lead-acid batteries

Abstract

To provide a lead-acid battery that improves lifespan performance while suppressing electrolyte loss and self-discharge. [Solution] A lead-acid battery comprising an electrode group and an electrolyte, wherein the electrode group comprises a positive electrode plate, a negative electrode plate 2, and a separator interposed between the positive electrode plate and the negative electrode plate 2, the positive electrode plate comprises a positive electrode current collector and a positive electrode material, the negative electrode plate 2 comprises a negative electrode current collector 21 and a negative electrode material 22, the positive electrode current collector contains the element Sb, the negative electrode current collector 22 has a negative electrode lug portion 211 connected to a negative electrode strap 23 and a negative electrode grid portion 212 continuous with the negative electrode lug portion 211, a first fatty acid is detected from the negative electrode lug portion 211, and the first fatty acid contains 8 to 30 carbon atoms.

Description

[Technical Field]

[0001] This invention relates to a lead-acid battery. [Background technology]

[0002] Patent Document 1 proposes a lead-acid battery comprising an unformed positive electrode plate and an unformed negative electrode plate in which a negative electrode active material is held in a negative electrode grid, wherein the negative electrode active material is a mixture of lead powder, water, sulfuric acid, and oil, and the oil contains oleic acid.

[0003] Patent Document 2 proposes a lead-acid battery in which an active material is filled into the positive electrode and the negative electrode current collector, characterized in that the surface of at least one of the positive electrode and the negative electrode current collector is coated with a substance having acid resistance and water repellency, and that the substance is at least one selected from the group formed by stearic acid, oleic acid, naphthenic acid, cetyl alcohol, and saturated hydrocarbons.

[0004] Patent Document 3 proposes a liquid lead-acid battery manufactured by a so-called battery case chemicalization method, in which a battery is made using unchemically formed positive and negative electrode plates, and then a predetermined dilute sulfuric acid is injected into the battery and current is passed through it to chemically form these electrode plate groups within the battery case, characterized in that a negative electrode active material to which fatty acids have been added is used.

[0005] Patent Document 4 proposes a sealed lead-acid battery manufactured by a so-called battery case chemicalization method, in which a battery is made using unchemically formed positive and negative electrode plates, and then a predetermined dilute sulfuric acid is injected into the battery and an electric current is passed through it to chemically form these electrode plate groups within the battery case, characterized in that a negative electrode active material to which fatty acids or salts thereof are added together with lignin or its derivatives is used.

[0006] Patent documents 3 and 4 further propose that "the amount of fatty acid added should be 0.05 to 1% by weight" and that "the fatty acid added should be stearic acid or a salt thereof." [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-65827 [Patent Document 2] Japanese Patent Publication No. 2000-331689 [Patent Document 3] Japanese Patent Application Publication No. 10-302785 [Patent Document 4] Japanese Patent Application Publication No. 10-208746 [Overview of the project] [Problems that the invention aims to solve]

[0008] The use of lead alloys containing Sb (Pb-Sb alloys) for the positive electrode current collector is being considered. The use of Pb-Sb alloys is thought to have advantages in improving the mechanical strength of the positive electrode current collector, the adhesion between the positive electrode current collector and the positive electrode material, and corrosion resistance. In particular, when Pb-Sb alloys are used for the positive electrode current collector of lead-acid batteries for large vehicles such as trucks and buses, it is expected that the detachment of the positive electrode material from the positive electrode current collector will be prevented, and the cycle characteristics will be improved.

[0009] On the other hand, due to various factors, the temperature of lead-acid batteries can reach over 60°C. In such operating environments, electrolyte depletion is significantly accelerated, and the frequency of needing to replenish electrolyte may increase. In particular, when using a Pb-Sb alloy, Sb dissolved in the electrolyte precipitates on the negative electrode plate (especially the negative electrode lugs), which reduces the hydrogen generation overvoltage on the negative electrode plate, accelerating the hydrogen generation reaction and electrolyte depletion. Furthermore, Sb tends to form a local cell with the negative electrode plate, accelerating self-discharge. These phenomena promote the accumulation of lead sulfate, which may cause lead-acid batteries to reach the end of their lifespan prematurely. [Means for solving the problem]

[0010] In view of the above, one aspect of the present disclosure relates to a lead-acid battery comprising an electrode plate group and an electrolyte, wherein the electrode 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 current collector and a positive electrode material, the negative electrode plate comprises a negative electrode current collector and a negative electrode material, the positive electrode current collector contains the element Sb, the negative electrode current collector has a negative electrode lug connected to a negative electrode strap and a negative electrode grid continuous with the negative electrode lug, a first fatty acid is detected from the negative electrode lug, and the first fatty acid contains 8 to 30 carbon atoms. [Effects of the Invention]

[0011] In lead-acid batteries (especially liquid-type lead-acid batteries for large vehicles), the lifespan performance is improved, while suppressing electrolyte loss and self-discharge. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front view of the negative electrode plate of a lead-acid battery according to one embodiment of the present invention. [Figure 2] This is a partially cutaway exploded perspective view showing the external appearance and internal structure of a lead-acid battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0014] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0015] The lead-acid battery relating to this disclosure may be a valve-regulated lead-acid battery (VRLA) or a sealed lead-acid battery, but a liquid-type battery (vented battery) is preferred because it can benefit from the effect of reducing the electrolyte level.

[0016] A lead-acid battery comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte. The electrolyte contains sulfuric acid. Charging and discharging proceed through the movement of sulfate ions between the positive and negative electrode plates and the electrolyte. During discharge, sulfate ions move to the positive and negative electrode plates, causing the density of the electrolyte to decrease. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte, causing the density of the electrolyte to increase.

[0017] A positive electrode plate, a negative electrode plate, and a separator constitute an electrode plate group. The electrode plate group, together with the electrolyte, constitutes a cell. One electrode plate group constitutes one cell. A lead-acid battery comprises one or more cells by comprising one or more electrode groups. A lead-acid battery may contain one cell or two or more cells. If a lead-acid battery comprises multiple cells (in other words, multiple electrode plate groups), the multiple electrode plate groups may be connected in series. There is no particular limit to the number of positive and negative electrode plates included in a single electrode plate group. An electrode plate group comprising a lead-acid battery according to this disclosure may, for example, include a total of 12 or more positive and negative electrode plates. Multiple electrode plate groups are usually housed in separate cell chambers and connected in series with one another.

[0018] The positive electrode plate includes a positive electrode material. The positive electrode material includes lead dioxide. More specifically, the positive electrode material, as a positive electrode active material that exhibits capacity through a redox reaction, contains at least lead dioxide during charging and at least lead sulfate during discharging.

[0019] The negative electrode plate includes a negative electrode material. The negative electrode material includes lead. More specifically, the negative electrode material, as a negative electrode active material that exhibits capacity through oxidation-reduction reactions, contains at least lead during charging and at least lead sulfate during discharging.

[0020] The negative electrode material and the positive electrode material refer to the portion of the electrode plate excluding the current collector. The electrode plate may have materials such as mats or pasting paper attached to it. Such attached materials are used integrally with the electrode plate and are therefore included in the electrode plate. When the electrode plate includes attached materials, the electrode material refers to the portion of the electrode plate excluding the current collector and attached materials.

[0021] This disclosure includes the following technologies: (1) A lead-acid battery according to one embodiment of the present disclosure includes an electrode group and an electrolyte. The electrode group includes 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 current collector and a positive electrode material. The negative electrode plate comprises a negative electrode current collector and a negative electrode material. The positive electrode current collector contains the element Sb. The negative electrode current collector has a negative electrode lug connected to a negative electrode strap and a negative electrode grid continuous with the negative electrode lug. A primary fatty acid is detected from the negative electrode lug. The primary fatty acid contains 8 to 30 carbon atoms.

[0022] The lead-acid batteries described in (1) above have excellent lifespan. The positive electrode current collector containing Sb element has high mechanical strength and excellent adhesion to the positive electrode material. Since the positive electrode material is less likely to detach from such a positive electrode current collector, lifespan is improved. This improvement in lifespan is particularly noticeable in lead-acid batteries for large vehicles that may be subjected to severe vibrations.

[0023] However, Sb leaches into the electrolyte from the positive electrode current collector containing Sb. The leached Sb deposits on the negative electrode plate, reducing the hydrogen generation overpotential at the negative electrode plate. This reduction in hydrogen generation overpotential promotes the hydrogen generation reaction, which involves electrolyte loss. Furthermore, the reduction in hydrogen generation overpotential promotes self-discharge due to the formation of a local cell.

[0024] It has been found that approximately 50% or more of the Sb dissolved in the electrolyte precipitates concentrated in the negative electrode lug. Such findings are not generally known. To reduce the effect of Sb precipitation, it is effective to suppress the action of Sb that precipitates in the negative electrode lug.

[0025] Therefore, in this disclosure, a first fatty acid is applied to the negative electrode lug where Sb deposition is concentrated. When the first fatty acid is detected from the negative electrode lug, electrolyte loss and self-discharge are suppressed. In addition, the amount of overcharged electricity in the lead-acid battery is reduced. Furthermore, the charge acceptance of the negative electrode plate is improved. These phenomena are thought to be achieved, at least in part, by the first fatty acid increasing the hydrogen generation overvoltage at the negative electrode lug. Such phenomena are related to the fact that the first fatty acid contains 8 to 30 carbon atoms.

[0026] As described above, the lead-acid batteries (especially liquid-type lead-acid batteries for large vehicles) have excellent lifespan performance, and electrolyte loss and self-discharge are suppressed. In addition, the amount of overcharged electricity in the lead-acid battery is reduced, and the charge acceptance of the negative electrode plate is improved.

[0027] (2) In the lead-acid battery described in (1) above, the mass of the first fatty acid detected from the negative electrode lug may be 10 ppm or more relative to the mass of the negative electrode lug. In this case, the lifespan performance is stably improved and electrolyte loss is stably suppressed.

[0028] The important point here is not the magnitude of the first fatty acid detected from the negative electrode ear, but the fact that the first fatty acid is detected at a rate of at least 10 ppm by mass.

[0029] In this disclosure, the first fatty acid containing 8 to 30 carbon atoms is actively applied to the negative electrode lug portion, which constitutes a part of the negative electrode current collector. For example, the first fatty acid itself or a material containing the first fatty acid at a high concentration (for example, a solution containing the first fatty acid at a concentration of 1.0% by mass or more) may be applied to the negative electrode lug portion. In that case, a sufficient amount of the first fatty acid will adhere to the negative electrode lug portion. Therefore, even if the negative electrode lug portion is very thick, the ratio of the mass of the first fatty acid to the mass of the negative electrode lug portion will be 10 ppm or more.

