Negative electrode plate for lead-acid batteries and lead-acid batteries

Abstract

A negative electrode plate, for a lead storage battery, according to the present invention includes a negative electrode current collector and a negative-electrode electrode material. The negative electrode current collector comprises frame sections having ears, and a lattice section that is continuous with the frame sections. The lattice section comprises a plurality of quadrilateral boxes, and the quadrilateral boxes comprise a pair of first vertices that form a diagonal in a first direction from the frame sections toward the lattice section, and a pair of second vertices that form a diagonal in a second direction that intersects the first direction. The angle θ between the two sides forming the second vertices is 55° or greater and 100° or less. The negative-electrode electrode material includes an organic condensate.

Description

Technical Field

[0001] The present invention relates to a negative electrode plate for a lead storage battery and a lead storage battery.

Background Art

[0002] Lead storage batteries are used in various applications, including in-vehicle and industrial applications. A lead storage battery includes a negative electrode plate, a positive electrode plate, and an electrolyte. The negative electrode plate includes a current collector and a negative electrode active material. An organic shrinkage inhibitor is added to the negative electrode active material. As the organic shrinkage inhibitor, in addition to natural-derived organic shrinkage inhibitors such as sodium lignin sulfonate, synthetic organic shrinkage inhibitors are also used.

[0003] Cold Cranking Amps (CCA) is known as an important index indicating the performance of a lead storage battery. For example, the higher the terminal voltage at the 30th second after the start of discharge measured according to a predetermined procedure, the higher the CCA performance. Generally, a lead storage battery with higher CCA performance has better low-temperature high-rate performance.

[0004] Patent Document 1 teaches a negative electrode plate for a lead storage battery in which a lignin sulfonate is dispersed and contained in an active material layer, wherein the lignin sulfonate has an average molecular weight of 4000 to 10000 and a sulfonation rate of 90% or more.

[0005] Further, Patent Document 2 teaches a lead storage battery in which the negative electrode plate contains an organic shrinkage inhibitor having an S element content of 3900 μmol / g or more and 6000 μmol / g or less, and the ratio of the volume of the electrolyte to the total volume of the positive and negative electrode plates is 1.8 or more and 3.0 or less, and the concentration of the organic shrinkage inhibitor in the negative electrode active material is 0.05 mass% or more and 0.3 mass% or less, from the viewpoint of providing a lead storage battery having excellent low-temperature high-rate discharge performance and practical low-rate discharge performance.

[0006] On the other hand, in Patent Document 3, in the volume V of the positive electrode plate excluding the current collecting ear portion and the mass W of the positive electrode expanded lattice body excluding the current collecting ear portion, the ratio (W / V) of the W to the V is 1.20 g / cm 3The above conditions are met, and the ratio of the area S to the perimeter L of the positive electrode expanded grid (S / L) is 2.3 mm or less, the angle θ between two sides of the expanded grid is less than 90°, and the apparent density of the positive electrode active material filled in the positive electrode expanded grid is 4.0 g / cm³. 3 A valve-regulated lead-acid battery characterized by the above features has been proposed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-144305 [Patent Document 2] Japanese Patent Publication No. 2019-53998 [Patent Document 3] Japanese Patent Publication No. 2007-157613 [Overview of the project] [Problems that the invention aims to solve]

[0008] The demand for improved low-temperature high-rate performance of lead-acid batteries is increasing year by year, but the methods described in Patent Documents 1 and 2 are insufficient to adequately meet these higher demands. [Means for solving the problem]

[0009] One aspect of the present invention relates to a negative electrode plate for a lead-acid battery, comprising a negative electrode current collector and a negative electrode material, wherein the negative electrode current collector has a frame portion having ears and a grid portion provided continuously with the frame portion, the grid portion has a plurality of square cells, each square cell has a pair of first vertices with a diagonal in a first direction from the frame portion toward the grid portion and a pair of second vertices with a diagonal in a second direction intersecting the first direction, the angle θ formed by the two sides forming the second vertices is 55° or more and 100° or less, and the negative electrode material contains an organic condensate. [Effects of the Invention]

[0010] The negative electrode plate for lead-acid batteries according to the present invention makes it possible to significantly improve the low-temperature high-rate performance of lead-acid batteries. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view showing the structure of the negative electrode current collector. [Figure 2] Figure 1 is an enlarged view of the grid portion of the negative electrode current collector. [Figure 3] This is a partially cutaway exploded perspective view showing the external appearance and internal structure of a lead-acid battery. [Figure 4] This graph shows the relationship between the angle θ formed by the two sides that make up the second vertex of the negative electrode current collector and the CCA performance. [Figure 5] This graph shows the relationship between the width L of the inner dimensions in the second direction of the rectangular grid of the negative electrode current collector and the CCA performance, when the angle θ formed by the two sides that make up the second vertex of the negative electrode current collector is 50°. [Figure 6] This graph shows the relationship between the width L of the inner dimensions in the second direction of the rectangular grid of the negative electrode current collector and the CCA performance, when the angle θ between the two sides forming the second vertex of the negative electrode current collector is 80°. [Modes for carrying out the invention]

[0012] [Lead acid battery] An embodiment of the present invention comprises a negative electrode plate, a positive electrode plate, and an electrolyte containing sulfuric acid, which will be described later.

[0013] The lead-acid battery may be either a valve-regulated (sealed) lead-acid battery or a liquid-type (vented) lead-acid battery.

[0014] In this specification, the fully charged state of a flooded lead-acid battery is defined according to JIS D 5301:2006. More specifically, in a water bath at 25°C ± 2°C, the lead-acid battery is charged with a current (A) that is 0.2 times the numerical value of Ah described as the rated capacity, and the terminal voltage during charging measured every 15 minutes or the electrolyte density converted to a temperature of 20°C is charged until it shows a constant value with three significant figures continuously for three times, and this state is defined as the fully charged state. Also, in the case of a controlled valve type lead-acid battery, the fully charged state means that in an air bath at 25°C ± 2°C, the lead-acid battery is charged with a constant current and constant voltage of 2.23 V / cell with a current (A) that is 0.2 times the numerical value of Ah described as the rated capacity, and the charging is terminated when the charging current (A) during constant voltage charging becomes 0.005 times the numerical value described as the rated capacity. Note that the numerical value of Ah described as the rated capacity is a numerical value with the unit of Ah. The unit of the current set based on the numerical value described as the rated capacity is A.

[0015] A fully charged lead-acid battery refers to a pre-charged, fully charged lead-acid battery. The full charge of the lead-acid battery may be immediately after formation if it is after formation, or may be performed after a certain period of time has elapsed since formation. For example, it is also possible to fully charge a lead-acid battery during use (preferably in the initial stage of use) after formation. The battery in the initial stage of use refers to a battery that has not elapsed much time since the start of use and has hardly deteriorated.

[0016] Also, the CCA performance is evaluated based on the terminal voltage at 30 seconds after the start of discharge measured according to the following procedure in accordance with JIS D 5301:2006. The higher the voltage value, the higher the starting performance. (a) After the full charge is completed, after a rest of 1 to 5 hours, place the lead-acid battery in a cooling chamber at -18°C ± 1°C until at least 24 hours have passed or it can be confirmed that the electrolyte temperature of any cell in the center is -18°C ± 1°C. (b) After the cooling is completed, discharge for 30 seconds at CCA 310A. (c) Record the terminal voltage at 30 seconds after the start of discharge.

[0017] Hereinafter, the lead-acid battery according to the embodiment of the present invention will be described for each main component, but the present invention is not limited to the following embodiments.

[0018] (Negative electrode plate) A negative electrode plate for a lead-acid battery according to one aspect of the present invention includes a negative electrode current collector and a negative electrode material. The negative electrode current collector has a frame portion having ears and a grid portion provided continuously with the frame portion. The grid portion has a plurality of square cells. Each square cell has a pair of first vertices whose diagonals are in a first direction from the frame portion toward the grid portion, and a pair of second vertices whose diagonals are in a second direction intersecting the first direction. Here, the angle θ (hereinafter also simply referred to as angle θ) formed by the two sides that form the second vertex is 55° or more and 100° or less.

