Liquid lead storage battery

Abstract

The liquid lead storage battery includes an electrode plate group, an electrolyte solution, and a cell chamber that houses the electrode plate group and the electrolyte solution. The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator that is interposed between the positive electrode plate and the negative electrode plate. The difference (s-t) between the sum s of the distances between the positive electrode plates and the negative electrode plates facing each other in the electrode plate group and the sum t of the thicknesses of the separators is less than 0.10 mm. The positive electrode plate contains a positive electrode material. The negative electrode plate contains a negative electrode material. The negative electrode material contains an organic shrink-proofing agent that has an elemental sulfur content of 2,000 μmol / g or more. The ratio Cn / Cp of the theoretical capacity Cn of the negative electrode material to the theoretical capacity Cp of the positive electrode material satisfies 0.8 < Cn / Cp < 1.2.

Description

liquid lead acid battery

[0001] The present invention relates to a flooded lead-acid battery.

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. Lead-acid batteries include negative and positive plates, separators (or mats), and electrolytes. Each plate includes a current collector and an electrode material. Various attempts have been made to improve the performance of lead-acid batteries, such as improving the separator and using additives in the plates.

[0003] Patent Document 1 proposes a lead-acid battery comprising: an electrode plate group including a negative electrode plate, a positive electrode plate, and a separator interposed between the negative electrode plate and the positive electrode plate; and an electrolyte; the negative electrode plate includes a negative electrode material including a first carbon material and a second carbon material; the first carbon material has a particle diameter of 32 μm or more; the second carbon material has a particle diameter of less than 32 μm; a ratio R2 / R1 of a powder resistance R2 of the second carbon material to a powder resistance R1 of the first carbon material is 20 or more and 200 or less; and a distance D between the positive electrode plate and the negative electrode plate and a maximum thickness T of the separator satisfy −0.1 mm≦D−T≦0.1 mm.

[0004] Patent Document 2 proposes a lead-acid battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, in which the negative electrode has a negative electrode material containing a chemically treated mixture containing a raw material for a negative electrode active material and particles containing barium, the particles having an average primary particle size of 0.10 μm or less before the chemical treatment, and the electrolyte contains sodium ions.

[0005] International Publication No. WO 2019 / 188056 International Publication No. WO 2018 / 100639

[0006] The negative electrode plate of a lead-acid battery may contain an organic shrinkage inhibitor. Examples of organic shrinkage inhibitors include lignin compounds and synthetic organic shrinkage inhibitors. Synthetic organic shrinkage inhibitors have a relatively high sulfur content (e.g., 2000 μmol / g or more). Compared to the use of lignin compounds, the use of synthetic organic shrinkage inhibitors tends to provide superior high-temperature resistance. However, in flooded lead-acid batteries, the use of organic shrinkage inhibitors with a high sulfur content (e.g., 2000 μmol / g or more) results in a tradeoff: the amount of electrolyte lost increases.

[0007] One aspect of the present disclosure relates to a flooded lead-acid battery, the flooded lead-acid battery including: a plate assembly, an electrolyte, and a cell chamber that accommodates the plate assembly and the electrolyte; the plate assembly includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate; a difference (s-t) between a total distance s between the positive electrode plate and the negative electrode plate facing each other in the plate assembly and a total thickness t of the separator is less than 0.10 mm; the positive electrode plate includes a positive electrode material; the negative electrode plate includes a negative electrode material; the negative electrode material includes an organic shrinkage inhibitor having an elemental sulfur content of 2000 μmol / g or more; and a ratio Cn / Cp of a theoretical capacity Cn of the negative electrode material to a theoretical capacity Cp of the positive electrode material satisfies 0.8<Cn / Cp<1.2.

[0008] In flooded lead-acid batteries, the amount of electrolyte lost can be reduced.

[0009] 1 is a partially cutaway exploded perspective view schematically illustrating the appearance and internal structure of a lead-acid battery according to one aspect of the present invention.

[0010] Negative electrode materials for lead-acid batteries are prone to degradation in high-temperature environments, and organic shrink-regulating agents with a high sulfur content (e.g., 2000 μmol / g or more) exhibit superior high-temperature resistance compared to organic shrink-regulating agents with a low sulfur content (e.g., less than 2000 μmol / g), such as lignin compounds. Hereinafter, organic shrink-regulating agents with a sulfur content of 2000 μmol / g or more may be referred to as the "first organic shrink-regulating agent," and organic shrink-regulating agents with a sulfur content of less than 2000 μmol / g may be referred to as the "second organic shrink-regulating agent." The superior high-temperature resistance achieved when using the first organic shrink-regulating agent is believed to be due to the first organic shrink-regulating agent's high effectiveness in suppressing degradation of the negative electrode material in high-temperature environments, thereby maintaining a large specific surface area of ​​the negative electrode material and thereby achieving excellent discharge performance. On the other hand, when the first organic shrinkage inhibitor is used, the reactivity with protons during overcharge is higher and a larger amount of hydrogen gas is generated, resulting in a more significant decrease in the electrolyte solution, compared to when the second organic shrinkage inhibitor is used. Hereinafter, the decrease in the electrolyte solution will be referred to as "liquid reduction," and the amount of decrease in the electrolyte solution will be referred to as "amount of reduced electrolyte solution."

[0011] In view of the above, (1) a flooded lead-acid battery according to one aspect of the present invention includes a plate assembly, an electrolyte, and a cell chamber that accommodates the plate assembly and the electrolyte. The plate assembly includes positive plate(s), negative plate(s), and a separator interposed between the positive plate(s) and negative plate(s). The difference (s-t) between the total distance (s) between the opposing positive plate(s) and negative plate(s) in the plate assembly and the total thickness (t) of the separator(s) is less than 0.10 mm. The positive plate(s) includes a positive electrode material. The negative plate(s) includes a negative electrode material. The negative electrode material includes an organic shrinkage preventer (i.e., a first organic shrinkage preventer) having a sulfur element content of 2000 μmol / g or more. The ratio (Cn / Cp) of the theoretical capacity (Cn) of the negative electrode material to the theoretical capacity (Cp) of the positive electrode material satisfies 0.8<Cn / Cp<1.2. The flooded lead-acid battery is also called a vented lead-acid battery.

[0012] When a first organic shrink-proofing agent is used and (st) ≧ 0.10 mm, the tendency for liquid loss does not change even if the ratio Cn / Cp changes. When a second organic shrink-proofing agent is used, the tendency for liquid loss with respect to the ratio Cn / Cp does not change significantly, whether (st) < 0.10 mm or (st) ≧ 0.10 mm. Furthermore, when a first organic shrink-proofing agent is used and (st) < 0.10 mm, the amount of liquid loss at Cn / Cp = 0.8 or Cn / Cp = 1.2 tends to be similar to or slightly reduced when (st) ≧ 0.10 mm. In contrast, when a first organic shrink-proofing agent is used and 0.8 < Cn / Cp < 1.2 is satisfied, the amount of liquid loss can be significantly reduced when (st) < 0.10 mm.

[0013] In the lead-acid battery according to one aspect of the present invention, the reduction in the amount of liquid loss is believed to be due to the following (a) and (b): (a) By satisfying (st)<0.10 mm and 0.8<Cn / Cp<1.2, a gas absorption reaction occurs even though the battery is a flooded lead-acid battery; and (b) the gas absorption efficiency of the first organic shrinkage inhibitor is higher than that of the second organic shrinkage inhibitor.

[0014] Regarding (a) above, when (st) < 0.10 mm, the space between the plates is more closed, making it difficult for oxygen generated at the positive plate to escape to the outside of the space between the plates. This increases the oxygen concentration in the space between the plates, allowing oxygen to be efficiently supplied to the negative electrode. Furthermore, by setting the Cn / Cp ratio within the above range, it becomes easier to balance the amount of oxygen gas generated at the positive plate and the amount of hydrogen gas generated at the negative plate during charging. As a result, a gas absorption reaction is thought to occur despite the battery being a flooded lead-acid battery. Furthermore, since much of the generated gas is consumed in the gas absorption reaction, the gas absorption reaction is highly efficient and the amount of gas not consumed in the gas absorption reaction is reduced. As a result, the amount of liquid loss is reduced.

[0015] When (st)<0.10 mm, the space between the plates is narrower and more closed than when (st)≧0.10 mm. Even when a rib (first rib) described below is formed on the separator, the space between the first rib, surrounded by the separator (more specifically, the base portion described below) and the positive plate, is narrower and more closed. In these cases, the relative reduction in the space between the plates is referred to as a relative increase in the degree of space closure. It is believed that the increased closure of the space between the plates allows a gas absorption reaction to occur in the lead-acid battery of one aspect of the present invention, despite being a liquid-type battery.

[0016] Regarding the above (b), when the first organic shrink-proofing agent is used, the specific surface area of ​​the negative electrode material is larger than when the second organic shrink-proofing agent is used, and the organic shrink-proofing agent is less likely to aggregate on the surface of the negative electrode plate. As a result, when the first organic shrink-proofing agent is used, the movement of oxygen on the negative electrode plate is less likely to be hindered than when the second organic shrink-proofing agent is used, and it is thought that this results in a higher gas absorption efficiency.

