Electrode group and lead-acid battery

Abstract

This electrode group 10 for a lead storage battery comprises: positive electrodes 20; negative electrodes 30; and separators 40 disposed between the positive electrodes 20 and the negative electrodes 30. The separators 40 are bag-shaped separators that accommodate the negative electrodes 30. Ribs 46 are disposed on inner surfaces 42 of the separators 40. The ribs 46 are disposed in regions 42a that are in the inner surfaces 42 and that face active material regions of the negative electrodes 30 and in regions 42b that are in the inner surfaces 42 and that do not face the active material regions of the negative electrodes 30. The contained amount of oil components in the separators 40 is more than 0 mass% but not more than 12 mass%.

Description

[Technical Field]

[0001] The present disclosure relates to an electrode group, a lead-acid battery, and the like. [Background technology]

[0002] Lead-acid batteries are one type of secondary battery that has been used for a long time, and are widely used as secondary batteries for industrial and consumer purposes due to their reliability, low cost, etc. In particular, there is a high demand for lead-acid batteries as lead-acid batteries for automobiles, electric vehicles, power supply devices, etc.

[0003] Lead-acid batteries are charged as frequently as the end user desires. If lead-acid batteries are not charged for a long period of time, stratification of the electrolyte (sulfuric acid) can occur. Stratification occurs when sulfate ions (SO4 2- Stratification occurs due to the tendency of lead sulfate to settle to the bottom. When stratification occurs, the concentration of dilute sulfuric acid at the bottom of the electrode increases, causing sulfation. Sulfation is a phenomenon in which lead sulfate, a discharge product, does not easily return to a charged state. As sulfation progresses, battery capacity decreases and crystals adhere to the surface of the negative electrode, reducing the contact area between the electrode and the electrolyte and slowing down the charging speed. This can reduce the lifespan of lead-acid batteries.

[0004] To address the issue of layering, Patent Document 1 below describes a technique related to a separator for a lead-acid battery, characterized in that an acid-resistant microporous resin film sheet and an acid-resistant nonwoven fabric sheet are laminated together. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-22389 Summary of the Invention [Problem to be solved by the invention]

[0006] Lead-acid batteries are required to have excellent charge acceptance in addition to suppressing deterioration in life characteristics.

[0007] An object of one aspect of the present disclosure is to provide an electrode group for obtaining a lead-acid battery having excellent charge acceptance.An object of another aspect of the present disclosure is to provide a lead-acid battery including the electrode group. [Means for solving the problem]

[0008] A first embodiment of an electrode group according to one aspect of the present disclosure relates to an electrode group for a lead-acid battery, comprising: a positive electrode; a negative electrode; and a separator disposed between the positive electrode and the negative electrode, wherein the separator is a bag-shaped separator that houses the negative electrode; ribs are disposed on an inner surface of the bag-shaped separator; the ribs are disposed in an area of ​​the inner surface that faces an active material region of the negative electrode and an area of ​​the inner surface that does not face the active material region of the negative electrode; and the content of an oil component in the separator is greater than 0 mass% and not more than 12 mass%.

[0009] A second embodiment of an electrode group according to one aspect of the present disclosure relates to an electrode group for a lead-acid battery, which includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a glass mat disposed between the positive electrode and the separator, wherein the content of an oil component in the separator is greater than 0 mass% and not more than 12 mass%.

[0010] A third embodiment of an electrode group according to one aspect of the present disclosure relates to an electrode group for a lead-acid battery, which includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the electrode group includes the same number of positive electrodes and negative electrodes, and the content of an oil component in the separator is greater than 0 mass % and not more than 12 mass %.

[0011] With these electrode groups, a lead-acid battery having excellent charge acceptance can be obtained.

[0012] A lead-acid battery according to another aspect of the present disclosure relates to a lead-acid battery including the above-described electrode group and a battery case that houses the electrode group. [Effects of the Invention]

[0013] According to one aspect of the present disclosure, it is possible to provide an electrode group for obtaining a lead-acid battery having excellent charge acceptance. According to another aspect of the present disclosure, it is possible to provide a lead-acid battery including the electrode group. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an end view showing an example of an electrode group and a lead-acid battery. [Figure 2] FIG. 2 is an end view showing another example of an electrode group and a lead-acid battery. [Figure 3] FIG. 3 is an end view showing another example of an electrode group and a lead-acid battery. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to the following embodiments.

[0016] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. Because specific gravity varies with temperature, in this specification, the specific gravity is defined as the specific gravity converted at 20°C.

[0017] The electrode group according to this embodiment (including the first, second, and third embodiments described below) is an electrode group for a lead-acid battery, and has a positive electrode (e.g., a positive electrode plate), a negative electrode (e.g., a negative electrode plate), and a separator disposed between the positive and negative electrodes. The lead-acid battery according to this embodiment includes the electrode group according to this embodiment and a battery case that houses the electrode group.

