Lead-acid battery

Abstract

DEPCT64 A lead-acid battery has a section with a group of electrodes, which are arranged in layers, including a positive electrode plate. Multiple plates and multiple negative electrode plates, separated by a separator, cell compartments that store groups of electrodes and... An electrolyte solution will contain 0.03 to 0.3 mol / L of Na when two electrode plates are connected. Specifically, these are the positive electrode plates or negative electrode plates (end plates) located at both ends of the group. The electrodes are placed close to the inner wall of the cell compartment; the gap between the electrodes W will be -0.1. Up to +0.15mm, which is obtained from the equation W={(L-d1) / N}-d2, where the distance used for maximum separation is... The thickness between the two end surfaces facing the inner wall is L, which is the total thickness. The value of the positive and negative electrode plates in the electrode group is d1, the amount of space between them. The number of electrodes in the cell compartment is equal to N, and the total thickness of one separator placed between them. The positive and negative electrode plates have a coefficient of d2, and the separator has one ridge on its side. That is the negative electrode plate. -----------------------------------------------------------

Description

lead acid battery

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

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. A lead-acid battery includes a negative electrode plate, a positive electrode plate, a separator interposed between the negative and positive electrodes, and an electrolyte, which is typically a sulfuric acid solution.

[0003] Patent Document 1 describes a lead acid battery in which the electrolyte contains sodium ions in the range of 0.01 to 0.45 mol / L.

[0004] Patent Document 2 describes a lead acid battery in which an active material layer containing sodium sulfate added in an amount of 0.5% by weight to 10% by weight of the positive electrode active material is disposed near the surface of the positive electrode plate.

[0005] International Publication No. 2014 / 097522 Pamphlet Japanese Patent Application Laid-Open No. 2000-340252

[0006] Lead-acid batteries are sometimes used in a state of insufficient charge called a partial state of charge (PSOC). For example, lead-acid batteries are used in PSOC during charge control or idle stop-start (ISS). Therefore, lead-acid batteries are required to have excellent life performance in cycle tests under PSOC conditions (hereinafter referred to as PSOC life performance).

[0007] If the battery is continued to be used in a PSOC state, stratification of the electrolyte progresses, which accelerates softening of the positive electrode active material and accumulation of lead sulfate (sulfation) in the positive and negative electrode active materials, shortening the battery life.

[0008] In addition, when the battery is overdischarged and the specific gravity of the electrolyte drops to a level close to that of water, the solubility of lead increases, making it more likely to develop a permeation short circuit. Furthermore, in an overdischarged state, the resistance of the electrolyte increases, making charging difficult. To prevent these problems, sodium is added to the electrolyte, but this reduces charge acceptance in PSOC and promotes the accumulation of lead sulfate (sulfation) in the negative electrode.

[0009] One aspect of the present invention provides a battery comprising: an electrode plate assembly in which a plurality of positive electrode plates and a plurality of negative electrode plates are stacked with separators interposed therebetween; a cell chamber that houses the electrode plate assembly; and an electrolyte, wherein the electrolyte contains 0.03 to 0.3 mol / L of Na; When a first end plate, which is the positive electrode plate or the negative electrode plate located at one end of the electrode plate pack, is disposed adjacent to one of the opposing inner walls of the cell chamber, and a second end plate, which is the positive electrode plate or the negative electrode plate located at the other end of the electrode plate pack, is disposed adjacent to the other inner wall, L is the inter-plate distance, which is the maximum separation distance between the surface of the first end plate facing the inner wall and the surface of the second end plate facing the inner wall, d1 is the total thickness of the positive electrode plate and the negative electrode plate in the electrode plate pack, N is the number of inter-electrode spaces, which is the number of regions where the positive electrode plate and the negative electrode plate face each other in the cell chamber, and d2 is the total thickness of one separator interposed between the positive electrode plate and the negative electrode plate, the inter-electrode gap W calculated by the following formula is −0.1 to +0.15 mm: W={(L−d1) / N}−d2 The separator is provided with a first rib on the negative electrode plate side.

[0010] In lead-acid batteries, accumulation of lead sulfate is suppressed, and excellent PSOC life performance is obtained.

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

[0012] A lead-acid battery according to one aspect of the present invention includes an electrode plate assembly in which a plurality of positive electrode plates and a plurality of negative electrode plates are stacked with separators interposed therebetween, a cell chamber for accommodating the electrode plate assembly, and an electrolyte solution, the electrolyte solution containing 0.03 to 0.3 mol / L of Na. Furthermore, when a first end plate, which is either a positive or negative electrode plate located at one end of the electrode plate pack, is positioned adjacent to one of the opposing inner walls of the cell chamber, and a second end plate, which is either a positive or negative electrode plate located at the other end of the electrode plate pack, is positioned adjacent to the other inner wall, the inter-electrode gap W, which is calculated by the following formula: W = {(L - d1) / N} - d2, is -0.1 to +0.15 mm. The separator has a first rib on the negative electrode plate side.