[0017] In addition, in a flooded lead-acid battery according to one aspect of the present invention, the negative electrode material contains a first organic shrinkage inhibitor, which provides higher high-temperature resistance than a negative electrode material containing a second organic shrinkage inhibitor. Therefore, even when the battery is overcharged at a high temperature (e.g., 50°C or higher and 80°C or lower) and then discharged at a high rate, deterioration of the negative electrode material is suppressed, ensuring a long discharge duration. Therefore, both high high-temperature resistance and excellent suppression of liquid loss can be achieved.

[0018] (2) In the above (1), the ratio Cn / Cp may satisfy 0.9≦Cn / Cp≦1.1. In this case, the amount of liquid loss can be further reduced.

[0019] (3) In the above (1) or (2), the difference (s−t) may be 0.07 mm or less, which can further reduce the amount of liquid loss.

[0020] Flooded lead-acid batteries are sometimes used in a state of insufficient charge known as a partial state of charge (PSOC). When a lead-acid battery is used in PSOC, stratification, in which the electrolyte density gradually decreases in the upper part of the battery and increases in the lower part of the battery, is likely to occur. As stratification progresses, lead sulfate accumulates significantly in the lower part of the negative electrode plate, making sulfation, in which lead sulfate crystals form, more likely to occur. This leads to a decrease in capacity and uneven charge / discharge reactions, which deteriorate the electrode plates and shorten the life of the lead-acid battery. In this specification, idle reduction (IDS) is sometimes simply referred to as IS. An example of an IS application is a vehicle equipped with an idle reduction system. In such applications, a high life performance in PSOC is required. Hereinafter, life performance in PSOC may be referred to as PSOC life performance.

[0021] (4) In any one of (1) to (3) above, in a cross section of the flooded lead-acid battery parallel to the bottom of the cell chamber, the ratio Ra (= Se / Sg = (S1-Sg) / Sg) of the area (Se) obtained by subtracting the cross-sectional area (Sg) of the plate pack from the cross-sectional area (S1) of the cell chamber interior to the cross-sectional area (Sg) of the plate pack may be 0.20 or less. In this case, the amount of electrolyte loss can be further reduced. The area (= Se = S1-Sg) obtained by subtracting the cross-sectional area of ​​the plate pack from the cross-sectional area of ​​the cell chamber interior corresponds to the cross-sectional area of ​​the electrolyte present outside the outer edge of the plate pack (outside the plate pack) in the cross section (in other words, the electrolyte surrounding the plate pack in the cell chamber in which the plate pack is housed). Therefore, when Ra ≦ 0.20, the amount of electrolyte present outside the plate pack can be said to be smaller than when Ra > 0.20. When Ra≦0.20, the amount of oxygen generated in the positive electrode plate that migrates to the electrolyte present outside the electrode plate assembly is smaller than when Ra>0.20, allowing a high concentration of oxygen to remain between the electrodes. Therefore, when Ra≦0.20, more oxygen is supplied to the negative electrode than when Ra>0.20, which is thought to make the gas absorption reaction more likely to occur. Furthermore, when Ra≦0.20, the PSOC life performance is significantly improved compared to when Ra>0.20. This is thought to be because the relatively small amount of electrolyte present outside the electrode plate assembly suppresses stratification and plate deterioration.

[0022] (5) In any one of (1) to (4) above, the electrolyte may further contain at least one metal cation selected from the group consisting of Na ions, Li ions, and Al ions. When the gap between the electrodes is narrow, such that the difference (s-t) is less than 0.10 mm, permeation short-circuiting is likely to occur. When the electrolyte contains the above metal cation, the growth of lead into a dendritic shape is suppressed, thereby suppressing permeation short-circuiting.

[0023] (6) In the above (5), the concentration of the metal cation in the electrolyte may be 0.03 mol / L or more, which can further suppress permeation short-circuiting.

[0024] (7) In any one of (1) to (6) above, the number of positive plates in the electrode plate group may be one less than the number of negative plates. In this case, all positive plates are sandwiched between negative plates. This allows oxygen generated at the positive plates to be trapped between the positive and negative plates, making it easier to supply oxygen to the negative plates. As a result, the reduction in the liquid can be further suppressed.

[0025] (8) In any one of (1) to (7) above, the volume median pore diameter of the positive electrode material may be 0.50 μm or less. In this case, the size of the oxygen gas generated at the positive electrode plate is reduced, and the amount of dissolved oxygen in the electrolyte is increased, making it easier to retain oxygen between the positive electrode plate and the negative electrode plate. This allows for a larger amount of oxygen to be supplied to the negative electrode plate, and the gas absorption reaction can be carried out more efficiently. As a result, the loss of liquid can be further suppressed.

[0026] The volume median pore diameter of the positive electrode material is the pore diameter corresponding to the median of the cumulative pore volume in the volumetric pore distribution determined by mercury intrusion porosimetry.

[0027] (9) In any one of (1) to (8) above, the separator may have at least a rib (first rib) protruding toward the positive electrode plate. The presence of the first rib increases the sealing of the space surrounded by the separator and the positive electrode plate. The increased oxygen concentration in this space facilitates the supply of more oxygen to the negative electrode plate. This facilitates the gas absorption reaction, further reducing the amount of liquid loss. The separator may also have a rib (second rib) protruding toward the negative electrode plate, as needed. The first rib is formed, for example, on a portion of the separator facing the portion where the positive electrode material is present. The second rib is formed, for example, on a portion of the separator facing the portion where the negative electrode material is present. The separator typically has a base portion. In a separator with ribs, the rib protrudes from the surface of the base portion. The base portion of the separator refers to the portion of the separator excluding protrusions such as ribs, and is the sheet-like portion that defines the separator's outer shape.

[0028] (10) In the above (9), the average spacing between the first ribs may be 1.0 cm or less. In this case, the space formed between the separator and the positive electrode plate between adjacent first ribs becomes more closed, making it easier for the gas absorption reaction to occur, thereby further reducing the amount of liquid loss.

[0029] The flooded lead-acid battery according to one aspect of the present invention will be described in more detail below, including the above (1) to (10). At least one selected from the components described below can be arbitrarily combined with at least one of the above (1) to (10) for the flooded lead-acid battery according to one aspect of the present invention, as long as such combination is technically possible.

[0030] [Flooded Lead Acid Battery] A flooded lead acid battery may include at least one cell. The cell includes a plate assembly, an electrolyte, and a cell chamber that accommodates the plate assembly and the electrolyte. The plate assembly includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates.

[0031] In a flooded lead-acid battery according to one aspect of the present invention, the difference (s-t) is less than 0.10 mm. When the difference (s-t) is this small, the amount of liquid loss can be reduced by including a first organic shrinkage inhibitor in the negative electrode material and ensuring that the ratio Cn / Cp satisfies 0.8<Cn / Cp<1.2. From the perspective of further reducing the amount of liquid loss, the difference (s-t) may be 0.07 mm or less, or even 0.05 mm or less. From the perspective of reducing permeation short circuits and suppressing stratification, the difference (s-t) may be, for example, -0.15 mm or more, or even -0.10 mm or more.

[0032] The difference (s−t) may be −0.15 mm or more (or −0.10 mm or more) and less than 0.10 mm, −0.15 mm or more (or −0.10 mm or more) and 0.07 mm or less, or −0.15 mm or more (or −0.10 mm or more) and 0.05 mm or less.

[0033] The ratio Cn / Cp may be greater than 0.8 and equal to or greater than 0.9. The ratio Cn / Cp may be less than 1.2 and equal to or less than 1.1. When the ratio Cn / Cp is in such a range, liquid loss can be suppressed.

[0034] The ratio Cn / Cp may be greater than 0.8 (or 0.9 or greater) and less than 1.2, or greater than 0.8 (or 0.9 or greater) and 1.1 or less.

[0035] (Measurement of the Difference (s-t)) The difference (s-t) is measured using a plate pack removed from a fully charged lead-acid battery. The total distance s between the opposing positive and negative plates in the plate pack is the length between the outer surfaces of the plates at both ends in the direction parallel to the stacking direction of the plate pack minus the total thickness of the positive and negative plates, divided by (the number of plates - 1) (unit: mm).

[0036] The thickness of each positive and negative electrode plate is determined using the following procedure: All positive and negative electrodes are removed from the electrode assembly. The thickness of all positive electrodes included in the electrode assembly is measured with a vernier caliper and averaged to determine the thickness of the positive plate. In a lead-acid battery with multiple electrode assembly groups, the thickness of the positive plate is determined for one electrode assembly located at the end and one electrode assembly located near the center, and the average thickness is then determined to determine the thickness of the positive plate (average value). The thickness of the negative electrode plate is determined in the same manner as for the positive plate.

[0037] The total thickness t of the separators in the electrode plate assembly is the total value (unit: mm) obtained by measuring the thickness of all separators present between adjacent positive and negative electrode plates in the electrode plate assembly. The thickness of the separator is measured with a vernier caliper. When the separator has a rib (specifically, a first rib, or a first rib and a second rib) in the portion facing the electrode material, the thickness of the separator is measured in the portion where the rib is present. When the positions of the first rib and the second rib are misaligned, the vernier caliper is used to measure the sum s1 of the thickness of the base portion and the height of the first rib in the portion of the first rib, and the sum s2 of the thickness of the base portion and the height of the second rib in the portion of the second rib, and the thickness t of only the base portion is calculated. ｂ Measure s1+s2-t ｂ The thickness of the separator is determined by measuring the thickness at multiple locations (for example, five locations) in the electrode plate assembly and averaging the measurements.