[0018] The content of the oil component in the separator is more than 0 mass% and not more than 12 mass% based on the total mass of the separator. In this case, excellent charge acceptance can be obtained. It is presumed that the oil component content in this range improves the diffusibility of sulfate ions, thereby obtaining excellent charge acceptance. However, the factors that result in excellent charge acceptance are not limited to these. Charge acceptance can be evaluated using a lead-acid battery having the same number of positive electrodes and negative electrodes as a comparative lead-acid battery.

[0019] The oil component is a component soluble in acetone (25°C). The oil component can be used to suppress oxidative degradation of the separator. The oil component may include mineral oil. Examples of mineral oil include paraffin-based process oil, lubricating oil, liquid paraffin, polyethylene wax, polypropylene wax, petroleum asphalt, and Vaseline.

[0020] The content of the oil component in the separator may be within the following ranges based on the total weight of the separator. From the viewpoint of easily suppressing short circuits caused by separator degradation (oxidative degradation, etc.) and therefore easily obtaining excellent life characteristics, the content of the oil component may be 1% by mass or more, 3% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 7.5% by mass or more, 8% by mass or more, 9% by mass or more, 10% by mass or more, or 11% by mass or more. From the viewpoint of easily obtaining excellent charge acceptance, the content of the oil component may be 11% by mass or less, 10% by mass or less, 9% by mass or less, 8% by mass or less, or 7.5% by mass or less. From these viewpoints, the content of the oil component may be 1 to 12% by mass, 7 to 12% by mass, 7 to 11% by mass, or 10 to 12% by mass. The content of the oil component is the content of components soluble in acetone (25°C). The content of the oil component can be measured by the method described in the Examples as the change in mass when the separator is immersed in acetone. The content of the oil component can be adjusted by the amount of oil component used when producing the separator.

[0021] Examples of the constituent material of the separator (constituent material of the base material constituting the separator, excluding oil components) include organic binders. Examples of organic binders include olefin resins, acrylic resins, urethane resins, and styrene resins. Examples of olefin resins include polyethylene and polypropylene. The separator does not need to contain glass.

[0022] The ash content of the separator may be in the following ranges. The ash content of the separator may be 30% by mass or more, 40% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 63% by mass or more, or 65% by mass or more. The ash content of the separator may be 90% by mass or less, 80% by mass or less, 70% by mass or less, 65% by mass or less, or 63% by mass or less. From these perspectives, the ash content of the separator may be 30 to 90% by mass, 40 to 80% by mass, or 50 to 70% by mass. The ash content of the separator can be measured by the method described in the Examples.

[0023] The porosity of the separator may be in the following ranges. The porosity of the separator may be 30% by volume or more, 40% by volume or more, 50% by volume or more, 55% by volume or more, 57% by volume or more, 60% by volume or more, or 61% by volume or more. The porosity of the separator may be 90% by volume or less, 80% by volume or less, 70% by volume or less, 65% by volume or less, 61% by volume or less, 60% by volume or less, or 57% by volume or less. From these perspectives, the porosity of the separator may be 30 to 90% by volume, 40 to 80% by volume, or 50 to 70% by volume. The porosity of the separator can be measured by the method described in the Examples.

[0024] The separator disposed between the positive electrode and the negative electrode may be at least partially disposed between the positive electrode and the negative electrode. The electrode group may include a plurality of separators. The separator may be in the form of a bag or a sheet.

[0025] The pouch-shaped separator can accommodate an electrode (positive electrode or negative electrode) and has an internal space for accommodating the electrode (positive electrode or negative electrode). In a "bagged separator," the internal space covers at least a portion (partial or all) of one side and the other side of the electrode, and supports the electrode at the lower vertical position when the electrode group is accommodated in a lead-acid battery, thereby holding the electrode in the internal space. The pouch-shaped separator may have an opening for accommodating the electrode (an opening through which the electrode can be inserted). In a pouch-shaped separator, at least a portion (partial or all) of the portion located below the opening direction for accommodating the electrode (the height direction (e.g., vertical direction) of the battery case when the electrode group is accommodated in a lead-acid battery; the same applies below) may be sealed. The pouch-shaped separator may be configured by folding back a single substrate (the folded portion of the substrate is the sealed portion), or may be configured by multiple substrates, with the substrates joined together at a portion located lower in the opening direction (the joint between the substrates is the sealed portion). The pouch-shaped separator may have at least one (one end or both ends) of its ends (the side of the pouch-shaped separator when the electrode group is housed in the lead-acid battery) in a direction intersecting (e.g., perpendicular to) the opening direction and substantially parallel to the inner surface (main surface) of the separator, and the end may be sealed at the joint between the substrates. The joint between the substrates may be a welded portion, a crimped portion (mechanical seal portion), or the like.