[0030] On the other hand, as described in the aforementioned patent documents, there is a proposal to include fatty acids that may fall under the category of primary fatty acids in the negative electrode material. In that case, a small amount of fatty acid may leach from the negative electrode material into the electrolyte and adhere to the negative electrode lug along with the electrolyte. However, the mass of fatty acid that may adhere to the negative electrode lug is far smaller than the mass of the negative electrode lug and is usually below the detection limit.

[0031] Similarly, it is possible to propose adding fatty acids that may fall under the category of primary fatty acids to the electrolyte. In that case, the fatty acids may adhere to the negative electrode ear along with the electrolyte. However, unless the electrolyte contains fatty acids at a very high concentration, the mass of fatty acids that may adhere to the negative electrode ear is far smaller than the mass of the negative electrode ear and is usually below the detection limit.

[0032] In other words, unless fatty acids are actively applied to the negative electrode ear, it can be said that fatty acids of 10 ppm or more will not be detected from the negative electrode ear. Therefore, in this disclosure, the detection of at least 10 ppm or more of the primary fatty acid by mass is limited to cases such as when the primary fatty acid itself or a material containing the primary fatty acid at a high concentration (for example, a solution containing the primary fatty acid at a concentration of 1.0 mass% or more) is applied to the negative electrode ear.

[0033] (3) In the lead-acid battery described in (1) or (2) above, the negative electrode lug can be divided into nine parts in a 3x3 matrix. The negative electrode lug can be divided into nine equal parts, for example. However, the meaning of equal division is not strict. The nine regions divided in a 3x3 matrix do not necessarily have to have the same mass. Among the nine regions divided in a matrix so as to be roughly equal, the mass difference between the region with the smallest mass and the region with the largest mass may be within 30% of the mass of the region with the smallest mass. The negative electrode lug can also be divided into nine parts in a matrix so as to be roughly equal by two horizontal dividing lines parallel to the surface of the electrolyte and two vertical dividing lines perpendicular to the surface of the electrolyte. In this case, it is preferable that the first fatty acid is detected in all nine regions.

[0034] In the lead-acid battery described in (3) above, the hydrogen generation overvoltage is large in all nine regions. Therefore, in all nine regions (i.e., in almost the entire region of the negative electrode lug), the reaction that promotes electrolyte loss and the self-discharge reaction are suppressed.

[0035] (4) In the nine regions of the lead-acid battery described in any one of (1) to (3) above, the amount of primary fatty acid detected from the three regions closest to the negative electrode grid may be greater than the amount of primary fatty acid detected from the three regions closest to the negative electrode strap. Primary fatty acid may be detected only from the three regions closest to the negative electrode grid.

[0036] In the lead-acid battery described in (4) above, there is no need to apply a large amount of primary fatty acid to any region other than the three regions closest to the negative electrode strap. It is sufficient to preferentially apply a sufficient amount of primary fatty acid to the three regions closest to the negative electrode grid. Such a design reduces the region where primary fatty acid is applied (which can also be called the coating region) and the amount of primary fatty acid used. On the other hand, in the negative electrode ear portion, the region closest to the negative electrode grid, which is in easy contact with the electrolyte and where Sb is easily deposited, can efficiently increase the hydrogen generation overvoltage.

[0037] (5) The mass of the first fatty acid detected from the three regions near the negative electrode grid in the lead-acid battery described in any one of (1) to (4) above may be 10 ppm or more relative to the mass of each region.

[0038] In the lead-acid battery described in (5) above, the hydrogen generation overvoltage can be sufficiently increased throughout the entire negative electrode lug. As a result, effects such as reduced electrolyte loss and self-discharge, reduced overcharge amount, and improved charge acceptance become significant.

[0039] (6) In the lead-acid battery described in any one of (1) to (5) above, the negative electrode material may contain a secondary fatty acid. The secondary fatty acid may contain 8 to 30 carbon atoms.

[0040] In the lead-acid battery described in (6) above, the hydrogen generation overvoltage can be increased across the entire negative electrode plate. As a result, effects such as reduced electrolyte loss and self-discharge, reduced overcharge amount, and improved charge acceptance become even more pronounced.

[0041] Furthermore, more than 50% of the Sb dissolved from the positive electrode current collector into the electrolyte may be concentrated and deposited on the negative electrode lugs, while the remaining Sb may be deposited on the surface of the negative electrode material. By incorporating a secondary fatty acid containing 8 to 30 carbon atoms into the negative electrode material, it becomes possible to achieve effects such as reduced electrolyte loss and self-discharge, reduced overcharge, and improved charge acceptance throughout the entire negative electrode plate.

[0042] (7) In the lead-acid battery described in any one of (1) to (6) above, the content Cf of the secondary fatty acid in the negative electrode material may be 20 ppm or more and 600 ppm or less by mass.

[0043] In the lead-acid battery described in (7) above, the Cf content of secondary fatty acids is within the above range, resulting in excellent charge acceptance of the negative electrode material. Generally, it is believed that the charge acceptance of lead decreases when it is covered with fatty acids. On the other hand, secondary fatty acids tend to adhere thinly to the lead surface, so their effect on charge acceptance is less pronounced. This is thought to be because secondary fatty acids tend to adhere thinly to the lead surface. Rather, secondary fatty acids have the effect of reducing electrolyte loss and self-discharge, as well as reducing the amount of overcharged electricity, which tends to improve charge acceptance. Improved charge acceptance leads to improved lifespan performance in charge-discharge cycles.

[0044] (8) In the lead-acid battery described in any one of (1) to (7) above, the content of the second fatty acid Cf in the negative electrode material and the specific surface area Sn(m²) of the negative electrode material 2 Ratio of Cf / Sn ( / g): 20 ppm·m -2 • It may be greater than or equal to g.

[0045] In the lead-acid battery described in (8) above, controlling the Cf content of secondary fatty acids per unit surface area of ​​the negative electrode material Sn further improves lifespan performance and enhances the effect of suppressing the outflow of carbonaceous material due to secondary fatty acids.

[0046] (9) In the lead-acid battery described in any one of (1) to (8) above, the negative electrode material may include a carbonaceous material having a particle size of less than 32 μm. The carbonaceous material content Cc in the negative electrode material may be 0.4% by mass or more.

[0047] The lead-acid batteries relating to this disclosure may be used in an undercharged state called a Partial State of Charge (PSOC). For example, in idle-stop start (or Idle Reduction) applications or charge control applications, lead-acid batteries are used in PSOC. In this specification, idle-stop start may be simply referred to as "ISS". When lead-acid batteries are repeatedly charged and discharged in PSOC, lead sulfate tends to accumulate, and their lifespan performance tends to decrease.

[0048] To reduce lead sulfate accumulation, it is effective to improve the charge acceptance of the negative electrode material by incorporating carbonaceous material (especially carbonaceous material with a particle size of less than 32 μm) into the negative electrode material. The carbonaceous material improves the conductivity of the negative electrode material, increasing its charge acceptance, and even when lead-acid batteries are used in PSOCs, the reduction of lead sulfate to lead is made easier during charging. Therefore, lead sulfate accumulation is reduced, and the deterioration of life performance can be suppressed. On the other hand, when carbonaceous material is incorporated into the negative electrode material, the carbonaceous material leaches into the electrolyte during the charge-discharge cycle. The higher the carbonaceous material content, the more pronounced the leaching of carbonaceous material from the negative electrode plate into the electrolyte becomes. In particular, when the negative electrode plate is converted in the battery case, gasshing is likely to occur during conversion, and the leaching of carbonaceous material near the surface of the negative electrode plate becomes pronounced. When carbonaceous material leaches into the electrolyte, the electrolyte becomes cloudy, and the visibility of the liquid level sensor decreases.

[0049] In the lead-acid battery described in (9) above, the charge acceptance of the negative electrode material is further improved by the action of the carbonaceous material. Furthermore, the carbonaceous material has a high affinity for secondary fatty acids, and secondary fatty acids preferentially adhere to the carbonaceous material rather than to lead. On the other hand, secondary fatty acids adhering to the lead surface tend to become thinner in the presence of the carbonaceous material, which is advantageous for improving charge acceptance. In addition, the adhesion of secondary fatty acids to the carbonaceous material reduces the outflow of carbonaceous material into the electrolyte during the charge-discharge cycle. As a result, the advantageous effect on charge acceptance is sustained, and the turbidity of the electrolyte can be reduced, thus suppressing the decrease in the visibility of the liquid level sensor.

[0050] (10) In a lead-acid battery described in any one of (1) to (9) above, the ratio of the content of secondary fatty acids Cf in the negative electrode material to the amount of DBP oil absorbed Y by the carbonaceous material, Cf / Y, is 0.1 ppm·mL -1 • It may be 100g or more.

[0051] In the lead-acid battery described in (10) above, the content Cf of secondary fatty acids per DBP oil absorption Y of the carbonaceous material is controlled. In other words, the amount of secondary fatty acids that preferentially adhere to the carbonaceous material over lead is controlled. Therefore, the outflow of carbonaceous material into the electrolyte can be reduced more significantly.

[0052] Within the limits of what is technically consistent, the configurations described in (1) to (10) above may be combined in any way.

[0053] Furthermore, the detection of the first fatty acid in the negative electrode ear, the content of the second fatty acid Cf in the negative electrode material, the content of carbonaceous material Cc and DBP oil absorption Y of the carbonaceous material in the negative electrode material, the specific surface area Sn of the negative electrode material, and the Sb content of the positive electrode current collector are all measured on a fully charged lead-acid battery. That is, the samples used for measurement are taken from the negative and positive electrode plates removed from a fully charged lead-acid battery.

[0054] A fully charged lead-acid battery is a lead-acid battery that has been charged to its full capacity after chemical formation. The timing for charging a lead-acid battery to its full capacity can be immediately after chemical formation, or after some time has passed since formation (for example, 1440 hours or less). For example, a lead-acid battery that has been chemically formed and is in use (preferably in the early stages of use) may be charged.

[0055] A battery in its initial stages of use is one that has not been used for very long and has not deteriorated significantly (for example, a battery that has been in use for less than 1440 hours, including the time since its initial use).