[0038] A separator sample for measurement (Sample W) was prepared by removing sulfuric acid from a separator removed from a fully charged lead-acid battery by washing with water. The size of the separator was measured within 10 minutes after washing while the separator was still wet with water.

[0039] If the battery includes a plurality of electrode plate groups, s and t are found for one of the outermost electrode plate groups and one of the electrode plate groups near the center, and s−t is calculated.

[0040] (Measurement of Ratio Cn / Cp) The ratio Cn / Cp is the ratio of the theoretical capacity Cn of all negative electrode materials contained in one cell of a lead-acid battery to the theoretical capacity of all positive electrode materials contained in one cell. When a lead-acid battery includes two or more cells, the ratio Cn / Cp is the average value of the ratios Cn / Cp obtained for two cells. When a lead-acid battery includes three or more cells, the ratio Cn / Cp is the average value of the ratios Cn / Cp obtained for one cell located at the end of the lead-acid battery and one cell located near the center.

[0041] To determine each theoretical capacity, first determine the total mass of the positive electrode material and the negative electrode material contained in the cell, and then multiply each total mass by the theoretical capacity per gram of lead (positive electrode: 0.224 Ah / g, negative electrode: 0.259 Ah / g) to determine Cp and Cn, and then calculate Cn / Cp.

[0042] The total mass of each electrode material is determined using the following procedure. (Total Mass of Positive Electrode Materials) A fully charged lead-acid battery is disassembled to obtain a positive electrode plate to be analyzed. The obtained positive electrode plate is washed with water to remove sulfuric acid from the positive electrode plate. The washing is continued until a pH test paper is pressed against the washed positive electrode surface and no color change is confirmed. The washed positive electrode plate is dried in a thermostatic chamber at 50°C ± 2°C for at least 12 hours. After drying, if the positive electrode plate contains an adhesive material, the adhesive material is removed from the positive electrode plate by peeling. The mass of the dried product (positive electrode plate) is measured. Next, the positive electrode material is removed from the positive electrode current collector, and the positive electrode material adhering to the positive electrode current collector is removed using a mannitol treatment. The resulting positive electrode current collector is washed with water, dried, and then the mass of the positive electrode current collector is measured. The mass of the positive electrode material is determined by subtracting the mass of the positive electrode current collector from the mass of the positive electrode plate. The mass of the positive electrode material in the cell is determined by summing the masses of the positive electrode material for all positive plates in the cell, and this mass value of the positive electrode material is used to calculate Cp and the ratio Cn / Cp.

[0043] (Total Mass of Negative Electrode Material) First, a fully charged lead-acid battery is disassembled to obtain a negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative electrode plate and no color change is confirmed. However, the washing time is limited to 2 hours or less. The washed negative electrode plate is dried under reduced pressure at 60±5°C for approximately 6 hours. If an adhesive material is included in the negative electrode plate after drying, the adhesive material is removed by peeling. The mass of the dried product (negative electrode plate) is measured. Next, the negative electrode material is scraped off and separated from the negative electrode current collector to obtain a sample (hereinafter referred to as sample R). Sample R is crushed as necessary and used for analysis of the components of the negative electrode material.

[0044] The negative electrode material is further removed from the negative electrode current collector from which the negative electrode material has been scraped off, and the negative electrode current collector is then rubbed with a brush or the like to remove any negative electrode material adhering to the negative electrode current collector. The resulting negative electrode current collector is washed with water, dried, and then the mass of the negative electrode current collector is measured. The mass of the negative electrode material is determined by subtracting the mass of the negative electrode current collector from the mass of the negative electrode plate. The mass of the negative electrode material in the cell is determined by summing the masses of the negative electrode material for all negative electrode plates in the cell. The mass value of the negative electrode material determined in this manner is used to calculate Cn and the ratio Cn / Cp.

[0045] In a flooded lead-acid battery, the plate assembly may include a plurality of positive plates, a plurality of negative plates, and a separator interposed between the positive and negative plates. The positive and negative plates are alternately stacked with the separator interposed therebetween. The width direction of the plate assembly (hereinafter referred to as the "x direction") is perpendicular to the stacking direction of the positive plates, negative plates, and separators (hereinafter referred to as the "y direction") and perpendicular to the up-down direction (vertical direction). The up-down direction (vertical direction) is referred to as the z direction. Each direction is based on the arrangement direction of the lead-acid battery during use.

[0046] A flooded lead-acid battery typically includes a battery case. The battery case has a bottom, side walls rising from the periphery of the bottom, and a lid that closes the open end of the side walls. The interior of the battery case may be divided into multiple spaces (cell chambers) by partition walls. For example, the interior of the battery case may be divided into multiple spaces (e.g., six) by parallel partition walls. The interior of the battery case may also be divided into multiple spaces (e.g., four or more) by multiple partition walls that intersect with each other. If the battery case is not divided into multiple cell chambers or does not have a cell chamber, the battery case is considered to have a single cell chamber. Each cell chamber is formed, for example, such that the dimension X in the x direction (width direction of the electrode plate pack) is greater than the dimension Y (pack length) in the y direction (stacking direction) of the electrode plate pack.

[0047] The components of the flooded lead-acid battery will be described in more detail below.

[0048] (Positive Electrode Plate) As the positive electrode plate, for example, a paste type positive electrode plate is used. The paste type positive electrode plate includes, for example, a positive electrode current collector and a positive electrode material.

[0049] The positive electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead sheet or a lead alloy sheet. Examples of processing methods include expanding and punching. A lattice-shaped current collector is preferably used as the positive electrode current collector because it is easy to support the positive electrode material.

[0050] As the lead alloy used for the positive electrode current collector, a Pb—Sb alloy, a Pb—Ca alloy, or a Pb—Ca—Sn alloy is preferred in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have a surface layer. The surface layer and the inner layer of the positive electrode current collector may have different compositions. The surface layer may be formed so as to cover the entire positive electrode current collector, or may be formed on only a part of the positive electrode current collector. The surface layer may be formed only on the grid portion, the lug portion, or the frame portion of the positive electrode current collector.

[0051] The positive electrode material contained in the positive electrode plate typically contains a positive electrode active material (lead dioxide or lead sulfate) that generates capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed.

[0052] The volume median pore diameter of the positive electrode material may be 1.5 μm or less. From the viewpoint of increasing the dissolved oxygen in the electrolyte and more efficiently carrying out the gas absorption reaction, the volume median pore diameter of the positive electrode material may be 1.0 μm or less or 0.50 μm or less. The volume median pore diameter of the positive electrode material may be 0.01 μm or more or 0.05 μm or more.

[0053] The volume median pore diameter of the positive electrode material may be 0.01 μm or more (or 0.05 μm or more) to 1.5 μm or less, 0.01 μm or more (or 0.05 μm or more) to 1.0 μm or less, or 0.01 μm or more (or 0.05 μm or more) to 0.50 μm or less.

[0054] The volume median pore diameter can be adjusted, for example, by adjusting at least one selected from the group consisting of the dry solids content in the positive electrode paste used to prepare the positive electrode plate and the bulk density of the positive electrode material.

[0055] (Measurement of Volume Median Pore Diameter) For the measurement, sample A was obtained by scraping and separating the positive electrode material from a positive electrode plate obtained by drying using the same procedure as described above (Total Mass of Positive Electrode Material). The average pore diameter of unpulverized sample A was measured by mercury intrusion porosimetry. More specifically, the cumulative pore volume distribution of sample A was measured using a mercury porosimeter to determine the relationship between pore diameter and cumulative pore volume. The pore diameter (volume median pore diameter) corresponding to the median of the cumulative pore volume was determined. The measurement pressure range was 0.5 psia to 0.55 psia (≒ 3.45 kPa to 3.79 kPa). The pore distribution was determined for a pore diameter range of 17 nm to 340 μm. An automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation was used as the mercury porosimeter.

[0056] 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 kneading lead powder, other additives (reinforcing materials (e.g., resin fibers), water, and sulfuric acid. The unformed positive electrode plates are then chemically formed to obtain positive electrode plates.

[0057] The formation of the unformed positive plate may be carried out, for example, by placing a plate assembly including the unformed positive plate and an electrolyte containing sulfuric acid in a battery case of a lead-acid battery, and charging the plate assembly in a state in which the electrolyte has permeated the plate assembly. However, the formation may also be carried out before assembling the lead-acid battery or the plate assembly.

[0058] (Negative Electrode Plate) The negative electrode plate includes a negative electrode material and usually includes a negative electrode current collector.

[0059] The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead sheet or a lead alloy sheet. Examples of processing methods include expanding and punching. A lattice-shaped current collector is preferably used as the negative electrode current collector because it is easy to support the negative electrode material.

[0060] The lead alloy used for 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 element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element.

[0061] The negative electrode current collector may have a surface layer. The surface layer and the inner layer of the negative electrode current collector may have different compositions. The surface layer may be formed so as to cover the entire negative electrode current collector, or may be formed on only a part of the negative electrode current collector. The surface layer may be formed, for example, only on the grid portion, only on the edge portion, or only on the frame portion of the negative electrode current collector.