[0026] In the separator, the ribs may be arranged on at least one main surface selected from the group consisting of one surface and the other surface, and in the bag-shaped separator, the ribs may be arranged on at least one main surface selected from the group consisting of the inner surface and the outer surface.

[0027] Ribs may be arranged on the surface (main surface) of the separator facing the negative electrode. If the contact area between the negative electrode and the separator is large, dendrite shorts may occur, resulting in a decrease in life characteristics. In contrast, by arranging ribs on the surface facing the negative electrode, the contact area between the negative electrode and the separator can be reduced, making it easier to obtain excellent life characteristics. Note that ribs do not necessarily have to be arranged on the surface (main surface) of the separator facing the negative electrode.

[0028] The separator may not have ribs on its positive electrode side (main surface). In this case, the distance between the positive electrode and the negative electrode is prevented from widening, making it easier to obtain excellent charge acceptance. However, the separator may have ribs on its positive electrode side (main surface).

[0029] The rib may be an elongated member extending in one direction, and may extend in the opening direction (the height direction (e.g., vertical direction) of the battery case when the electrode group is housed in the lead-acid battery). The expression "the rib extending in the height direction of the battery case when the electrode group is housed in the lead-acid battery" means that the rib extends from the lower part (bottom) to the upper part of the battery case, and the rib may extend in a direction perpendicular to the bottom surface of the battery case, or may extend in a direction inclined relative to the perpendicular to the bottom surface of the battery case.

[0030] The separator can have at least one rib, and may have multiple ribs. The ribs may be arranged in a region facing the active material region of the electrode, or may be arranged in a region facing the active material region of the electrode and a region not facing the active material region of the electrode. The "active material region of the electrode" is a region of the electrode (positive electrode or negative electrode) in which active material is arranged. By arranging the ribs in a region facing the active material region of the electrode, it is possible to reduce the contact area between the active material region of the electrode and the separator, making it easier to obtain even better life characteristics. By arranging the ribs in a region not facing the active material region of the electrode, even if the electrode is misaligned, it is easier to reduce the contact area between the electrode and the separator after the misalignment.

[0031] When at least one of the ends of the bag-shaped separator in a direction intersecting the opening direction and substantially parallel to the inner surface of the separator is sealed, the inner surfaces of the separator may approach each other (the internal space may become narrower) toward the end. In this case, the inner surface of the separator and the electrode (e.g., the active material region of the electrode) tend to approach each other at or near the end, making contact between the separator and the electrode more likely. In contrast, the ribs arranged on the inner surface of the bag-shaped separator may include ribs arranged at a position that intersects (e.g., perpendicular to) the opening direction of the opening for accommodating the electrode (e.g., a negative electrode) and faces the end of the active material region of the electrode in a direction substantially parallel to the inner surface. That is, the internal space of the pouch-shaped separator may have a first space in the center in a second direction that intersects (e.g., perpendicular to) a first direction, which is the opening direction of the opening for accommodating an electrode (e.g., a negative electrode) and is substantially parallel to the inner surface of the pouch-shaped separator, and a second space in which an end of the active material region of the negative electrode in the second direction is located, the second space being narrower than the first space, and the rib may include a rib disposed in the second space. In this case, even if the end of the active material region of the electrode is located in a space that easily brings the inner surface of the separator and the electrode into close proximity, the contact area between the electrode and the separator can be easily reduced.

[0032] In the pouch-shaped separator, the ribs arranged on the inner surface of the pouch-shaped separator may be a plurality of ribs extending in the opening direction of the opening for accommodating an electrode (e.g., a negative electrode). The ribs may be spaced apart from one another from one end to the other end of the inner surface of the pouch-shaped separator (excluding the joint between the substrates) in a direction intersecting (e.g., perpendicular to) the opening direction (a direction intersecting the opening direction and substantially parallel to the inner surface of the pouch-shaped separator). In this case, even if the electrode is displaced, the contact area between the electrode and the separator after the displacement is easily reduced. The plurality of ribs may be arranged at substantially equal intervals. The rib intervals may be 0.1 to 10 mm, 0.5 to 5 mm, 0.5 to 1 mm, or 1 to 5 mm.

[0033] The separator may have a base and ribs disposed on at least one surface (main surface) of the base. The thickness T of the base, the height H of the ribs, or the ratio H / T of the height H of the ribs to the thickness T of the base (rib height H / thickness of the base T) may be within the following ranges to easily obtain excellent charge acceptance.

[0034] The thickness T of the base portion may be 0.01 mm or more, 0.05 mm or more, 0.1 mm or more, 0.15 mm or more, or 0.2 mm or more. The thickness T of the base portion may be 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.25 mm or less, or 0.2 mm or less. From these viewpoints, the thickness T of the base portion may be 0.01 to 0.5 mm, 0.05 to 0.4 mm, or 0.1 to 0.3 mm.