[0056] The fully charged state of a liquid-type lead-acid battery is defined according to JIS D 5301:2019. More specifically, a fully charged state is defined as the state in which the lead-acid battery is charged at a current (A) equal to 0.2 times the value indicated as the rated capacity (a value in Ah) until the terminal voltage (in V) during charging, measured every 15 minutes, or the electrolyte density converted to 20°C, shows a constant value with three significant figures for three consecutive times in a water bath at 25°C ± 2°C. The value indicated as the rated capacity is a value in Ah (ampere-hours). The unit of the current set based on the value indicated as the rated capacity is A (ampere). Furthermore, in the case of valve-regulated lead-acid batteries, a fully charged state is defined as a state where charging is performed in an air chamber at 25°C ± 2°C with a constant current and constant voltage of 2.67V / cell (16.00V for a lead-acid battery with a nominal voltage of 12V) at a current (A) equal to 0.5 times the stated rated capacity (a value expressed in Ah), and charging is completed when the total charging time reaches 24 hours.

[0057] The vertical direction of a lead-acid battery and its components (positive plate, negative plate, battery case, separator, etc.) refers to the vertical direction of the lead-acid battery in its operating state. The positive and negative plates each have tabs for connecting to external terminals. Typically, in lead-acid batteries (especially liquid-type lead-acid batteries), tabs are provided on the top of the plates, protruding upwards. The negative tab is connected to the negative strap, and the positive tab is connected to the positive strap.

[0058] The lead-acid batteries according to the embodiments of this disclosure will be described in more detail below, with reference to the drawings from time to time. However, the present invention is not limited to the following embodiments.

[0059] The following describes examples of components of a lead-acid battery. (Negative electrode plate) The negative electrode plate comprises a negative electrode current collector and a negative electrode material. Figure 2 shows a front view of an example of the negative electrode plate 2. The negative electrode current collector 21 has a negative electrode ear portion 211 connected to the negative electrode strap 23 and a negative electrode grid portion 212 continuous with the negative electrode ear portion 211. The negative electrode material 22 is filled into the negative electrode grid portion 212. A first fatty acid is detected from the negative electrode ear portion 211.

[0060] (Negative electrode current collector) The negative electrode current collector has a negative electrode lug and a negative electrode grid. The negative electrode material is held in the negative electrode grid. The negative electrode lug is provided on the upper part of the negative electrode plate so as to protrude upward and is used for connection to the negative electrode strap.

[0061] 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 or punching.

[0062] The lead alloy used for the negative electrode current collector may be any of the following: a Pb-Sb alloy, a Pb-Ca alloy, or a Pb-Ca-Sn (tin) alloy. The lead or lead alloy may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc.

[0063] The negative electrode current collector may have a surface layer. The surface layer of the negative electrode current collector may have a different composition from the inner layer. The surface layer may be formed to cover the entire negative electrode current collector, or it may be formed on a part of the negative electrode current collector. The surface layer may be formed on the negative electrode lug. The surface layer of the negative electrode lug may contain Sn (tin) or a Sn (tin) alloy. The surface layer may be formed by attaching a metal foil to the negative electrode lug. The metal foil constitutes a part of the negative electrode lug. In this case, the first fatty acid is applied from the outside of the metal foil attached to the negative electrode lug.

[0064] The negative electrode ear portion contains a primary fatty acid with 8 to 30 carbon atoms. For example, when the negative electrode ear portion is divided into 9 sections in a 3x3 matrix, the primary fatty acid is detected in at least one of the 9 regions. It is preferable that the primary fatty acid is detected in all 9 regions.

[0065] As shown in Figure 1, the negative electrode lug portion 211 may be divided into nine 3x3 matrix sections by two horizontal and two vertical dividing lines. Specifically, the negative electrode lug portion 211 is divided into three rows of a, b, and c, all having the same height, starting from its upper end, and then further divided into three columns of x, y, and z, all having the same width, starting from its left end. As a result, the negative electrode lug portion 211 is divided into nine regions: (a,x), (a,y), (a,z), (b,x), (b,y), (b,z), (c,x), (c,y), and (c,z).

[0066] In the 9 regions, it is preferable that the amount of primary fatty acid detected from the 3 regions closest to the negative electrode lattice (row c) is greater than the amount of primary fatty acid detected from the 3 regions closest to the negative electrode strap (row a). Primary fatty acids may also be detected only from the 3 regions closest to the negative electrode lattice.

[0067] The mass of primary fatty acid detected from the negative electrode ear may be, for example, 10 ppm or more relative to the mass of the negative electrode ear. In this case, the negative electrode ear contains a sufficient amount of primary fatty acid. When the negative electrode ear is divided into nine equal parts in a 3x3 matrix, the mass of primary fatty acid detected from each of the nine regions may be 10 ppm or more relative to the mass of each region. In this case, the entire region of the negative electrode ear contains a sufficient amount of primary fatty acid.

[0068] (1st fatty acid) The carbon number of the first fatty acid is 8 or more, preferably 9 or more. The carbon number of the first fatty acid is 30 or less, may be 24 or less, or 20 or less. The carbon number of the first fatty acid is 8 or more (or 9 or more) and 30 or less, may be 8 or more (or 9 or more) and 24 or less, or 8 or more (or 9 or more) and 20 or less.

[0069] The first fatty acid may be either a saturated or unsaturated fatty acid. The number of carbon-carbon unsaturated bonds in the first fatty acid may be, for example, 6 or less, 4 or less, or 2 or less, depending on the number of carbon atoms in the first fatty acid. The number of carbon-carbon unsaturated bonds in the first fatty acid may be 1 or more. It is thought that the hydrophobicity of the hydrocarbon moiety is involved in the increase of the hydrogen generation overpotential at the negative electrode ear.

[0070] Specific examples of first fatty acids include octanoic acid, nonanoic acid (pelargonic acid), capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, arachidonic acid, behenic acid, eicosaheptaenoic acid, and docosahexaenoic acid.

[0071] Only one type of primary fatty acid may be detected from the negative electrode ear, or two or more types of primary fatty acids may be detected.

[0072] The first fatty acid may be a hydrocarbon having one carboxyl group. The carboxyl group of the first fatty acid interacts with hydroxyl groups or water contained in the oxide layer or adsorbed water layer formed on the surface of lead by at least one of covalent bonds and hydrogen bonds. This is thought to result in binding with lead. On the other hand, it is thought that the balance between the hydrophobicity of the hydrocarbon part and the hydrophilicity of the carboxyl group is involved in increasing the hydrogen generation overpotential at the negative electrode ear. From the viewpoint of increasing the hydrogen generation overpotential at the negative electrode ear, it is preferable that the first fatty acid has no substituents other than one carboxyl group.

[0073] (Analysis of primary fatty acids) The following describes the method for analyzing the first fatty acid in the negative electrode ear. Prior to measurement or analysis, a fully charged lead-acid battery is disassembled to obtain the negative electrode plate to be analyzed. Next, the negative electrode plate, including the negative electrode ear, is washed with water to remove sulfuric acid, and then the negative electrode plate is dried. The negative electrode ear is collected from the dried negative electrode plate. The negative electrode ear may be used as the sample for analysis (hereinafter referred to as "sample X"), or it may be divided into nine parts as described above to obtain nine samples Xn (n=1~9). Alternatively, it may be divided into three regions, a, b, and c, to obtain three samples Xm (m=1~3).

[0074] (1) Qualitative analysis of primary fatty acids Sample X or Xn is used as is without grinding. 150.0 ± 0.1 mL of chloroform is added to 150.0 ± 0.1 g of the sample, and it is immersed at 20 ± 5 °C for 16 hours to extract the first fatty acid. 150.0 ± 0.1 g of the sample may be taken from multiple fully charged lead-acid batteries of the same product. Solids are then removed by filtration. The structure of the first fatty acid is determined from the chloroform solution containing the extracted first fatty acid, or from the first fatty acid obtained by drying this chloroform solution, by obtaining information from at least one selected from, for example, infrared spectroscopy, ultraviolet-visible absorption spectroscopy, NMR spectroscopy, LC-MS, and pyrolysis GC-MS.

[0075] (2) Quantitative analysis of the first fatty acid The appropriate amount of the primary fatty acid obtained by drying the above chloroform solution was measured with an accuracy of ±0.0001 g. r (g) Dissolve in deuterated chloroform together with tetrachloroethane (TCE), 1 Measure the 1H-NMR spectrum. The integral value of the peak originating from the first fatty acid, where the chemical shift is 2.34 ppm (S a ) and the integral value of the peak originating from TCE (S r ) is calculated, and the ratio of the mass of the first fatty acid to the mass of the negative electrode ear is C from the following formula. n1(ppm) is determined. Note that polypropylene glycol (PPG) described later can be analyzed in the same manner as the first fatty acid.

[0076] C n1 =S a / S r ×N r / N a ×M a / M r ×m r / m×1000000 (In the formula, M a is the molecular weight of the structure showing a peak with a chemical shift of [2.34 ppm] (more specifically, the molecular weight showing the structure of the first fatty acid in the chemical shift), and N a is the number of hydrogen atoms bonded to the carbon atoms of the main chain. N r、 M r are the number of hydrogens contained in the molecule of the reference substance and the molecular weight of the reference substance, respectively, and m (g) is the mass of the sample X or Xn used for extraction.) Note that since the reference substance in this analysis is TCE (trichloroethylene), N r = 2, M r = 168. Also, m = 100. For example, when the first fatty acid is oleic acid, M a is

[59] , and N a is 2.

[0077] 1 The 1H-NMR spectrum is measured under the following conditions. Apparatus: JEOL Ltd., AL400 type nuclear magnetic resonance apparatus Observation frequency: 395.88 MHz Pulse width: 6.30 μs Pulse repetition time: 74.1411 seconds Number of integrations: 32 Measurement temperature: room temperature (20 - 35 °C) Reference: 7.24 ppm Sample tube diameter: 5 mm

[0078] Note that in quantitative analysis, 1The integral values ​​of the peaks in the H-NMR spectrum are determined using the data processing software "ALICE" manufactured by JEOL Ltd.

[0079] (Negative electrode material) The negative electrode material may contain a secondary fatty acid and a carbonaceous material in addition to the negative electrode active material. The negative electrode material may further contain additives such as an organic shrinkage inhibitor and barium sulfate.

[0080] (Negative electrode active material) The negative electrode active material is lead or lead sulfate, and its capacity is developed through oxidation-reduction reactions. In a fully charged lead-acid battery after chemical conversion, the negative electrode active material present in the negative electrode plate is spongy lead.