[0013] During discharge, lead-acid batteries produce lead sulfate at both the positive and negative electrodes, and water at the positive electrode. During charge, metallic lead, lead dioxide, and sulfuric acid are produced from the lead sulfate and water.

[0014] If the PSOC continues to be used in an undercharged state, the amount of lead sulfate accumulated inevitably increases toward the end of its life, causing a decrease in the specific gravity of the electrolyte. This decrease in the specific gravity of the electrolyte is particularly noticeable during overdischarge. Furthermore, if the electrolyte is not sufficiently stirred during charging, a difference in the concentration of sulfuric acid between the upper and lower parts of the electrolyte (stratification) occurs. Continued use under such conditions leads to the progression of sulfation in the lower part of the electrolyte, where the specific gravity is higher.

[0015] The addition of Na to the electrolyte has the effect of suppressing permeation short-circuiting and improving charge recovery from overdischarge. However, it is known that the addition of Na reduces charge acceptance and promotes the accumulation of lead sulfate (sulfation) in the negative electrode.

[0016] However, the present inventors have found that applying a moderate amount of pressure to the electrode assembly can suppress the accumulation of lead sulfate, which is believed to be due to the mechanical suppression of expansion of the negative electrode material (negative electrode active material).

[0017] The degree of compression of the electrode plate assembly can be evaluated using the inter-electrode gap W, which is expressed by the following formula: (Inter-electrode gap W) = {(distance between end plates L) - (total thickness of positive and negative electrode plates d1)} / (number of inter-electrode gaps N) - (total thickness of one separator d2)

[0018] Here, the total thickness d1 of the positive and negative plates is the sum of the total thickness of the positive plates, which is the sum of the thicknesses of the positive plates constituting the electrode group, and the total thickness of the negative plates, which is the sum of the thicknesses of the negative plates constituting the electrode group. If the number of positive or negative plates in the cell chamber exceeds 10, the thickness of the positive or negative plates is determined by measuring the thickness of each pre-formed, fully charged electrode plate at six locations (measured at three locations, top, middle, and bottom, divided into three equal parts in the height direction, on the left and right sides of the electrode plate) with a vernier caliper and averaging the measurements for the 10 plates. The total thickness of the positive or negative plates is determined by multiplying the average thickness of the positive or negative plates determined above by the number of positive or negative plates. If the number of positive or negative plates in the cell chamber is 10 or less, the thickness of each positive or negative plate is measured using the above method, and the total thickness is calculated by summing the thicknesses. The number of inter-electrode spaces N is the number of regions in the cell chamber where positive and negative electrode plates face each other, and in the case of an electrode plate group in which positive and negative electrode plates are alternately stacked, the number of inter-electrode spaces N is equal to the number of positive electrode plates + the number of negative electrode plates - 1. If ribs are provided on one or both sides of the separator, the total thickness d2 of one separator is the sum of the base thickness of the separator and the height of the ribs on one or both sides.

[0019] The distance L between the end plates is expressed as the maximum distance between the surface of the first end plate facing the cell chamber inner wall and the surface of the second end plate facing the cell chamber inner wall when the positive or negative plate located at one end of the electrode plate pack (hereinafter referred to as the "first end plate") is positioned adjacent to one of the opposing inner walls of the cell chamber, and the positive or negative plate located at the other end of the electrode plate pack (hereinafter referred to as the "second end plate") is positioned adjacent to the other inner wall. When no ribs are provided in the cell chamber to adjust the position of the electrode plate pack and both end plates directly contact the inner walls of the cell chamber without a separator between them, the distance L between the end plates is equal to the distance between the inner walls of the cell chamber (i.e., the internal dimension of the cell chamber).

[0020] Ribs may be provided inside the cell chamber to adjust the position of the electrode plate assembly. In this case, the first end plate and / or the second end plate do not contact the inner wall of the cell chamber, but contact the ribs provided in the cell chamber, and face the inner wall of the cell chamber via the ribs provided in the cell chamber. In this case, the distance L between the end plates is calculated by subtracting the height of the ribs provided in the cell chamber from the inner dimension of the cell chamber. If ribs are provided on both inner walls of the cell chamber, the heights of the two ribs provided on both inner walls are added together and subtracted from the inner dimension of the cell chamber to determine the distance L between the end plates.

[0021] Alternatively, the cell chamber may not have ribs for adjusting the position of the electrode plate assembly, but the electrode plates constituting the first end plate and / or the second end plate may be housed in a pouch-shaped separator. In this case, the end plates face the inner wall of the cell chamber via the separator. In this case, the distance L between the end plates is calculated by subtracting the total thickness of the separator (the sum of the separator rib height and base thickness) from the inner dimensions of the cell chamber. When both the first end plate and the second end plate are housed in a pouch-shaped separator, the total thickness of the two separators is subtracted to determine the distance L between the end plates. Here, the separator rib height refers to the maximum height of the rib provided in the area facing the area where the electrode material of the positive or negative electrode plate is present.