[0062] The negative electrode material includes a first organic shrinkage inhibitor. The negative electrode material includes a negative electrode active material (lead or lead sulfate) that exhibits capacity through an oxidation-reduction reaction. The negative electrode material may include additives other than the first organic shrinkage inhibitor, as needed. Examples of additives include a second organic shrinkage inhibitor, a carbonaceous material, and barium sulfate. In addition to these additives, the negative electrode material may also include a reinforcing material (such as resin fiber).

[0063] (First organic shrink-proofing agent) Organic shrink-proofing agents are generally broadly classified into lignin compounds and synthetic organic shrink-proofing agents. Synthetic organic shrink-proofing agents can also be said to be organic shrink-proofing agents other than lignin compounds. The first organic shrink-proofing agent is often a synthetic organic shrink-proofing agent.

[0064] The synthetic organic shrink-proofing agent is an organic compound (e.g., an organic polymer) containing elemental sulfur, and generally contains multiple aromatic rings in the molecule and elemental sulfur as a sulfur-containing group. Among the sulfur-containing groups, a sulfonic acid group or a sulfonyl group, which are stable, is preferred. The sulfonic acid group may exist in an acid form or in a salt form such as a sodium salt. The first organic shrink-proofing agent preferably contains elemental sulfur in the form of at least a sulfonic acid group or a salt thereof.

[0065] It is also preferable to use a condensate containing at least an aromatic compound unit as the first organic shrink-proofing agent. Examples of such condensates include condensates of an aromatic compound with an aldehyde compound (at least one selected from the group consisting of aldehydes (e.g., formaldehyde) and condensates thereof). The first organic shrink-proofing agent may contain one type of aromatic compound unit, or may contain two or more types of aromatic compound units. The aromatic compound unit refers to a unit derived from an aromatic compound incorporated into the condensate.

[0066] Examples of aromatic rings possessed by aromatic compounds include benzene rings and naphthalene rings. When an aromatic compound has multiple aromatic rings, the multiple aromatic rings may be linked by a direct bond or a linking group (e.g., an alkylene group (including an alkylidene group), a sulfone group), or the like. Examples of such structures include bisarene structures (biphenyl, bisphenylalkane, bisphenylsulfone, etc.). Examples of aromatic compounds include compounds having the above-mentioned aromatic rings and at least one selected from the group consisting of a hydroxy group and an amino group. The hydroxy group or amino group may be directly bonded to the aromatic ring, or may be bonded as an alkyl chain having a hydroxy group or an amino group. The hydroxy group also includes salts of the hydroxy group (-OMe). The amino group also includes salts of the amino group (specifically, salts with an anion). Examples of Me include alkali metals (e.g., Li, K, Na), and metals of Group 2 of the periodic table (e.g., Ca, Mg), etc.

[0067] Preferred aromatic compounds include bisarene compounds (bisphenol compounds, hydroxybiphenyl compounds, bisarene compounds having an amino group (such as bisarylalkane compounds having an amino group, bisarylsulfone compounds having an amino group, and biphenyl compounds having an amino group), hydroxyarene compounds (such as hydroxynaphthalene compounds and phenol compounds), and aminoarene compounds (such as aminonaphthalene compounds and aniline compounds (such as aminobenzenesulfonic acid and alkylaminobenzenesulfonic acid)). The aromatic compounds may further have a substituent. The first organic shrink-proofing agent may contain one or more residues of these compounds. Preferred bisphenol compounds include bisphenol A, bisphenol S, and bisphenol F.

[0068] The first organic shrink-proofing agent may include a condensate containing at least a unit of an aromatic compound having the above-mentioned sulfur-containing group. The condensate may include at least a unit of a bisphenol compound as the aromatic compound unit. The sulfur-containing group may be directly bonded to an aromatic ring contained in the compound, or may be bonded to the aromatic ring as, for example, an alkyl chain having the sulfur-containing group.

[0069] The first organic shrink-preventing agent may be, for example, a condensate containing at least one selected from the group consisting of the above-mentioned bisarene compound units and monocyclic aromatic compound units (e.g., hydroxyarene compounds and / or aminoarene compounds). The first organic shrink-preventing agent may also contain at least a condensate containing a bisarene compound unit and a monocyclic aromatic compound unit (e.g., a hydroxyarene compound). Examples of such condensates include condensates of a bisarene compound with a monocyclic aromatic compound and an aldehyde compound. Preferred hydroxyarene compounds are phenolsulfonic acid compounds (e.g., phenolsulfonic acid or its substitution products). Preferred aminoarene compounds are aminobenzenesulfonic acid, alkylaminobenzenesulfonic acid, and the like. Preferred monocyclic aromatic compounds are hydroxyarene compounds.

[0070] The sulfur element content of the first organic shrink-proofing agent is 2000 μmol / g or more. The upper limit of the sulfur element content of the first organic shrink-proofing agent is not particularly limited, and from the viewpoint of further suppressing the liquid loss, it may be 9000 μmol / g or less, 8000 μmol / g or less, or 7000 μmol / g or less.

[0071] The weight average molecular weight (Mw) of the first organic shrink-proofing agent may be 7,000 or more. The Mw of the first organic shrink-proofing agent is, for example, 100,000 or less, and may be 20,000 or less. In this specification, the Mw of the organic shrink-proofing agent is a value measured using sodium polystyrene sulfonate as a standard substance. The Mw of the organic shrink-proofing agent is measured using gel permeation chromatography (GPC).

[0072] The mass ratio of the first organic shrink-proofing agent to the total of the first organic shrink-proofing agent and the second organic shrink-proofing agent is, for example, 50 mass% or more, or may be 75 mass% or more, or may be 85 mass% or more. The mass ratio of the first organic shrink-proofing agent is 100 mass% or less.

[0073] (Second organic shrink-proofing agent) The sulfur element content in the second organic shrink-proofing agent is less than 2000 μmol / g, and may be 1000 μmol / g or less, or 800 μmol / g or less. The lower limit of the sulfur element content in the second organic shrink-proofing agent is not particularly limited, and is, for example, 400 μmol / g or more.

[0074] Examples of the second organic shrink-proofing agent include a lignin compound and a synthetic organic shrink-proofing agent. Examples of the synthetic organic shrink-proofing agent include the synthetic organic shrink-proofing agents exemplified as the first organic shrink-proofing agent. However, the sulfur element content of the synthetic organic shrink-proofing agent is less than 2000 μmol / g. A lignin compound may be used as the second organic shrink-proofing agent. The negative electrode material may contain one type of second organic shrink-proofing agent, or two or more types.

[0075] Examples of lignin compounds include lignin and lignin derivatives. Examples of lignin derivatives include lignosulfonic acid or its salts. Examples of salts of lignosulfonic acid include alkali metal salts (such as sodium salts).

[0076] The Mw of the second organic shrink-proofing agent is, for example, less than 7000. The Mw of the second organic shrink-proofing agent is, for example, 3000 or more.

[0077] The content of the organic shrink-preventing agent in the negative electrode material (the total content of the first organic shrink-preventing agent and the second organic shrink-preventing agent) is, for example, 0.01% by mass or more. The content of the organic shrink-preventing agent is, for example, 1% by mass or less, and may be 0.5% by mass or less. The content of the first organic shrink-preventing agent in the negative electrode material may be within this range.

[0078] Examples of carbonaceous materials that can be used include carbon black, graphite, hard carbon, and soft carbon. Examples of carbon black include acetylene black, furnace black, and lamp black. Furnace black also includes Ketjen Black (trade name). Graphite is a carbonaceous material containing a graphite-type crystalline structure. Graphite may be either artificial graphite or natural graphite. The negative electrode material may contain one type of carbonaceous material, or two or more types. The negative electrode material may contain at least graphite. For example, the negative electrode material may contain graphite and a carbonaceous material other than graphite from the above carbonaceous materials.

[0079] The content of the carbonaceous material in the negative electrode material is, for example, 0.05% by mass or more, or may be 0.1% by mass or more, and the content of the carbonaceous material is, for example, 5% by mass or less.

[0080] The content of barium sulfate in the negative electrode material is, for example, 0.05% by mass or more, or may be 0.1% by mass or more, and the content of barium sulfate is, for example, 3% by mass or less.

[0081] (Other) An unformed negative electrode plate is produced, for example, by applying or filling a negative electrode paste onto a negative electrode current collector, followed by aging and drying. The negative electrode active material in a charged state is sponge lead, but an unformed negative electrode plate is usually produced using lead powder. More specifically, the negative electrode paste used to produce an unformed negative electrode plate is prepared, for example, by adding water and sulfuric acid (or an aqueous sulfuric acid solution) to lead powder and, if necessary, various additives (such as an organic shrinkage inhibitor or a carbonaceous material), and kneading the mixture. When aging, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and at high humidity. A negative electrode plate is produced, for example, by chemically converting an unformed negative electrode plate.

[0082] The formation may be performed, for example, by placing a plate assembly including unformed negative plates and an electrolyte containing sulfuric acid in a lead-acid battery container, and charging the plate assembly while the electrolyte is permeated into the plate assembly. However, the formation may also be performed before assembling the lead-acid battery or the plate assembly. The formation produces spongy lead.