[0019] The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. The negative electrode material contains organic condensates as an organic shrinkage inhibitor. An organic shrinkage inhibitor is an organic compound that has the function of suppressing the shrinkage of lead, which is the negative electrode active material, when the lead-acid battery is repeatedly charged and discharged. Organic shrinkage inhibitors include organic condensates in addition to lignin compounds. Organic condensates are synthetic products that can be obtained using a condensation reaction and do not include lignin compounds. Note that lignin compounds, which are commonly used in lead-acid batteries, are natural materials and are therefore excluded from organic condensates, which are synthetic products. Synthetic shrinkage inhibitors used in lead-acid batteries are usually organic condensates.

[0020] The negative electrode plate may have materials such as mats or pasting paper attached to it. Since such materials (attached materials) are used integrally with the negative electrode plate, they are included in the negative electrode plate. Furthermore, when the negative electrode plate includes attached materials, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and attached materials. However, if attached materials such as mats are attached to the separator, the thickness of the attached materials is included in the thickness of the separator.

[0021] The negative electrode plate can be formed by applying or filling a negative electrode paste onto a negative electrode current collector, then curing and drying it to produce an uncured negative electrode plate, and subsequently curing the uncured negative electrode plate. The negative electrode paste is prepared by kneading lead powder, an organic shrinkage inhibitor, and various additives as needed, with water and sulfuric acid. During curing, it is preferable to cure the uncured negative electrode plate at a temperature higher than room temperature and at high humidity.

[0022] The chemical conversion can be carried out by immersing the electrode plate group, including the unconverted negative electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and then charging the electrode plate group. However, the chemical conversion may also be performed before the assembly of the lead-acid battery or the electrode plate group. Spongy lead is produced by the chemical conversion.

[0023] Generally, the angle θ is set to around 50°. If the angle θ is larger than this, the square grid becomes closer to a perfect square, reducing the bonding force between the negative electrode current collector and the negative electrode material. This is thought to cause cracks at the interface between the negative electrode current collector and the negative electrode material, and even detachment of the negative electrode material. In particular, in the case of an expanded grid, the larger the angle θ, the greater the degree of expansion with the first direction as the expansion direction. Consequently, the residual stress on the negative electrode current collector increases, and the aforementioned cracks and detachment of the negative electrode material become more pronounced. These phenomena are expected to negatively affect current collection efficiency and reduce CCA performance.

[0024] However, contrary to the general predictions above, it was found that even when the angle θ is increased to 55° or more, CCA performance can be improved if the angle θ is 100° or less, depending on other conditions. In other words, CCA performance does not depend solely on the angle θ, but also on other conditions. In particular, it was found that when the negative electrode material contains an organic condensate instead of a lignin compound, increasing the angle θ to 55° or more improves CCA performance. In particular, using the specified organic condensate described later significantly improves CCA performance. From the viewpoint of maximizing the improvement in CCA performance, the angle θ may be 60° or more, 70° or more, or 80° or more. That is, the range of θ may be, for example, 55°~100°, 60°~100°, 70°~100°, or 80°~100°.

[0025] The following is a possible mechanism for the significant improvement in CCA performance. First, the inclusion of organic condensates in the negative electrode material improves the bonding strength between the negative electrode current collector and the negative electrode material. Unlike naturally occurring lignin compounds, organic condensates readily form parts with planar structures within their molecules. Therefore, once dissolved, organic condensates readily adsorb to the lead contained in the negative electrode plate. Organic condensates adsorbed at the interface between the current collector and the negative electrode material refine the structure of spongy lead, improve the mechanical strength at the interface, and enhance the bonding strength between the negative electrode current collector and the negative electrode material. In contrast, lignin compounds have a complex three-dimensional network structure and are more easily dissolved from the negative electrode material than organic condensates. Furthermore, lignin compounds have inferior adsorption properties to the lead contained in the negative electrode plate compared to organic condensates. Therefore, it is difficult to obtain the above-mentioned bonding strength improvement effect with lignin compounds.

[0026] On the other hand, increasing the angle θ to 55° or more is thought to reduce the voltage drop in the current collection path from the grid to the frame. Furthermore, by mitigating the negative effects on current collection efficiency as described above through improved bonding force, the effect of reducing the voltage drop in the current collection path is enhanced, and the improvement in CCA performance is thought to become significant. The degree of improvement in CCA performance tends to increase with increasing angle θ. However, if the angle θ exceeds 100°, a decrease in the structural strength of the negative electrode current collector may become apparent. To strike a good balance between improved CCA performance and the strength of the negative electrode current collector, the angle θ should be set to 100° or less.

[0027] (Negative electrode current collector) 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. Using a negative electrode grid as the negative electrode current collector is preferable because it makes it easier to support the negative electrode material.

[0028] The lead alloy used for the negative electrode current collector may be any of the following: Pb-Sb alloy, Pb-Ca alloy, or Pb-Ca-Sn alloy. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. 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 on a part of the negative electrode current collector. The surface layer may be formed on the lugs of the negative electrode current collector. The surface layer of the lugs may contain Sn or a Sn alloy.

[0029] Next, in the negative electrode current collector, the inner width of the square grid in the second direction (hereinafter referred to as width L) may be 11 mm or more and 22.5 mm or less. The larger the width L, the larger the square grid becomes, and the total amount of lattice bones constituting the grid decreases. When the square grid becomes larger, the bonding force between the negative electrode current collector and the negative electrode material tends to decrease, and the current collection efficiency tends to decrease. In addition, the decrease in the total amount of lattice bones directly leads to a decrease in the current collection path and reduces the interface between the negative electrode current collector and the negative electrode material, thus also decreasing the bonding force between the negative electrode current collector and the negative electrode material. Therefore, when the width L is 11 mm or more, the CCA performance usually decreases significantly.

[0030] On the other hand, even when the angle θ is increased to 55° or more, and the width L is increased to 11 mm or more, the decrease in CCA performance is significantly suppressed. Furthermore, when the negative electrode material contains an organic condensate, the decrease in CCA performance associated with the increase in width L is suppressed even more significantly. This is thought to be because increasing the angle θ to 55° or more and using an organic condensate enhances the effect of reducing the voltage drop in the current collection path, as described above. However, when the width L exceeds 22.5 mm, although the effect of suppressing the decrease in CCA performance is significant, the effects of a decrease in the bonding force between the negative electrode current collector and the negative electrode material, and a reduction in the current collection path become significant. From the viewpoint of ensuring sufficiently practical CCA performance, it is desirable to keep the width L at 22.5 mm or less.

[0031] Next, the negative electrode current collector may be a punched grid or a cast grid, but as already mentioned, it may also be an expanded grid with the first direction being the grid expansion direction. Expanded grids are easy to manufacture because the angle θ can be easily controlled by the expansion process, and the width L can also be easily controlled by slitting before expansion. Furthermore, because expanded grids have a large residual stress in the negative electrode current collector, cracks at the interface between the negative electrode current collector and the negative electrode material, and detachment of the negative electrode material are usually noticeable. However, when the angle θ is 55° or more and an organic condensate is used, the effect of reducing the voltage drop in the current collection path is enhanced, making it easier to improve CCA performance. In other words, when the negative electrode current collector is an expanded grid, it is extremely effective to set the angle θ to 55° or more and to use an organic condensate.

