is preferable that the oil content Ce in at least one of the third end and the fourth end satisfies Ce < Cc. From the viewpoint of increasing the reactivity at both side ends of the electrode plate and ensuring higher IS life performance, it is preferable that the oil content Ce is less than Cc at both the third end and the fourth end.

[0043] The ratio Ce / Cc of the oil content Ce to the oil content Cc is preferably 0.50 or more, and more preferably 0.53 or more. When the ratio Ce / Cc is in such a range, the oxidation resistance of the separator is enhanced, and higher high-temperature overcharge life performance can be ensured. The ratio Ce / Cc may be less than 1. From the viewpoint of enhancing the effect of making the reactivity of the entire electrode plate more uniform and obtaining higher IS life performance, it is preferably 0.95 or less, more preferably 0.93 or less, and even more preferably 0.9 or less.

[0044] The ratio Ce / Cc may be 0.50 or more (or 0.53 or more) and less than 1, 0.50 or more (or 0.53 or more) and 0.95 or less, 0.50 or more (or 0.53 or more) and 0.93 or less, or 0.50 or more (or 0.53 or more) and 0.9 or less.

[0045] The average oil content in the separator is, for example, 5% by mass or more. From the viewpoint of further enhancing the effect of suppressing oxidation degradation 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 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, it is easier to further reduce the resistance of the separator.

[0046] The average oil content of the separator may be 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), or 13% by mass or more and 20% by mass or less (or 18% by mass or less).

[0047] The separator has a portion outside the main portion that does not face the electrode material. More specifically, the separator has an upper end, a lower end, and both side end portions outside the main portion. The oil content in these portions is not particularly limited. From the viewpoint of easily adjusting the oil content at each end of the separator's main portion, the portion outside the separator's main portion may have the same oil content as the end of the adjacent main portion. For example, the upper end of the separator is adjacent to the first end of the main portion and may have the same oil content as the oil content Ce1 of the first end. The both side end portions of the separator are adjacent to the third and fourth ends of the main portion, respectively, and may have the same oil content as the third and fourth ends, respectively.

[0048] The separator may be in the form of a sheet. Alternatively, a sheet folded in an accordion shape may be used as the separator. The separator may be formed in a bag shape, and either the positive electrode plate or the negative electrode plate may be wrapped in the bag-shaped separator. In either form, the center and each end of the essential part are determined by viewing the surface (specifically, the top surface) of the separator from a direction perpendicular to the surface when the separator is placed on a flat surface.

[0049] The separator may or may not have ribs. A separator with ribs includes, for example, a base portion and ribs extending from the surface of the base portion. The ribs may be provided on only one surface of the separator or each base portion, or on both surfaces. The base portion of the separator refers to the portion of the separator that excludes protrusions such as ribs, and is the sheet-like portion that defines the outer shape of the separator.

[0050] The separator can be obtained, for example, by 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 penetrating agent (surfactant) into a sheet, and then removing the pore-forming agent. By removing at least a portion of the pore-forming agent, micropores are formed in the base polymer matrix. The oil content in the central portion and each end portion can be adjusted by adjusting the amount of oil removed from each of the separator's main portions, the central portion, and each end portion. For example, by removing a larger amount of oil from at least one end portion other than the first end portion than from the first end portion and the central portion, the oil content Ce can be adjusted to be less than the oil content Cc. The sheet-shaped separator may be folded into an accordion shape or processed into a bag shape as needed.

[0051] In a separator having ribs, the ribs may be formed on the sheet when the resin composition is extrusion-molded, or may be formed by pressing the sheet with a roller having grooves corresponding to each rib after molding the resin composition into a sheet or after removing the pore-forming agent.

[0052] The base polymer contained in the separator is not particularly limited as long as it is a base polymer used in separators for lead-acid batteries. Polyolefin is often used as the base polymer. Polyolefin may be used in combination with another base polymer as the base polymer. The proportion of polyolefin in the entire base polymer contained in the separator is, for example, 50% by mass or more, or 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 be composed of polyolefin alone. When the proportion of polyolefin is this high, oxidation resistance tends to be low. However, even in such a case, a high high-temperature overcharge life performance can be ensured because a certain amount of oil is contained in the first end and central portion of the separator.

[0053] The polyolefin may, for example, be at least C 2-3 Polymers containing olefins as monomer units are also included. 2-3 The olefin may be at least one selected from the group consisting of ethylene and propylene. The polyolefin may be, for example, polyethylene, polypropylene, C 2-3 Copolymers containing olefins as monomer units (e.g., ethylene-propylene copolymers) are more preferred. Among polyolefins, polyolefins containing at least ethylene units (polyethylene, ethylene-propylene copolymers, etc.) are preferred. Polyolefins containing ethylene units (polyethylene, ethylene-propylene copolymers, etc.) may be used in combination with other polyolefins.

