Liquid lead storage battery

Abstract

This liquid lead storage battery comprises: an electrode plate group; an electrolyte; and a cell chamber for accommodating the electrode plate group and the electrolyte. The electrode plate group comprises a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode material. The negative electrode plate includes a negative electrode material. The negative electrode material contains an organic shrinkage inhibitor having a sulfur element content of 2000 μmol / g or more. In a cross section, parallel to the bottom of the cell chamber, of the liquid lead storage battery, the ratio Ra (=Se / Sg) of the area Se (=S1-Sg), which is obtained by subtracting the cross-sectional area Sg of the electrode plate group from the cross-sectional area S1 of the inside of the cell chamber, to the cross-sectional area Sg of the electrode plate group is 0.20 or less.

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, a separator (or mat), and an electrolyte. Each plate includes a current collector and an electrode material. Various attempts have been made to improve the performance of lead-acid batteries, including improving the battery structure, adding additives to the plates, and adjusting the amount of electrode material or electrolyte.

[0003] Patent Document 1 discloses a battery comprising a battery case having a cell chamber, a plate group provided in the cell chamber and including separators and positive and negative plates stacked alternately with the separators interposed therebetween, and an electrolyte contained in the cell chamber, wherein the positive plate has a positive electrode material filled portion made of a positive electrode material, a positive electrode current collector supporting the positive electrode material filled portion, and a positive electrode lug provided on the upper peripheral edge of the current collector, and the negative electrode plate has a negative electrode material filled portion made of a negative electrode material, a negative electrode current collector supporting the negative electrode material filled portion, and a negative electrode lug provided on the upper peripheral edge of the current collector, and where S1 is the total surface area of ​​the positive electrode material filled portion and the negative electrode material filled portion, and V1 is the total apparent volume of the positive electrode material filled portion and the negative electrode material filled portion, S1 / V1 is 89 cm －１ The lead-acid battery proposed is as above, in which p1 / n1 is 1.35 or more, where p1 is the mass of the positive electrode material and n1 is the mass of the negative electrode material.

[0004] Patent Document 2 proposes a sealed lead-acid battery using fine glass fibers between positive and negative electrode plates, characterized in that the ratio (X / Y) of the width dimension (X) of the main surface of the positive and / or negative electrode plates to the width dimension (Y) between the inner wall of the battery case that houses these electrode plates and that is perpendicular to the main surface of the electrode plates is 0.92 or more.

[0005] Patent Document 3 proposes a sealed lead-acid battery having a structure in which almost all of the electrolyte is retained within an electrode plate group made up of a porous positive electrode plate mainly composed of lead dioxide, a porous negative electrode plate mainly composed of metallic lead, and a separator mainly composed of fine glass fiber, fine polymer fiber, or fine silica powder, and characterized in that, when the thickness of the electrode plate group is T, the width of the positive electrode plate constituting the electrode plate group is W, and the height of the positive electrode plate is H, a volume of electrolyte equivalent to 20% or more of the volume of the electrode plate group, expressed as W x H x T, is retained within the positive electrode plate.

[0006] Patent Document 4 proposes a lead-acid battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the negative electrode plate comprises a negative electrode material, the ratio of the theoretical capacity of the electrolyte in a single cell to the theoretical capacity of the negative electrode in the single cell [theoretical capacity of the electrolyte in the single cell / theoretical capacity of the negative electrode in the single cell] is 45% or more in percentage, the negative electrode material contains an organic shrinkage inhibitor, the negative electrode material contains barium sulfate, and the content of sulfur element (S element) in the organic shrinkage inhibitor is greater than 3000 μmol / g.

[0007] International Publication No. 2017 / 099144 JP 6-314572 JP 4-104476 JP 2018-18747

[0008] 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.

[0009] One aspect of the present disclosure relates to a flooded lead-acid battery comprising: a plate assembly, an electrolyte, and a cell chamber accommodating the plate assembly and the electrolyte; the plate assembly comprises positive electrode plates, negative electrode plates, and a separator interposed between the positive electrode plates and the negative electrode plates; the positive electrode plates comprise a positive electrode material; the negative electrode plates comprise a negative electrode material; and the negative electrode material comprises an organic shrinkage inhibitor having a sulfur element content of 2000 μmol / g or more; and in a cross section of the flooded lead-acid battery parallel to a 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 assembly from a cross-sectional area S1 inside the cell chamber to the cross-sectional area Sg of the plate assembly is 0.20 or less.