[0081] The chemical conversion can be carried out by placing an electrode group containing an unconverted negative electrode and an electrolyte containing sulfuric acid inside the lead-acid battery case, and then charging the electrode group. Alternatively, the chemical conversion of the negative electrode may be performed before assembling the lead-acid battery or the electrode group. Spongy lead is produced by the chemical conversion.

[0082] Unformed negative electrode plates are typically manufactured using lead powder. For example, an unformed negative electrode plate can be obtained by applying or filling a negative electrode paste onto a negative electrode current collector, aging it at a temperature higher than room temperature and high humidity, and then drying it. The negative electrode paste is prepared, for example, by kneading lead powder with various additives (carbonaceous materials, secondary fatty acids, organic shrinkage inhibitors, barium sulfate, etc.) and water and sulfuric acid (or an aqueous solution of sulfuric acid).

[0083] (Second fatty acid) Sb leached from the positive electrode current collector precipitates not only in the negative electrode lugs but also elsewhere, reducing the hydrogen generation overpotential. On the other hand, when secondary fatty acids are detected in the negative electrode material, the decrease in hydrogen generation overpotential in the negative electrode material is suppressed, thereby suppressing fluid loss and self-discharge.

[0084] Generally, in negative electrode materials, when the surface of lead is covered with organic components, the charge acceptance capacity decreases. In contrast, when the negative electrode material contains secondary fatty acids, the decrease in charge acceptance capacity at the negative electrode plate can be mitigated. This is thought to be because secondary fatty acids have relatively low molecular weight and therefore adhere to the lead surface in a thin layer.

[0085] The second fatty acid may be arbitrarily selected from the fatty acids described as the first fatty acid. The negative electrode material may contain only one type of second fatty acid, or it may contain two or more types. The first and second fatty acids may be the same or different.

[0086] The content of secondary fatty acids (Cf) in the negative electrode material is, for example, 20 ppm to 600 ppm by mass. From the viewpoint of increasing the hydrogen generation overpotential in the negative electrode material and enhancing the effect of suppressing the outflow of carbonaceous material, Cf is preferably 20 ppm or more by mass, and may be 50 ppm or more. Cf is, for example, 1000 ppm or less by mass. From the viewpoint of further improving the charge acceptance of the negative electrode material, Cf is preferably 600 ppm or less by mass.

[0087] The content of the secondary fatty acid (Cf) in the negative electrode material may be between 20 ppm and 600 ppm by mass, or between 50 ppm and 600 ppm.

[0088] (tertiary fatty acid) The negative electrode material may contain fatty acids other than secondary fatty acids (hereinafter referred to as tertiary fatty acids). Examples of tertiary fatty acids include at least one selected from the group consisting of fatty acids with 7 or fewer carbon atoms and fatty acids with more than 30 carbon atoms. From the viewpoint of obtaining a higher effect in suppressing the outflow of carbonaceous material and ensuring higher charge acceptance, a lower content of tertiary fatty acids is preferable. The content of tertiary fatty acids in the negative electrode material may be, for example, 10 ppm or less, or 5 ppm or less. It is also preferable that the negative electrode material does not contain tertiary fatty acids. In this case, the presence of tertiary fatty acids in the negative electrode material is below the detection limit.

[0089] (carbonaceous material) As the carbonaceous material included in the negative electrode material, a carbonaceous material having a particle size of less than 32 μm (hereinafter also referred to as "first carbonaceous material") is preferred. Here, "particle size" refers to the particle size based on the size of the sieve opening. Specifically, the first carbonaceous material is a carbonaceous material that passes through the sieve opening when sieved using a sieve with a 32 μm opening in a wet sieving method (JIS Z8815:1994).

[0090] The primary carbonaceous material preferably contains at least carbon black. Carbon black has a well-developed secondary particle structure, which is susceptible to the binding properties of secondary fatty acids.

[0091] Examples of carbon black include acetylene black, furnace black (e.g., Ketjenblack (trade name)), and lamp black. The negative electrode material may contain only one type of primary carbonaceous material, or it may contain two or more types.

[0092] The content Cc1 of the first carbonaceous material in the negative electrode material is, for example, 0.4% by mass or more, and may be 0.5% by mass or more. When the content Cc1 is within this range, it is easy to ensure high charge acceptance. On the other hand, the outflow of the first carbonaceous material into the electrolyte can be reduced by the action of the second fatty acid. The content Cc1 may be 5% by mass or less, and may be 3% by mass or less. From the viewpoint of ensuring high charge acceptance while keeping the outflow of the first carbonaceous material into the electrolyte low, a content Cc1 of 2% by mass or less is preferable.

[0093] The content of the first carbonaceous material, Cc1, may be 0.4% by mass or more (or 0.5% by mass or more) and 5% by mass or less, 0.4% by mass or more (or 0.5% by mass or more) and 3% by mass or less, or 0.4% by mass or more (or 0.5% by mass or more) and 2% by mass or less.

[0094] When the negative electrode material contains a secondary fatty acid, the binding action of the carboxyl group of the secondary fatty acid and the action of the hydrocarbon moiety attached to the primary carbonaceous particles are thought to suppress the outflow of primary carbonaceous particles. The balance between the hydrophobicity of the hydrocarbon moiety and the hydrophilicity of the carboxyl group is thought to be involved in the effect of suppressing the outflow of primary carbonaceous particles. When the secondary fatty acid has 8 to 30 carbon atoms, the hydrocarbon moiety is thought to be more selectively attached to the particles of the primary carbonaceous material than to lead. When the primary fatty acid has 8 to 30 carbon atoms and one carboxyl group, the secondary fatty acid is more likely to attach to the primary carbonaceous particles and lead, so the elution of the secondary fatty acid itself into the electrolyte and the outflow of primary carbonaceous particles are thought to be significantly suppressed.

[0095] The specific surface area Sc of the first carbonaceous material is, for example, 20 m². 2 / g or more, 25m 2 / g or more or 28m 2 It may be greater than or equal to / g. When the specific surface area Sc is within this range, excessive adsorption of the second fatty acid by the first carbonaceous material is suppressed, making it easier to ensure high charge acceptance. The specific surface area Sc of the first carbonaceous material is, for example, 1500m². 2 It is less than / g and 1300m 2 It may be less than / g. From the viewpoint of further suppressing the outflow of the first carbonaceous material, the specific surface area Sc should be 800m 2 Preferably less than / g, 200m 2 / g or less or 150m 2 It may be less than / g.

[0096] In this specification, the specific surface area Sc of the first carbonaceous material and the specific surface area Sn of the negative electrode material described later refer to the specific surface area (BET specific surface area) (unit: m²) obtained by the gas adsorption method using nitrogen gas and the BET (Brunauer-Emmett-Teller) formula. 2 The specific surface area Sc of the carbonaceous material and the specific surface area Sn of the negative electrode material are values ​​obtained for a negative electrode plate removed from a fully charged lead-acid battery.

[0097] The specific surface area (Sc) of the first carbonaceous material is 20 m². 2 / g or more (or 25m 2 / g or more) 1500m 2 / g or less, 20m 2 / g or more (or 25m 2 / g or more) 1300m 2 / g or less, 20m 2 / g or more (or 25m 2 / g or more) 800m 2 / g or less, 20m 2 / g or more (or 25m 2 / g or more)200m 2 / g or less, 20m 2 / g or more (or 25m 2 / g or more) 150m 2 / g or less, 28m 2 / g or more 1500m 2 / g or less (or 1300m 2 / g or less), 28m 2 / g or more 800m 2 / g or less (or 200m 2 (less than / g), or 28m 2 / g or more 150m 2 It may be less than / g.

[0098] The DBP oil absorption Y of the first carbonaceous material is, for example, 30 mL / 100 g or more, may be 50 mL / 100 g or more, or 65 mL / 100 g or more. When the DBP oil absorption Y is within this range, excessive adsorption of the second fatty acid by the first carbonaceous material is suppressed, making it easier to ensure high charge acceptance. Furthermore, the effect of suppressing the outflow of the first carbonaceous material into the electrolyte is further enhanced. The DBP oil absorption Y of the first carbonaceous material is, for example, 600 mL / 100 g or less, or 500 mL / 100 g or less. From the viewpoint of further suppressing the outflow of the first carbonaceous material, the DBP oil absorption Y is preferably 400 mL / 100 g or less, may be 360 ​​mL / 100 g or less, or 200 mL / 100 g or less.

[0099] DBP oil absorption refers to the amount (mL) of dibutyl phthalate (DBP) adsorbed or absorbed by 100g of powder. Therefore, the unit of DBP oil absorption is expressed as mL / 100g. The method for measuring DBP oil absorption is specified in JIS K 6217-4-2017. In primary carbonaceous materials, primary particles aggregate to form secondary particles. DBP is absorbed into the voids between primary particles in the secondary particles, and these voids are reflected in the DBP oil absorption amount.

[0100] DBP oil absorption Y is 30 mL / 100g or more and 600 mL / 100g or less (or 500 mL / 100g or less), 30 mL / 100g or more and 400 mL / 100g or less (or 360 mL / 100g or less), 30 mL / 100g or more (or 50 mL / 100g or more) and 200 mL / 100g or less, 50 mL / 100g or more and 600 mL / 100g or less (or 500 mL / 1 It may be 00g or less, 50mL / 100g or more and 400mL / 100g or less (or 360mL / 100g or less), 65mL / 100g or more and 600mL / 100g or less (or 500mL / 100g or less), 65mL / 100g or more and 400mL / 100g or less (or 360mL / 100g or less), or 65mL / 100g or more and 200mL / 100g or less.

[0101] The content of secondary fatty acids Cf in the negative electrode material and the specific surface area Sn(m²) of the negative electrode material. 2 The ratio of Cf / Sn (in grams) is 20 ppm·m. -2 It may be greater than or equal to g. By controlling the content of the second fatty acid Cf according to the specific surface area Sn of the negative electrode material, the effect of suppressing the outflow of the first carbonaceous material into the electrolyte is enhanced.

[0102] Generally, increasing the specific surface area of ​​the negative electrode material improves charge acceptance and increases the amount of overcharged electricity. On the other hand, when the negative electrode material contains a secondary fatty acid, the carboxyl group of the secondary fatty acid thinly coats the surface of the lead, which suppresses the decrease in charge acceptance and reduces side reactions during overcharging, thereby reducing the amount of overcharged electricity.