[0032] Each of the multiple rectangular grid cells is surrounded by four grid ribs. When any one of the four grid ribs is cut perpendicular to its length to form a cross-section, the resulting cross-section is rectangular. Of the four sides constituting the rectangle, the lengths of two sides correspond to the thickness of the negative electrode current collector. In the case of expanded grids or punched grids, the lengths of two sides constituting the rectangle correspond to the thickness of the lead or lead alloy sheet being expanded or punched. Here, let x be the length of each of the two sides corresponding to the sheet thickness. Let y be the length of each of the remaining two sides. The sides with length y correspond to the front and back surfaces of the sheet being expanded or punched. If the sheet thickness is the same, the larger the ratio of y to x: y / x, the larger the mass of the negative electrode current collector, which is advantageous for CCA performance. Also, the larger y / x, the easier it is for the negative electrode current collector to maintain sufficient strength even when the angle θ is large, and the easier it is to suppress cracks and detachment of the negative electrode material. For example, y / x is preferably greater than 0.75, more preferably 0.8 or greater and 1.4 or less, and even more preferably 0.85 or greater and 1.1 or less.

[0033] Figure 1 shows a plan view of an example of a negative electrode current collector according to one embodiment of the present invention. The negative electrode current collector shown in Figure 1 is an expanded grid. The expanded grid 20 has an upper frame frame portion 22 having ears 21, a lower frame frame portion 23 facing the upper frame frame portion 22, and a grid portion 24 continuous with the upper frame frame portion 22 and the lower frame frame portion 23. The grid portion 24 has grid bones 24b that form a plurality of square grids 24a.

[0034] Figure 2 shows an enlarged view of the grid portion 24 of the expanded grid 20. Each square 24a has a pair of first vertices P11 and P12 with the first direction D1 as its diagonal, and a pair of second vertices P21 and P22 with the second direction D2 intersecting the first direction D1 as its diagonal. The angle θ between the two sides forming the second vertices P21 and P22 is between 55° and 100°. The width L of the inner dimension of the square 24a in the second direction D2 corresponds to the distance between the second vertices P21 and P22.

[0035] (Negative electrode material) The negative electrode material contains a negative electrode active material (lead or lead sulfate) that exhibits capacity through a redox reaction. The negative electrode material may also contain at least one selected from the group consisting of organic shrinkage inhibitors, carbonaceous materials, and other additives. Examples of additives include, but are not limited to, barium sulfate and fibers (such as resin fibers). The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually made using lead powder.

[0036] (Organic shrinkage inhibitor) As previously mentioned, the negative electrode material contains an organic condensate as an organic shrinkage inhibitor. The organic shrinkage inhibitor may be synthesized by known methods, for example, or a commercially available product may be used. The negative electrode material may contain one type of organic shrinkage inhibitor, or two or more types.

[0037] The negative electrode material may contain a lignin compound as an organic shrinkage inhibitor, but from the viewpoint of improving or enhancing the bonding strength between the negative electrode current collector and the negative electrode material, it contains at least an organic condensate as an organic shrinkage inhibitor other than a lignin compound.

[0038] Here, lignin compounds include not only lignin but also lignin derivatives. Lignin derivatives include those having a lignin-like three-dimensional structure. Examples of lignin derivatives include at least one selected from the group consisting of modified lignin, ligninsulfonic acid, modified ligninsulfonic acid, and salts thereof (alkali metal salts (such as sodium salts), magnesium salts, calcium salts, etc.).

[0039] Organic condensates (hereinafter simply referred to as condensates), which are organic shrinkage inhibitors, are synthetic products and are generally also called synthetic shrinkage inhibitors. Condensates may contain aromatic compound units (hereinafter also referred to as aromatic compound units). An aromatic compound unit is a unit derived from an aromatic compound incorporated into the condensate. In other words, an aromatic compound unit is a residue of an aromatic compound. A condensate may contain one type of aromatic compound unit or multiple types.

[0040] Examples of condensates include those formed by the reaction of aromatic compounds with aldehyde compounds. Such condensates can be synthesized by reacting aromatic compounds with aldehyde compounds. Here, condensates containing sulfur can be obtained by carrying out the reaction between the aromatic compound and the aldehyde compound in the presence of sulfite, or by using an aromatic compound containing sulfur (e.g., bisphenol S) as the aromatic compound. For example, the sulfur content in the condensate can be adjusted by adjusting the amount of sulfite and / or the amount of the sulfur-containing aromatic compound. This method may also be followed when using other raw materials. The aromatic compounds used in the condensation to obtain the condensate may be one or two or more. The aldehyde compound may be an aldehyde (e.g., formaldehyde), or an aldehyde condensate.

[0041] Aromatic compounds may have sulfur-containing groups. That is, the condensate may be an organic polymer containing multiple aromatic rings within the molecule and an element sulfur as a sulfur-containing group. The sulfur-containing group may be directly bonded to the aromatic ring of the aromatic compound, or it may be bonded to the aromatic ring as an alkyl chain having a sulfur-containing group, for example. Among sulfur-containing groups, stable forms such as sulfonic acid groups or sulfonyl groups are preferred. Sulfonic acid groups may exist in acid form or in salt form, such as a sodium salt.

[0042] Sulfur-containing groups are functional groups with strong negative polarity. In the electrolyte, such functional groups form stable bonds with water molecules, hydrogen ions, and bisulfate ions, and therefore tend to be concentrated on the surface of the condensate. Because functional groups concentrated on the surface have an electric charge, electrostatic repulsion occurs between the aggregates of the condensate, limiting the aggregation of colloidal particles and making it easier to reduce the size of the colloidal particles. As a result, the pore size of the negative electrode material is reduced, and the resistivity of the negative electrode material tends to decrease. In relation to this, condensates containing aromatic compound units with sulfur-containing groups have a significant effect in refining the structure of spongy lead at the interface between the current collector and the negative electrode material, improving the mechanical strength at the interface and enhancing adhesion. Thus, condensates containing aromatic compound units with sulfur-containing groups have a significant effect in improving the bonding strength between the negative electrode current collector and the negative electrode material.

[0043] Aromatic rings in aromatic compounds include benzene rings and naphthalene rings. When an aromatic compound has multiple aromatic rings, these rings may be directly bonded or linked by linking groups (e.g., alkylene groups (including alkylidene groups), sulfone groups, etc.). Examples of such structures include bisarene structures (biphenyl, bisphenylalkane, bisphenylsulfone, etc.).

[0044] Examples of aromatic compounds include compounds having the above-mentioned aromatic ring and functional groups such as hydroxyl groups and amino groups. The functional groups such as hydroxyl groups and amino groups may be directly bonded to the aromatic ring, or they may be bonded as an alkyl chain having a functional group. Note that the hydroxyl group also includes salts of the hydroxyl group (-OMe). The amino group also includes salts of the amino group (salts with anions). Examples of Me include alkali metals (Li, K, Na, etc.) and Group 2 metals of the periodic table (Ca, Mg, etc.).

[0045] The hydroxyl group in the aromatic compound is preferably a phenolic hydroxyl group. In condensates of aromatic compounds having a phenolic hydroxyl group with an aldehyde compound, the condensation mainly occurs at least one of the ortho and para positions (especially the ortho position) relative to the phenolic hydroxyl group. On the other hand, in condensates of monocyclic aromatic compounds having an amino group with an aldehyde compound, the condensation occurs via the amino group. Therefore, when using a monocyclic aromatic compound having a phenolic hydroxyl group, the twisting between the aromatic rings in the organic shrinkage inhibitor molecule is less than when using a monocyclic aromatic compound having an amino group, making it easier to adopt a more planar structure and thus easier to act on lead. In addition, phenolic hydroxyl groups tend to result in negatively charged organic condensates compared to amino groups, etc., making it easier to obtain high adsorption properties for lead.

[0046] On the other hand, if the organic condensate contains nitrogen atom-containing groups such as amino groups, the negative charge of the organic condensate decreases. Therefore, it is preferable to have a low content of nitrogen atom-containing groups in the organic condensate. The nitrogen atom content in the organic shrinkage inhibitor is preferably 1% by mass or less, and may be 0.1% by mass or less.

[0047] The aromatic compound that forms the basis of the aromatic compound unit may include at least one selected from the group consisting of bisarene compounds and monocyclic compounds. In this case, even when the lead-acid battery experiences a temperature environment higher than room temperature, aggregation of condensates in the negative electrode material can be suppressed, preventing coarsening of the microstructure of the negative electrode material and tending to prevent impairment of low-temperature high-rate performance.