[0054] Examples of pore-forming agents include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent contains at least oil. The use of oil further enhances the effect of suppressing oxidative degradation of the separator, resulting in high IS life performance. One type of pore-forming agent may be used alone, or two or more types may be used in combination. Oil may be used in combination with another pore-forming agent. A liquid pore-forming agent may be used in combination with a solid pore-forming agent. At room temperature (a temperature of 20°C or higher and 35°C or lower), liquid pore-forming agents are classified as liquid pore-forming agents, and solid pore-forming agents are classified as solid pore-forming agents.

[0055] The liquid pore-forming agent is preferably a mineral oil, a synthetic oil, etc. Examples of the liquid pore-forming agent include paraffin oil and silicone oil. Examples of the solid pore-forming agent include polymer powder.

[0056] The amount of pore-forming agent in the separator may vary depending on the type. The amount of pore-forming agent in the separator is, for example, 30 parts by mass or more per 100 parts by mass of the base polymer. The amount of pore-forming agent is, for example, 60 parts by mass or less per 100 parts by mass of the base polymer.

[0057] The surfactant used as the penetrating agent may be, for example, either an ionic surfactant or a nonionic surfactant. The surfactant may be used alone or in combination of two or more.

[0058] 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, and may be 10% by mass or less, or 5% by mass or less.

[0059] The content of the penetrant in the separator may be 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.

[0060] The separator (or the resin composition used to produce the separator) may contain inorganic particles. When the separator contains inorganic particles, the IS life performance can be further improved.

[0061] The inorganic particles are preferably, for example, ceramic particles, and examples of ceramics constituting the ceramic particles include at least one selected from the group consisting of silica, alumina, and titania.

[0062] The content of inorganic particles in the separator is, for example, 40% by mass or more, and may be 50% by mass or more. When the content of inorganic particles is in this range, higher IS life performance can be obtained. The content of inorganic particles may be, for example, 80% by mass or less, 75% by mass or less, or 70% by mass or less.

[0063] The content of inorganic particles in the separator may be 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) and 70% by mass or less.

[0064] The thickness of the separator's main portion is, for example, 0.15 mm or more. From the viewpoint of keeping the separator's resistance low, the thickness of the separator is preferably 0.25 mm or less, and more preferably 0.20 mm or less. The thickness of the separator's main portion means the average thickness of the main portion. When the separator has, in the main portion, a base portion and ribs erected from at least one surface of the base portion, the thickness of the separator's main portion is the average thickness of the base portion. When an attachment member (such as a mat or pasting paper) is attached to the separator, the thickness of the attachment member is not included in the thickness of the separator.

[0065] When the separator has ribs, the rib height may be 0.05 mm or more. Alternatively, the rib height may be 1.2 mm or less. The rib height is the height of the part that protrudes from the surface of the base part (protrusion height).

[0066] The height of the ribs provided in the region of the separator facing the positive electrode plate may be 0.4 mm or more, or 1.2 mm or less.

[0067] (Separator analysis or size measurement) For separator analysis or size measurement, unused separators or separators removed from lead-acid batteries in a fully charged state after initial use are used. The separators removed from the lead-acid batteries are washed and dried prior to analysis or measurement.

[0068] The separator removed from the lead-acid battery is washed and dried using the following procedure: The separator is immersed in pure water for one hour to remove the sulfuric acid from the separator. The separator is then removed from the liquid and left to dry for at least 16 hours in an environment of 25°C ± 5°C.

[0069] (oil content in separator) The separator is divided into 16 regions as described above. The four central regions are cut into strips to prepare samples for measuring the oil content Cc of the central region. The two upper regions of the four central regions are cut into strips to prepare samples for measuring the oil content Ce1 of the first end. The two lower regions of the four central regions are cut into strips to prepare samples for measuring the oil content of the second end. The two outer regions of the four central regions in the second direction are cut into strips to prepare samples for measuring the oil content of the third and fourth ends. For separators with ribs, each sample is cut so as not to include the ribs.

[0070] Approximately 0.5 g of each sample is taken and accurately weighed to determine the initial sample mass (m0). The weighed sample is placed in an appropriately sized glass beaker and 50 mL of n-hexane is added. Next, ultrasonic waves are applied to the sample in the beaker for approximately 30 minutes to dissolve the oil contained in the sample into n-hexane. The sample is then removed from the n-hexane and dried in the air at room temperature (a temperature of 20°C to 35°C), and then weighed to determine the mass (m1) of the sample after oil removal. The oil content is then calculated using the following formula. The oil content is determined for each sample a total of 10 times and the average value is calculated. The obtained average value is taken as the oil content at the center or each end. Oil content (mass%) = (m0 - m1) / m0 x 100

[0071] The average oil content in the separator is determined from a sample cut into strips from the four regions in the second row from the top out of the 16 regions into which the separator is divided. Except for using such a sample, the oil content is determined a total of 10 times in the same manner as for the oil content in the center or each end, and the average is calculated. The resulting average is the average oil content in the separator.