[0035] The rib height H may be 0.01 mm or more, 0.05 mm or more, 0.1 mm or more, or 0.15 mm or more. The rib height H may be 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, or 0.15 mm or less. From these perspectives, the rib height H may be 0.01 to 0.5 mm, 0.05 to 0.4 mm, or 0.1 to 0.3 mm. The heights of all ribs in the separator may be within these ranges.

[0036] The ratio H / T may be 0.1 or more, 0.3 or more, 0.5 or more, 0.7 or more, or 0.75 or more. The ratio H / T may be 2 or less, 1.5 or less, 1 or less, less than 1, 0.8 or less, or 0.75 or less. From these viewpoints, the ratio H / T may be 0.1 to 2, 0.3 to 1.5, or 0.5 to 1.

[0037] The electrode group may have a plurality of positive electrodes and a plurality of negative electrodes. The number of positive electrodes and negative electrodes in the electrode group may or may not be the same. When the number of positive electrodes and negative electrodes is not the same, the number of negative electrodes may be greater than the number of positive electrodes. The number of positive electrodes or negative electrodes in the electrode group may be 5 or more, 6 or more, 7 or more, or 8 or more. The number of positive electrodes or negative electrodes in the electrode group may be 10 or less, 9 or less, 8 or less, or 7 or less. The number of positive electrodes or negative electrodes in the electrode group may be 5 to 10, 6 to 9, or 7 to 8. At least one (one or both) of the outermost electrodes in the electrode group may be a negative electrode.

[0038] The positive electrode has a positive electrode current collector and a positive electrode active material supported on the positive electrode current collector. The negative electrode has a negative electrode current collector and a negative electrode active material supported on the negative electrode current collector. The positive electrodes and negative electrodes may be arranged alternately with a separator interposed between them. The positive electrode excluding the positive electrode current collector is referred to as the "positive electrode active material," and the negative electrode excluding the negative electrode current collector is referred to as the "negative electrode active material."

[0039] The positive electrode current collector serves as a conductive path for current from the positive electrode active material and holds the positive electrode active material. The negative electrode current collector serves as a conductive path for current from the negative electrode active material and holds the negative electrode active material. The negative electrode current collector may be the same as or different from the positive electrode current collector. Examples of materials constituting the current collector include lead alloys such as lead-calcium-tin alloys and lead-antimony-arsenic alloys. Depending on the application, selenium, silver, bismuth, etc. may be added to the current collector. The current collector has, for example, a lattice shape and may be a cast lattice, an expanded lattice, etc. The current collector can be obtained by forming a lead alloy into a lattice shape using a gravity casting method, an expanding method, a punching method, etc.

[0040] The plurality of positive electrodes may be electrically connected to one another by connecting the lugs provided on the positive electrode current collectors via straps. The positive electrode straps may be provided with positive electrode poles for connecting the positive electrodes to positive electrode terminals. The plurality of negative electrodes may be electrically connected to one another by connecting the lugs provided on the negative electrode current collectors via straps. The negative electrode straps may be provided with negative electrode poles for connecting the negative electrodes to negative electrode terminals.

[0041] The positive electrode active material may contain β-PbO2 as a Pb component. The positive electrode active material may contain α-PbO2 or may not contain α-PbO2. The positive electrode active material may contain Pb components other than PbO2 (e.g., PbSO4), additives, etc., as necessary.

[0042] Additives that can be contained in the positive electrode active material include carbon materials (excluding carbon fiber), short reinforcing fibers, etc. Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and ketjen black. Examples of short reinforcing fibers include acrylic fiber, polyethylene fiber, polypropylene fiber, polyethylene terephthalate fiber, and carbon fiber.

[0043] The negative electrode active material may contain Pb as a Pb component. The negative electrode active material may contain porous spongy lead. The negative electrode active material may contain Pb components other than Pb (e.g., PbSO4), additives, etc., as necessary.

[0044] Additives that can be included in the negative electrode active material include resins having sulfo groups and / or sulfonate groups, barium sulfate, carbon materials (excluding carbon fiber), and short reinforcing fibers. Examples of resins having sulfo groups and / or sulfonate groups include lignin sulfonic acid, lignin sulfonate salts (e.g., sodium lignin sulfonate), and condensates of phenols, aminoarylsulfonic acid, and formaldehyde (e.g., condensates of bisphenol, aminobenzenesulfonic acid, and formaldehyde). The negative electrode active material may contain at least one selected from the group consisting of lignin sulfonic acid, lignin sulfonate salts, and bisphenol-based resins, which facilitates excellent charge acceptance. In particular, the negative electrode active material may contain a bisphenol-based resin, which facilitates excellent charge acceptance. Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black, and ketjen black. Examples of reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, and carbon fibers.