[0048] Examples of bisarene compounds include bisphenol compounds, hydroxybiphenyl compounds, and 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). Among these, bisphenol compounds are preferred.

[0049] Preferred bisphenol compounds include bisphenol A, bisphenol S, and bisphenol F. For example, the bisphenol compound may include at least one selected from the group consisting of bisphenol A and bisphenol S. Among these, condensates containing bisphenol S units have sulfur-containing groups, and because more functional groups with strong negative polarity can be present on the surface of the condensate, the effect of improving the bonding strength between the negative electrode current collector and the negative electrode material is even greater. When the bisphenol compound contains both bisphenol A and bisphenol S, the molar ratio of bisphenol A to bisphenol S may be in the range of, for example, 1:9 to 9:1, and is preferably in the range of 2:8 to 8:2.

[0050] A bisphenol compound only needs to have a bisphenol skeleton, and the bisphenol skeleton may have substituents. That is, bisphenol A only needs to have a bisphenol A skeleton, and that skeleton may have substituents. Bisphenol S only needs to have a bisphenol S skeleton, and that skeleton may have substituents.

[0051] Preferred monocyclic compounds include hydroxyarene compounds and aminoarene compounds. Among these, hydroxyarene compounds are preferred.

[0052] Examples of hydroxyarene compounds include hydroxynaphthalene compounds and phenol compounds. For example, it is preferable to use phenol sulfonic acid compounds (phenol sulfonic acid or its derivatives, etc.), which are phenol compounds. A condensate containing a phenol sulfonic acid compound unit has a phenolic hydroxyl group and a sulfonic acid group. Both the phenolic hydroxyl group and the sulfonic acid group have strong negative polarity and high affinity for metals. In addition, phenol sulfonic acid makes it easier for the condensate to adopt a planar structure. Therefore, a condensate containing a phenol sulfonic acid compound unit is easily adsorbed onto the negative electrode current collector, and has a particularly great effect in improving the bonding strength between the negative electrode current collector and the negative electrode material. Furthermore, a condensate containing a phenol sulfonic acid compound unit has low solubility in the electrolyte (sulfuric acid aqueous solution) and tends to remain in the negative electrode material even after repeated deep discharge cycles. Therefore, it has a great effect in suppressing the expansion of the negative electrode material. As already mentioned, the phenolic hydroxyl group also includes the salt of the phenolic hydroxyl group (-OMe).

[0053] Examples of aminoarene compounds include aminonaphthalene compounds and aniline compounds (such as aminobenzenesulfonic acid and alkylaminobenzenesulfonic acid).

[0054] The aromatic compounds that form the basis of the aromatic compound unit may include both bisaren compounds and monocyclic compounds. This is because monocyclic compounds inhibit the formation of intramolecular bonds through interactions between aromatic ring π electrons, which is a characteristic of bisaren compounds, thereby imparting flexibility to the linear chain of the molecule. For this reason, it is thought that it is easier to expose more negatively polar functional groups on the surface.

[0055] When the aromatic compound that forms the basis of the aromatic compound unit contains both a bisarene compound and a monocyclic compound, the molar ratio of the bisarene compound to the monocyclic compound may be in the range of, for example, 1:9 to 9:1, and preferably in the range of 2:8 to 8:2.

[0056] The sulfur content of the organic condensate may be, for example, 2000 μmol / g or more, and preferably 3000 μmol / g or more. In this case, the amount of sulfur-containing groups in the organic condensate is large, the colloidal particle size of the organic condensate tends to be small, and the structure of the negative electrode material can be kept fine, thus suppressing the deterioration of low-temperature high-rate properties. However, the organic condensate may also include those with a sulfur content of less than 2000 μmol / g.

[0057] When we say that the sulfur content in an organic condensate is X μmol / g, it means that the amount of sulfur contained per gram of the organic condensate is X μmol.

[0058] There is no particular upper limit to the sulfur content of organic condensates, but it may be, for example, 9000 μmol / g or less, 8000 μmol / g or less, or 7000 μmol / g or less. These lower and upper limits can be combined arbitrarily.

[0059] The sulfur content of the organic condensate may be, for example, 2000 μmol / g or more (or 3000 μmol / g or more) and 9000 μmol / g or less, 2000 μmol / g or more (or 3000 μmol / g or more) and 8000 μmol / g or less, or 2000 μmol / g or more (or 3000 μmol / g or more) and 7000 μmol / g or less.

[0060] The weight-average molecular weight (Mw) of the organic condensate is preferably, for example, 7,000 or more. The Mw of the organic condensate may be, for example, 100,000 or less, or 20,000 or less.

[0061] In this specification, the Mw of organic condensates or organic shrinkage inhibitors shall be determined by GPC. The standard substance used when determining Mw shall be sodium polystyrene sulfonate. Mw is measured using the following equipment under the following conditions. GPC equipment: Build-up GPC system SD-8022 / DP-8020 / AS-8020 / CO-8020 / UV-8020 (manufactured by Tosoh Corporation) Column: TSKgel G4000SWXL, G2000SWXL (7.8mm I.D. × 30cm) (Manufactured by Tosoh Corporation) Detector: UV detector, λ=210nm Eluent: Mixed solution of 1 mol / L NaCl aqueous solution and acetonitrile (volume ratio = 7:3) Flow rate: 1mL / min. Concentration: 10mg / mL Injection volume: 10μL Standard substance: Sodium polystyrene sulfonate (Mw = 275,000, 35,000, 12,500, 7,500, 5,200, 1,680)

[0062] When the negative electrode material contains a lignin compound in addition to an organic condensate, the sulfur content of the lignin compound may be, for example, 1000 μmol / g or less, or 800 μmol / g or less. There is no particular lower limit to the sulfur content of the lignin compound, but for example, it is 400 μmol / g or more.

[0063] The Mw of a lignin compound is, for example, less than 7000. The Mw of a lignin compound is, for example, 3000 or more.

[0064] When using an organic condensate and a lignin compound in combination, their mass ratio can be arbitrarily selected. However, from the viewpoint of significantly improving the bonding strength between the negative electrode current collector and the negative electrode material, the ratio of the organic condensate to the total amount of the organic condensate and lignin compound is preferably 20% by mass or more, may be 50% by mass or more, or 80% by mass or more.

[0065] The content of the organic shrinkage inhibitor in the negative electrode material may be, for example, 0.01% by mass or more, and may also be 0.05% by mass or more. The content of the organic shrinkage inhibitor may be, for example, 1.0% by mass or less, and may also be 0.5% by mass or less. These lower and upper limits can be combined arbitrarily.

[0066] The content of the organic shrinkage inhibitor in the negative electrode material may be 0.01% by mass or more and 1.0% by mass or less, 0.05% by mass or more and 1.0% by mass or less, 0.01% by mass or more and 0.5% by mass or less, or 0.05% by mass or more and 0.5% by mass or less.

[0067] (Barium sulfate) The negative electrode material may contain barium sulfate. The barium sulfate content in the negative electrode material may be, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The barium sulfate content in the negative electrode material may be 3% by mass or less, and may be 2% by mass or less. These lower and upper limits can be combined arbitrarily.

[0068] The barium sulfate content in the negative electrode material may be 0.05% by mass or more and 3% by mass or less, 0.05% by mass or more and 2% by mass or less, 0.10% by mass or more and 3% by mass or less, or 0.10% by mass or more and 2% by mass or less.

[0069] (carbonaceous material) The negative electrode material may include carbonaceous materials. Examples of carbonaceous materials 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 Ketjenblack (trade name). Graphite may be any carbonaceous material containing a graphite-type crystal structure, and may be either artificial graphite or natural graphite. One type of carbonaceous material may be used alone, or two or more types may be used in combination.

[0070] The carbonaceous material content in the negative electrode material is preferably, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The carbonaceous material content is, for example, 5% by mass or less, and may be 3% by mass or less. These lower and upper limits can be combined arbitrarily.