[0022] When ribs for adjusting the position of the electrode plate assembly are provided in the cell chamber and the electrode plates constituting the first end plate and / or second end plate are housed in a pouch-shaped separator, the distance L between the end plates is calculated by subtracting the height of the ribs provided in the cell chamber and the total thickness of the separator from the inner dimensions of the cell chamber. However, the ribs (external ribs) provided on the outer surface of the pouch-shaped separator may or may not contact the ribs provided in the cell chamber. For example, when the electrode plate assembly is inserted into the cell chamber, the external ribs of the pouch-shaped separator may be positioned so as to intersect with the ribs provided in the cell chamber. In this case, the ribs provided in the cell chamber contact the external ribs of the pouch-shaped separator. In this case, the distance L between the end plates is calculated by subtracting the height of the ribs provided in the cell chamber and the total thickness of the separator (including the heights of the internal and external ribs) from the inner dimensions of the cell chamber. On the other hand, when the electrode plate assembly is inserted into the cell chamber, the outer ribs of the pouch-shaped separator may be positioned so as to fit into the gaps between the ribs without intersecting with the ribs on the cell chamber. In this case, the ribs on the cell chamber do not contact the outer ribs of the pouch-shaped separator, but rather contact the base surface of the pouch-shaped separator. In this case, the distance L between the end plates can be calculated by subtracting the height of the ribs on the cell chamber and the base thickness of the separator from the inner dimensions of the cell chamber, and further subtracting the height of the inner ribs if ribs (inner ribs) are provided on the inner surface of the pouch-shaped separator.

[0023] That is, the inter-electrode gap W is expressed as W = {(L - d1) / N} - d2, and is the size of the gap per area where the positive and negative plates, excluding the end plates, can freely move within the cell chamber when the first and second end plates, located at both ends of the electrode plate pack, are positioned as close as possible to both side walls of the cell chamber so as to maximize the distance between the end plates. A negative inter-electrode gap W indicates that pressure has been applied to the positive and negative plates since the lead-acid battery was first manufactured. Even if the inter-electrode gap W is positive, pressure may still be applied due to expansion of the plates as the battery is used.

[0024] Applying pressure to the electrode plate assembly can suppress the accumulation of lead sulfate. However, applying pressure to the electrode plate assembly also reduces the diffusibility of the electrolyte near the negative electrode, which tends to reduce charge / discharge performance. If pressure does not provide sufficient space between the negative electrode plate and the separator, sulfuric acid cannot be sufficiently diffused during discharge, which tends to reduce the specific gravity of the electrolyte near the negative electrode and reduce discharge performance. Furthermore, during charging, the separator prevents sulfuric acid released from the negative electrode from diffusing, causing high-concentration sulfuric acid to remain near the negative electrode, which tends to reduce charging efficiency.

[0025] The rib (first rib) provided on the negative electrode plate side ensures a space between the negative electrode plate and the separator to retain the electrolyte even under pressure. This maintains the diffusibility of the electrolyte near the negative electrode even under pressure, suppressing a decrease in charge / discharge performance. During discharge, the decrease in specific gravity of the electrolyte near the negative electrode is suppressed, suppressing a decrease in discharge performance. Furthermore, during charge, sulfuric acid released from the negative electrode plate can diffuse into the space between the negative electrode plate and the separator, reducing the specific gravity of the electrolyte near the negative electrode, thereby improving charging efficiency.

[0026] Furthermore, the first rib provided on the negative electrode plate side enhances the diffusibility of the electrolyte, synergistically suppressing the accumulation of lead sulfate, resulting in a lead-acid battery with excellent PSOC life performance.

[0027] As the Na content (concentration) in the electrolyte increases, lead sulfate tends to accumulate. However, by providing the first rib and appropriately compressing the electrode plate assembly, it is possible to suppress lead sulfate accumulation. A Na content of 0.3 mol / L or less can maintain a low amount of lead sulfate accumulation and suppress a decrease in discharge performance. On the other hand, from the viewpoint of ensuring charge recovery from an overdischarge state and resistance to permeation short circuits, the Na content is preferably 0.02 mol / L or more, and more preferably 0.03 mol / L or more. According to one aspect of the present invention, the provision of the first rib can suppress permeation short circuits even with a Na content as low as 0.02 mol / L. Therefore, from the viewpoint of suppressing lead sulfate accumulation and permeation short circuits and achieving excellent PSOC life performance, the Na content in the electrolyte is preferably 0.02 to 0.3 mol / L, and more preferably 0.03 to 0.3 mol / L.