[0045] The positive electrode active material and the negative electrode active material can be obtained by aging and drying an active material paste containing raw materials for the active materials to obtain an unformed active material, and then chemically converting the unformed active material. The positive electrode and the negative electrode can be obtained by aging and drying an active material paste supported on a current collector to obtain an unformed active material, and then chemically converting the unformed active material. The active material paste may contain a solvent and / or sulfuric acid. Examples of the solvent include water (e.g., ion-exchanged water) and organic solvents. The unformed positive electrode active material may contain tribasic lead sulfate as a main component. Examples of raw materials for the positive electrode active material include lead powder and red lead (Pb3O4). The unformed negative electrode active material may contain tribasic lead sulfate as a main component. Examples of raw materials for the negative electrode active material include lead powder.

[0046] The electrode group may include a glass mat disposed between the positive electrode and the separator. In this case, excellent life characteristics are easily obtained by suppressing the detachment of the active material from the positive electrode. The glass mat is a member containing glass, for example, a member formed by processing glass fibers into a mat shape. The glass mat may contain a resin material, such as an acrylic resin. The electrode group may include multiple glass mats. The electrode group may be a laminate of a positive electrode, a glass mat, a separator, and a negative electrode. The glass mat does not have to be bag-shaped. The electrode group does not necessarily have to include a glass mat disposed between the positive electrode and the separator.

[0047] The glass mat may cover at least a portion of the active material region of the positive electrode, or may cover the entire active material region (region where the positive electrode active material is disposed) of the positive electrode (at least one positive electrode). The larger the area of ​​the active material region of the positive electrode that is covered with the glass mat, the easier it is to suppress the active material from falling off in the positive electrode.

[0048] The electrode group according to the first embodiment has a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, the separator being a bag-shaped separator that houses the negative electrode, with ribs disposed on the inner surface of the bag-shaped separator, the ribs being disposed in an area of ​​the inner surface facing the active material region of the negative electrode and an area of ​​the inner surface not facing the active material region of the negative electrode, and the content of oil components in the separator is greater than 0% by mass and 12% by mass or less. In the lead-acid battery according to the first embodiment, it is sufficient that at least one rib is disposed in each of the area facing the negative electrode and the area not facing the negative electrode.

[0049] By arranging ribs on the inner surface of the pouch-shaped separator, the contact area between the electrode and the separator can be reduced, making it easier to obtain excellent life characteristics. On the other hand, in conventional batteries, the distance between the positive electrode and the negative electrode increases due to the arrangement of ribs, which can sometimes reduce charge acceptance. However, with the lead-acid battery according to the first embodiment, excellent charge acceptance can be obtained by obtaining the effects resulting from the content of the oil component described above. In other words, with the lead-acid battery according to the first embodiment, both excellent charge acceptance and life characteristics can be achieved.

[0050] The electrode group according to the second embodiment includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a glass mat disposed between the positive electrode and the separator, and the separator contains an oil component with a content of more than 0% by mass and 12% by mass or less. The glass mat disposed between the positive electrode and the separator prevents active material from falling off from the positive electrode, making it easier to achieve excellent life characteristics. Meanwhile, in conventional battery designs, the distance between the positive electrode and the negative electrode increases due to the presence of the glass mat, which can reduce charge acceptance. However, the electrode group according to the second embodiment achieves excellent charge acceptance by utilizing the effects resulting from the content of the oil component. In other words, the lead-acid battery according to the second embodiment achieves both excellent charge acceptance and life characteristics.

[0051] The electrode group according to the third embodiment includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The electrode group includes the same number of positive and negative electrodes, and the separator contains an oil component content of more than 0% by mass and 12% by mass or less. Generally, the active material utilization rate of the positive electrode is lower than that of the negative electrode. Therefore, to increase the active material utilization rate of the positive electrode, it is desirable to configure the electrode group with one more negative electrode than positive electrodes. While adding one positive electrode to achieve the same number of positive and negative electrodes may improve cold cranking performance, this may result in a decrease in the active material utilization rate of the positive electrode and a decrease in charge acceptance. However, the electrode group according to the third embodiment achieves the effects resulting from the oil component content described above, thereby achieving excellent charge acceptance even when the number of positive and negative electrodes is the same.

[0052] The electrode group according to the first embodiment may or may not include a glass mat disposed between the positive electrode and the separator. In the electrode group according to the first embodiment, the number of positive electrodes and the number of negative electrodes may or may not be the same. In the electrode group according to the second embodiment, the number of positive electrodes and the number of negative electrodes may or may not be the same.

[0053] The lead-acid battery according to this embodiment may include a plurality of electrode groups, and the lead-acid battery according to this embodiment may include the electrode group according to the first embodiment, the electrode group according to the second embodiment, or the electrode group according to the third embodiment as at least one of the plurality of electrode groups.