[0071] The carbonaceous material content in the negative electrode material may be, for example, 0.05% by mass or more and 5% by mass or less, 0.05% by mass or more and 3% by mass or less, 0.10% by mass or more and 5% by mass or less, or 0.10% by mass or more and 3% by mass or less.

[0072] (Analysis of the constituent components of the negative electrode material) The following describes the method for analyzing the negative electrode material or its constituent components. Prior to the analysis, the lead-acid battery, after chemical conversion, is fully charged and then disassembled to obtain the negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid. Washing is continued until a pH test paper is pressed against the surface of the washed negative electrode plate and the color of the test paper does not change. However, the washing time should be no more than 2 hours. The washed negative electrode plate is dried under reduced pressure at 60±5℃ for about 6 hours. After drying, if the negative electrode plate contains adhesive material, the adhesive material is removed from the negative electrode plate by peeling. Next, a sample (hereinafter referred to as Sample A) is obtained by separating the negative electrode material from the negative electrode plate. Sample A is crushed as needed and subjected to analysis.

[0073] (1) Analysis of organic shrinkage inhibitors (or organic condensates) (1-1) Qualitative analysis of organic shrinkage inhibitors in negative electrode materials The pulverized sample A is immersed in a 1 mol / L sodium hydroxide (NaOH) aqueous solution to extract the organic shrinkage inhibitor. Next, if the extract contains multiple organic shrinkage inhibitors, the multiple organic shrinkage inhibitors are separated from the extract. For each of the isolates containing each organic shrinkage inhibitor, insoluble components are removed by filtration, the resulting solution is desalted, concentrated, and dried. Desalting is performed using a desalting column, by passing the solution through an ion exchange membrane, or by placing the solution in a dialysis tube and immersing it in distilled water. By drying this, a powder sample of the organic shrinkage inhibitor (hereinafter referred to as sample B) is obtained.

[0074] The type of organic shrinkage inhibitor is identified by combining information obtained from the infrared spectroscopic spectrum measured using sample B of the organic shrinkage inhibitor obtained in this way, the ultraviolet-visible absorption spectrum measured with an ultraviolet-visible absorbance meter after diluting sample B with distilled water or the like, or the NMR spectrum of a solution obtained by dissolving sample B in a predetermined solvent such as heavy water.

[0075] If the above extract contains multiple organic shrinkage inhibitors, their separation shall be carried out as follows.

[0076] First, the extract is measured using at least one of infrared spectroscopy, NMR, and GC-MS to determine whether it contains multiple types of organic shrinkage inhibitors. Next, the molecular weight distribution of the extract is measured by GPC analysis, and if the multiple types of organic shrinkage inhibitors can be separated by molecular weight, the organic shrinkage inhibitors are separated by column chromatography based on the differences in molecular weight.

[0077] Organic shrinkage inhibitors have different solubility if at least one of their functional groups differs: the type of functional group and the amount of functional groups. When it is difficult to separate organic shrinkage inhibitors based on differences in molecular weight, one of the organic shrinkage inhibitors can be separated by precipitation separation, utilizing this difference in solubility. For example, when two types of organic shrinkage inhibitors are present, one of the organic shrinkage inhibitors can be separated by agglutination and separation by adjusting the pH of the mixture by adding sulfuric acid aqueous solution to a mixture obtained by dissolving the above extract in NaOH aqueous solution. If separation by agglutination is difficult, the organic shrinkage inhibitors can be separated by ion exchange chromatography or affinity chromatography, utilizing the difference in at least one of the functional groups and the amount of functional groups. The separated material is dissolved again in NaOH aqueous solution, and insoluble components are removed by filtration as described above. Alternatively, the remaining solution after separating one organic shrinkage inhibitor is concentrated. The resulting concentrate contains the other organic shrinkage inhibitor, and insoluble components are removed from this concentrate by filtration as described above.

[0078] (1-2) Determination of the content of organic shrinkage inhibitors in the negative electrode material As in (1-1) above, solutions are obtained after removing insoluble components from each of the separated products containing the organic shrinkage inhibitors by filtration. The ultraviolet-visible absorption spectrum is measured for each obtained solution. The content of each organic shrinkage inhibitor in the negative electrode material is determined using the intensity of the peaks characteristic of each organic shrinkage inhibitor and a calibration curve prepared in advance.

[0079] Furthermore, when obtaining lead-acid batteries with an unknown organic shrinkage inhibitor content and measuring the content, it may not be possible to use the same organic shrinkage inhibitor in the calibration curve because the structural formula of the organic shrinkage inhibitor cannot be precisely identified. In such cases, a calibration curve is created using the organic shrinkage inhibitor extracted from the negative electrode of the battery and a separately available organic polymer that exhibits a similar shape in its ultraviolet-visible absorption spectrum, infrared spectroscopic spectrum, and NMR spectrum, and the content of the organic shrinkage inhibitor is measured using the ultraviolet-visible absorption spectrum.

[0080] (1-3) Sulfur element content in organic shrinkage inhibitors As in (1-1) above, after obtaining sample B of the organic shrinkage inhibitor, the sulfur element in 0.1 g of the organic shrinkage inhibitor is converted to sulfuric acid by the oxygen combustion flask method. At this time, by burning sample B in a flask containing the adsorbent, an eluate is obtained in which sulfate ions are dissolved in the adsorbent. Next, the sulfur element content (C1) in 0.1 g of the organic shrinkage inhibitor 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) in 1 g of the organic shrinkage inhibitor.

[0081] (1-4) Analysis of nitrogen element content in organic shrinkage inhibitors Similarly to (1-1) above, after obtaining sample B of the organic shrinkage inhibitor, the nitrogen atom content in the organic shrinkage inhibitor can be determined by analyzing sample B using an organic elemental analyzer (CHN analyzer). (2) Determination of carbonaceous material and barium sulfate To 10 g of pulverized sample A, 50 ml of 20% by mass nitric acid is added and heated for approximately 20 minutes to dissolve the lead component as lead nitrate. Next, the solution containing lead nitrate is filtered to separate the carbonaceous material, barium sulfate, and other solid components.

[0082] The obtained solids are dispersed in water to form a dispersion, and then components other than the carbonaceous material and barium sulfate (e.g., reinforcing materials) 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, along with the filtered sample, is dried in a dryer at 110°C ± 5°C. The resulting sample is a mixed sample of carbonaceous material and barium sulfate (hereinafter referred to as Sample C). The mass of Sample C (M) is obtained by subtracting the mass of the membrane filter from the total mass of Sample C and the membrane filter after drying. m The mass of barium sulfate (M) is measured. Then, the dried sample C is placed in a crucible with a membrane filter and incinerated at over 700°C. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate and the mass of barium sulfate (M) is measured. B We will find the mass M. m From mass M B Subtract the amount to calculate the mass of the carbonaceous material.

[0083] (Positive plate) The positive electrode plates of lead-acid batteries can be classified into paste type, clad type, and others. A paste-type positive electrode plate comprises a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. In a paste-type positive electrode plate, the positive electrode material is the positive electrode plate with the positive electrode current collector removed. 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. Processing methods include, for example, expansion or punching. Using a grid-shaped current collector as the positive electrode current collector is preferable because it makes it easier to support the positive electrode material. A clad-type positive electrode plate comprises a plurality of porous tubes, a core metal inserted into each tube, a current collecting section connecting the plurality of core metals, a positive electrode material filled into the tubes into which the core metals are inserted, and a connecting seat connecting the plurality of tubes. In clad-type positive electrode plates, the positive electrode material is the portion of the positive electrode plate excluding the tube, core metal, current collector, and connecting plate. In clad-type positive electrode plates, the core metal and current collector are sometimes collectively referred to as the positive electrode current collector.

[0084] Positive electrode plates may have materials such as mats or pasting paper attached to them. Since such materials (attached materials) are used integrally with the positive electrode plate, they are included in the positive electrode plate. Furthermore, when a positive electrode plate includes such materials, the positive electrode material, in the case of a paste-type positive electrode plate, is the portion of the positive electrode plate excluding the positive electrode current collector and the attached materials.