[0010] In flooded lead-acid batteries, the amount of electrolyte lost can be reduced.

[0011] 1 is a partially cutaway exploded perspective view schematically showing the appearance and internal structure of a flooded lead-acid battery according to one aspect of the present invention. FIG.

[0012] 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 fact that the first organic shrink-regulating agent itself is less susceptible to degradation in high-temperature environments, the first organic shrink-regulating agent's effectiveness in suppressing degradation of the negative electrode material, and the large specific surface area of ​​the negative electrode material is maintained, resulting in superior discharge performance.

[0013] On the other hand, when the first organic shrinkage inhibitor is used, the reactivity with protons during overcharge is higher than when the second organic shrinkage inhibitor is used, resulting in a larger amount of hydrogen gas generated, resulting in a significant decrease in electrolyte. Hereinafter, the decrease in electrolyte will be referred to as "loss of electrolyte," and the amount of decrease in electrolyte will be referred to as "amount of electrolyte loss." Furthermore, flooded lead-acid batteries require water replenishment. When the amount of electrolyte loss becomes significant due to the use of the first organic shrinkage inhibitor, the frequency of water replenishment increases, making maintenance more complicated.

[0014] 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.

[0015] 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 a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates. 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 preventer (i.e., a first organic shrinkage preventer) with a sulfur element content of 2000 μmol / g or more. In a cross section of the flooded lead-acid battery parallel to the bottom of the cell chamber, the ratio Ra (= Se / Sg) of the area Se (= S1 - Sg), obtained by subtracting the cross-sectional area Sg of the plate assembly from the cross-sectional area S1 inside the cell chamber, to the cross-sectional area Sg of the plate assembly, is 0.20 or less. The flooded lead-acid battery is also sometimes called a vented lead-acid battery.

[0016] When the first organic shrinkage inhibitor is used, the amount of liquid loss is generally greater than when the second organic shrinkage inhibitor is used. In the flooded lead-acid battery according to one aspect of the present invention, by satisfying Ra≦0.20, the amount of liquid loss when the first organic shrinkage inhibitor is used is significantly reduced, and the amount of liquid loss can be reduced more than when the second organic shrinkage inhibitor is used.

[0017] 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 Ra≦0.20, 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.

[0018] Regarding the ratio Ra in (a) above, the area obtained by subtracting the cross-sectional area of ​​the electrode assembly from the cross-sectional area inside the cell chamber (= Se = S1 - Sg) corresponds to the cross-sectional area of ​​the electrolyte present outside the outer edge of the electrode assembly (outside the electrode assembly) in the cross section (in other words, the electrolyte surrounding the electrode assembly in the cell chamber in which the electrode assembly is housed). Therefore, when Ra ≦ 0.20, the amount of electrolyte present outside the electrode assembly is relatively small compared to when Ra > 0.20. When Ra ≦ 0.20, the amount of oxygen generated at the positive electrode plate migrates less into the electrolyte present outside the electrode assembly compared to 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 plate than when Ra > 0.20, which is thought to be why a gas absorption reaction occurred despite the battery being a liquid battery. The cross-sectional area S1 of the inside of the cell chamber corresponds to the area of ​​the region surrounded by the inner edge of the cell chamber in the above cross section.

[0019] 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.

[0020] 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.

[0021] In addition, when Ra≦0.20, PSOC life performance is significantly improved compared to when Ra>0.20. 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 Ra≦0.20, the amount of electrolyte present outside the electrode plate assembly is relatively small, which tends to block the upward convection of the electrolyte between the electrode plate assembly and the battery case wall that occurs during charging. This suppresses stratification and plate deterioration, which is thought to improve PSOC life performance.

[0022] (2) Regarding (1) above, in the cross section, the ratio Rb (=Sp / S1) of the cross-sectional area Sp of the positive electrode plate to the cross-sectional area S1 of the cell chamber interior may be 0.30 or greater. In this case, PSOC life performance is significantly improved. This is believed to be due to the fact that stratification is suppressed and stratification is no longer a factor in life. More specifically, this is believed to be due to the following reasons. Stratification progresses during charging through the following processes (i) to (iv): (i) Lead sulfate is oxidized to generate sulfuric acid inside the electrode plate. (ii) The sulfuric acid migrates inside the electrode plate to the interface between the electrode plate and the electrolyte. (iii) The sulfuric acid migrates from the inside to the outside of the electrode plate. (iv) The density difference in the electrolyte causes natural convection, causing the sulfuric acid to settle. Compared to the negative electrode plate, the positive electrode plate has a finer internal structure, making it more difficult for sulfuric acid to migrate inside the electrode plate. Therefore, increasing the ratio Rb suppresses the process (ii) and reduces stratification. Furthermore, in the flooded lead-acid battery according to one aspect of the present invention, since Ra≦0.2, natural convection due to differences in the density of the electrolyte is suppressed, and it is thought that high-concentration sulfuric acid generated during charging is less likely to settle. Therefore, the process (iv) is suppressed, and stratification can be reduced.