[0028] The electrolyte may also contain, in addition to Na, other alkali metal ions such as Al and Li, or alkaline earth metal ions. Sulfate compounds of these metal ions have higher solubility than lead sulfate, and the presence of these metal ions in the electrolyte makes it difficult for lead ions to dissolve. This contributes to the prevention of permeation short circuits.

[0029] The content of Na or other metal ions in the electrolyte can be determined by disassembling a fully charged lead-acid battery, extracting the electrolyte, and performing inductively coupled plasma (ICP) emission spectrometry. More specifically, atomic absorption spectrometry is performed using an ICP emission spectrometer (Shimadzu Corporation, ICPS-8000), and the concentration of the metal ions is determined using a calibration curve.

[0030] The inter-electrode gap W is preferably −0.1 to +0.15 mm. By setting the inter-electrode gap W to 0.15 mm or less, the accumulation of lead sulfate due to compression can be suppressed. On the other hand, as the inter-electrode gap W is reduced and the compression is increased, the discharge characteristics deteriorate. Furthermore, it becomes difficult to insert the electrode plate assembly into the cell chamber. From the viewpoint of maintaining the discharge characteristics and facilitating the insertion of the electrode plate assembly into the cell chamber, the inter-electrode gap W is preferably −0.1 mm or more.

[0031] According to one aspect of the present invention, the electrolyte contains 0.03 to 0.3 mol / L of Na, the inter-electrode gap W is −0.1 to +0.15 mm, and a first rib is provided on the negative electrode plate side, thereby significantly suppressing the accumulation of lead sulfate and realizing a lead-acid battery with excellent charge-discharge characteristics.

[0032] The separator has a first rib provided on the negative plate side. The first rib prevents the separator from coming into close contact with the negative plate. The first rib improves the diffusibility of the electrolyte near the negative plate, thereby preventing a decrease in the specific gravity of the electrolyte near the negative plate during discharge. Furthermore, the first rib prevents an increase in the specific gravity of the electrolyte near the negative plate during charge. This improves charging efficiency. Furthermore, in combination with the effect of compressing the plate assembly, this synergistically prevents the accumulation of lead sulfate, improving PSOC life performance.

[0033] The separator may further include a second rib provided on the positive electrode plate side. The second rib prevents the separator from coming into close contact with the positive electrode plate. The second rib improves the diffusion of the electrolyte near the positive electrode plate and suppresses oxidation degradation of the separator, thereby further improving the PSOC life performance.

[0034] The separator may be bag-shaped. When a bag-shaped separator is used, the electrolyte tends to stagnate. However, providing a first rib and a second rib increases the diffusibility of the electrolyte within the separator, further improving PSOC life performance. Because water is generated at the positive electrode during discharge, the change in the specific gravity of the electrolyte is greater there than near the negative electrode plate. However, when a bag-shaped separator houses a positive electrode plate, the diffusibility of the electrolyte near the positive electrode plate is increased, making it easier to suppress stratification of the electrolyte. On the other hand, when a bag-shaped separator houses a negative electrode plate, it makes it easier to suppress short circuits due to expansion of the positive electrode grid. Furthermore, forming a first rib within the bag increases the diffusibility of the electrolyte near the negative electrode plate, making it easier to suppress stratification.

[0035] Furthermore, the negative electrode plate preferably includes a negative electrode material, and the negative electrode material may include conductive carbon particles. Adding carbon to the electrode material suppresses lead sulfate accumulation and improves PSOC life performance. On the other hand, if the carbon particles include first carbon particles having a particle diameter of less than 32 μm and the first carbon particles include second carbon particles having a particle diameter smaller than the average pore diameter of the separator, the carbon particles that have leaked into the electrolyte may clog the pores of the separator, resulting in a decrease in battery performance (e.g., low-temperature high-rate performance). However, by providing a first rib on the negative electrode plate side, the pores of the separator are less likely to be clogged by the carbon particles, thereby suppressing performance degradation. The content of the first carbon particles in the negative electrode material is preferably 0.2% by mass or more and 2% by mass or less.

[0036] The lead-acid battery may include a fiber mat interposed between the positive and negative electrode plates. When the fiber mat is provided, the electrode plates are compressed by the fiber mat, reducing the amount of electrolyte around the electrode plates and reducing diffusibility. However, by providing a first rib at least on the negative electrode plate side of the separator, even when the fiber mat is provided, the electrolyte can be retained near the negative electrode plate and the diffusibility of the electrolyte can be improved.