[0085] As lead alloys used for the positive electrode current collector, Pb-Sb alloys, Pb-Ca alloys, and Pb-Ca-Sn alloys are 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 on a part of the positive electrode current collector. The surface layer may be formed only on the grid portion, only on the lug portion, or only on the frame portion of the positive electrode current collector.

[0086] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacity through a redox reaction. The positive electrode material may also contain other additives as needed.

[0087] Unformed paste-type positive electrode plates are obtained by filling a positive electrode current collector with positive electrode paste, then allowing it to mature and dry. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. Unformed clad-type positive electrode plates are formed by filling porous tubes, into which core metals connected at the current collector are inserted, with lead powder or slurry-like lead powder, and then joining multiple tubes together. Subsequently, positive electrode plates are obtained by forming these unformed positive electrode plates. Formation can be carried out by charging the electrode group, including the unformed positive electrode plates, while immersed in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery. However, formation may also be carried out before the assembly of the lead-acid battery or the electrode group.

[0088] Chemical treatment can be carried out by immersing the electrode plate group, including the untreated positive electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and then charging the electrode plate group. However, chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group.

[0089] (Separator) A separator can be placed between the negative electrode plate and the positive electrode plate. At least one of nonwoven fabrics and microporous membranes can be used as the separator. The thickness of the separator between the negative and positive electrode plates should be selected according to the distance between the electrodes. The number of separators should be selected according to the number of electrodes.

[0090] Nonwoven fabrics are mats made by intertwining fibers without weaving, and are primarily composed of fibers. For example, nonwoven fabrics are formed of fibers by 60% or more by mass. As fibers, glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (polyethylene terephthalate fibers, etc.), etc.), pulp fibers, etc. can be used. Among these, glass fibers are preferred. Nonwoven fabrics may also contain components other than fibers, such as acid-resistant inorganic powders and polymers as binders.

[0091] On the other hand, a microporous membrane is a porous sheet mainly composed of materials other than fiber components. For example, it can be obtained by extruding a composition containing a pore-forming agent (such as polymer powder and / or oil) into a sheet, and then removing the pore-forming agent to form pores. Microporous membranes are preferably made of acid-resistant materials, and those mainly composed of polymer components are preferred. Polyolefins (such as polyethylene and polypropylene) are preferred as polymer components.

[0092] The separator may be composed of, for example, only a nonwoven fabric, or only a microporous membrane. Furthermore, the separator may, as needed, be a laminate of a nonwoven fabric and a microporous membrane, a combination of different or the same type of material, or a combination of different or the same type of material with interlocking protrusions and indentations.

[0093] The separator may be in the form of a sheet or a bag. A single sheet-like separator may be placed between the positive and negative electrode plates. Alternatively, the electrodes may be sandwiched between a single folded sheet-like separator. In this case, the positive electrode plate sandwiched between the folded sheet-like separators and the negative electrode plate sandwiched between the folded sheet-like separators may be stacked on top of each other, or one of the positive and negative electrode plates may be sandwiched between the folded sheet-like separators and stacked on top of the other electrode plate. Furthermore, the sheet-like separator may be folded into an accordion shape, and the positive and negative electrode plates may be sandwiched between the accordion-shaped separators so that the separator is interposed between them. When using a bellows-shaped separator, the separator may be positioned so that the bends align with the horizontal direction of the lead-acid battery (for example, so that the bends are parallel to the horizontal direction), or so that they align with the vertical direction (for example, so that the bends are parallel to the vertical direction). In a bellows-shaped separator, recesses are formed alternately on both main surfaces of the separator. Since tabs are usually formed on the upper part of the positive and negative electrodes, when the separator is positioned so that the bends align with the horizontal direction of the lead-acid battery, the positive and negative electrodes are placed only in the recesses on one main surface of the separator (that is, a double separator is interposed between adjacent positive and negative electrodes). When the separator is positioned so that the bent portion is aligned with the vertical direction of the lead-acid battery, the positive electrode plate can be housed in the recess on one main surface side, and the negative electrode plate can be housed in the recess on the other main surface side (that is, a single layer of separator can be interposed between adjacent positive and negative electrode plates). When a bag-shaped separator is used, the bag-shaped separator may house either the positive electrode plate or the negative electrode plate.

[0094] In this specification, the up and down directions of the electrode plates are defined as the side with the lugs being the upper side and the side opposite the lugs being the lower side. The up and down directions of the electrode plates may be the same as or different from the up and down directions of the lead-acid battery in the vertical direction. In other words, the lead-acid battery may be mounted vertically or horizontally.

[0095] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, which may be gelled if necessary. The electrolyte may optionally contain at least one selected from the group consisting of cations (e.g., metal cations) and anions (e.g., anions other than sulfate anions (e.g., phosphate ions)). Examples of metal cations include at least one selected from the group consisting of sodium ions, lithium ions, magnesium ions, and aluminum ions.

[0096] The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 or higher, and may be 1.25 or higher. The specific gravity of the electrolyte at 20°C is 1.35 or lower, and preferably 1.32 or lower. These lower and upper limits can be combined arbitrarily. The specific gravity of the electrolyte at 20°C may be 1.20 or higher and 1.35 or lower, 1.20 or higher and 1.32 or lower, 1.25 or higher and 1.35 or lower, or 1.25 or higher and 1.32 or lower.

[0097] A lead-acid battery can be obtained by a manufacturing method that includes the step of assembling the battery by housing a positive electrode plate, a negative electrode plate, and an electrolyte in a battery case. In the lead-acid battery assembly process, a separator is usually positioned between the positive electrode plate and the negative electrode plate. After housing the positive electrode plate, negative electrode plate, and electrolyte in the battery case, the lead-acid battery assembly process may optionally include a step of chemically forming at least one of the positive electrode plate and the negative electrode plate. The positive electrode plate, negative electrode plate, electrolyte, and separator are each prepared before being housed in the battery case.

[0098] Figure 3 shows the external appearance of an example of a lead-acid battery according to one embodiment of the present invention. The lead-acid battery 1 comprises a battery case 12 that houses an electrode plate group 11 and an electrolyte (not shown). The battery case 12 is divided into multiple cell chambers 14 by a partition wall 13. Each cell chamber 14 houses one electrode plate group 11. The opening of the battery case 12 is closed with a lid 15 equipped with a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a vent plug 18 for each cell chamber. When replenishing with water, the vent plug 18 is removed and the water is supplied. The vent plug 18 may also have a function of venting gas generated in the cell chamber 14 to the outside of the battery.

[0099] Each electrode plate group 11 is constructed by stacking multiple negative electrode plates 2 and positive electrode plates 3 via separators 4. Here, a bag-shaped separator 4 that houses the negative electrode plates 2 is shown, but the shape of the separator is not particularly limited. In the cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects multiple negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode shelf 5 that connects multiple positive electrode plates 3 in parallel is connected to a positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 on the outside of the lid 15. In the cell chamber 14 located at the other end of the battery case 12, a negative electrode column 9 is connected to the negative electrode shelf 6, and a through connector 8 is connected to the positive electrode shelf 5. The negative electrode column 9 is connected to a negative electrode terminal 16 on the outside of the lid 15. Each through connector 8 passes through a through hole provided in the partition wall 13 and connects the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0100] The positive electrode shelf 5 is formed by welding the tabs provided on the upper part of each positive electrode plate 3 together using a cast-on-strap method or a burning method. The negative electrode shelf 6 is also formed in the same manner as the positive electrode shelf 5, by welding the tabs provided on the upper part of each negative electrode plate 2 together.

[0101] The cover 15 of the lead-acid battery is a single-layer structure (single cover), but is not limited to the illustrated example. The cover 15 may have a double-layer structure, for example, comprising an inner cover and an outer cover (or top cover). A cover with a double-layer structure may have a recirculation structure between the inner cover and the outer cover for returning the electrolyte to the inside of the battery (inside the inner cover) from a recirculation port provided in the inner cover.