[0103] From the perspective of enhancing the above effect, the ratio Cf / Sn is 23 ppm·m -2 It may be greater than or equal to 1000 ppm·m. As the specific Cf / Sn ratio increases, the effect of suppressing the outflow of primary carbonaceous material tends to improve. On the other hand, charge acceptance tends to decrease. Specific Cf / Sn is 1000 ppm·m -2 It may be less than or equal to 910 ppm·m -2 It may be less than or equal to 1g. As described above, controlling the content of the secondary fatty acid Cf per unit surface area of ​​the negative electrode material makes it easier to ensure higher charge acceptance. Note that ppm in the unit of specific Cf / Sn is based on the mass basis of the Cf content.

[0104] The ratio Cf / Sn is 20 ppm·m -2 •g or more (or 23 ppm·m) -2 ·g or more) 1000ppm·m -2 Less than 1 / 2g, or 20 ppm·m -2 •g or more (or 23 ppm·m) -2 ·g or more)910ppm·m -2 It may be less than g.

[0105] The specific surface area Sn of the negative electrode material is, for example, 0.3 m². 2 It is 0.5 m² or more. From the standpoint of easily ensuring higher charge acceptance, the specific surface area Sn is 0.5 m². 2 Preferably 0.8 m 2 A value of 1 / g or more is more preferable. The specific surface area Sn is, for example, 4m². 2 It is less than / g. From the perspective of further enhancing the effect of suppressing the amount of overcharged electricity, the specific surface area Sn is 2.7m². 2 Preferably less than / g, and 2.5m 2 It is more preferable that the value be less than / g. From the viewpoint of further enhancing the effect of suppressing the outflow of the first carbonaceous material, the specific surface area of ​​Sn should be 1m². 2 Preferably less than / g, and 0.88m 2 A value of less than / g is more preferable. The specific surface area Sn of the negative electrode material may be adjusted, for example, by the specific surface area and / or content of the constituent components of the negative electrode material (particularly the first carbonaceous material).

[0106] The specific surface area Sn of the negative electrode material is 0.3 m 2 / g or more (or 0.5 m 2 / g or more) and 4 m 2 / g or less, 0.3 m 2 / g or more (or 0.5 m<00OO082> / g or more) and 2.7 m 2 / g or less, 0.3 m 2 / g or more (or 0.5 m 2 / g or more) and 2.5 m 2 / g or less, 0.3 m 2 / g or more (or 0.5 m 2 / g or more) and 1 m 2 / g or less, 0.3 m 2 / g or more (or 0.5 m 2 / g or more) and 0.88 m 2 / g or less, 0.8 m 2 / g or more and 4 m 2 / g or less (or 2.7 m 2 / g or less), 0.8 m 2 / g or more and 2.5 m 2 / g or less (or 1 m 2 / g or less), or 0.8 m 2 / g or more and 0.88 m 2 / g or less may also be acceptable. <00005३0> The ratio Cf / Y of the content rate Cf of the second fatty acid to the DBP oil absorption amount Y of the first carbonaceous material in the negative electrode material may be 0.1 ppm·mL -1 ·100 g or more. By controlling the content rate Cf of the second fatty acid according to the DBP oil absorption amount Y of the first carbonaceous material, the amount of the second fatty acid adhering to the first carbonaceous material is appropriately controlled, and the effect of suppressing the outflow of the first carbonaceous material into the electrolytic solution is enhanced.

[0108] From the viewpoint of further enhancing the effect of suppressing the outflow of the first carbonaceous material and further reducing the overcharge amount of electricity, the ratio Cf / Y may be 0.12 ppm·mL -1 ·100 g or more. The ratio Cf / Y is, for example, 12 ppm·mL -1 ·100 g or less, and 9.5 ppm·mL -1• It may be 100g or less. In this case, it is easier to ensure higher charge acceptance. From the viewpoint of further improving charge acceptance, the relative Cf / Y is 5 ppm·mL. -1 • 100g or less or 3.5ppm·mL -1 It may be 100g or less. Note that ppm in the ratio Cf / Y is derived from the mass-based content of Cf, and therefore is based on mass.

[0109] The ratio Cf / Y is 0.1 ppm·mL -1 • 100g or more (or 0.12 ppm / mL) -1 ·100g or more)12ppm·mL -1 ·100g or less, 0.1ppm·mL -1 • 100g or more (or 0.12 ppm / mL) -1 ·100g or more)9.5ppm·mL -1 ·100g or less, 0.1ppm·mL -1 • 100g or more (or 0.12 ppm / mL) -1 ·100g or more)5ppm·mL -1 • 100g or less, or 0.1 ppm·mL -1 • 100g or more (or 0.12 ppm / mL) -1 ·100g or more)3.5ppm·mL -1 It can be 100g or less.

[0110] The negative electrode material may include carbonaceous materials other than the first carbonaceous material (hereinafter also referred to as the "second carbonaceous material"). The second carbonaceous material has a particle size of 32 μm or larger. Here, "particle size" refers to the particle size based on the size of the sieve opening, and is the carbonaceous material that does not pass through the sieve opening when sieved using a 32 μm sieve in a wet sieving method (JIS Z8815:1994).

[0111] Examples of secondary carbonaceous materials include graphite, hard carbon, and soft carbon. The negative electrode material may contain one secondary carbonaceous material or two or more. Using a primary carbonaceous material and a secondary carbonaceous material in combination tends to improve PSOC lifetime performance. It is preferable that the secondary carbonaceous material contains at least graphite.

[0112] Furthermore, among the second carbonaceous materials, the Raman spectrum at 1300 cm⁻¹ -1 More than 1350cm -1 The peak (D band) that appears in the following range and 1550cm -1 More than 1600cm -1 Intensity ratio I of the peak (G band) appearing in the following range D / I G However, carbonaceous materials with a value between 0 and 0.9 shall be called graphite. The graphite may be either artificial graphite or natural graphite.

[0113] The content of the secondary carbonaceous material Cc2 in the negative electrode material may be 0.01% by mass or more, or 0.05% by mass or more. When the content Cc2 is within this range, life performance tends to improve. Charge acceptance also tends to improve. From the viewpoint of keeping the amount of overcharged electricity low, the content Cc2 may be 0.5% by mass or less, or 0.1% by mass or less.

[0114] The content of the secondary carbonaceous material Cc2 in the negative electrode material may be 0.01% by mass or more (or 0.05% by mass or more) and 0.5% by mass or less, or 0.01% by mass or more (or 0.05% by mass or more) and 0.1% by mass or less.

[0115] The proportion of the first carbonaceous material (such as carbon black) in the total carbonaceous material (for example, the total amount of the first carbonaceous material and the second carbonaceous material) may be, for example, 50% by mass or more, but may also be 75% by mass or more, 80% by mass or more, or 90% by mass or more. When the proportion of the first carbonaceous material is within this range, the outflow of the first carbonaceous material into the electrolyte tends to be significant, but an excellent outflow suppression effect can be obtained through the action of the second fatty acid. Furthermore, higher charge acceptance can be ensured. The proportion of the first carbonaceous material (such as carbon black) in the total carbonaceous material (for example, the total amount of the first carbonaceous material and the second carbonaceous material) may be, for example, 100% by mass or less, but may also be 95% by mass or less. The carbonaceous material may consist only of the first carbonaceous material. The carbonaceous material may contain at least carbon black and graphite.

[0116] The proportion of the first carbonaceous material to the total amount of the carbonaceous material (for example, the total amount of the first carbonaceous material and the second carbonaceous material) may be 50% by mass or more and 100% by mass or less (or 95% by mass or less), 75% by mass or more and 100% by mass or less (or 95% by mass or less), 80% by mass or more and 100% by mass or less (or 95% by mass or less), or 90% by mass or more and 100% by mass or less (or 95% by mass or less).

[0117] (Organic shrinkage inhibitor) Examples of organic shrinkage inhibitors include lignin compounds and synthetic organic shrinkage inhibitors. Examples of lignin compounds include lignin, lignin derivatives (e.g., lignin sulfonic acid or its salts (such as alkali metal salts like sodium salts)), etc. Synthetic organic shrinkage inhibitors are organic polymers containing sulfur elements. Examples of synthetic organic shrinkage inhibitors include condensates of compounds having sulfur-containing groups and aromatic rings (phenol compounds, aniline compounds, etc.) with aldehyde compounds (aldehydes or their condensates, such as formaldehyde). However, organic shrinkage inhibitors are not limited to these specific examples.

[0118] The negative electrode material may contain one organic shrinkage inhibitor, or two or more.

[0119] The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more. The content of the organic shrinkage inhibitor may be, for example, 1% by mass or less, or 0.5% by mass or less.

[0120] (Barium sulfate) The barium sulfate content in the negative electrode material is, for example, 0.05% by mass or more, and may be 0.1% by mass or more. The barium sulfate content is, for example, 3% by mass or less.

[0121] (Analysis or measurement of negative electrode material) The following describes the method for analyzing the negative electrode material or its components. Prior to measurement or analysis, a fully charged lead-acid battery is 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. If the negative electrode plate contains adhesive material, remove the adhesive material as necessary. 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 necessary and subjected to analysis.

[0122] (1) Measurement of the specific surface area Sn of the negative electrode material The BET specific surface area Sn of the negative electrode material is evaluated using the following procedure. First, a fully charged lead-acid battery is disassembled and the negative electrode plate is removed. Next, the sulfuric acid in the negative electrode plate is removed by washing it with water, and then the negative electrode plate is dried. The negative electrode material is collected from the dried negative electrode plate. The collected negative electrode material is pre-treated by heating it in a nitrogen flow at a temperature of 150°C for 1 hour. The BET specific surface area of ​​the pre-treated material is determined by mass measurement, gas adsorption method measurement, and calculation using the BET formula. Specifically, the BET specific surface area is determined by measurement using the following apparatus and conditions, and by calculation using the following calculation method. Measurement device: TriStar3000 manufactured by Micromerities Corporation Adsorption gas: Nitrogen gas with a purity of 99.99% or higher. Adsorption temperature: Boiling point temperature of liquid nitrogen (77K) Method for calculating BET specific surface area: Conforms to JIS Z 8830:2013, section 7.2.