[0054] The lead-acid battery according to this embodiment has a hollow case with an internal space for accommodating the electrode group. The lead-acid battery according to this embodiment may include a lid for sealing the case. The lid may include a control valve for controlling the pressure inside the case, a positive electrode terminal for connecting the positive electrode to the outside, and a negative electrode terminal for connecting the negative electrode to the outside.

[0055] The lead-acid battery according to this embodiment may include a spacer member disposed between the electrode group and the battery case (the inner wall of the battery case). The spacer member may be a laminate of a glass mat and another sheet different from the glass mat. In this case, compared to when only a single-layer sheet is used as the spacer member, the frictional force between the electrode group and the spacer member is increased, which makes it easier to prevent the electrode group from shifting when inserting the electrode group into the battery case or during operation of the lead-acid battery, thereby making it easier to obtain excellent charge acceptance.

[0056] The sheet other than the glass mat may be a pulp sheet or the like. The glass mat and the other sheet may be bonded to each other. The glass mat and the other sheet may be bonded to each other with an adhesive.

[0057] In this laminate, the glass mat may be disposed on the electrode group side (facing the electrode group) to further prevent the electrode group from being displaced. When the electrode group has a positive electrode as the outermost electrode, the glass mat may face the outermost electrode (positive electrode) to prevent the active material from falling off the positive electrode and thereby obtain excellent life characteristics.

[0058] That is, the lead-acid battery according to this embodiment may have a spacer member disposed between the electrode group and the battery case, the spacer member being a laminate of a glass mat and another sheet different from the glass mat, with the glass mat of the spacer member disposed on the electrode group side. In this case, the lead-acid battery according to this embodiment may have a structure in which the electrode group has a positive electrode as the outermost electrode, and the glass mat of the spacer member faces the outermost electrode (positive electrode).

[0059] The lead-acid battery according to this embodiment may include an electrolyte. The electrolyte may be accommodated in a battery case. The electrolyte may contain sulfuric acid and may contain sulfate ions. The electrolyte may contain metal ions such as aluminum ions.

[0060] The specific gravity of the electrolyte (after chemical formation) may be within the following ranges. From the viewpoint of easily obtaining excellent charge acceptance, the specific gravity of the electrolyte may be 1.35 or less, 1.33 or less, 1.32 or less, 1.31 or less, 1.3 or less, 1.29 or less, 1.28 or less, 1.27 or less, or 1.26 or less. The specific gravity of the electrolyte may be 1.23 or more, 1.24 or more, 1.25 or more, 1.26 or more, 1.27 or more, or 1.28 or more. From these viewpoints, the specific gravity of the electrolyte may be 1.23 to 1.35, 1.25 to 1.3, or 1.26 to 1.28. The specific gravity of the electrolyte can be measured by the method described in the Examples.

[0061] Examples of an electrode group and a lead-acid battery are shown using Figures 1 to 3. Figures 1 to 3 show a lead-acid battery equipped with an electrode group having a pouch-shaped separator, and are end views of the electrode group and the lead-acid battery in the opening direction of the pouch-shaped separator.

[0062] 1 includes an electrode group 10, an electrolyte (not shown), and a battery case (not shown) that accommodates the electrode group 10 and the electrolyte. The electrode group 10 includes a plurality of positive electrodes 20, a plurality of negative electrodes 30, a plurality of separators 40 disposed between the positive electrodes 20 and the negative electrodes 30, and a plurality of glass mats 50 disposed between the positive electrodes 20 and the separators 40.

[0063] The positive electrodes 20 and the negative electrodes 30 are alternately arranged with separators 40 and glass mats 50 interposed therebetween. The negative electrodes 30 are housed in the internal space of the separator 40, which is a bag-shaped separator. The negative electrodes 30 have one surface 30a and the other surface 30b, which are covered by the separator 40. The separator 40 has an opening (the opening on the front side of the paper) for housing the negative electrodes 30.

[0064] The separator 40 has an inner surface 42 facing the negative electrode 30 and an outer surface 44 facing the positive electrode 20. The inner surface 42 has a region 42a facing the active material region of the negative electrode 30 and a region 42b not facing the active material region of the negative electrode 30. A plurality of ribs 46 are arranged on the inner surface 42 of the separator 40, with the ribs 46 being arranged in the region 42a and the region 42b, respectively. The ribs 46 extend in the opening direction of the separator 40 (a direction perpendicular to the paper surface) and are spaced apart from one another from one end to the other of the inner surface 42 of the separator 40 in a direction perpendicular to the opening direction and substantially parallel to the inner surface 42 of the separator 40. No ribs are arranged on the outer surface 44, and the outer surface 44 is in close contact with a glass mat 50. The glass mat 50 covers the entire active material region of the positive electrode 20.