[0023] (3) In the above (2), Rb may be 0.32 or more, which can further improve the PSOC life performance.

[0024] (4) In any one of the above (1) to (3), the ratio of the theoretical capacity Cn of the negative electrode material to the theoretical capacity Cp of the positive electrode material (= Cn / Cp) may be greater than 0.8. In this case, the amount of liquid loss can be further reduced. This is thought to be because the larger Cn further increases the gas absorption efficiency of the negative electrode plate.

[0025] (5) In any one of (1) to (4) above, the ratio of the theoretical capacity Cn of the negative electrode material to the theoretical capacity Cp of the positive electrode material (= Cn / Cp) may be 1.3 or less. Even if the ratio Cn / Cp increases, the effect of suppressing the liquid loss reaches a plateau. When Cn / Cp is 1.3 or less, a higher effect of suppressing the liquid loss can be obtained. Also, a higher low-rate discharge capacity tends to be obtained.

[0026] The electrode plate group typically includes multiple positive electrode plates, multiple negative electrode plates, and separators interposed between the positive and negative electrode plates. The positive and negative electrode plates are alternately stacked with the separators interposed between them. The width direction of the electrode plate group (hereinafter referred to as the "x direction") is perpendicular to the stacking direction of the positive electrode plates, negative electrode 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 when in use.

[0027] 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 (e.g., six) spaces by parallel partition walls. The interior of the battery case may also be divided into multiple (e.g., four or more) spaces by multiple intersecting partition walls. If the battery case is not divided into multiple cell chambers or does not have a cell chamber, the battery case is considered to be 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. Hereinafter, each parameter may be determined for each of the multiple cell chambers and an average value may be calculated.

[0028] The x-direction dimension X and z-direction dimension Z of the electrode plate assembly are regulated by the x-direction dimension (x) and z-direction dimension (z) of the electrode plate. The dimension X of the electrode plate assembly can be considered as the dimension (x) of the electrode plate. The x-direction dimension (x1) of the positive electrode plate and the x-direction dimension (x2) of the negative electrode plate are usually substantially the same. If (x1) and (x2) are different, the average of (x1) and (x2) can be used as (x). The y-direction dimension Y of the electrode plate assembly corresponds to the distance between the outermost portions of the two outermost components (positive electrode plate, negative electrode plate, or separator) in the stacking direction. The cross-sectional area Sg of the electrode plate assembly is expressed as X x Y.

[0029] However, if there is a rib on the surface of the battery case facing the electrode plate group, a separator is arranged on the outermost side in the stacking direction, there is a rib on the surface of that separator facing the battery case, and the group length Y is greater than the distance between the tips of the opposing ribs of the battery case, the distance between the tips of the ribs shall be taken as the group length Y.

[0030] 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 (5). At least one selected from the components described below can be arbitrarily combined with at least one of the above (1) to (5) for the flooded lead-acid battery according to one aspect of the present invention, as long as such combination is technically possible.

[0031] [Flooded Lead-Acid Battery] In a flooded lead-acid battery according to one aspect of the present invention, the ratio Ra (=(S1-Sg) / Sg=Se / Sg) is 0.20 or less. When the ratio Ra≦0.20, the amount of electrolyte loss can be reduced despite the use of the first organic shrinkage inhibitor. Furthermore, stratification is suppressed, thereby achieving high PSOC life performance. In addition, the use of the first organic shrinkage inhibitor results in high high-temperature resistance. From the viewpoint of easily adjusting the balance between the electrolyte and the electrode material, the ratio Ra may be 0.10 or more, or may be 0.12 or more.

[0032] The ratio Rb (= Sp / S1) may be 0.30 or more, or 0.32 or more. The cross-sectional area of ​​the positive electrode plate (Sp) is the sum of the cross-sectional areas of all the positive electrode plates included in one electrode plate group housed in the cell chamber. A large cross-sectional area of ​​the positive electrode plate means a large volume of the positive electrode plate. When the ratio Rb is 0.30 or more or 0.32 or more, it can be said that the volume of the positive electrode plate in the electrode plate group is designed to be as large as possible.