[0123] (2) Analysis of di-fatty acids (2-1) Qualitative analysis of di-fatty acids The pulverized sample A is used. 150.0 ± 0.1 mL of chloroform is added to 100.0 ± 0.1 g of sample A, and the mixture is stirred at 20 ± 5 °C for 16 hours to extract the dia-fatty acid. The solids are then removed by filtration. The structure of the dia-fatty acid is determined from the chloroform solution containing the extracted dia-fatty acid, or from the dia-fatty acid obtained by drying this chloroform solution, by obtaining information from at least one of the following: infrared spectroscopy, ultraviolet-visible absorption spectroscopy, NMR spectroscopy, LC-MS, and pyrolysis GC-MS.

[0124] (2-2) Quantitative analysis of di-fatty acids The appropriate amount of the di-fatty acid obtained by drying the above chloroform solution was measured with an accuracy of ±0.0001g. r (g) Dissolve in deuterated chloroform together with tetrachloroethane (TCE), 1 Measure the 1H-NMR spectrum. The integral value of the peak originating from the second fatty acid, where the chemical shift is 2.34 ppm (S a ) and the integral value of the peak originating from TCE (S r ) and calculate the ratio C of the mass of the first fatty acid to the mass of the negative electrode ear. n1 Similarly, the mass-based content C of the second fatty acid in the negative electrode material can be calculated from the following formula. n2 Calculate (ppm).

[0125] C n2 =S a / S r ×N r / N a ×M a / M r xmr / m × 1,000,000

[0126] 1 The measurement conditions for the H-NMR spectrum were the ratio of the mass of the first fatty acid to the mass of the negative electrode ear (C). n1 The measurement conditions are the same as those for [another measurement].

[0127] (3) Analysis of carbonaceous materials (3-1) Separation and quantification of carbonaceous materials The pulverized sample A is used. 30 mL of a 60% by mass nitric acid aqueous solution is added to 5 g of sample A, and the mixture is heated at 70°C ± 5°C. Furthermore, 10 g of disodium ethylenediaminetetraacetate, 30 mL of ammonia water at a 28% by mass concentration, and 100 mL of water are added to 5 g of sample A, and heating is continued to dissolve the soluble components. The sample pretreated in this manner is collected by filtration. The collected sample is passed through a sieve with a mesh size of 500 μm to remove larger components such as reinforcing materials, and the components that pass through the sieve are collected as carbonaceous material.

[0128] Next, the primary carbonaceous material and the secondary carbonaceous material are separated using the following procedure. When the recovered carbonaceous material is sieved wet using a sieve with a mesh size of 32 μm, the material that does not pass through the sieve and remains on the sieve is designated as the second carbonaceous material, and the material that passes through the sieve is designated as the first carbonaceous material. In other words, the particle size of each carbonaceous material is based on the mesh size of the sieve. For details on wet sieving, refer to JIS Z8815:1994.

[0129] Specifically, the carbonaceous material is placed on a sieve with a mesh size of 32 μm, and the sieve is gently shaken for 5 minutes while deionized water is sprayed on it to separate the material. The secondary carbonaceous material remaining on the sieve is collected by pouring deionized water over it and separated from the deionized water by filtration. The primary carbonaceous material that has passed through the sieve is collected by filtration using a nitrocellulose membrane filter (mesh size 0.1 μm). The collected primary and secondary carbonaceous materials are each dried at a temperature of 100°C ± 5°C for 2 hours. As the sieve with a mesh size of 32 μm, a sieve with a nominal mesh size of 32 μm, as specified in JIS Z 8801-1:2019, is used.

[0130] (3-2) Specific surface area of ​​the first carbonaceous material Sc The BET specific surface area Sc of the first carbonaceous material is determined using the BET formula by gas adsorption using the first carbonaceous material separated by the procedure in (3-1) above. The first carbonaceous material is pretreated by heating in a nitrogen flow at a temperature of 150°C for 1 hour to remove moisture. Using the pretreated first carbonaceous material, the BET specific surface area of ​​the first carbonaceous material is determined in accordance with the case of the specific surface area Sn of the negative electrode material in (1) above.

[0131] (3-3) DBP oil absorption amount Y of the first carbonaceous material The amount of DBP absorbed by the first carbonaceous material Y is measured using an absorbometer in accordance with JIS K 6217-4:2017, using the first carbonaceous material separated by the procedure described in (3-1) above. More specifically, a fixed amount of carbonaceous material is placed in the mixing chamber of the absorbometer, and the rotor is rotated at 125 rpm while dibutyl phthalate (DBP) is simultaneously dropped from an automatic burette at a rate of 4 ml / min. As time progresses, mixing occurs, and the powder in the mixing chamber turns into a paste, creating resistance to the rotor's rotation. At a certain point, the torque rises sharply in response to an increase in the amount of DBP added, and then follows a downward curve. In the downward curve, the point where the torque reaches 70% of the maximum value is used as the endpoint, and the amount of DBP used is taken as the adsorption amount. For example, the S410E manufactured by Asahi Research Institute is used as the absorbometer. The measurement is performed by ensuring that no air bubbles enter the DBP when it is added to the automatic burette of the absorbometer.

[0132] (4) Determination of organic shrinkage inhibitors The pulverized sample A is immersed in a 1 mol / L NaOH aqueous solution to extract the organic shrinkage inhibitor. Insoluble components are removed from the NaOH aqueous solution containing the extracted organic shrinkage inhibitor by filtration, and the filtrate (hereinafter also referred to as filtrate C) is collected.

[0133] A predetermined amount of filtrate C is measured, desalted, concentrated, and dried to obtain a powder of organic shrinkage inhibitor (hereinafter also referred to as sample D). Desalting can be performed using a desalting column, by passing filtrate C through an ion exchange membrane, or by placing filtrate C in a dialysis tube and immersing it in distilled water.

[0134] The organic shrinkage inhibitor is identified by combining information obtained from the infrared spectroscopic spectrum of sample D, the ultraviolet-visible absorption spectrum of the solution obtained by dissolving sample D in distilled water or the like, the NMR spectrum of the solution obtained by dissolving sample D in a solvent such as heavy water, or from pyrolysis GC-MS, which can provide information on the individual compounds constituting the substance.

[0135] The ultraviolet-visible absorption spectrum of filtrate C is measured. The content of the organic shrinkage inhibitor in the negative electrode material is quantified from the spectral intensity, a pre-prepared calibration curve, the amount of filtrate C measured, and the mass of sample A. If the structural formula of the organic shrinkage inhibitor to be analyzed cannot be precisely identified and a calibration curve for the same organic shrinkage inhibitor cannot be used, a calibration curve is created using an available organic shrinkage inhibitor that exhibits a similar ultraviolet-visible absorption spectrum, infrared spectroscopic spectrum, NMR spectrum, etc.

[0136] (5) Determination of 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 ions. The resulting solution is filtered to separate the carbonaceous material, barium sulfate, and other solid components.

[0137] 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 is dried together with the filtered sample in a dryer at 110°C ± 5°C. The filtered sample is a mixed sample of 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 obtain the mass of sample E (M m ) is measured. Then, sample E is placed in a crucible with a membrane filter and incinerated at over 1300°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 B )

[0138] (Positive plate) The positive electrode plates of lead-acid batteries are classified into paste type, clad type, etc. Either paste type or clad type positive electrode plate may be used. The positive electrode plate comprises a positive electrode current collector and a positive electrode material. A clad type positive electrode plate comprises a plurality of porous tubes, a core metal inserted into each tube, a current collector connecting the plurality of core metals, a positive electrode material filled into the tubes in which the core metals are inserted, and a connecting seat connecting the plurality of tubes.

[0139] (Positive electrode current collector) The positive electrode current collector of a paste-type positive electrode plate has a positive electrode lug and a positive electrode grid. The positive electrode material is held in the positive electrode grid. The positive electrode lug is provided on the top of the positive electrode plate so as to protrude upward and is used for connection to the positive electrode strap. The positive electrode current collector of a clad-type positive electrode plate consists of a core metal and a current collector.

[0140] The positive electrode current collector may be formed by casting a lead alloy or by processing a lead alloy sheet. Examples of processing methods include expanding and 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.

[0141] The positive electrode current collector contains the element Sb. That is, the lead alloy used for the positive electrode current collector may be a Pb-Sb alloy. The use of a Pb-Sb alloy improves the mechanical strength of the positive electrode current collector, the adhesion between the positive electrode current collector and the positive electrode material, and the corrosion resistance.

[0142] On the other hand, when a Pb-Sb alloy is used, Sb dissolved in the electrolyte precipitates on the negative electrode plate (especially the negative electrode lugs). As a result, the hydrogen generation overpotential of the negative electrode plate decreases, promoting the hydrogen generation reaction and electrolyte reduction, and Sb tends to form a local cell with the negative electrode plate, promoting self-discharge. These phenomena can be suppressed by adding a primary fatty acid to at least the negative electrode lugs.

[0143] The Sb content in the positive electrode current collector may be 3.5% by mass or more, or 5% by mass or more. The Sb content in the positive electrode current collector may be 10% by mass or less, or 8% by mass or less. For example, the Sb content in the positive electrode current collector may be 3.5% by mass or more, or 10% by mass or less, or 5% by mass or more, and 8% by mass or less.

[0144] Pb-Sb alloys may contain trace components other than Pb and Sb. The content of such trace components may be more than 0% by mass and 1% by mass or less (for example, more than 0% by mass and 0.5% by mass or less). Examples of such trace components include As, S, Se, Sn, and Ag.

[0145] As mentioned above, the positive electrode plate may be a clad-type positive electrode plate. In that case, the positive electrode current collector may include a core metal. The core metal is a long, slender rod (for example, a round rod). The diameter of the core metal (the diameter of a round rod-shaped core metal) may be 2.4 mm or more, 2.7 mm or more, and less than 3.6 mm or 3.3 mm or less. For example, the diameter may be 2.4 mm or more and less than 3.6 mm, or 2.7 mm or more and 3.3 mm or less.

[0146] There are no particular limitations on the length of the core wire; it is selected according to the size of the positive electrode plate. The length of the core wire may be, for example, 100 mm or more and 400 mm or less.