[0065] The lead-acid battery 100a shown in FIG. 2 differs from the lead-acid battery 100 in that the electrode group 10 does not include the glass mat 50. Therefore, in the lead-acid battery 100a, the outer surface 44 of the separator 40 is in close contact with the positive electrode 20. The lead-acid battery 100b shown in FIG. 3 differs from the lead-acid battery 100 in that the separator 40 does not have a rib 46. Therefore, in the lead-acid battery 100b, the inner surface 42 of the separator 40 is in close contact with the negative electrode 30.

[0066] 1 to 3, the content of oil components in the separator 40 is more than 0 mass % and not more than 12 mass %. Such lead-acid batteries 100, 100a, 100b can achieve excellent charge acceptance.

[0067] An automobile, electric vehicle, or power supply device according to this embodiment is equipped with the lead-acid battery according to this embodiment. Examples of electric vehicles include electric forklifts and golf carts. Examples of power supply devices include uninterruptible power supplies (UPS), power supplies for disaster prevention (emergency) radios, and power supplies for telephones. This embodiment provides a lead-acid battery for an automobile, electric vehicle, or power supply device. [Example]

[0068] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0069] <Making a lead-acid battery> (Preparation of positive electrode plate) Lead powder and red lead (Pb3O4) were used as raw materials for the positive electrode active material (lead powder:red lead = 96:4 (mass ratio)). The raw materials for the positive electrode active material were mixed and kneaded with 0.07 mass% of reinforcing short fibers (acrylic fibers) based on the total mass of the raw materials for the positive electrode active material, and water. Next, dilute sulfuric acid (specific gravity: 1.28) was added little by little while kneading to prepare a positive electrode material paste. This positive electrode material paste was filled into a lead alloy grid (current collector) prepared by gravity casting. Next, the grid filled with the positive electrode material paste was aged for 24 hours in an atmosphere at a temperature of 50°C and a humidity of 98%. The positive electrode material paste was then dried to prepare an unformed positive electrode plate including the positive electrode material.

[0070] (Preparation of negative electrode plate) Lead powder was used as the raw material for the negative electrode active material. A mixture containing 1% by mass of barium sulfate particles, 0.2% by mass of Additive A or Additive B shown in Tables 1 and 2, 0.1% by mass of short reinforcing fibers (acrylic fibers), and 0.2% by mass of carbon material (oil furnace black) was mixed with the lead powder and then dry-mixed (the amount of each component is based on the total mass of the raw material (lead powder) for the negative electrode active material). Additive A was sodium lignosulfonate (manufactured by Nippon Paper Industries Co., Ltd., product name "Vanilex N"), and Additive B was bisphenol-based resin (manufactured by Nippon Paper Industries Co., Ltd., product name "Bispers P215"). Water was then added and the mixture was kneaded. Dilute sulfuric acid (specific gravity: 1.28) was gradually added and kneaded to prepare a negative electrode material paste. This negative electrode material paste was filled into a grid (current collector) prepared by expanding a rolled lead alloy sheet. Next, the grid filled with the negative electrode material paste was aged for 24 hours in an atmosphere at a temperature of 50°C and a humidity of 98%. After that, the negative electrode material paste was dried to prepare an unformed negative electrode plate including the negative electrode material.

[0071] (Preparing the separator) A bag-shaped separator was fabricated by folding a sheet (constituent material: polyethylene) having multiple long ribs on one side so that the side with the ribs was facing inward, and then mechanically sealing both ends of the sheet in a direction perpendicular to the longitudinal direction of the ribs. The ribs extended from one end of the sheet to the other and were arranged at approximately equal intervals from the center of the sheet to both ends in a direction perpendicular to the longitudinal direction of the ribs. No ribs were arranged on the other side of the sheet, and no ribs were arranged on the outside of the bag-shaped separator. The length of the bag-shaped separator in the longitudinal direction of the ribs was 122 mm, and the length of the bag-shaped separator in the direction perpendicular to the longitudinal direction of the ribs was 152 mm. The thickness T of the base of the sheet was 0.2 mm, the height H of the ribs was 0.15 mm, and the ribs were spaced 1 mm apart.

[0072] The oil amount (oil component content), ash content, and porosity of the bag-shaped separator were measured by the following procedures. The measurement results are shown in Tables 1 and 2.

[0073] The amount of oil was determined by measuring the change in mass when the sample was immersed in acetone (25°C). Specifically, the mass of the sample was measured before immersion. Next, acetone was poured into the beaker containing the sample, and the mixture was left for 18 hours while being slowly stirred. After air drying, the mass of the sample was measured. The mass of the sample before and after immersion was calculated as the amount of oil.

[0074] The ash content was determined by measuring the change in mass when the sample was heated at high temperature. Specifically, the sample was first dried and then its mass was measured. Next, the crucible containing the sample was heated for 3 hours in a firing furnace maintained at 600°C. After that, the crucible containing the sample was allowed to cool in a desiccator, and the mass of the sample was measured. The mass of the sample before and after heating was determined as the ash content.