[0037] In this specification, the fully charged state of a lead-acid battery refers to a state in which, for a flooded battery, the battery is charged in a water tank at 25°C at a constant current of 0.2 CA until a voltage of 2.5 V / cell is reached, followed by a further constant current charge of 0.2 CA for 2 hours. For a valve-regulated battery, the fully charged state refers to a state in which the battery is charged in an air tank at 25°C at a constant current and constant voltage of 0.2 CA to a voltage of 2.23 V / cell, and charging is terminated when the charging current during constant voltage charging drops to 1 mCA or less. Note that, in this specification, 1 CA is the current value (A) that is the same as the nominal capacity (Ah) of the battery. For example, for a battery with a nominal capacity of 30 Ah, 1 CA is 30 A, and 1 mCA is 30 mA.

[0038] Hereinafter, the lead-acid battery according to the embodiment of the present invention will be described in detail for each of its main components, but the present invention is not limited to the following embodiment.

[0039] (Separator) The separator includes a base portion made of a microporous membrane and a rib protruding from one main surface of the base portion. More preferably, the separator may further include a rib protruding from the other main surface of the base portion. The rib protruding from one main surface of the base portion is arranged so as to be located on the negative electrode plate side. This rib located on the negative electrode plate side is referred to as the first rib. The rib protruding from the other main surface of the base portion is arranged on the positive electrode plate side (i.e., facing the positive electrode plate). This rib located on the positive electrode plate side is referred to as the second rib. The first rib can increase the diffusibility of the electrolyte near the negative electrode plate, thereby further improving PSOC life performance and suppressing permeation short circuits.

[0040] The separator is formed of a polymer material (but different from fibers). At least the base portion is a porous sheet and can also be called a porous film. The average pore size of the base portion may be considered the average pore size of the separator. The separator may contain a filler (e.g., a particulate filler such as silica and / or a fibrous filler) dispersed in a matrix formed of a polymer material. The separator is preferably made of an acid-resistant polymer material. Such a polymer material is preferably a polyolefin such as polyethylene or polypropylene.

[0041] The average pore diameter of the base portion of the separator is, for example, 0.01 μm or more and 0.5 μm or less, and preferably 0.03 μm or more and 0.3 μm or less. When the average pore diameter is in this range, it is advantageous because low electrical resistance and excellent short-circuit resistance can be achieved at the same time.

[0042] The average pore diameter of the separator can be determined by mercury intrusion porosimetry. More specifically, the separator is placed in a measurement vessel, evacuated, and then pressure is applied to fill it with mercury. The pore distribution is determined from the relationship between the pressure and the volume of mercury forced into the separator, and the average pore diameter is determined from this pore distribution. An automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation is used to measure the average pore diameter.

[0043] The average thickness of the base portion is, for example, 100 μm or more and 300 μm or less, and preferably 150 μm or more and 250 μm or less. When the average thickness of the base portion is in this range, it is easy to ensure the height of the first rib and, if necessary, the second rib while ensuring high capacity. The average thickness of the base portion is determined by measuring the thickness of the base portion at five arbitrarily selected points in a cross-sectional photograph of the separator and averaging the measured values.

[0044] The first rib is formed on the surface of the separator facing the negative electrode plate. The height of the first rib is, for example, 0.05 mm or more, preferably 0.07 mm or more. When the height of the first rib is within this range, the electrolyte solution is more easily diffused. From the viewpoint of ensuring high capacity, the height of the first rib is, for example, 0.40 mm or less, preferably 0.20 mm or less. These lower and upper limits can be combined arbitrarily.

[0045] Unless otherwise specified, the height of the first rib refers to the maximum height of the first rib present in the region of the negative electrode plate facing the region where the negative electrode material is present. The height of each first rib is the distance from one main surface of the base to the top of the first rib. If the main surface of the base is not flat, the height of the first rib is defined as the distance from the highest point on one main surface of the base to the highest point of the top of the first rib at a predetermined position on the first rib when the separator is placed flat with the first rib side facing up.

[0046] The pattern of the first ribs on one main surface of the base portion is not particularly limited, and the first ribs may be formed randomly, or in a striped, curved, or lattice pattern. From the viewpoint of facilitating the diffusion of the electrolyte, it is preferable to form a plurality of first ribs arranged in a striped pattern on one main surface of the base portion. The orientation of the striped first ribs is not particularly limited, and, for example, the plurality of first ribs may be formed along the height direction or width direction of the negative electrode plate. Since the specific gravity of the electrolyte is likely to differ between the top and bottom of the electrode plate, it is preferable to form the plurality of first ribs in a striped pattern along the height direction of the negative electrode plate from the viewpoint of further enhancing the diffusibility of the electrolyte.

[0047] The negative and positive electrode plates usually have a tab at one end for extracting current from the electrode assembly. The vertical direction of the negative and positive electrode plates with the tab facing up is referred to as the height direction of the negative and positive electrode plates. The width direction of the negative and positive electrode plates is the direction perpendicular to the height direction and across the main surfaces of the negative and positive electrode plates.