[0147] (Method for analyzing the composition of the positive electrode current collector) The quantitative analysis of elements other than lead (including Sb) contained in the positive electrode current collector can be performed according to the lead-separated inductively coupled plasma emission spectroscopy method described in JIS H2105. When analyzing the elemental content of the positive electrode current collector of a positive electrode plate removed from a lead-acid battery, first, the positive electrode plate is vibrated to detach the positive electrode material from the positive electrode current collector, and then the remaining positive electrode material around the positive electrode current collector is removed using a ceramic knife. After that, a portion of the positive electrode current collector with metallic luster is taken as a sample and its mass is measured. The collected sample is dissolved in tartaric acid and dilute nitric acid to obtain an aqueous solution. Hydrochloric acid is added to the obtained aqueous solution to precipitate lead chloride, and the solution is filtered and the filtrate is collected. The elements in the filtrate are analyzed using a calibration curve method with an inductively coupled plasma (ICP) emission spectrometer (e.g., Shimadzu Corporation, ICPS-8000). From the above analysis results, the elemental content (mass%) in the positive electrode current collector is determined.

[0148] 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 to cover the entire positive electrode current collector, or it may be formed on only a part of the positive electrode current collector. The surface layer may be formed only on the positive electrode grid portion, only on the positive electrode lugs portion, or only on the frame portion of the positive electrode current collector.

[0149] (Positive electrode material) The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacity through an oxidation-reduction reaction. The positive electrode material may also contain other additives as needed. In a clad positive electrode plate, the positive electrode material is the portion of the positive electrode plate excluding the tube, core metal, current collector, and connecting seat.

[0150] 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 section are inserted, with lead powder or slurry-like lead powder, and then joining multiple tubes together. Subsequently, the unformed positive electrode plates are formed to obtain a positive electrode plate.

[0151] Chemical treatment may 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.

[0152] (Separator) A separator may be placed between the negative electrode plate and the positive electrode plate. As the separator, at least one selected from nonwoven fabric and microporous membrane can be used.

[0153] Nonwoven fabric is a mat made by intertwining fibers without weaving, and is primarily composed of fibers. For example, a nonwoven fabric is 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. may be used. Among these, glass fibers are preferred. Nonwoven fabric may also contain components other than fibers (for example, acid-resistant inorganic powders, polymers as binders, etc.).

[0154] 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 into a sheet, and then removing the pore-forming agent to form pores. Microporous membranes are preferably composed of acid-resistant materials, and microporous membranes mainly composed of polymer components are preferred. As polymer components, polyolefins (polyethylene, polypropylene, etc.) are preferred. As pore-forming agents, at least one selected from the group consisting of polymer powders and oils can be used.

[0155] 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.

[0156] The separator may be in the form of a sheet or a bag. A single sheet-shaped separator may be placed between the positive and negative electrode plates. Alternatively, the plates may be sandwiched between a single folded sheet-shaped separator. In this case, the positive electrode plate sandwiched between the folded sheet-shaped separators and the negative electrode plate sandwiched between the folded sheet-shaped 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-shaped separators and stacked on top of the other electrode plate. Alternatively, the sheet-shaped 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 a bag-shaped separator is used, the bag-shaped separator may contain either the positive electrode plate or the negative electrode plate.

[0157] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled if necessary.

[0158] The electrolyte may optionally contain cations (e.g., metal cations) and / or anions (e.g., anions other than sulfate anions, such as phosphate ions). Examples of metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0159] The density of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 g / cm³. 3 The above is 1.25 g / cm³. 3 The above is also acceptable. The density of the electrolyte at 20°C is 1.35 g / cm³. 3 The following is the value: 1.32 g / cm³ 3The following is preferable:

[0160] The density of the electrolyte at 20°C is 1.20 g / cm³. 3 More than 1.35g / cm 3 Below, 1.20g / cm 3 More than 1.32g / cm 3 Below 1.25g / cm 3 More than 1.35g / cm 3 The following, or 1.25 g / cm³ 3 More than 1.32g / cm 3 The following is also acceptable.

[0161] Figure 1 shows the 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.

[0162] 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 strap 6 connecting multiple negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode strap 5 connecting 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 strap 6, and a through connector 8 is connected to the positive electrode strap 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, connecting the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0163] The positive electrode strap 5 is formed by welding together the positive electrode lugs provided on the upper part of each positive electrode plate 3. The negative electrode strap 6 is formed by welding together the negative electrode lugs provided on the upper part of each negative electrode plate 2.

[0164] The elements described herein can be combined in any way.

[0165] (evaluation) Self-discharge, lifespan, overcharge capacity, charge acceptance, and leakage of primary carbonaceous material into the electrolyte are evaluated using a test battery with a nominal voltage of 12V and a rated 5-hour rate capacity of 55Ah, following the procedures shown in (A) to (E) below. Here, the rated 5-hour rate capacity is the capacity when discharged to the discharge termination voltage at a current (A) of 1 / 5 of the Ah value stated in the rated capacity.

[0166] (A) Self-discharge rate (a) Place a fully charged lead-acid battery in a 25°C water bath and confirm that the electrolyte temperature in the cells is 25±2°C. After confirmation, discharge the battery to 1.75V / cell with a current (A) equal to 1 / 5 of the Ah value indicated in the rated capacity and record the discharge capacity D1. Then, charge the battery to 1.3 times the rated capacity with a current (A) equal to 1 / 5 of the Ah value indicated in the rated capacity. (b) Store the lead-acid battery with the vent caps tightly closed, clean and dry on the surface, at a temperature of 50±2℃ for 20 days. During storage, the lead-acid battery should be kept in an open circuit state, and no connecting clamps or cables should be attached to the positive and negative terminals. (c) Place the lead-acid battery in a 25°C water tank and confirm that the electrolyte temperature inside the cell is 25±2°C. After confirmation, discharge the lead-acid battery with a current (A) equal to 1 / 5 of the Ah value indicated in the rated capacity until the terminal voltage is 1.75V / cell, and record the discharge capacity D2. (d) Let the self-discharge rate (%) be (D1-D2) / D1.

[0167] (B) Life performance (heavy load simulation pattern test) The heavy-load life is evaluated based on the number of cycles until the end of the life cycle is reached in a charge-discharge cycle test under the following conditions, which simulates the test described in JIS D5301:2019 10.5. Here, (a) to (e) are performed in a water bath at 40°C ± 2°C.

[0168] (a) Discharge: Discharge for 1 hour at a current (A) equal to 0.36 times the Ah value indicated in the rated capacity. (b) Charging: Charge for 5 hours at a current (A) equal to 0.09 times the Ah value indicated in the rated capacity. (c) Repeat: Repeat steps (a) and (b) above 24 times, with each step counting as one cycle. (d) Discharge for judgment: After (c) above, perform continuous discharge at 20A until the voltage reaches 1.70V / cell, and record the discharge duration. (e) Charging: Charge the lead-acid battery at a current (A) of 0.09 times the Ah value indicated in the rated capacity, until the terminal voltage or electrolyte density (converted to 25°C) of the lead-acid battery, measured every 15 minutes, shows a constant value for three consecutive times.

[0169] Here, the number of cycles until the end of the lifespan is the number of cycles in which the capacity (Ah) obtained from the product of the discharge duration and discharge current measured in (d) above becomes 50% or less of the 5-hour rate capacity.

[0170] Furthermore, the discharge and charge cycles described in (d) and (e) above are also added to the cycle count.

[0171] (C) Overcharged electricity To create overcharge conditions beyond the standard 4-minute-10-minute test specified in JIS D5301:2019, a 1-minute discharge-10-minute charge test (1-minute-10-minute test) is conducted at 75°C ± 3°C (high-temperature light-load test). In the high-temperature light-load test, the charge-discharge cycle is repeated 1220 times. The amount of overcharged electricity (charged electricity - discharged electricity) in each cycle up to 1220 cycles is totaled and averaged to determine the amount of overcharged electricity (Ah) per cycle. Discharge: 25A, 1 minute Charging: 2.47V / cell, 25A, 10 minutes Tank temperature: 75℃±3℃ Furthermore, if the rated 5-hour rate capacity exceeds 70Ah, a discharge current of 50A and a maximum charge current of 50A will be used. For rated 5-hour rate capacities of 70Ah or less, the stated values ​​will be used as is.

[0172] (D) Charge acceptance The charge at 10 seconds will be measured using a fully charged test battery. Specifically, the test battery will be discharged for 30 minutes at a current (A) equal to 1 / 5 of the Ah value indicated on the rated capacity, and then left in a water tank for 16 hours. After that, the test battery will be charged at a constant current and constant voltage of 2.42V / cell with a current limit of 200A, and the cumulative charge at 10 seconds will be measured. All operations will be performed in a water tank at 25℃±2℃. The cumulative charge at 10 seconds will be used as an indicator for evaluating charge acceptance.

[0173] (E) Leakage of the first carbonaceous material into the electrolyte Multiple standard solutions with different concentrations are prepared by dispersing a primary carbonaceous material in the electrolyte at concentrations ranging from 1 ppm to 300 ppm by mass. The turbidity of an electrolyte sample taken from a fully charged lead-acid battery is visually compared with that of the standard sample solutions. The concentration of the primary carbonaceous material in the standard sample solution with the closest turbidity is taken as the concentration of the primary carbonaceous material in the sample. Based on this concentration, the outflow of the primary carbonaceous material into the electrolyte is evaluated. When the concentration of carbonaceous material in the electrolyte is 3 ppm or less by mass, the mark used to visually check the liquid level in the lead-acid battery is clearly visible, but when it exceeds 3 ppm, the mark becomes difficult to see.

[0174] [Examples] The present invention will be described below in detail based on examples and comparative examples, but the present invention is not limited to the following examples.

[0175] Lead-acid battery R1 (a) Fabrication of the negative electrode plate The lead powder raw material, the primary carbonaceous material (carbon black), the organic shrinkage inhibitor (sodium ligninsulfonate), and barium sulfate are mixed with an appropriate amount of sulfuric acid aqueous solution to obtain a negative electrode paste.

[0176] The negative electrode paste is prepared by mixing the components such that the carbon black content Cc in the negative electrode material, determined by the procedure described above, is 0.5 mass%, the organic shrinkage inhibitor content is 0.1 mass%, and the barium sulfate content is 0.4 mass%. The specific surface area Sc of the carbon black, determined by the procedure described above, is 69 m². 2 The DBP oil absorption Y is 193 mL / 100 g.

[0177] The negative 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 negative electrode plate.

[0178] (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-Sb alloy, and then aged and dried to obtain an unformed positive electrode plate. The Sb content of the Pb-Sb alloy is 1.7% by mass.