[0075] The porosity was measured using an Autopore IV9520 manufactured by Shimadzu Corporation.

[0076] (Preparing the glass mat) An acrylic resin-containing glass mat was prepared, measuring 121 mm x 150 mm.

[0077] (Battery assembly) [Battery A] A negative electrode component was obtained by placing an unformed negative electrode plate in a pouch-shaped separator. Ribs were positioned on the inner surface of the pouch-shaped separator, in an area facing the active material region of the negative electrode plate and an area not facing the active material region of the negative electrode plate. Next, seven unformed positive electrode plates and eight negative electrode components were alternately stacked with a glass mat placed between the positive electrode plates and the negative electrode components. Subsequently, the lugs of plates of the same polarity were welded together using the cast-on-strap (COS) method to form an electrode assembly. The electrode assembly was inserted into an 80D26 battery case and the lid was welded to assemble an unformed 2V single-cell battery (corresponding to a D26-size single cell as specified in JIS D 5301). An electrolyte (sulfuric acid solution) was then poured into the battery, and formation was performed at a constant current of 16 A for 18 hours at 40°C to obtain a lead-acid battery. The specific gravity of the electrolyte after formation is shown in Table 1. The specific gravity of the electrolyte was measured using a portable density and specific gravity meter (product name: DA-130N) manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0078] [Battery B] A lead-acid battery was obtained in the same manner as battery A, except that the number of unformed positive plates was changed to eight and an unformed 12V battery (corresponding to size D26 specified in JIS D 5301) was assembled. The specific gravity of the electrolyte (sulfuric acid solution) after formation is shown in Table 2.

[0079] <Evaluation> The charge acceptance was evaluated based on the charge acceptance test 2 in accordance with JIS D 5301:2019. Battery A was evaluated relative to the result of the charge acceptance evaluation of Comparative Example A1, which was set to 100, and Battery B was evaluated relative to the result of the charge acceptance evaluation of Comparative Example B1, which was set to 100. The results are shown in Tables 1 and 2.

[0080] [Table 1]

[0081] [Table 2] [Explanation of symbols]

[0082] 10...electrode group, 20...positive electrode, 30...negative electrode, 30a...one side, 30b...other side, 40...separator, 42...inner surface, 42a, 42b...region, 44...outer surface, 50...glass mat, 100, 100a, 100b...lead-acid battery.

Claims

1. a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; the separator is a bag-shaped separator that accommodates the negative electrode, Ribs are arranged on the inner surface of the bag-shaped separator, the ribs are arranged in a region of the inner surface facing the active material region of the negative electrode and a region of the inner surface not facing the active material region of the negative electrode, An electrode group for a lead-acid battery, wherein the content of an oil component in the separator is 7.2 to 12 mass %.

2. 2. The electrode group according to claim 1, wherein the rib includes a rib arranged at a position facing an end of the active material region of the negative electrode in a direction that intersects with an opening direction of the opening for accommodating the negative electrode and is substantially parallel to the inner surface.

3. 3. The electrode group according to claim 1, wherein the ribs are a plurality of ribs extending in an opening direction of the opening for accommodating the negative electrode, and are arranged at a distance from one end to the other end of the inner surface in a direction intersecting the opening direction.

4. The electrode group according to claim 1 , further comprising a glass mat disposed between the positive electrode and the separator.

5. a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a glass mat disposed between the positive electrode and the separator; An electrode group for a lead-acid battery, wherein the content of an oil component in the separator is 7.2 to 12 mass %.

6. The electrode group according to claim 5 , wherein the glass mat covers the entire active material region of the positive electrode.

7. The electrode group according to any one of claims 1 to 6, wherein the number of the positive electrodes and the negative electrodes in the electrode group is the same.

8. An electrode group having a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the number of positive electrodes and the number of negative electrodes in the electrode group are equal, An electrode group for a lead-acid battery, wherein the content of an oil component in the separator is 7.2 to 12 mass %.

9. The electrode group according to any one of claims 5 to 8, wherein the separator is a bag-shaped separator that houses the negative electrode.

10. The electrode group according to any one of claims 1 to 9, wherein no rib is arranged on the surface of the separator on the positive electrode side.

11. A lead-acid battery comprising: the electrode group according to any one of claims 1 to 10; and a battery case that houses the electrode group.

12. The battery further includes a spacer member disposed between the electrode group and the battery case, the spacer member is a laminate of a glass mat and another sheet different from the glass mat, The lead-acid battery according to claim 11 , wherein the glass mat of the spacer member is disposed on the electrode group side.

13. the electrode group has the positive electrode as an outermost electrode, 13. The lead-acid battery according to claim 12, wherein the glass mat of the spacer member faces the outermost electrode.

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