[0083] (Analysis or Measurement of Negative Electrode Material) Analysis or measurement of the negative electrode material is performed on a negative electrode plate taken out from a fully charged lead-acid battery.

[0084] Prior to analysis or measurement, the negative electrode material is extracted from the negative plate by the following procedure.

[0085] First, a fully charged lead-acid battery is disassembled to obtain a negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative electrode plate and no color change is confirmed. However, the washing time is limited to 2 hours or less. The washed negative electrode plate is dried at 60°C ± 5°C for approximately 6 hours under reduced pressure. If an adhesive material is present on the negative electrode plate after drying, the adhesive material is removed by peeling. The mass of the dried product (negative electrode plate) is measured. Next, the negative electrode material is scraped off and separated from the negative electrode current collector to obtain a sample (hereinafter referred to as Sample B). Sample B is crushed as necessary and used for analysis of the components of the negative electrode material.

[0086] (Analysis of Components in Negative Electrode Material) (a) Qualitative Analysis of Organic Shrinkage-Preventing Agent in Negative Electrode Material A predetermined amount of pulverized Sample B is collected and weighed, and immersed in a 1 mol / L NaOH aqueous solution to extract the organic shrinkage-preventing agent. Next, the first organic shrinkage-preventing agent and the second organic shrinkage-preventing agent are separated from the extract. For each of the separated products containing each organic shrinkage-preventing agent, insoluble components are removed by filtration, and the resulting solution (hereinafter also referred to as Solution C) is desalted, concentrated, and dried. Desalting is performed using a desalting column, by passing Solution C through an ion exchange membrane, or by placing Solution C in a dialysis tube and immersing it in distilled water. Drying this yields a powder of the organic shrinkage-preventing agent (hereinafter also referred to as Sample D).

[0087] The organic shrinkage preventer is identified by combining information obtained from the infrared spectrum of sample D, the ultraviolet-visible absorption spectrum of a solution obtained by dissolving sample D in distilled water or the like, the nuclear magnetic resonance (NMR) spectrum of a solution obtained by dissolving sample D in a solvent such as heavy water, or gas chromatography mass spectrometry (GC-MS) which can obtain information on the individual compounds constituting the substance.

[0088] The first and second organic shrink-control agents are separated from the extract as follows. First, the extract is analyzed by infrared spectroscopy, NMR, and / or GC-MS to determine whether it contains multiple organic shrink-control agents. Next, the molecular weight distribution of the extract is measured by GPC. If the multiple organic shrink-control agents can be separated by molecular weight, the organic shrink-control agents are separated by column chromatography based on their molecular weight differences. If separation based on molecular weight differences is difficult, one of the organic shrink-control agents is separated by precipitation separation, utilizing the difference in solubility depending on the type and / or amount of functional groups possessed by the organic shrink-control agents. Specifically, the extract is dissolved in aqueous NaOH solution, and a sulfuric acid solution is added dropwise to the mixture to adjust the pH of the mixture, thereby flocculating and separating one of the organic shrink-control agents. The separated product is then dissolved again in aqueous NaOH solution, and the insoluble components are removed by filtration as described above. Furthermore, the remaining solution after separating the one of the organic shrink-control agents is concentrated. The resulting concentrate contains the other organic shrinkage inhibitor, and the insoluble components are removed from the concentrate by filtration as described above.

[0089] (b) Determination of the Content of Organic Shrinkage Inhibitor in the Negative Electrode Material As in (a) above, for each of the separated products containing the organic shrinkage inhibitor, insoluble components are removed by filtration to obtain Solution C. The ultraviolet-visible absorption spectrum of each of the obtained Solutions C is measured. The content of each organic shrinkage inhibitor in the negative electrode material is determined using the intensity of the peak characteristic of each organic shrinkage inhibitor and a calibration curve prepared in advance.

[0090] When a lead-acid battery with an unknown content of organic shrinkage preventer is obtained and the content of the organic shrinkage preventer is measured, it may be impossible to use the same organic shrinkage preventer for the calibration curve because the structural formula of the organic shrinkage preventer cannot be precisely identified. In this case, a calibration curve is created using a separately available organic compound that shows similar shapes in the ultraviolet-visible absorption spectrum, infrared spectroscopy spectrum, NMR spectrum, etc. to the organic shrinkage preventer extracted from the negative electrode of the battery, and the content of the organic shrinkage preventer is measured using the ultraviolet-visible absorption spectrum.

[0091] (c) Sulfur Content in Organic Shrinkage Resistant: After obtaining powder sample D of the organic shrinkage resistant in the same manner as in (a) above, the sulfur element in 0.1 g of the organic shrinkage resistant is converted to sulfuric acid by the oxygen combustion flask method. The powder sample is then burned in a flask containing an adsorption solution, yielding an eluate in which sulfate ions have dissolved in the adsorption solution. Next, the sulfur element content (C1) in 0.1 g of the organic shrinkage resistant is determined by titrating the eluate with barium perchlorate using thorin as an indicator. Next, C1 is multiplied by 10 to calculate the sulfur element content (μmol / g) per gram of the organic shrinkage resistant.

[0092] (d) Quantitative determination of carbonaceous material and barium sulfate 50 mL of 20% by mass nitric acid was added to 10 g of pulverized sample B, and the mixture was heated for approximately 20 minutes to dissolve the lead component as lead ions. The resulting solution was filtered to separate the carbonaceous material, barium sulfate, and other solid components.

[0093] The obtained solid content is dispersed in water to form a dispersion, and then components other than the carbonaceous material and barium sulfate (e.g., reinforcing material) are removed from the dispersion using a sieve. Next, the dispersion 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 filtered sample is a mixed sample of the carbonaceous material and barium sulfate. The mass of the membrane filter is subtracted from the total mass of the dried mixed sample (hereinafter referred to as Sample E) and the membrane filter to determine the mass of Sample E (M ｍ ) is measured. Then, Sample E is placed in a crucible together with the membrane filter and burnt at 1300°C or higher for ashing. 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 From 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 ratios (percentages) of the mass of the obtained barium sulfate and the mass of the carbonaceous material to the mass of Sample B are calculated. In this manner, the barium sulfate content and the carbonaceous material content in the negative electrode material are calculated.

[0094] (Separator) A separator can be disposed between the negative electrode plate and the positive electrode plate. As the separator, at least one material selected from a nonwoven fabric and a microporous membrane can be used.

[0095] A nonwoven fabric is a mat of intertwined fibers, primarily composed of fibers. For example, 60% or more by mass of the nonwoven fabric is made of fibers. Examples of fibers that can be used include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (e.g., polyethylene terephthalate fibers), pulp fibers, and the like. Among these, glass fibers are preferred. The nonwoven fabric may also contain components other than fibers (e.g., acid-resistant inorganic powder, polymers as binders, etc.).

[0096] A microporous membrane is a porous sheet mainly composed of components other than fiber components, and can be obtained, for example, by extruding a composition containing a pore-forming agent into a sheet, and then removing the pore-forming agent to form pores. The microporous membrane is preferably made of an acid-resistant material, and a microporous membrane mainly composed of a polymer component is preferred. The polymer component is preferably polyolefin (polyethylene, polypropylene, etc.). The pore-forming agent can be at least one selected from the group consisting of polymer powder and oil.

[0097] The separator may be made of, for example, only a nonwoven fabric or only a microporous membrane. Furthermore, the separator may be a laminate of a nonwoven fabric and a microporous membrane, a laminate of different or the same materials, or a laminate of different or the same materials with recesses and protrusions interlocked, as needed.

[0098] The separator may be sheet-shaped or bag-shaped. A single sheet-shaped separator may be sandwiched between the positive electrode plate and the negative electrode plate. Alternatively, the electrode plates may be sandwiched between a single folded sheet-shaped separator. In this case, a positive electrode plate sandwiched between folded sheet-shaped separators may be stacked on top of a negative electrode plate sandwiched between folded sheet-shaped separators, or one of the positive electrode plate and the negative electrode plate may be sandwiched between folded sheet-shaped separators and stacked on top of the other electrode plate. Alternatively, a sheet-shaped separator may be folded into an accordion shape, and the positive electrode plate and the negative electrode plate may be sandwiched between the accordion-shaped separators so that the separator is interposed between them. When using a separator folded like an accordion, the separator may be arranged so that the folded portions are aligned with the horizontal direction of the lead-acid battery (e.g., so that the folded portions are parallel to the horizontal direction) or so that the folded portions are aligned with the vertical direction (e.g., so that the folded portions are parallel to the vertical direction). In a separator folded like an accordion, recesses are formed alternately on both main surfaces of the separator. Because the positive and negative plates usually have lugs on the top, when the separator is arranged so that the folded portions are aligned with the horizontal direction of the lead-acid battery, the positive and negative plates are positioned in the recesses on only one main surface of the separator (i.e., a double separator is interposed between adjacent positive and negative plates). When the separator is arranged so that the folded portion is aligned with the vertical direction of the lead-acid battery, the positive electrode plate can be accommodated in the recess on one main surface side, and the negative electrode plate can be accommodated in the recess on the other main surface side (that is, a single separator can be interposed between adjacent positive and negative electrode plates). When a pouch-shaped separator is used, the pouch-shaped separator may accommodate either the positive electrode plate or the negative electrode plate.