[0072] (Inorganic particle content in separator) A sample (hereinafter referred to as Sample A) is prepared by cutting the main part of the separator into strips. For separators with ribs, Sample A is prepared by cutting the base part of the main part of the separator into strips so as not to include the ribs.

[0073] A portion of sample A is taken and accurately weighed, then placed in a platinum crucible and heated with a Bunsen burner until no white smoke is emitted. The resulting sample is then heated in an electric furnace (in an oxygen stream, 550°C ± 10°C) for approximately 1 hour to incinerate it, and the ashes are weighed. The ratio (percentage) of the mass of the ashes to the mass of sample A is calculated, and this is taken as the inorganic particle content (mass%) in the separator. The inorganic particle content is determined a total of 10 times, and the average value is calculated. The resulting average value is taken as the inorganic particle content in the separator.

[0074] (Percentage of penetrant in separator) A portion of Sample A prepared in the same manner as above was taken, accurately weighed, and dried for at least 12 hours at room temperature (20°C to 35°C) under reduced pressure below atmospheric pressure. The dried material was placed in a platinum cell and placed in a thermogravimetric analyzer. The temperature was raised from room temperature to 800°C ± 1°C at a rate of 10 K / min. The weight loss upon raising the temperature from room temperature to 250°C ± 1°C was taken as the mass of the penetrant, and the percentage of the mass of the penetrant relative to the mass of Sample A was calculated, giving the penetrant content (mass%) in the separator. A TA Instruments Q5000IR thermogravimetric analyzer was used. The penetrant content was measured 10 times and the average value was calculated. The average value obtained was taken as the penetrant content in the separator.

[0075] (Separator thickness and rib height) The thickness of the separator is determined by measuring the thickness at five arbitrarily selected points on the base of the main part in a cross-sectional photograph of the separator and averaging the measurements.

[0076] The height of the rib is determined by averaging the heights of the base portion of the rib from one surface measured at 10 arbitrarily selected points on the rib in a cross-sectional photograph of the separator.

[0077] FIG. 1 is a schematic plan view showing a state where a separator according to an embodiment of the present invention is stacked on an electrode plate. A main part 105 of the separator 104 faces a portion where the electrode material of the electrode plate 102 exists. The separator 104 contains oil. The separator 104 includes, in the main part 105, a central part 110, a first end part 111 and a second end part 112 located at both ends in the first direction D1, and a third end part 113 and a fourth end part 114 located at both ends in the second direction D2. 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 electrode plate in a lead storage battery. The first end part 111 and the second end part 112 are located outside the upper and lower ends of the central part 110. The third end part 113 and the fourth end part 114 are located outside both side ends of the central part 110, the first end part 111 and the second end part 112. The separator 104 is stacked on the electrode plate 102 such that the first end part 111 faces the upper end part of the electrode plate 102. The oil content rate Ce1 at the first end part 111 and the oil content rate Cc at the central part 110 satisfy Ce1≧Cc. The oil content rate Ce at at least one of the second end part 112, the third end part 113 and the fourth end part 114 and the oil content rate Cc satisfy Ce<Cc. By controlling the oil content rate in this way, high IS life performance and high high-temperature overcharge life performance can be ensured in a lead storage battery.

[0078] FIG. 2 is a schematic plan view illustrating the areas where samples are taken to determine the oil content in the center and each end of the separator shown in FIG. 1 . The length of the main portion 105 of the separator 104 in the first direction D1 is L1, and the length in the second direction D2 is L2. As shown by the dotted lines in FIG. 2 , the main portion 105 is divided into four equal parts in the first direction D1 and four equal parts in the second direction D2, resulting in a total of 16 regions. The oil content Cc in the center portion 110 is determined from samples taken from four regions 110a, 110b, 110c, and 110d near the center of the main portion 105. The oil content Ce1 in the first end portion 111 is determined from samples taken from two regions 111a and 111b located at the upper end of the main portion 105. The oil content at the second end 112 is determined for samples taken from two regions 112a and 112b located at the bottom of the main portion 105. The oil content at the third end 113 is determined for samples taken from two regions 113a and 113b located at the side ends of the main portion 105 (specifically, outside regions 110a and 110c of the four regions 110a to 110d from which samples are taken in the central portion 110). The oil content at the fourth end 114 is determined for samples taken from two regions 114a and 114b located at the side ends of the main portion 105 (specifically, outside regions 110b and 110d of the four regions 110a to 110d from which samples are taken in the central portion 110). The average oil content in the separator 104 is determined for samples taken from the four regions 113a, 110a, 110b, and 114a in the second row from the top.