[0102] The lead-acid battery according to the present invention is described below. (1) comprising a negative electrode current collector and a negative electrode material, The negative electrode current collector has a frame portion having ears and a grid portion provided continuously with the frame portion. The aforementioned grid section has multiple square cells, The square grid has a pair of first vertices whose diagonals are in a first direction extending from the frame to the grid, and a pair of second vertices whose diagonals are in a second direction intersecting the first direction. The angle θ between the two sides forming the second vertex is 55° or more and 100° or less. A negative electrode plate for a lead-acid battery, wherein the negative electrode material includes an organic condensate.

[0103] (2) A negative electrode plate for a lead-acid battery, wherein the width of the inner dimensions of the square grid in the second direction is 11 mm or more and 22.5 mm or less, as in (1) above.

[0104] (3) A negative electrode plate for a lead-acid battery, wherein the negative electrode current collector is an expanded grid body with the first direction as the grid unfolding direction.

[0105] (4) In any one of (1) to (3) above, in a cross section perpendicular to the length direction of any one of the four grid bones surrounding the square grid, when the length of each of the two sides corresponding to the thickness of the negative electrode current collector is x and the length of each of the remaining two sides is y, the ratio of y to x: y / x is 0.8 or more and 1.4 or less, a negative electrode plate for a lead-acid battery.

[0106] (5) In any one of the above (1) to (4), the organic condensate includes units of aromatic compounds, The aforementioned aromatic compound is a negative electrode plate for a lead-acid battery having a sulfur-containing group.

[0107] (6) A negative electrode plate for a lead-acid battery, wherein the aromatic compound in (5) above includes at least one selected from the group consisting of bisarene compounds and monocyclic compounds.

[0108] (7) A negative electrode plate for a lead-acid battery, wherein the aromatic compound in (6) above includes both a bisarene compound and a monocyclic compound.

[0109] (8) In the above (6) or (7), the bisarene compound comprises a bisphenol compound, and is a negative electrode plate for a lead-acid battery.

[0110] (9) A negative electrode plate for a lead-acid battery, wherein the bisphenol compound in (8) above comprises at least one selected from the group consisting of bisphenol A and bisphenol S.

[0111] (10) In any one of the above (6) to (9), the monocyclic compound comprises a hydroxyarene compound, wherein the negative electrode plate is for a lead-acid battery.

[0112] (11) In (10) above, the hydroxyarene compound comprises a phenolsulfonic acid compound, and is a negative electrode plate for a lead-acid battery.

[0113] (12) A negative electrode plate for a lead-acid battery, wherein in any one of (1) to (11) above, the sulfur element content of the organic condensate is 2000 μmol / g or more.

[0114] (13) A negative electrode plate for a lead-acid battery as described in any one of (1) to (12) above, Positive plate and A lead-acid battery comprising an electrolyte containing sulfuric acid.

[0115] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0116] Lead-acid batteries E1-E6 and ER1 (a) Fabrication of the negative electrode plate As the negative electrode current collector, an expanded grid made of Pb-Ca-Sn alloy, as shown in Figures 1 and 2, is prepared. In the square grid of the expanded grid, the angle θ formed by the two sides that make up the second vertex is the angle shown in Table 1 (50° to 100°). Also, the width L of the inner dimensions in the second direction of the square grid is the length shown in Table 1 (22.5 mm to 15.9 mm). The mass of the expanded grid was kept constant.

[0117] The raw materials—lead powder, barium sulfate, carbon black, and an organic shrinkage inhibitor—are mixed with an appropriate amount of sulfuric acid aqueous solution to obtain a negative electrode paste. At this time, the components are mixed so that the content of the organic shrinkage inhibitor in the negative electrode material is 0.1% by mass, the content of barium sulfate is 0.6% by mass, and the content of carbon black is 0.3% by mass, as determined by the previously described procedure. The negative electrode paste is filled into the mesh of an expanded grid made of Pb-Ca-Sn alloy, and aged and dried to obtain an unformed negative electrode plate.

[0118] The following are used as organic shrinkage inhibitors. Condensate A: Condensate of bisphenol S compound and phenolsulfonic acid with formaldehyde (sulfur content: 4000 μmol / g, Mw = 8000)

[0119] (b) Fabrication of the positive electrode plate Lead powder is mixed with an aqueous sulfuric acid solution to obtain a positive electrode paste. The positive electrode paste is filled into the mesh of an expanded grid made of Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed positive electrode plate.

[0120] (c) Preparation of test batteries Each unformed negative electrode plate was housed in a bag-shaped separator, forming an electrode plate group with 7 unformed negative electrode plates and 6 unformed positive electrode plates per cell. The tabs of the positive electrode plates and the tabs of the negative electrode plates were welded to the positive and negative electrode shelves, respectively, using the cast-on-strap (COS) method. The electrode plate groups were inserted into a polypropylene battery case, electrolyte was poured in, and the formation process was carried out within the battery case to assemble liquid-type lead-acid batteries E1-E6 and ER1 with a rated voltage of 12V and a rated capacity of 30Ah (5-hour rate capacity (capacity when discharged at a current (A) of 1 / 5 of the Ah value stated in the rated capacity)). Six electrode plate groups are connected in series within the battery case. The specific gravity of the electrolyte after formation is 1.28. Note that lead-acid batteries E1 to E6 are examples, and ER1 is a comparative example.

[0121] [Table 1]

[0122] Lead-acid batteries C1-C6 and CR1 In the fabrication of the negative electrode plate, lignin (sulfur content: 600 μmol / g, Mw=5500) is used instead of condensate A, except that lead-acid batteries C1-C6 and CR1 are fabricated in the same manner as lead-acid batteries E1-E6 and ER1, as shown in Table 2. Note that lead-acid batteries C1-C6 and CR1 are all comparative examples.

[0123] [Table 2]

[0124] [evaluation] The CCA performance of each battery will be evaluated. Specifically, in accordance with JIS D 5301:2006, the terminal voltage 30 seconds after the start of discharge will be measured using the procedure described above. A higher voltage value indicates better starting performance. The CCA performance of each battery is evaluated as a percentage (%) when the measured value of lead-acid battery CR1 is set to 100.

[0125] 《Lead acid battery ER2~ER4》 In the square grid of the expanded grid, the angle θ between the two sides forming the second vertex is kept constant at 50°, and the width L of the inner dimensions in the second direction of the square grid is set to the lengths shown in Table 3 (22.5 mm to 8 mm). The mass of the expanded grid of each battery is shown in Table 3 as a relative value with the grid of battery ER1 set to 100. Lead-acid batteries ER2 to ER4 are manufactured in the same manner as lead-acid battery ER1. Note that lead-acid batteries ER2 to ER4 are all comparative examples.

[0126] [Table 3]

[0127] 《Lead acid battery CR2~CR4》 In the square grid of the expanded grid, the angle θ between the two sides forming the second vertex is kept constant at 50°, and the width L of the inner dimensions in the second direction of the square grid is set to the length shown in Table 3 (22.5 mm to 8 mm). The mass of the expanded grid of each battery is shown in Table 4 as a relative value with the grid of battery CR1 (ER1) set to 100. Other than that, lead-acid batteries CR2 to CR4 are manufactured in the same manner as lead-acid battery CR1. Note that lead-acid batteries CR2 to CR4 are all comparative examples.

[0128] [Table 4]

[0129] 《Lead acid battery E7~E11》 In the square grid of the expanded grid, the angle θ between the two sides forming the second vertex is kept constant at 80°, and the width L of the inner dimensions in the second direction of the square grid is set to the length shown in Table 5 (22.5 mm to 8 mm). The mass of the expanded grid of each battery is shown in Table 5 as a relative value with the grid of battery E8 set to 100. Otherwise, lead-acid batteries E7 to E11 are manufactured in the same manner as lead-acid battery E4. Note that lead-acid batteries E7 to E11 are all examples.