[0099] The separator may have at least a first rib protruding toward the positive electrode plate. More specifically, the separator may have a base portion and a first rib protruding from one surface of the base portion toward the positive electrode plate. The presence of the first rib makes it easier for the gas absorption reaction to occur, further suppressing liquid loss. The separator may further have a second rib protruding from the other surface of the base portion toward the negative electrode plate. The first rib and the second rib are each formed in a portion facing the electrode material.

[0100] The average height of the first rib may be 0.3 mm or more. From the viewpoint of ensuring a high capacity, the average height of the first rib may be 1.0 mm or less, or may be 0.7 mm or less.

[0101] The separator may have a plurality of first ribs. The plurality of first ribs may extend, for example, along the longitudinal direction of the separator. In this specification, the longitudinal direction of the separator refers to the direction along the vertical direction of a flooded lead-acid battery housing the separator (in other words, the height direction of the electrode plates). The acute angle formed between the average direction in which the first ribs extend and the height direction of the electrode plates (or the vertical direction in the flooded lead-acid battery) is, for example, 30° or less, and may be 15° or less. The average direction in which the first ribs extend and the height direction of the electrode plates (or the vertical direction in the lead-acid battery) may be parallel.

[0102] The average spacing between the first ribs may be 1.3 cm or less. From the viewpoint of easily forming a more closed space between the base portion and the positive electrode plate between adjacent first ribs, the average spacing between the first ribs may be 1.0 cm or less. The average spacing between the first ribs refers to the average spacing between adjacent first ribs. The average spacing between the first ribs may be 4 mm or more.

[0103] The average spacing between the first ribs is measured using a measurement separator sample A. More specifically, the spacing between adjacent first ribs is measured with a vernier caliper at multiple locations on the separator included in the electrode plate assembly, and the measurements are averaged. If the battery includes multiple electrode plate assemblies, the average spacing between the first ribs is determined for one of the outermost electrode plate assemblies and one of the electrode plate assemblies near the center, and then the measurements are averaged.

[0104] The average height of the second ribs may be 0.10 mm or less. The average height of the second ribs may be 0.02 mm or more. Furthermore, from the viewpoint of efficiently carrying out the gas absorption reaction on the negative electrode plate side, it is preferable that the average height of the second ribs is low, for example, 0.05 mm or less. Furthermore, the separator does not need to have the second ribs.

[0105] The separator may have a plurality of second ribs. The second ribs may extend along the longitudinal direction of the separator, similar to the first ribs. The average spacing between the second ribs may be selected from the ranges described for the first ribs.

[0106] The separator may have a rib (third rib) other than the first rib on the main surface (first main surface) on which the first rib is formed. The third rib is a rib formed in a region of the first main surface that does not face the positive electrode material. Furthermore, the separator may have a rib (fourth rib) formed in a region of the main surface (second main surface) opposite the main surface on which the first rib is formed, that does not face the negative electrode material, as necessary. When the separator has a second rib, the second rib is formed in a region of the second main surface that faces the negative electrode material.

[0107] The average thickness of the base portion may be 0.10 mm or more, or 0.15 mm or more, or 0.30 mm or less.

[0108] (Electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte may contain a polymer that swells in the electrolyte, if necessary. The electrolyte preferably has fluidity at the temperature at which it is used, and more preferably is a liquid at 25°C.

[0109] The electrolytic solution may contain cations (e.g., metal cations) and / or anions (e.g., anions other than sulfate anions (e.g., phosphate ions)) as needed. Examples of metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions. In particular, when the electrolytic solution contains at least one metal cation selected from the group consisting of Na ions, Li ions, and Al ions, a high permeation short-circuit suppression effect can be obtained.

[0110] From the viewpoint of further suppressing permeation short-circuiting, the concentration of metal cations in the electrolyte may be 0.03 mol / L or more. From the viewpoint of ensuring high charge acceptance during regenerative charging, the concentration of metal cations in the electrolyte may be 0.5 mol / L or less, 0.3 mol / L or less, or 0.1 mol / L or less.

[0111] The density of the electrolyte in a fully charged lead acid battery at 20°C is, for example, 1.20 g cm －３ The density of the electrolyte at 20°C may be 1.35 g cm －３ Here, the density of the electrolytic solution is the density of the electrolytic solution (more specifically, an aqueous sulfuric acid solution) in a state that does not contain additives such as metal cations that are added to the electrolytic solution.

[0112] (Other) A lead-acid battery may include one cell or two or more cells. When a lead-acid battery includes multiple cells (in other words, multiple electrode plate groups), the multiple electrode plate groups may be connected in series.

[0113] The number of each electrode plate in the electrode plate group may be one or two or more. From the viewpoint of ensuring higher capacity, the number of negative electrode plates included in the electrode plate group is preferably two or more, and may be four or more, or six or more. Note that, if the number of negative electrode plates included in the electrode plate group is m, the number of positive electrode plates is (m-1) or more and (m+1) or less when m≧2, and is 1 or 2 when m=1.

[0114] In the electrode plate group, the number of positive electrode plates is preferably one less than the number of negative electrode plates. In this case, the number m of negative electrode plates is equal to or greater than 1. In this case, since all positive electrode plates are sandwiched between negative electrode plates, oxygen generated at the positive electrode plates is easily supplied to the negative electrode plates, and the loss of liquid can be further suppressed.

[0115] The ratio Ra (=(S1-Sg) / Sg=Se / Sg) may be 0.30 or less. From the viewpoint of further suppressing the loss of electrolyte, the ratio Ra may be 0.25 or less, or 0.24 or less, or may be 0.20 or less. Moreover, from the viewpoint of ensuring a higher PSOC life performance, the ratio Ra is preferably 0.20 or less. The wall surfaces (side walls or partition walls) of the cell chamber are close to the periphery of the electrode plate assembly, limiting the volume in which the electrolyte can remain. When the ratio Ra is 0.20 or less, the amount of electrolyte present outside the electrode plate assembly is relatively small, which tends to block upward convection of the electrolyte between the electrode plate assembly and the battery case wall during charging. Therefore, stratification is suppressed, and deterioration of the electrode plates is suppressed, which is thought to result in a high PSOC life performance. From the viewpoint of ensuring ease of insertion of the electrode assembly into the battery case, the ratio Ra may be 0.10 or more, or may be 0.12 or more.

[0116] The ratio Ra is determined at a portion parallel to the bottom of the cell chamber (or battery case) of a fully charged lead-acid battery, and at a height of 4.5 cm to 5.5 cm from the bottom of the cell chamber (more specifically, the inner bottom surface). Based on this determination method, in this specification, the cross section parallel to the bottom of the cell chamber, from which the ratio Ra is determined, is treated as the cross section of the flooded lead-acid battery at a position parallel to the bottom of the cell chamber of a fully charged lead-acid battery, and at a height of 5 cm from the bottom of the cell chamber (more specifically, the inner bottom surface).

[0117] More specifically, the ratio Ra can be determined by the following procedure. First, the cross-sectional area S1 inside the cell chamber (or battery case) is determined by the following procedure. After removing the electrode plate group and electrolyte from the battery case, the battery case is washed with water, dried, and then placed on a flat surface. Water is then poured into the battery case up to a position parallel to the bottom and 4.5 cm above the bottom. Next, water is poured in up to a position 5.5 cm above the bottom, and the volume of the poured water (cm ３ ) is calculated by dividing the volume of the added water by the height of 1 cm. ２If the battery case is divided into multiple cells, the cross-sectional area (cm ２ ) by the number of cell chambers to obtain the cross-sectional area S1 (cm ２ In addition, in the case of a lead-acid battery, if there are parts other than the electrode plate group and the electrolyte inside the case or cell chamber (for example, other members such as spacers and hollow parts (spaces not filled with electrolyte, etc.)), the cross-sectional area S1 inside the case or cell chamber is determined by the above procedure with these parts present.

[0118] The plate assembly removed from a fully charged lead-acid battery is disassembled into positive plates, negative plates, and separators, and the thickness of the positive plates, negative plates, and total separator thickness are determined using the procedure described above. However, in this case, the thicknesses are measured using vernier calipers at a position 5 cm above the bottom (more specifically, the inner bottom surface) of the cell chamber (or battery case). The thickness of the positive plates multiplied by the number of positive plates, the thickness of the negative plates multiplied by the number of negative plates, and the total thickness of the separators multiplied by the number of separators between the positive and negative plates (in the case of pouch-shaped separators, the total thickness of the separators multiplied by the number of pouch-shaped separators multiplied by 2) are calculated and summed. This determines the thickness (dimension y) of the plate assembly in the stacking direction (y direction). Next, the width (dimension in the x direction) of the plate assembly is measured using a scale at a position 5 cm above the bottom (more specifically, the inner bottom surface) of the cell chamber (or battery case). When the widths of the positive and negative plates are different, the average width is calculated and used as the plate width (the dimension in the x direction of the plate assembly). The cross-sectional area Sg of the plate assembly is calculated by multiplying this plate width by the thickness (dimension y) of the plate assembly in the stacking direction. The total thickness of the separator corresponds to the sum of the separator thicknesses t mentioned above.

[0119] From S1 and Sg, Se = S1 - Sg is calculated. Then, Se is divided by Sg to obtain the ratio Ra. In a lead-acid battery containing multiple cells, the ratio Ra is obtained by averaging the ratios Ra obtained for the cells located at the ends and the cells located near the center.