[0179] (c) Preparation of test batteries The test battery is a lead-acid battery with a nominal voltage of 12V and a rated 5-hour rate capacity of 55Ah. The test battery's electrode assembly consists of 7 positive plates and 8 negative plates. The negative plates are housed in a bag-shaped separator made of a microporous polyethylene membrane and are stacked alternately with the positive plates to form the electrode assembly. The electrode assembly is placed in a polypropylene battery case together with an electrolyte (sulfuric acid aqueous solution), and chemical conversion is carried out in the case to produce test battery R1 of the liquid lead-acid battery. Through chemical conversion, the lead-acid battery is brought to a nearly fully charged state. The density of the electrolyte in a fully charged lead-acid battery at 20°C is 1.28 g / cm³. 3 That is the case.

[0180] 《Lead acid batteries E1~E3》 Test batteries E1 to E3 are prepared in the same manner as test battery R1, except that an appropriate amount of oleic acid or berargonic acid is applied as the primary fatty acid to the c-row region ((c,x) region, (c,y) region, (c,z) region) when the negative electrode lugs of the negative electrode current collector are divided into nine sections in a 3x3 matrix on both sides. Table 1 shows the number of carbon atoms in the primary fatty acid and the ratio of the mass of the primary fatty acid detected from the negative electrode lugs by the method described above to the mass of the negative electrode lugs.

[0181] 《Lead acid battery C1》 Test battery C1 was prepared in the same manner as test battery R1, except that an appropriate amount of butyric acid was applied as a third fatty acid to the entire surface of both sides of the negative electrode lug of the negative electrode current collector. Table 1 shows the number of carbon atoms in the third fatty acid and the ratio of the mass of the third fatty acid detected from the negative electrode lug in the same manner as for the first fatty acid to the mass of the negative electrode lug.

[0182] 《Lead acid battery C2》 Test battery C2 was prepared in the same manner as test battery R1, except that an appropriate amount of polypropylene glycol (PPG) was applied to the entire surface of both sides of the negative electrode lug of the negative electrode current collector. Table 1 shows the ratio of the mass of PPG detected from the negative electrode lug to the mass of the negative electrode lug, using the same method as for the first fatty acid.

[0183] 《Lead acid battery C3》 Except for using an expanded grid made of Pb-Ca-Sn alloy as the positive electrode current collector, test battery C3 is constructed in the same manner as test battery R1.

[0184] 《Lead acid battery C4, C5》 Test batteries C4 and C5 were prepared in the same manner as test battery C3, which uses an expanded grid made of Pb-Ca-Sn alloy as the positive electrode current collector, except that an appropriate amount of oleic acid was applied as the primary fatty acid to the entire surface of both sides of the negative electrode lug of the negative electrode current collector. Table 1 shows the number of carbon atoms in the primary fatty acid and the ratio of the mass of the primary fatty acid detected from the negative electrode lug by the method described above to the mass of the negative electrode lug. (2) Evaluation The fabricated lead-acid battery (test battery) will be used to perform the evaluations described in (A) to (E) and (F).

[0185] (A) Self-discharge rate The self-discharge rate of the test battery is evaluated using the procedure described above. The self-discharge rate of the test battery in each example is evaluated as a relative value when the self-discharge rate (%) of test battery R1 = (D1 - D2) / D1 is set to 100. The smaller this value (self-discharge rate), the better the capacity preservation characteristics.

[0186] (B) Life performance The lifespan of the test battery in the heavy-load life test is evaluated using the procedure described above. The lifespan performance of each test battery is evaluated as a relative value, with the number of cycles until test battery R1 reaches the end of its lifespan set to 100. A higher value indicates better lifespan performance.

[0187] (C) Overcharged electricity The amount of overcharged charge in the test battery is evaluated using the procedure described above. The amount of overcharged charge in each example of the test battery is expressed as a percentage (%) to which the cumulative value of the overcharged charge of test battery R1 is set to 100%.

[0188] (D) Charge acceptance The charge acceptance of the test battery is evaluated using the procedure described above. The charge acceptance of the test battery in each example is expressed as a percentage (%) relative to the cumulative charge of the test battery R1 over 10 seconds, which is set to 100%.

[0189] (E) Amount of carbonaceous material leached into the electrolyte Using the procedure described above, the degree of carbon black leakage into the electrolyte immediately after chemical conversion (the concentration of carbon black in the electrolyte) is determined. If the concentration of carbon black in the electrolyte is 3 ppm or less by mass, it can be said that a high carbon black leakage suppression effect has been achieved.

[0190] (F) Specific surface area of ​​the negative electrode material Sn Using the negative electrode material sampled from the negative electrode plate removed from the test battery according to the procedure described above, the specific surface area Sn is calculated.

[0191] The results are shown in Table 1.

[0192] [Table 1]

[0193] The results in Table 1 show that when 10 ppm or more of the primary fatty acid is detected from the negative electrode lug, the self-discharge rate and overcharge rate are significantly reduced, and the lifespan performance and charge acceptance are significantly improved. Furthermore, it can be understood that the remarkable effect of such improvements is unique to the use of a Pb-Sb alloy as the positive electrode current collector.

[0194] 《Lead acid batteries E4~E6》 Test batteries E4 to E6 were prepared and evaluated in the same manner as test battery R1, except that an appropriate amount of oleic acid was applied as the primary fatty acid to the b and c regions ((b,x) region, (b,y) region, (b,z) region, (c,x) region, (c,y) region, (c,z) region) when the negative electrode lugs of the negative electrode current collector were divided into nine sections in a 3x3 matrix on both sides. Table 2 shows the number of carbon atoms in the primary fatty acid, the ratio of the mass of the primary fatty acid detected from the negative electrode lugs (and each region) using the method described above to the mass of the negative electrode lugs, and the evaluation results.

[0195] [Table 2]

[0196] The results in Table 2 show that the effects of reducing self-discharge and overcharge, as well as improving lifespan and charge acceptance, are more pronounced when the amount of primary fatty acid detected in the region closer to the negative electrode grid than the strap side of the negative electrode ear is greater.

[0197] 《Lead acid batteries E7~E13, C6~C11》 In test batteries E7-E11, E13, and C6-C9, the negative electrode material contains secondary fatty acids at the concentrations shown in Table 3A. In test battery C10, butyric acid is included as a third fatty acid in the negative electrode material at the concentration shown in Table 3A. In the test battery C6, an expanded grid made of Pb-Ca-Sn alloy is used as the positive electrode current collector. In test battery C11, the negative electrode material contains PPG at the concentration shown in Table 3A. For test batteries C7 to C11, the first fatty acid was not applied to the negative electrode lug. In test batteries E12 and E13, the carbon black content in the negative electrode material is changed to 0.3% by mass as shown in Table 3B.

[0198] Except as described above, test batteries E7 to E13 and C6 to C11 are produced in the same manner as test battery E1. The number of carbon atoms in the first fatty acid, the ratio of the mass of the first fatty acid detected from the negative electrode ear part (and each region) to the mass of the negative electrode ear part by the method described above, the number of carbon atoms in the first and second fatty acids, the content rate Cf of the second fatty acid and the carbon black content rate Cc in the negative electrode material, the specific surface area Sn of the negative electrode material, the Cf / Sn ratio, and the Cf / Y ratio are shown in Table 3A and Table 3B. Also, the evaluation results are shown in Table 3C.

[0199]

Table 3A

[0200]

Table 3B

[0201]

Table 3C

[0202] The results in Tables 3A to 3C show that simply including the second fatty acid in the negative electrode material has a small effect on reducing the self-discharge amount and overcharge amount, and improving the life performance and charge acceptance. Conversely, when the first fatty acid is imparted to the negative electrode ear part and the second fatty acid is included in the negative electrode material, these effects become more significant. It can also be understood that by controlling Cf / Sn or Cf / Y, an effect of suppressing the outflow of the carbonaceous material can be obtained together with the above effects.

Industrial Applicability

[0203] The lead-acid battery relating to this disclosure can be suitably used, for example, as a starting power source installed in large vehicles. This disclosure is particularly suitable for lead-acid batteries controlled by an ISS (Instrument Starter System). However, these are merely examples, and the applications of lead-acid batteries are not limited to these. [Explanation of Symbols]

[0204] 1:Lead acid battery 2: Negative plate 3: Positive plate 4: Separator 5: Positive terminal strap 6: Negative electrode strap 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 21: Negative electrode current collector 22: Negative electrode material 23: Negative electrode strap 211: Negative electrode ear portion 212: Negative electrode grid section

Claims

1. It includes an electrode group and an electrolyte, The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode material. The negative electrode plate comprises a negative electrode current collector and a negative electrode material. The positive electrode current collector contains the element Sb, The negative electrode current collector has a negative electrode ear portion connected to the negative electrode strap, and a negative electrode grid portion continuous with the negative electrode ear portion. The first fatty acid was detected from the negative electrode ear portion. The first fatty acid contains 8 to 30 carbon atoms, and is a lead-acid battery.

2. The lead-acid battery according to claim 1, wherein the mass of the first fatty acid detected from the negative electrode ear portion is 10 ppm or more relative to the mass of the ear portion.

3. When the negative electrode portion is divided into nine sections in a 3x3 matrix, The lead-acid battery according to claim 1, wherein the first fatty acid is detected in all nine of the aforementioned regions.

4. The lead-acid battery according to claim 1, wherein in the nine regions, the amount of the first fatty acid detected from the three regions closest to the negative electrode grid is greater than the amount of the first fatty acid detected from the three regions closest to the negative electrode strap.

5. The lead-acid battery according to claim 3, wherein the mass of the first fatty acid detected from the three regions near the negative electrode grid is 10 ppm or more relative to the mass of each of the regions.

6. The negative electrode material contains a second fatty acid, The lead-acid battery according to claim 1, wherein the second fatty acid contains 8 to 30 carbon atoms.

7. The lead-acid battery according to claim 6, wherein the content Cf of the second fatty acid in the negative electrode material is 20 ppm or more and 600 ppm or less by mass.

8. The content Cf of the second fatty acid in the negative electrode material and the specific surface area Sn (m²) of the negative electrode material. ２ The ratio of Cf / Sn (per g) is 20 ppm·m －２ A lead-acid battery according to claim 6, wherein the amount is 1 g or more.

9. The negative electrode material includes a carbonaceous material having a particle size of less than 32 μm. The lead-acid battery according to claim 6, wherein the carbonaceous material content Cc in the negative electrode material is 0.4% by mass or more.

10. The ratio of the content of the second fatty acid Cf in the negative electrode material to the DBP oil absorption Y of the carbonaceous material, Cf / Y, is 0.1 ppm / mL. －１ A lead-acid battery according to claim 9, wherein the weight is 100g or more.

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