[0033] The ratios Ra and Rb are each determined at a section 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 ratios Ra and Rb are 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).

[0034] (How to determine Ra) 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 in parallel to the bottom of the battery case up to a height of 4.5 cm from the bottom. Next, water is poured in up to a height of 5.5 cm from 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.

[0035] An electrode plate group removed from a fully charged lead-acid battery is disassembled into positive electrode plates, negative electrode plates, and separators, and the thickness of the positive electrode plates, the thickness of the negative electrode plates, and the total thickness of the separator are determined.

[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 ｂThe 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 A) 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] The thicknesses of the positive electrode plate, negative electrode plate, and separator are measured with a vernier caliper at a position 5 cm above the bottom (more specifically, the inner bottom surface) of the cell chamber (or battery case).

[0040] The thickness of the positive electrode plate × the number of positive electrode plates, the thickness of the negative electrode plate × the number of negative electrode plates, and the total thickness of the separator × the number of separators between the positive and negative electrode plates (in the case of a pouch-shaped separator, the total thickness of the separator × the number of pouch-shaped separators × 2) are calculated and added together. This gives the thickness (dimension Y) of the electrode plate assembly in the stacking direction (y direction). Next, the width (dimension in the x direction) of the electrode plate assembly is measured using a scale at a height of 5 cm from the bottom (more specifically, the inner bottom surface) of the cell chamber (or battery case). If the widths of the positive and negative electrode plates are different, the average width is calculated and used as the electrode plate width (dimension in the x direction of the electrode plate assembly). The cross-sectional area Sg of the electrode plate assembly is calculated by multiplying this electrode plate width by the thickness (dimension y) of the electrode plate assembly in the stacking direction.

[0041] From S1 and Sg, Se=S1-Sg is calculated, and then the ratio Ra is calculated by dividing Se by Sg.

[0042] The cross-sectional area Se of the electrolyte present outside the electrode assembly is the difference (Se = S1 - Y x (x)) between the cross-sectional area inside the cell chamber (S1) and the cross-sectional area of ​​the electrode assembly (Sg = Y x (x)). In other words, the ratio Ra is expressed as (S1 - Y x (x)) / (Y x (x)) = (S1 - Sg) / Sg = Se / Sg.

[0043] 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. 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.

[0044] 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.

[0045] (How to Calculate Rb) Rb is expressed as the ratio (= Sp / S1) of the cross-sectional area of ​​the positive electrode plate (Sp) to the internal cross-sectional area (S1) of the cell chamber in the above cross section. The cross-sectional area Sp of the positive electrode plate is calculated using the x-direction dimension (x1) of the positive electrode plate, the thickness (d) of the positive electrode plate, and the number (n) of positive electrodes included in one electrode plate group, as follows: Sp = x1 x d x n. S1 is calculated from the formula for Se used to calculate the ratio Ra: Se = S1 - Y x x, the Se value calculated above, the y-direction dimension Y of the electrode plate group, and the x-direction dimension x of the electrode plate. The thickness d of the positive electrode plate is calculated using the procedure described for the ratio Ra.

[0046] In calculating the ratio Rb, the thickness of the positive electrode plate, the dimensions of the electrode plate group or electrode plate, etc. are measured at a position corresponding to a height of 5 cm from the bottom (more specifically, the inner bottom surface) of the cell chamber (or battery case).

[0047] In a flooded lead-acid battery including multiple cells, the ratios Ra and Rb are obtained by averaging the ratios Ra and Rb obtained for the cells located at the ends and the cells located near the center, respectively.

[0048] A flooded lead-acid battery includes 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. The components of a flooded lead-acid battery are described in more detail below.

[0049] (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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] (Negative Electrode Plate) The negative electrode plate includes a negative electrode material and usually includes a negative electrode current collector.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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).

[0060] (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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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).

[0069] 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.

[0070] (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.

[0071] 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.

[0072] 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).

[0073] 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.

[0074] 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.

[0075] (Carbonous Material) 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 that includes a graphite-type crystalline structure. The 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.

[0076] 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.

[0077] (Barium Sulfate) 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.