[0048] The pitch of the striped or lattice-shaped first ribs is, for example, 0.3 mm to 10 mm, preferably 0.5 mm to 5 mm. When the separator includes a region where the first ribs are formed at a pitch in this range, the effect of improving the diffusion of the electrolyte near the negative electrode plate is easily obtained. In the separator, the first ribs are preferably formed at such a pitch in the region facing the negative electrode plate. For example, it is preferable that the first ribs are formed at such a pitch over 70% or more of the area of ​​the region facing the negative electrode plate. In regions not facing the negative electrode plate, such as the end of the separator, first ribs may or may not be formed, and multiple first ribs may be formed densely (for example, at an average pitch of 0.5 mm to 5 mm).

[0049] The pitch of the first ribs is the distance between the tops of adjacent first ribs (more specifically, the distance between the centers of adjacent first ribs in a direction across the first ribs). The average pitch of the first ribs is determined by averaging the pitches of the first ribs measured at 10 arbitrarily selected locations. If the first ribs are densely formed in an area that does not face the negative electrode plate, the average pitch can be calculated excluding this area. The average pitch of the first ribs in the area that does not face the negative electrode plate can be calculated in the same manner as described above for this area.

[0050] The second rib is formed on the surface of the separator facing the positive electrode plate. The height of the second rib is, for example, 0.3 mm or more, preferably 0.4 mm or more. When the height of the second rib is within this range, oxidation degradation of the separator is easily suppressed. From the viewpoint of ensuring high capacity, the height of the second rib may be, for example, 1.0 mm or less, or 0.7 mm or less. These lower and upper limits can be arbitrarily combined. Unless otherwise specified, the height of the second rib refers to the maximum height of the second rib present in the region of the positive electrode plate facing the region where the positive electrode material is present. The maximum height of the second rib is determined in the same manner as for the first rib. The height of each second rib is the distance from one main surface of the base portion to the top of the second rib.

[0051] The pattern and orientation of the second ribs are not particularly limited and may be selected from those described for the first ribs, for example. The pitch of the striped or lattice-shaped second ribs is, for example, 1 mm to 15 mm, preferably 5 mm to 10 mm. When the separator includes a region in which the second ribs are formed at a pitch within this range, the effect of suppressing oxidative degradation of the separator is further enhanced. In the separator, the second ribs are preferably formed at such a pitch in the region facing the positive electrode plate. For example, the second ribs are preferably formed at such a pitch over 70% or more of the area of ​​the region facing the positive electrode plate. In regions not facing the positive electrode plate, such as the ends of the separator, second ribs may or may not be formed, and multiple second ribs may be formed densely (for example, with an average pitch of 0.5 mm to 5 mm). The pitch of the second ribs refers to the distance between the tops of adjacent second ribs (more specifically, the distance between the centers of adjacent second ribs in a direction across the second ribs). The average pitch of the second ribs can be calculated based on the average pitch of the first ribs.

[0052] A sheet-like separator may be sandwiched between the negative electrode plate and the positive electrode plate, or the negative electrode plate or the positive electrode plate may be housed in a bag-like separator, thereby interposing the separator between the negative electrode plate and the positive electrode plate. When a bag-like separator is used, the electrolyte is less likely to diffuse, but the provision of a first rib and a second rib improves the diffusibility. When the negative electrode plate is housed in a bag-like separator, the first rib makes it easier to increase the diffusibility of the electrolyte near the negative electrode plate, and can prevent short circuits due to separator tearing even if the positive electrode current collector stretches. When the positive electrode plate is housed in a bag-like separator, stratification of the electrolyte is more easily suppressed.

[0053] The separator can be obtained, for example, by extruding a resin composition containing a pore-forming agent (e.g., a solid pore-forming agent such as a polymer powder and / or a liquid pore-forming agent such as an oil) and a polymer material into a sheet, and then removing the pore-forming agent to form pores in the matrix of the polymer material. The ribs may be formed, for example, during extrusion molding, or by pressing the sheet with a roller having grooves corresponding to the ribs after molding or after removing the pore-forming agent. When a filler is used, it is preferably added to the resin composition.

[0054] (Electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte may be gelled as needed. The electrolyte may contain additives used in lead-acid batteries as needed. In this embodiment, the electrolyte contains Na at a concentration of 0.03 to 0.3 mol / L. The specific gravity of the electrolyte at 20°C in a lead-acid battery in a fully charged state after formation is, for example, 1.10 g / cm 3 1.35g / cm or more 3 The following is the result.

[0055] (Positive Electrode Plate) Positive electrode plates for lead-acid batteries are classified into paste type and clad type. Paste type positive electrode plates include a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. In the paste type positive electrode plate, the positive electrode material is the positive electrode plate excluding the positive electrode current collector. The positive electrode current collector may be formed in the same manner as the negative electrode current collector, and can be formed by casting lead or a lead alloy or processing a lead or lead alloy sheet.