[0079] (positive electrode plate) A paste-type positive electrode plate is used as the positive electrode plate. The paste-type positive electrode plate includes a positive electrode collector and a positive electrode material. The positive electrode material is held by the positive electrode collector. The positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector. Note that a member such as a mat or pasting paper may be attached to the electrode plate. Such a member (also referred to as an attachment member) is used integrally with the electrode plate and is therefore included in the electrode plate. When the positive electrode plate includes an attachment member, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector and the attachment member.

[0080] The positive electrode current collector included in the positive electrode plate may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. Examples of processing methods include expanding and punching. It is preferable to use a lattice-shaped current collector as the positive electrode current collector because it is easy to support the positive electrode material.

[0081] The lead alloy used for the positive electrode current collector is preferably a Pb-Ca alloy or a Pb-Ca-Sn alloy 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 multiple layers.

[0082] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that generates capacity through an oxidation-reduction reaction. The positive electrode material may also include other additives (such as reinforcing materials) as needed.

[0083] Examples of reinforcing additives include fibers (inorganic fibers, organic fibers, etc.). Examples of resins (or polymers) that constitute organic fibers include at least one selected from the group consisting of 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.

[0084] The amount of the reinforcing material in the positive electrode material is, for example, 0.03 mass % or more, and the amount of the reinforcing material in the positive electrode material is, for example, 0.5 mass % or less.

[0085] The amount of reinforcing material in the positive electrode material can be determined by the following procedure: Analysis of the reinforcing material is carried out using positive electrode material sampled from a positive electrode plate removed from a fully charged lead-acid battery.

[0086] Positive electrode material is recovered from the positive electrode plate using 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 from the positive electrode plate. The washed positive electrode plate is then dried in a thermostatic chamber at 60°C ± 5°C for at least 5 hours. After drying, if the positive electrode plate contains an adhesive material, the adhesive material is removed from the positive electrode plate by peeling. Positive electrode material for analysis (hereinafter referred to as sample B) is obtained by collecting the positive electrode material from near the center of the top, bottom, and left and right sides when viewed from the front. Sample B is crushed as necessary and used for analysis.

[0087] The crushed sample B is collected and accurately weighed. Next, sample B is added to a mixed solution of aqueous nitric acid (concentration: 25% by mass) and aqueous tartaric acid (concentration: 500 g / L) (mixing ratio (volume ratio) of aqueous nitric acid to aqueous tartaric acid = 7:2), and the soluble components are dissolved while stirring under heat. The resulting mixture is filtered using a membrane filter (average pore size: 0.45 μm or less). This leaves the reinforcing material contained in the positive electrode material as a solid on the filter paper. The resulting solid is washed with water and dried. The mass of the dried material is measured. The ratio (percentage) of the mass of the dried material to the mass of sample B is calculated. This ratio corresponds to the amount of reinforcing material in the positive electrode material.

[0088] Unformed paste-type positive electrode plates are obtained by filling a positive electrode current collector with a positive electrode paste, aging it, and drying it. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and optionally other additives (such as reinforcing materials), and kneading them.

[0089] A positive electrode plate can be obtained by chemically forming an unformed positive electrode plate. Chemical formation can be performed by immersing an electrode plate assembly including the unformed positive electrode plate in an electrolyte containing sulfuric acid in a battery container of a lead-acid battery and then charging the electrode plate assembly. However, chemical formation may also be performed before assembling the lead-acid battery or the electrode plate assembly.

[0090] (negative plate) The negative electrode plate of a lead-acid battery is composed of a negative electrode current collector and a negative electrode material. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. Note that an adhesive member such as that described above may be attached to the negative electrode plate. In this case, the adhesive member is included in the negative electrode plate. When the negative electrode plate includes an adhesive member, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive member.

[0091] 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 expanding. Electrode plates using current collectors formed by expanding tend to have greater variations in reactivity. Even in such cases, the use of the lead-acid battery separator according to one aspect of the present invention can make the reactivity of the entire electrode plate more uniform.

[0092] The lead alloy used in the negative electrode current collector may be any of a Pb-Sb alloy, a Pb-Ca alloy, and a Pb-Ca-Sn alloy. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, and Cu. The negative electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or multiple layers.

[0093] The negative electrode material contained in the negative electrode plate contains a negative electrode active material (lead or lead sulfate) that generates capacity through an oxidation-reduction reaction, and may also contain an organic shrinkage inhibitor, a carbonaceous material, barium sulfate, etc. The negative electrode material may also contain other additives (such as a reinforcing material) as necessary.