[0078] (Ratio Cn / Cp) In a flooded lead-acid battery, the theoretical capacity ratio Cn / Cp of the electrode material may be 0.8 or more. From the viewpoint of further reducing the amount of liquid loss, the ratio Cn / Cp is preferably greater than 0.8, and more preferably 0.9 or more. It is believed that an increase in Cn increases the gas absorption efficiency in the negative electrode plate, further suppressing liquid loss. From the viewpoint of obtaining an excellent effect of suppressing liquid loss and easily obtaining a higher low-rate discharge capacity, the ratio Cn / Cp is preferably 1.3 or less.

[0079] Cn / Cp is the ratio of the theoretical capacity Cn of all negative electrode materials contained in one cell of a flooded lead-acid battery to the theoretical capacity Cn of all positive electrode materials contained in one cell. When a flooded lead-acid battery includes two or more cells, Cn / Cp is the average value of Cn / Cp calculated for two cells. When a flooded lead-acid battery includes three or more cells, Cn / Cp is the average value of Cn / Cp calculated for one cell located at the end of the flooded lead-acid battery and one cell located near the center.

[0080] 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 electrode material (positive electrode: 0.224 Ah / g, negative electrode: 0.259 Ah / g) to determine Cp and Cn, and then calculate Cn / Cp.

[0081] 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 Cn / Cp ratio.

[0082] (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 in a reduced pressure environment at 60°C ± 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 from the negative electrode current collector and separated to obtain a sample (hereinafter referred to as sample B).

[0083] 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 rubbed with a brush or the like to remove the 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 Cn / Cp ratio.

[0084] (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 typically 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, a first organic shrinkage inhibitor, and, if necessary, various additives (such as a second organic shrinkage inhibitor and a carbonaceous material), and then 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.

[0085] 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.

[0086] (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.

[0087] For the analysis or measurement, the above-mentioned sample B is used. Sample B is pulverized as necessary and is subjected to analysis of the constituent components of the negative electrode material.

[0088] (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).

[0089] 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.

[0090] 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.

[0091] (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.

[0092] 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.

[0093] (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.

[0094] (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.

[0095] 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 calculate 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.

[0096] (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.

[0097] 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.).

[0098] 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.

[0099] 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.

[0100] 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.

[0101] The separator may have at least a rib (first rib) that protrudes toward the positive electrode plate. The separator may also have a rib (second rib) that protrudes toward the negative electrode plate, as necessary. The first rib and the second rib are each formed in a portion that faces the electrode material. The separator typically has a base portion. In a separator that has ribs, the ribs protrude from the surface of the base portion. The base portion of the separator refers to the portion of the separator that excludes protrusions such as ribs, and is the sheet-like portion that defines the outer shape of the separator.

[0102] 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.

[0103] 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 a 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 a lead-acid battery) may be parallel.

[0104] The average spacing between the first ribs may be 1.3 cm or less, or 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.

[0105] 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.

[0106] The average height of the second rib may be 0.10 mm or less, or 0.05 mm or less. The average height of the second rib may be 0.02 mm or more. Furthermore, the separator does not necessarily have to have the second rib.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] (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.

[0111] 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.

[0112] From the viewpoint of easily suppressing permeation short circuits, 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.

[0113] 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.

[0114] (Other) In the electrode plate assembly, the number of positive electrode plates may be the same as the number of negative electrode plates, or may be one less or one more. To increase the ratio Rb, the number of positive electrode plates constituting the electrode plate assembly may be the same as the number of negative electrode plates, or may be one more than the number of negative electrode plates. For example, a positive electrode plate may be arranged at one end of the electrode plate assembly in the stacking direction, and a negative electrode plate may be arranged at the other end. Alternatively, positive electrode plates may be arranged at both ends of the electrode plate assembly in the stacking direction. The positive electrode plates may be enclosed in a pouch-shaped separator. Generally, negative electrode plates are often arranged at both ends of the electrode plate assembly in the stacking direction to ensure low-temperature high-rate performance.

[0115] 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.

[0116] 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.

[0117] A flooded 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 flooded 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 flooded 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.

[0118] The method for manufacturing a flooded 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] <Flooded Lead-Acid Batteries E1-E20 and C1-C20> (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. The density of the negative electrode paste was adjusted so that the ratio Cn / Cp obtained by the previously described procedures was the value shown in the table. In this manner, an unformed negative electrode plate was obtained.

[0126] (b) Preparation of Positive Electrode Plate Lead powder, water, and dilute sulfuric acid were mixed to obtain a positive electrode paste. The positive electrode paste was filled into the mesh portion of an expanded lattice made of a Pb—Ca—Sn alloy as a positive electrode current collector, and then aged and dried. The density of the positive electrode paste was adjusted so that the ratio Cn / Cp obtained by the procedure described above was the value shown in the table. In this way, an unformed positive electrode plate was obtained.