[0056] A clad positive electrode plate includes multiple porous tubes, a metal core inserted into each tube, a positive electrode material filled into the tube with the metal core inserted, and a connecting seat connecting the multiple tubes. In a clad positive electrode plate, the positive electrode material is the positive electrode plate excluding the tubes, the metal core, and the connecting seat.

[0057] The lead alloy used for the positive electrode current collector is preferably a Pb—Ca alloy or a Pb—Ca—Sn alloy in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, or may have multiple alloy layers. The core metal is preferably made of a Pb—Ca alloy or a Pb—Sb alloy.

[0058] The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that generates capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed.

[0059] Unformed paste-type positive plates are obtained by filling a positive electrode current collector with positive electrode paste, aging it, and drying it, similar to the case of negative plates. The unformed positive plate is then formed. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. Unformed clad-type positive plates are formed by mixing additives with lead powder or lead powder slurry into a tube with a core metal inserted, filling the mixture, and connecting multiple tubes with a connecting rod.

[0060] (Negative Electrode Plate) The negative electrode plate of a lead-acid battery contains a negative electrode material. Typically, the negative electrode plate of a lead-acid battery is composed of a negative electrode current collector and a negative electrode material. The negative electrode material is the negative electrode plate excluding the negative electrode current collector. The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of processing methods include expanding and punching. Using a negative electrode grid as the negative electrode current collector is preferable because it is easy to support the negative electrode material.

[0061] The lead alloy used for the negative electrode current collector may be any of a Pb—Sb alloy, a Pb—Ca alloy, and a Pb—Ca—Sn alloy. These lead or lead alloys may further contain at least one element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element.

[0062] The negative electrode material contains a negative electrode active material (lead or lead sulfate) that exhibits capacity through an oxidation-reduction reaction, and may also contain a shrinkage inhibitor, a carbonaceous material such as carbon black, barium sulfate, etc., and may also contain other additives as necessary.

[0063] The negative electrode active material in the charged state is sponge lead, but the unformed negative electrode plate is usually made using lead powder.

[0064] The negative electrode material can contain carbon particles as an additive. Carbon particles are usually conductive. Examples of carbon particles include carbon black, graphite, hard carbon, and soft carbon. Examples of carbon black include acetylene black, furnace black, channel black, and lamp black. The graphite may be any carbon material containing a graphite-type crystalline structure, and may be either artificial graphite or natural graphite. The negative electrode material may contain one type of these carbon particles, or two or more types.

[0065] The carbon particles preferably include first carbon particles having a particle size of less than 32 μm, and the first carbon particles preferably include second carbon particles having a particle size smaller than the average pore size of the separator. The carbon particles included in the negative electrode material need only include the first carbon particles, and may include only the first carbon particles, or may include the first carbon particles and carbon particles (third carbon particles) having a particle size of 32 μm or more.

[0066] The second carbon particles preferably contain carbon black. Although the second carbon particles, such as carbon black, tend to leak into the electrolyte, the first rib prevents the pores of the separator from being blocked by the second carbon particles even if they leak into the electrolyte. Furthermore, when the first carbon particles contain the second carbon particles, such as carbon black, a more uniform conductive network is more easily formed in the negative electrode material.

[0067] The content of carbon particles in the negative electrode material is, for example, 0.2% by mass to 3.0% by mass, and preferably 0.3% by mass to 2.5% by mass, in which case the conductive network is likely to expand while maintaining high capacity.

[0068] The ratio of the first carbon particles to the carbon particles (total amount of carbon particles) contained in the negative electrode material is, for example, 10 mass% or more, and preferably 30 mass% or more. The ratio of the first carbon particles to the carbon particles (total amount of carbon particles) contained in the negative electrode material is 100 mass% or less, and may be 90 mass% or less. These lower and upper limits can be combined arbitrarily.

[0069] The content of the first carbon particles in the negative electrode material is preferably, for example, 0.2% by mass or more and 2% by mass or less. By combining a negative electrode plate including a negative electrode material containing the first carbon particles at such a content with a separator including a first rib, the diffusibility of the electrolyte near the negative electrode plate is increased, ensuring high PSOC life performance. When the content of the first carbon particles in the negative electrode material is 0.2% by mass or more, the second carbon particles contained in the first carbon particles tend to leak into the electrolyte during charge and discharge. However, the presence of the first rib prevents the leaked first carbon particles from clogging the separator pores. This prevents a decrease in battery performance, such as a decrease in low-temperature high-rate performance. Furthermore, by setting the content of the first carbon particles in the negative electrode material to 2% by mass or less, hardening of the negative electrode paste can be prevented, thereby preventing a decrease in the coating and filling properties of the paste on the current collector. Furthermore, even under conditions where permeation short circuits are likely to occur due to a longer life, the high diffusibility of the electrolyte reduces stratification, thereby preventing the occurrence of permeation short circuits. From the viewpoint of achieving a significant effect of the first rib in suppressing a decrease in low-temperature high-rate performance, the content of the first carbon particles in the negative electrode material is preferably 0.3% by mass or more and 2% by mass or less. Furthermore, from the viewpoint of keeping the amount of liquid loss during charging low, it is also preferable that the content of the first carbon particles in the negative electrode material be 1% by mass or less (e.g., 0.2% by mass or more and 1% by mass or less, or 0.3% by mass or more and 1% by mass or less).