[0094] Examples of the organic shrinkage inhibitor include lignin, lignin sulfonic acid, synthetic organic shrinkage inhibitors (such as formaldehyde condensates of phenol compounds), etc. The negative electrode material may contain one type of organic shrinkage inhibitor, or may contain two or more types.

[0095] The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more, and 1% by mass or less.

[0096] Examples of the carbonaceous material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, etc. The negative electrode material may contain one type of carbonaceous material or two or more types of carbonaceous materials.

[0097] The content of the carbonaceous material in the negative electrode material is, for example, 0.1 mass % or more, and may be, for example, 3 mass % or less.

[0098] The content of barium sulfate in the negative electrode material is, for example, 0.1% by mass or more, and 3% by mass or less.

[0099] Examples of the reinforcing material include fibers (inorganic fibers, organic fibers (such as organic fibers made of resin as described above for the reinforcing material of the positive electrode material)).

[0100] The amount of the reinforcing material in the negative electrode material is, for example, 0.03 mass % or more, and the amount of the reinforcing material in the negative electrode material is, for example, 0.5 mass % or less.

[0101] The negative electrode active material in the charged state is sponge lead, but the unformed negative electrode plate is usually made using lead powder.

[0102] The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying the paste to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is produced by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed, and kneading them. In the aging process, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature and at a high humidity.

[0103] The formation can be carried out by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery jar of a lead-acid battery and then charging the electrode plate assembly. However, the formation can also be carried out before assembling the lead-acid battery or the electrode plate assembly. The formation produces spongy lead.

[0104] (Analysis of negative electrode materials or their constituents) The following describes the method for quantifying the organic shrinkage inhibitor, carbonaceous material, barium sulfate, and reinforcing material in the negative electrode material. Quantitative analysis of the components of the negative electrode material is performed using negative electrode material sampled from a negative electrode plate removed from a fully charged lead-acid battery.

[0105] Negative electrode material is recovered from the negative plate using the following procedure. First, a fully charged lead-acid battery is disassembled to obtain the negative plate to be analyzed. The obtained negative plate is washed with water to remove sulfuric acid from the negative plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative plate and no color change is confirmed. However, the washing time should be within two hours. The washed negative plate is dried in a reduced pressure environment at 60±5°C for approximately six hours. After drying, if the negative plate contains an adhesive material, the adhesive material is removed from the negative plate by peeling. Next, the negative electrode material is separated from the negative plate to obtain a sample (hereinafter referred to as sample C). Sample C is crushed as necessary and subjected to analysis.

[0106] Quantitative determination of organic shrinkage inhibitors The crushed sample C is immersed in a 1 mol / L NaOH aqueous solution to extract the organic shrinkage inhibitor. Insoluble components are removed by filtration from the NaOH aqueous solution containing the extracted organic shrinkage inhibitor, and the filtrate (hereinafter also referred to as filtrate D) is recovered.

[0107] A predetermined amount of filtrate D is measured, desalted, concentrated, and dried to obtain a powder of the organic shrinkage preventer (hereinafter also referred to as sample E). Desalting can be performed using a desalting column, by passing filtrate D through an ion exchange membrane, or by placing filtrate D in a dialysis tube and immersing it in distilled water.

[0108] The organic shrinkage inhibitor is identified by combining information obtained from the infrared spectrum of sample E, the ultraviolet-visible absorption spectrum of a solution obtained by dissolving sample E in distilled water or the like, the NMR spectrum of a solution obtained by dissolving sample E in a solvent such as heavy water, or information obtained from pyrolysis GC-MS, which can obtain information on the individual compounds that make up the substance.

[0109] The ultraviolet-visible absorption spectrum of the filtrate D is measured. The content of the organic shrinkage inhibitor in the negative electrode material is quantified from the spectral intensity, the calibration curve prepared in advance, the measured amount of filtrate D, and the mass of sample C. If the structural formula of the organic shrinkage inhibitor to be analyzed cannot be precisely identified and a calibration curve for the same organic shrinkage inhibitor cannot be used, a calibration curve is prepared using an available organic shrinkage inhibitor that exhibits a similar ultraviolet-visible absorption spectrum, infrared spectrum, NMR spectrum, etc. to the organic shrinkage inhibitor to be analyzed.

[0110] Quantitative determination of carbonaceous materials, barium sulfate, and reinforcing materials 50 mL of 20% nitric acid was added to 10 g of crushed sample C and heated for approximately 20 minutes to dissolve the lead components as lead ions. The resulting solution was then filtered to separate out solids such as carbonaceous materials and barium sulfate.