[0120] When calculating the ratio Ra, the following points should be taken into consideration. First, even when pressure is applied to the electrode plate pack in the thickness direction, a gap may exist between the electrode plate pack and the battery case (or cell chamber). For example, if the outermost member is a separator with ribs on its outer surface that face the side wall or partition wall of the battery case, the height of the separator ribs is not included in the y-direction dimension of the electrode plate pack. On the other hand, if the tips of the ribs contact the side wall or partition wall, the height of the ribs controls the y-direction dimension of the cross-sectional area Sg of the electrode plate pack. Because the separator ribs have a certain degree of flexibility, they may be deformed by being pressed against the side wall or partition wall. In this case, the height of the ribs after deformation controls the y-direction dimension of the cross-sectional area Sg of the electrode plate pack.

[0121] Similarly, when determining the dimension in the y direction of the cross-sectional area Sg of the electrode plate pack, if the side wall or partition wall of the battery case has ribs, the height of the ribs is not included in the dimension in the y direction. If both the side wall or partition wall and the separator have ribs and the tips of the ribs are in contact with the side wall or partition wall, the sum of the height of the separator rib (or the height of the rib after deformation if deformed) and the height of the rib on the side wall or partition wall determines the dimension in the y direction of the cross-sectional area Sg of the electrode plate pack.

[0122] In a lead-acid battery, the opening of the battery case is usually closed with a lid. The lid includes, for example, a negative electrode terminal and a positive electrode terminal. The lid may have a single structure (single lid) or a double structure including an inner lid and an outer lid (or top lid). A lid having a double structure may include a reflux structure between the inner lid and the outer lid for returning the electrolyte to the battery (inside the inner lid) from a reflux port provided in the inner lid.

[0123] A lead-acid battery can be obtained, for example, by a manufacturing method including a step of housing a plate assembly and an electrolyte in a cell chamber of a battery case. Each cell of the lead-acid battery includes a plate assembly and an electrolyte housed in each cell chamber. The plate assembly is assembled, for example, by stacking positive electrode plates, negative electrode plates, and a separator with the separator interposed between the positive and negative electrode plates prior to housing in the cell chamber. The positive electrode plates, negative electrode plates, and separator are typically prepared prior to assembling the plate assembly. The electrolyte is prepared prior to housing in the cell chamber. When a lead-acid battery has one plate assembly, the battery case does not need to be divided into multiple cell chambers, and the plate assembly and the electrolyte may be housed in the battery case.

[0124] The method for manufacturing a lead-acid battery may include, after the step of housing the electrode plate group and the electrolyte in the cell chamber, a step of chemically converting at least one of the positive electrode plate and the negative electrode plate, as necessary.

[0125] 1 is a schematic diagram showing the external appearance and internal structure of an example of a flooded lead-acid battery according to one aspect of the present disclosure. However, the lead-acid battery according to one aspect of the present disclosure is not limited to the following embodiment.

[0126] The flooded lead-acid battery 1 includes a battery case 12 that contains a plate pack 11 and an electrolyte (not shown). The battery case 12 is divided into multiple cell chambers 14 by partitions 13. Each cell chamber 14 contains one plate pack 11. The opening of the battery case 12 is closed by a lid 15 equipped with a positive electrode terminal 16 and a negative 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 also have the function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0127] The electrode plate group 11 is formed by alternately stacking a plurality of negative electrode plates 3 and positive electrode plates 2 with separators 4 interposed therebetween. Here, the separators 4 are bag-shaped and individually package the positive electrode plates 2. However, the shape of the separator is not particularly limited. In a cell chamber 14 located at one end of the battery case 12, a positive electrode shelf 6 that connects the ears 2 a of a plurality of positive electrode plates 2 in parallel is connected to a through-connector 8, and a negative electrode shelf 5 that connects the ears 3 a of a plurality of negative electrode plates 3 in parallel is connected to a negative electrode pole 7. The negative electrode pole 7 is connected to a negative electrode terminal 17 outside the lid 15. In the cell chamber 14 located at the other end of the battery case 12, a positive electrode pole 9 is connected to the positive electrode shelf 6, and a through-connector 8 is connected to the negative electrode shelf 5. The positive electrode pole 9 is connected to a positive electrode terminal 16 outside the lid 15. Each of the through-connectors 8 passes through a through-hole provided in the partition wall 13 and connects the electrode plate assemblies 11 of adjacent cell chambers 14 in series.

[0128] The positive electrode shelf 6 is formed by welding, for example, by a cast-on-strap method or a burning method, the ears 2 a provided on the upper part of each positive electrode plate 2. The negative electrode shelf 5 is also formed by welding, in the same manner as the positive electrode shelf 6, the ears 3 a provided on the upper part of each negative electrode plate 3.

[0129] Although the lid 15 of the lead-acid battery has a single structure (single lid), this is not limited to the illustrated example. For example, the lid 15 may have a double structure as described above. A lid having a double structure may have a reflux structure.

[0130] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0131] <Flooded Lead-Acid Batteries E1-E57 and C1-C86> (1) Preparation of Lead-Acid Batteries (a) Preparation of Negative Electrode Plates Lead powder, water, dilute sulfuric acid, an organic shrinkage preventer (first organic shrinkage preventer or second organic shrinkage preventer) having the sulfur element content shown in the table, barium sulfate, and carbon black were mixed to obtain a negative electrode paste. The amounts of each component were adjusted so that the contents of the organic shrinkage preventer, barium sulfate, and carbon black in the negative electrode material obtained by the previously described procedures were 0.2 mass%, 0.6 mass%, and 0.3 mass%, respectively. The negative electrode paste was filled into the mesh portion of an expanded lattice made of a Pb—Ca—Sn alloy and aged and dried. In this manner, an unformed negative electrode plate was obtained.

[0132] (b) Preparation of Positive Electrode Plates: Lead powder, water, and dilute sulfuric acid were mixed to obtain a positive electrode paste. The positive electrode paste was filled into the mesh of a Pb—Ca—Sn alloy expanded grid as a positive electrode current collector, and then aged and dried. In this manner, an unformed positive electrode plate was obtained. The volume median pore diameter of the positive electrode material was adjusted by adjusting at least one of the dry solids content in the positive electrode paste and the bulk density of the positive electrode material. The volume median pore diameter of the positive electrode materials in Tables 1 to 5 was 0.20 μm.

[0133] (c) Fabrication of Flooded Lead Acid Battery The battery had a nominal voltage of 12 V (6 cells) and a rated 20-hour rate capacity of 60 Ah. The battery plate assembly consisted of seven positive plates and seven negative plates, excluding some batteries shown in Table 5. First, the unformed positive plates were housed in a pouch-shaped separator and stacked alternately with the negative plates. The resulting plate assembly composed of unformed plates was housed in a battery case together with an electrolyte (aqueous sulfuric acid solution), and formation was performed inside the battery case to fabricate a flooded lead acid battery. In Table 4, the ratio Ra calculated by the procedure described above was adjusted using a spacer to the value shown in Table 4. The density of the electrolyte in a fully charged lead acid battery at 20°C was 1.285 g cm without additives such as metal cations. －３ The lead-acid battery was fully charged by the above-mentioned formation. In Table 3, an aqueous sulfuric acid solution containing the metal cations shown in Table 3 at the concentrations shown in Table 3 was used as the electrolyte. For Table 5, the positive electrode plates and negative electrode plates in the numbers shown in Table 5 were alternately stacked to form an electrode plate group.

[0134] (2) Evaluation The following evaluations are performed using batteries with a nominal voltage of 12 V (6 cells) produced in the Examples or Comparative Examples. When the following evaluations are performed using other batteries, the evaluations are performed at a voltage that matches the number of cells in the battery.

[0135] (a) Amount of fluid loss Battery mass (M ０ ) was measured. The battery was charged at a constant voltage of 14.4 V with an upper limit current of 50 A for 42 days in a water bath at 60°C ± 2°C. When the liquid level reached the minimum liquid level line during charging, water was added up to the maximum liquid level line, and the amount of added water was recorded. After charging, the battery was removed from the water bath and left to cool to room temperature (20 to 35°C), and then the mass (M １ ) was measured. ０ From M １ Subtract the total amount of water replenished (M ａ ) was added together to determine the amount of liquid loss. In Tables 1, 4, and 6, the amount of liquid loss for each battery was evaluated as a relative value when the amount of liquid loss for battery C15 was set to 100. A smaller relative value indicates more suppressed liquid loss. In Table 5, when the number of negative plates was 8, the amount of liquid loss for battery C78 was set to 100, and when the number of negative plates was 7, the amount of liquid loss for each battery was evaluated as a relative value when the amount of liquid loss for battery C51 was set to 100.

[0136] (b) High temperature resistance In the above (a), mass M １ For each battery measured, 100 × I was measured at a temperature of -18 ° C ± 2 ° C. ２０ The battery was discharged at a constant current of (A) (high rate discharge) and the time (discharge duration) until the terminal voltage of the battery reached 6 V was determined. The longer the discharge duration, the better the high temperature resistance. The high temperature resistance of each battery was evaluated as a relative value when the discharge duration of battery C15 was set to 100. Here, I ｎ is a current value (unit: A) equivalent to the value obtained by dividing the rated n-hour rate capacity (unit: Ah) of the battery by n.