[0130] [Table 5]

[0131] 《Lead acid battery C7~C11》 In the square grid of the expanded grid, the angle θ between the two sides forming the second vertex is kept constant at 80°, and the width L of the inner dimensions in the second direction of the square grid is set to the length shown in Table 6 (22.5 mm to 8 mm). The mass of the expanded grid of each battery is shown in Table 6 as a relative value with the grid of battery C8 set to 100. Other than that, lead-acid batteries C7 to C11 are manufactured in the same manner as lead-acid battery C4. Note that lead-acid batteries C7 to C11 are all comparative examples.

[0132] [Table 6]

[0133] 《Lead acid battery E12, E13》 In the fabrication of the negative electrode plate, condensate B or condensate C is used instead of condensate A, except that lead-acid batteries E12 and E13 are fabricated in the same manner as lead-acid battery E8, as shown in Table 7.

[0134] Condensate B: Formaldehyde condensate of a naphthalene compound with a sulfonic acid group introduced (sulfur content: 6000 μmol / g, Mw = 6000) Condensate C: A condensate of a bisphenol A compound with a sulfonic acid group introduced and a bisphenol S compound, condensed with formaldehyde (sulfur content: 4000 μmol / g, Mw = 9000)

[0135] [Table 7]

[0136] Figure 4 summarizes the results from Tables 1 and 2. Generally, as the angle θ increases beyond 50°, the square grid becomes closer to a perfect square, reducing the bonding force between the negative electrode current collector and the negative electrode material, negatively impacting current collection efficiency, and consequently lowering CCA performance. In particular, in the case of expanded grids, the larger the angle θ, the greater the residual stress on the negative electrode current collector, and the more pronounced the negative effect is expected to be. However, in reality, as shown in Figure 4, even when the angle θ is increased to 55° or more, it is possible to improve CCA performance as long as the angle θ is 100° or less. Furthermore, when using condensate A, which is an organic condensate, increasing the angle θ to 55° or more significantly improves CCA performance. In particular, in the region θ = 60° to 100°, when lignin is used, the CCA performance improves by less than 2%, from 102 to 104, whereas when condensate A is used, the CCA performance improves by more than 6.5%, from 108 to 115.

[0137] Figure 5 summarizes the results from Tables 3 and 4, and Figure 6 summarizes the results from Tables 5 and 6. Figure 5 shows that when the angle θ is 50°, as the width L increases, the CCA performance decreases at roughly the same rate in both the case using lignin and the case using condensate A. On the other hand, when the angle θ is 80°, as the width L increases to 11 mm or more, the decrease in CCA performance is significantly suppressed when using condensate A compared to the case using lignin. Furthermore, the degree of suppression becomes more pronounced as the width L increases. This trend indicates that as the angle θ increases and the grid size increases, the difference in bonding force between the negative electrode current collector and the negative electrode material due to the difference in organic condensates becomes more pronounced, and the effect of reducing the voltage drop in the current collection path is enhanced.

[0138] Next, Table 7 shows that, as organic condensates, condensate A is the most desirable, followed by condensate C, and then condensate B. It is presumed that the sulfur content and molecular weight of the organic shrinkage inhibitors influence this order. While lignin has a sulfur content of 600 μmol / g, condensates A, B, and C all have a sulfur content of 2000 μmol / g or more. Furthermore, condensate A contains both bisarene compounds and monocyclic compounds (especially hydroxyarene compounds), while condensate C contains bisarene compound units. These structural differences result in differences in the bonding strength between the negative electrode current collector and the negative electrode material, which is thought to greatly influence the order in Table 7. [Industrial applicability]

[0139] The lead-acid battery according to the present invention can be suitably used, for example, as a starting power source for vehicles (automobiles, motorcycles, etc.) and as a power source for industrial energy storage devices (electric vehicles (forklifts, etc.)). It can also be used as an IS (Insulated Stability) lead-acid battery that is charged and discharged under PSOC (Partial State of Charge) conditions. It is useful. Lead-acid batteries for IS (Idle Stop) systems are suitable for vehicles with idle stop systems. Note that these applications are merely examples and are not the only applications for which this is possible. [Explanation of Symbols]

[0140] 1:Lead acid battery 2: Negative plate 3: Positive plate 4: Separator 5: Positive electrode shelf 6: Negative electrode shelf 7: Positive pole column 8: Through-connector 9: Negative pole column 11: Plate group 12:Battery container 13: Bulkhead 14: Cell Room 15: Lid 16: Negative terminal 17: Positive terminal 18: Liquid outlet stopper 20: Expanded lattice 21: Ear 22: Upper frame section 23: Lower frame section 24: Lattice part

Claims

1. It includes a negative electrode current collector and a negative electrode material, The negative electrode current collector comprises a frame portion having ears, and a grid portion provided continuously with the frame portion. It has, The aforementioned grid section has multiple square cells, The square grid has a pair of first vertices whose diagonals are in a first direction from the frame to the grid, and a pair of second vertices whose diagonals are in a second direction intersecting the first direction. The angle θ between the two sides forming the second vertex is 55° or more and 100° or less. In a cross-section perpendicular to the length direction of any one of the four grid bones surrounding the square grid, when the length of each of the two sides corresponding to the thickness of the negative electrode current collector is x, and the length of each of the remaining two sides is y, the ratio of y to x: y / x is 0.8 or greater and 1.4 or less. The negative electrode material includes an organic condensate, The aforementioned organic condensate includes units of aromatic compounds, The aforementioned aromatic compound has a sulfur-containing group, The aforementioned aromatic compound comprises both a bisarene compound and a monocyclic compound, and is used as a negative electrode plate for a lead-acid battery.

2. The negative electrode plate for a lead-acid battery according to claim 1, wherein the width of the inner dimensions of the square grid in the second direction is 11 mm or more and 22.5 mm or less.

3. The negative electrode plate for a lead-acid battery according to claim 1 or 2, wherein the negative electrode current collector is an expanded grid body with the first direction as the grid unfolding direction.

4. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 3, wherein the ratio of y to x: y / x is 0.85 or greater.

5. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 4, wherein the ratio of y to x: y / x is 1.1 or less.

6. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 5, wherein the bisarene compound comprises a bisphenol compound.

7. The negative electrode plate for a lead-acid battery according to claim 6, wherein the bisphenol compound comprises at least one selected from the group consisting of bisphenol A and bisphenol S.

8. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 7, wherein the monocyclic compound comprises a hydroxyarene compound.

9. The negative electrode plate for a lead-acid battery according to claim 8, wherein the hydroxyarene compound comprises a phenol sulfonic acid compound.

10. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 9, wherein the sulfur element content of the organic condensate is 2000 μmol / g or more.

11. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 10, wherein the sulfur element content of the organic condensate is 3,000 μmol / g or more.

12. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 11, wherein the sulfur element content of the organic condensate is 9,000 μmol / g or less.

13. The aromatic compound that forms the basis of the aromatic compound unit contains both bisarene compounds and monocyclic compounds, and the molar ratio of bisarene compounds to monocyclic compounds is A negative electrode plate for a lead-acid battery according to claim 1, wherein the ratio is in the range of 1:9 to 9:

1.

14. The aromatic compound that forms the basis of the aromatic compound unit contains both bisarene compounds and monocyclic compounds, and the molar ratio of bisarene compounds to monocyclic compounds is A negative electrode plate for a lead-acid battery according to claim 1, wherein the ratio is in the range of 2:8 to 8:

2.

15. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 14, wherein the content of nitrogen atom-containing groups in the organic condensate is 1% by mass or less.

16. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 15, wherein the weight-average molecular weight (Mw) of the organic condensate is 7,000 or more and 100,000 or less.

17. The negative electrode plate for a lead-acid battery according to any one of claims 1 to 16, wherein the content of the organic condensate contained in the negative electrode material is 0.01% by mass or more and 1.0% by mass or less.

18. A negative electrode plate for a lead-acid battery according to any one of claims 1 to 17, A lead-acid battery comprising a positive electrode plate and an electrolyte containing sulfuric acid.

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