[0111] The obtained solid content is dispersed in water to form a dispersion, and then the reinforcing material is recovered from the dispersion using a sieve. The reinforcing material is washed with water, dried, and its mass is measured. The ratio (percentage) of the mass of the dried material to the mass of sample C is calculated. This ratio corresponds to the content of the reinforcing material in the negative electrode material.

[0112] The dispersion liquid from which the reinforcing material has been removed is subjected to suction filtration using a membrane filter whose mass has been measured in advance, and the membrane filter together with the filtered sample is dried in a dryer at 110°C ± 5°C. The resulting sample is a mixed sample of carbonaceous material and barium sulfate (hereinafter also referred to as sample F). The mass of the membrane filter is subtracted from the total mass of sample F and the membrane filter after drying to determine the mass of sample F (M m ) is measured. After that, the dried sample F is placed in a crucible together with the membrane filter and burnt at 1300°C or higher to be incinerated. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate to determine the mass of barium sulfate (M B ) to find the mass M m to mass M B The mass of the carbonaceous material is calculated by subtracting the mass of the barium sulfate from the mass of the carbonaceous material obtained. The ratio (percentage) of the mass of the obtained barium sulfate and the mass of the carbonaceous material to the mass of sample C is calculated. In this way, the content of barium sulfate and the content of the carbonaceous material in the negative electrode material are determined.

[0113] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled if necessary.

[0114] 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.

[0115] When the electrolyte contains at least one of Al ions and Li ions, charge acceptance is improved, and therefore, a higher IS life performance can be ensured.

[0116] The concentration of Al ions in the electrolyte is preferably 0.02 mol / L or more, and may be 0.05 mol / L or more. When the concentration of Al ions is in this range, higher charge acceptance can be obtained. The concentration of Al ions in the electrolyte 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 in this range, a sufficient improvement in charge acceptance can be obtained, and high IS life performance can be ensured.

[0117] The concentration of Al ions in the electrolyte may be 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) and 0.15 mol / L or less.

[0118] The Li ion concentration in the electrolyte is preferably 0.02 mol / L or more, and may be 0.05 mol / L or more. When the Li ion concentration is in this range, higher charge acceptance can be obtained. The Li ion concentration in the electrolyte is, for example, 0.2 mol / L or less, and may be 0.15 mol / L or less. Even when the Li ion concentration is in this range, a sufficient improvement in charge acceptance can be obtained, and high IS life performance can be ensured.

[0119] The concentration of Li ions in the electrolyte may be 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) and 0.15 mol / L or less.

[0120] The concentration of metal ions in the electrolyte is determined by inductively coupled plasma (ICP) emission spectroscopy of the electrolyte removed from a fully charged lead-acid battery. More specifically, an ICP emission spectrometer is used to identify the type of metal ion in the electrolyte and measure the emission intensity of the metal ion. The concentration of metal ions in the electrolyte is determined from the measured emission intensity and a pre-prepared calibration curve. The ICP emission spectrometer used is an ICPS-8000 manufactured by Shimadzu Corporation.

[0121] The specific gravity of the electrolyte at 20° C. is, for example, 1.10 or more. The specific gravity of the electrolyte at 20° C. may be 1.35 or less. Note that these specific gravities are values ​​for the electrolyte of a fully charged lead-acid battery.

[0122] The items described in this specification can be combined in any manner.

[0123] FIG. 3 shows an external appearance of an example of a lead-acid battery according to an embodiment of the present invention. The lead-acid battery 1 includes a battery case 12 that contains a plate group 11 and an electrolyte (not shown). The battery case 12 is divided into multiple cell chambers 14 by partition walls 13. Each cell chamber 14 contains one plate group 11. The opening of the battery case 12 is closed by a lid 15 that has a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a vent plug 18 for each cell chamber. When rehydrating, the vent plug 18 is removed and rehydration liquid is added. The vent plug 18 may have the function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0124] Each electrode plate group 11 is formed by stacking multiple negative electrode plates 2 and multiple positive electrode plates 3 with separators 4 interposed between them. Here, a pouch-shaped separator 4 is shown housing the negative electrode plates 2, 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 6 that connects multiple negative electrode plates 2 in parallel is connected to a through-connector 8, and a positive electrode shelf 5 that connects multiple positive electrode plates 3 in parallel is connected to a positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 outside the lid 15. In a cell chamber 14 located at the other end of the battery case 12, a negative electrode column 9 is connected to the negative electrode shelf 6, and a 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 to connect the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0125] The evaluation method for each characteristic will be explained below.