[0127] (c) Fabrication of a 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's electrode plate assembly consisted of seven positive and eight negative electrode plates. First, the unformed positive electrode plates were housed in a pouch-shaped separator and stacked alternately with the negative electrode plates. The resulting electrode plate assembly consisting of the unformed electrode plates was housed in a battery case together with an electrolyte (aqueous sulfuric acid solution), and chemical formation was performed inside the battery case to fabricate a flooded lead acid battery. At this time, the ratio Ra obtained by the above-mentioned procedure was adjusted using a spacer to the value shown in the table. 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 after the above-mentioned chemical conversion.

[0128] (2) Evaluation The following evaluations were carried out using batteries with a nominal voltage of 12 V (6 cells) produced in the examples or comparative examples. When the following evaluations are carried out using other batteries, the evaluations are carried out at a voltage that matches the number of cells in the battery. (a) Amount of liquid loss The 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 refilled (M ａ In Tables 1 and 4, the amount of liquid loss for each battery was evaluated as a relative value when the amount of liquid loss for Battery C2 was set to 100. The smaller this relative value, the more suppressed the liquid loss.

[0129] (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 C2 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.

[0130] (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 C18 was taken as 100. The larger this value, the better the PSOC life performance. Here, I ｎis the current value (unit: A) equivalent to the value obtained by dividing the rated n-hour rate capacity (unit: Ah) of the battery by n. Step 1 (conditioning discharge): 4×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.

[0131] The evaluation results are shown in Tables 1 to 4. In these tables, E1 to E20 are examples, and C1 to C20 are comparative examples.

[0132]

[0133] As shown in Table 1, when Ra > 0.20, the amount of liquid loss was greater when the first organic shrink-proofing agent was used than when the second organic shrink-proofing agent was used. When Ra ≦ 0.20, the amount of liquid loss was somewhat smaller even when the second organic shrink-proofing agent was used. In contrast, when Ra ≦ 0.20, the amount of liquid loss was significantly reduced when the first organic shrink-proofing agent was used, and was significantly reduced even compared to when the second organic shrink-proofing agent was used. The results in Table 1 show that the behavior of liquid loss was completely different depending on the type of organic shrink-proofing agent when Ra > 0.20 and when Ra ≦ 0.20.

[0134]

[0135] 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.

[0136]

[0137] As shown in Table 3, when Ra≦0.20, PSOC life performance was improved compared to when Ra>0.20. When Ra≦0.20 and Rb≧0.30, significantly higher PSOC life performance was obtained compared to when Ra>0.20 or Rb<0.30 (E11, E12, E15, E16). However, when Ra>0.20, the improvement in PSOC life performance was small even when Rb≧0.30. The significantly higher PSOC life performance when Ra≦0.20 and Rb≧0.30 is thought to be due to the significant suppression of stratification.

[0138]

[0139] As shown in Table 4, the amount of liquid loss tended to decrease as the ratio Cn / Cp increased. When Cn / Cp was greater than 0.8 (preferably Cn / Cp ≥ 0.9), the amount of liquid loss was further reduced. Since the effect of reducing the amount of liquid loss tended to plateau as the ratio Cn / Cp increased, it is preferable that the ratio Cn / Cp be 1.3 or less.

[0140] 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.

[0141] 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; the positive electrode plate comprises a positive electrode material; the negative electrode plate comprises a negative electrode material; and the negative electrode material comprises an organic shrinkage inhibitor having an elemental sulfur content of 2000 μmol / g or more; and in a cross section of the flooded lead-acid battery parallel to a 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 group from a cross-sectional area S1 inside the cell chamber to the cross-sectional area Sg of the plate group is 0.20 or less.

2. The flooded lead-acid battery according to claim 1, wherein in said cross section, a ratio Rb (=Sp / S1) of a cross-sectional area Sp of said positive plate to a cross-sectional area S1 inside said cell chamber is 0.30 or more.

3. The flooded lead-acid battery according to claim 2, wherein Rb is 0.32 or more.

4. The flooded lead-acid battery according to claim 1 or 2, wherein the ratio of the theoretical capacity Cn of the negative electrode material to the theoretical capacity Cp of the positive electrode material (=Cn / Cp) is greater than 0.

8.

5. The flooded lead-acid battery according to claim 4, wherein the ratio Cn / Cp is 1.3 or less.

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