[0137] (c) PSOC Life Performance The PSOC life performance of flooded lead-acid batteries was evaluated using the following procedure. All steps were carried out in a water bath at 25°C ± 1°C. Steps 1 to 7 were repeated. The charge in step 2 and the discharge in step 3 were counted as one cycle, and the number of cycles at which the end-of-discharge voltage in step 3 fell below 10 V was determined. The PSOC life performance of each battery was evaluated as a relative value when the number of cycles for battery E48 was taken as 100. The larger this value, the better the PSOC life performance. Step 1 (conditioning discharge): 4 x I ２０ The battery was discharged for 2.5 hours at a current of 7.5 A. Step 2 (charging): The upper limit current was increased to 7 × I. ２０ A, and charging was performed at a constant voltage of 14.4 V for 40 minutes. ２０ Step 4: Steps 2 and 3 were repeated 85 times. Step 5 (charging): The upper limit current was increased to 2×I ２０ A, and charging was carried out at a constant voltage of 16.0 V for 18 hours. ２０ The battery was discharged at a current of 1 A until the voltage reached 10.5 V. Step 7 (charging): The upper limit current was increased to 5 × I ２０ A, and charging was carried out at a constant voltage of 16.0 V for 24 hours.

[0138] (d) Penetration Short Circuit The battery was subjected to the following charge / discharge cycles in a water bath at 25°C ± 1°C. Specifically, the following cycles (A) to (C) were repeated five times, and then cycle (D) was performed. <Charge / Discharge Conditions> (A) I ｎ (B) The battery was discharged to 1.0 V / cell at a constant current of 100 A (unit: A). A 10 Ω resistor was connected to the battery and the battery was left for 28 days. (C) The upper limit current was set to 50 A and the battery was charged at a constant voltage of 2.4 V / cell for 30 minutes. (D) I ｎ The battery was charged at a constant current of 1000 kJ / s (unit: A) for 27 hours. ｎThe amperage (A) is the current value (unit: A) corresponding to the rated n-hour rate capacity (unit: Ah) of the battery divided by n. After the above charge / discharge cycles, the battery was disassembled, the separator was removed, and the area of ​​the lead penetration marks (in other words, lead marks) was determined. The area of ​​the penetration marks was determined by image processing of a photograph of the separator. In a lead-acid battery having multiple serially connected electrode plate groups, the areas of the penetration marks of all separators included in one of the outermost electrode plate groups and one of the electrode plate groups located near the center were determined, and the average value per separator was calculated. The relative value of the penetration mark area of ​​each battery, with the penetration mark area of ​​battery E37 set to 100, was used as an index for evaluating the occurrence of permeation short circuits. A larger relative value suggests a higher incidence of permeation short circuits.

[0139] The evaluation results are shown in Tables 1 to 6. In these tables, E1 to E57 are examples, and C1 to C86 are comparative examples.

[0140]

[0141] As shown in Table 1, when (st) ≧ 0.10 mm, the tendency for liquid loss did not change even when the ratio Cn / Cp was changed. Furthermore, when the second organic shrink-proofing agent was used instead of the first organic shrink-proofing agent, the tendency for the amount of liquid loss versus the ratio Cn / Cp did not change significantly, either when (st) < 0.10 mm or when (st) ≧ 0.10 mm. When the first organic shrink-proofing agent was used when (st) < 0.10 mm, the amount of liquid loss at Cn / Cp = 0.8 or Cn / Cp = 1.2 tended to be similar to or slightly reduced when (st) ≧ 0.10 mm. In contrast, when the first organic shrink-proofing agent was used and 0.8 < Cn / Cp < 1.2 was used when (st) < 0.10 mm, liquid loss was significantly reduced (E1 to E36).

[0142] As shown in Table 2, when the first organic shrink-proofing agent was used, higher high temperature resistance was obtained than when the second organic shrink-proofing agent was used.

[0143]

[0144] As shown in Table 3, when the electrolyte contained metal cations such as Na ions, Li ions, and Al ions, permeation short-circuiting was more effectively suppressed than when these metal cations were not contained (comparison of E37 with E38 to E46). It should be noted that the smaller s-t, the more likely permeation short-circuiting was to occur. Even when s-t was small, less than 1, permeation short-circuiting was significantly suppressed by the inclusion of metal cations in the electrolyte, as shown in Table 3. Therefore, both liquid loss and permeation short-circuiting could be suppressed.

[0145]

[0146] As shown in Table 4, when Ra≦0.20, the amount of fluid loss was further reduced compared to when Ra>0.20. Also, when Ra≦0.20, the PSOC life performance was significantly improved compared to when Ra>0.20.

[0147]

[0148] As shown in Table 5, when the difference (s-t) was 0.10 mm, the tendency for the amount of liquid loss remained almost the same whether the number of positive and negative plates was the same or there was one less positive plate than the negative plate. The amount of liquid loss increased as the sulfur content of the organic shrinkage inhibitor increased (comparison of C78, ​​C80, and C81 with C51, C52, and C54). Furthermore, when the difference (s-t) was <0.10 mm and the second organic shrinkage inhibitor was used, the amount of liquid loss remained almost the same whether the number of positive and negative plates was the same or there was one less positive plate than the negative plate (comparison of C79 with C8). In contrast, when the difference (s-t) was <0.10 mm and the first organic shrinkage inhibitor was used, when there was one less positive plate than the negative plate, the amount of liquid loss was significantly reduced compared to when the number of positive and negative plates was the same (comparison of E50 and E51 with E17 and E19).

[0149]

[0150] As shown in Table 6, when the second organic shrink-proofing agent was used instead of the first organic shrink-proofing agent, the amount of liquid loss did not change significantly even when the volume median pore diameter of the positive electrode material changed. In contrast, when the first organic shrink-proofing agent was used, the amount of liquid loss tended to decrease as the volume median pore diameter decreased.

[0151] A flooded lead-acid battery according to one aspect of the present invention is suitable for applications including charging and discharging in a PSOC. Examples of such applications include power supplies for applications in which charging and discharging are controlled by a PSOC. Examples of applications in which charging and discharging are controlled by a PSOC include vehicles equipped with an idle reduction system as an IS lead-acid battery, charge control applications, and vehicle accessory applications. Furthermore, lead-acid batteries can be suitably used as starting power sources for vehicles (such as automobiles and motorcycles), power sources for vehicle accessories, and industrial power storage devices (such as power sources for electric vehicles (such as forklifts)). These are merely examples, and the applications of flooded lead-acid batteries are not limited to these.

[0152] 1: Flooded lead-acid battery 2: Positive electrode plate 2a: Ear of positive electrode plate 3: Negative electrode plate 3a: Ear of negative electrode plate 4: Separator 5: Negative electrode shelf 6: Positive electrode shelf 7: Negative electrode column 8: Through-connector 9: Positive electrode column 11: Plate group 12: Battery case 13: Partition wall 14: Cell chamber 15: Lid 16: Positive electrode terminal 17: Negative electrode terminal 18: Vent plug

Claims

1. A flooded lead-acid battery comprising: a plate group, an electrolyte, and a cell chamber accommodating the plate group and the electrolyte; the plate group comprises a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate; a difference (s-t) between a total distance s between the positive electrode plate and the negative electrode plate facing each other in the plate group and a total thickness t of the separator is less than 0.10 mm; the positive electrode plate comprises a positive electrode material; the negative electrode plate comprises a negative electrode material; the negative electrode material comprises an organic shrinkage inhibitor having an elemental sulfur content of 2000 μmol / g or more; and a ratio Cn / Cp of a theoretical capacity Cn of the negative electrode material to a theoretical capacity Cp of the positive electrode material satisfies 0.8<Cn / Cp<1.

2.

2. The flooded lead-acid battery according to claim 1, wherein the ratio Cn / Cp satisfies 0.9≦Cn / Cp≦1.

1.

3. The flooded lead-acid battery according to claim 1 or 2, wherein the difference (s-t) is 0.07 mm or less.

4. The flooded lead-acid battery according to claim 1 or 2, wherein, in a cross section of the flooded lead-acid battery parallel to the bottom of the cell chamber, a ratio Ra (=Se / Sg) of an area Se (=S1-Sg) obtained by subtracting a cross-sectional area Sg of the plate pack from a cross-sectional area S1 inside the cell chamber to the cross-sectional area Sg of the plate pack is 0.20 or less.

5. The flooded lead-acid battery according to claim 1 or 2, wherein the electrolyte further contains at least one metal cation selected from the group consisting of Na ions, Li ions, and Al ions.

6. The flooded lead-acid battery according to claim 5, wherein the concentration of the metal cations in the electrolyte is 0.03 mol / L or more.

7. The flooded lead-acid battery according to claim 1 or 2, wherein the number of said positive plates in said plate group is one less than the number of said negative plates.

8. The flooded lead-acid battery of claim 1 or 2, wherein the positive electrode material has a volume median pore diameter of 0.50 μm or less.

9. The flooded lead-acid battery according to claim 1 or 2, wherein the separator has a rib that protrudes toward at least the positive electrode plate.

10. The flooded lead-acid battery of claim 9, wherein the average spacing between said ribs is 1.0 cm or less.

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