[0126] (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. Note that the minute current discharge in (e) simulates a 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 confirm that the electrolyte temperature of one of the central cells is 0°C ± 1°C. (b) Discharge the battery at a discharge current of 300 A for 1.0 second. (c) Discharge the battery at a discharge current of 25A for 25 seconds. (d) The battery is charged at a voltage of 14.0 V for 30 seconds. (e) The discharge and charge cycles (b) to (d) are repeated, with a minute current (20 mA) being discharged for 6 hours every 30 cycles. (f) In (b) above, find the number of cycles when the terminal voltage falls below 7.2V.

[0127] (2) High temperature overcharge life performance A high-temperature overcharge durability test is conducted using the following procedure to measure the lifespan of a lead-acid battery. (a) The battery shall be kept in an air chamber at 75°C ± 3°C throughout the entire test period. (b) Connect the storage battery to a life test device and continuously repeat the following discharge and charge cycles. This discharge and charge cycle is considered one life (1 cycle). Discharge: Discharge current 25.0A ±0.1A for 60 seconds ±1 second Charging: 600 seconds ±1 second at charging voltage 14.80V ±0.03V (limited current 25.0A ±0.1A) (c) During the test, leave the battery for 56 hours after every 480 cycles, then discharge the battery continuously for 30 seconds at the rated cold cranking current of 390A and record the voltage at the 30th second. Then, charge the battery as described in (b). These discharges and charges are also included in the life cycle (number of cycles). (d) The test is terminated when it is confirmed that the voltage measured at 30 seconds in the test (c) is 7.2 V or less and does not rise again, and the total number of cycles at this point 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 after 30 seconds is 7.2V or higher when discharged at a temperature of -18°C ± 1°C.

[0128] [Example] 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.

[0129] Lead-acid batteries E1 to E6 and C1 to C4 Each lead-acid battery was fabricated according to 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 paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrating agent was extruded into a sheet, and then a portion of the pore-forming agent was removed to produce a microporous membrane. The ratio of the oil content Ce at each of the third and fourth ends to the oil content Cc at the center was adjusted by adjusting the amount of pore-forming agent removed from the third and fourth ends of the separator. Table 1 shows the ratios of the oil content Ce1 at the first end, the oil content Ce2 at the second end, the oil content Ce3 at the third end, and the oil content Ce4 at the fourth end to the oil content Cc at the center. The oil contents at the center and each end were determined using the procedure described above. Table 1 also shows the average oil content of the separator determined using the procedure described above. The silica particle content in the separator was 60% by mass.

[0130] Next, the sheet-like microporous membrane was folded in half to form a bag, and the overlapping ends were welded to obtain a bag-like separator. The bag-like separator had protruding ribs (external ribs) on its outer surface. The height of the external ribs was 0.6 mm, and the thickness of the base was 0.2 mm.

[0131] The oil content at the center and each end of the separator, the average oil content, the thickness of the base, the height of the ribs, and the content of silica particles were values ​​determined for the separator before fabrication into the lead-acid battery, but were almost the same as the values ​​measured by the above-mentioned procedure for the separator removed from the fabricated lead-acid battery.

[0132] (2) Preparation of the 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 into the mesh of an expanded grid made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed positive electrode plate measuring 100 mm wide, 110 mm high, and 1.6 mm thick.

[0133] (3) Preparation of negative electrode plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate, lignin, a reinforcing material (synthetic resin fiber), water, and sulfuric acid. The negative electrode paste was filled into the mesh of an expanded grid made of an antimony-free Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed negative electrode plate measuring 100 mm wide, 110 mm high, and 1.3 mm thick. The amounts of carbon black, barium sulfate, lignin, and synthetic resin fiber were adjusted so that the amounts of each component, measured using the previously described procedure on a negative electrode plate removed from a fully charged lead-acid battery, were 0.3 wt%, 2.1 wt%, 0.1 wt%, and 0.1 wt%, respectively.

[0134] (4) Preparation of lead-acid battery The unformed negative electrode plates were housed in a pouch-shaped separator and stacked with the positive electrode plates to form an electrode plate assembly consisting of seven unformed negative electrode plates and six unformed positive electrode plates.

[0135] The lugs of the positive and negative plates were welded to the positive and negative shelf sections, respectively, using the cast-on-strap (COS) method. The plate assembly was inserted into a polypropylene battery case, electrolyte was poured in, and chemical formation was performed inside the battery case to assemble a flooded lead-acid battery with a rated voltage of 12 V and a rated capacity of 30 Ah (5-hour rate capacity (capacity when discharged at a current (A) of 1 / 5 the Ah value listed on the rated capacity)). Six plate groups were connected in series inside the battery case.

[0136] The electrolyte used was a sulfuric acid aqueous solution or a sulfuric acid aqueous solution with aluminum sulfate dissolved in it. The specific gravity of the electrolyte after formation at 20°C was 1.285. The aluminum ion concentration in the electrolyte determined by the above-mentioned procedure is shown in Table 1.

[0137] (5) Evaluation The IS life performance and high-temperature overcharge life performance of the obtained lead-acid batteries were evaluated according to the procedures described above. The IS life performance and high-temperature overcharge life performance were evaluated as the ratio (%) of the number of cycles of each lead-acid battery to the number of cycles of lead-acid battery C1, which was set to 100.

[0138] The evaluation results are shown in Table 1. E1 to E6 are examples, and C1 to C4 are comparative examples.

[0139] [Table 1]

[0140] As shown in Table 1, when the oil content in the main part of the separator is uniform, as the average oil content decreases, the IS life performance improves, while the high-temperature overcharge life performance significantly decreases (C1 to C4).

[0141] In contrast, when Ce1 ≥ Cc is satisfied and the oil contents Ce3 and Ce4 at the third and fourth ends are less than Cc, high IS life is achieved while maintaining high high-temperature overcharge life (E1 to E6). When an electrolyte containing Al ions is used, even higher IS life is achieved (comparison of E1 and E6).

[0142] In the example, the case where the oil content at the third end and the fourth end is less than Cc is shown, but this is not limited to this case, and the same effect as above can be obtained even when the oil content at one of the third end and the fourth end is less than Cc. Furthermore, the same effect as above can be obtained even when the oil content at the second end is less than Cc. [Industrial Applicability]

[0143] The lead-acid battery separator according to the above aspect of the present invention is suitable for, for example, IS applications (such as lead-acid batteries for ISS vehicles) and as a starting power source for various vehicles (such as automobiles and motorcycles). The lead-acid battery separator can also be suitably used as a power source for industrial power storage devices such as electric vehicles (such as forklifts). These applications are merely examples. The applications of the lead-acid battery separator and lead-acid battery according to the above aspect of the present invention are not limited to these. [Explanation of symbols]

[0144] 102: electrode plate, 104: separator, 105: main part of separator, 110: center part of main part of separator, 111: first end part of main part of separator, 112: second end part of main part of separator, 113: third end part of main part of separator, 114: fourth end part of main part of separator, D1: first direction, D2: second direction, 110a, 110b, 110c, 110d: areas for taking samples to measure oil content Cc of central part, 111a, 111b: areas for taking samples to measure oil content Ce1 of first end part, 112 a, 112b: areas for taking samples to measure the oil content at the second end, 113a, 113b: areas for taking samples to measure the oil content at the third end, 114a, 114b: areas for taking samples to measure the oil content at the fourth end, 1: lead-acid battery, 2: negative electrode plate, 3: positive electrode plate, 4: separator, 5: positive electrode shelf, 6: negative electrode shelf, 7: positive electrode column, 8: feed-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 vent plug

Claims

1. A separator for a lead-acid battery, the separator contains oil and includes, in a main portion, a central portion, a first end portion and a second end portion located at both ends in a first direction, and a third end portion and a fourth end portion located at both ends in a second direction perpendicular to the first direction; the oil content Ce1 at the first end portion and the oil content Cc at the central portion satisfy Ce1≧Cc, an oil content Ce at at least one of the second end, the third end, and the fourth end and an oil content Cc at the central portion satisfy Ce<Cc; the first end faces upper ends of both a positive electrode plate and a negative electrode plate of a lead-acid battery to which the separator is applied, The separator for a lead-acid battery, wherein the first direction is parallel to a vertical direction of the positive electrode plate and the negative electrode plate.

2. 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 the oil content Ce and the oil content Cc in at least one of the third end and the fourth end satisfy Ce<Cc.

3. 3. The separator for a lead acid battery according to claim 1, wherein a ratio Ce / Cc of the oil content Ce to the oil content Cc is 0.50 or more and 0.95 or less.

4. The separator for a lead acid battery according to any one of claims 1 to 3, comprising inorganic particles.

5. The separator for a lead acid battery according to any one of claims 1 to 4, comprising a polyolefin.

6. A lead-acid battery, The lead-acid battery includes at least one cell including a plate pack 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 5.

7. The positive electrode plate includes a positive electrode current collector, The negative electrode plate includes a negative electrode current collector, The lead-acid battery according to claim 6, wherein at least one of the positive electrode current collector and the negative electrode current collector is formed by expanding.

8. 8. The lead-acid battery according to claim 6, wherein the electrolyte contains at least one of aluminum ions and lithium ions.

9. a 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 the lithium ions in the electrolyte is 0.02 mol / L or more and 0.2 mol / L or less.

10. The lead acid battery according to any one of claims 6 to 9, which is charged and discharged in a partial charged state.

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