[0070] The average particle diameter a1 of the second carbon particles (e.g., carbon black) contained in the first carbon particles is preferably 100 nm or less, more preferably 60 nm or less, and although there is no particular lower limit, it is preferably 10 nm or more and may be 20 nm or more. These upper and lower limit values ​​can be arbitrarily combined. When the average particle diameter of the first carbon particles is within this range, the first carbon particles tend to flow into the electrolyte solution and clog the pores of the separator. However, by using a separator having a first rib, it is possible to prevent the pores of the separator from being clogged and to prevent a decrease in low-temperature high-rate performance.

[0071] The third carbon particles preferably contain carbon particles other than carbon black among the above carbon particles, and particularly preferably contain graphite.

[0072] The ratio R (= a1 / a2) of the average particle size (a1) of the second carbon particles to the average pore size (a2) of the separator is preferably 0.8 or less, and more preferably 0.5 or less. When the ratio R is in this range, the second carbon particles tend to clog the pores of the separator, but the first rib of the separator ensures the diffusibility of the electrolyte near the negative electrode plate and prevents the pores of the separator from being clogged. This ensures high PSOC life performance and further prevents a decrease in low-temperature high-rate performance.

[0073] The contents of the carbon particles and the first carbon particles contained in the negative electrode material, as well as the average particle size of the second carbon particles and the proportion of the second carbon particles, can be determined as follows.

[0074] A fully charged lead-acid battery was disassembled using a pre-formed chemical process. The negative electrode plate was washed with water and dried to remove sulfuric acid, followed by vacuum drying (drying under a pressure lower than atmospheric pressure). Next, the electrode material was extracted from the negative electrode plate and pulverized. 30 mL of a 60% by weight aqueous nitric acid solution was added to 5 g of the pulverized sample and heated to 70°C to dissolve the lead as lead nitrate. To this mixture, 10 g of disodium ethylenediaminetetraacetate, 30 mL of a 28% by weight aqueous ammonia, and 100 mL of water were added, and heating was continued to dissolve the soluble components. The sample recovered by filtration was then passed through a 500 μm sieve to remove large components such as reinforcing materials, and the components that passed through the sieve were collected as carbon particles.

[0075] When the recovered carbon particles are wet sieved using a sieve with a mesh size of 32 μm, any particles that do not pass through the sieve and remain on the sieve are designated as third carbon particles, and any particles that pass through the sieve are designated as first carbon particles. For wet sieving, JIS Z8815:1994 can be referenced.

[0076] Specifically, the carbon particles are placed on a sieve with 32 μm mesh size, and the sieve is gently shaken for 5 minutes while spraying ion-exchanged water to sift through. The third carbon particles remaining on the sieve are recovered from the sieve by pouring ion-exchanged water over them, and then separated from the ion-exchanged water by filtration. The first carbon particles that passed through the sieve are recovered by filtration using a nitrocellulose membrane filter (0.1 μm mesh size). The recovered first carbon particles and third carbon particles are each dried at a temperature of 110°C for 2 hours. The 32 μm mesh size sieve used is one equipped with a sieve mesh with a nominal mesh size of 32 μm, as specified in JIS Z 8801-1:2006.

[0077] The first carbon particles that have passed through the sieve contain many second carbon particles having small primary particle diameters. The average particle diameter of these primary particles corresponds to the average particle diameter a1 of the second carbon particles, as described below. Since the particle diameter of these second carbon particles contained in the first carbon particles is smaller than the average pore diameter a2 of the separator, they flow into the electrolyte and cause blockage of the pores of the separator.

[0078] The content of the first carbon particles in the negative electrode material is determined by measuring the mass of the first carbon particles separated by the above procedure and calculating the proportion (mass %) of this mass in 5 g of a pulverized sample. The content (mass %) of carbon particles in the negative electrode material is determined by adding the proportion of the third carbon particles determined in the same manner as for the first carbon particles and the proportion of the first carbon particles. The average particle diameter a1 of the second carbon particles is determined by randomly selecting 100 primary particles from an electron microscope photograph of the first carbon particles that have a primary particle diameter smaller than the average pore diameter d2 of the separator, measuring the maximum diameter (major axis diameter) of each primary particle, and calculating the average.

[0079] The ratio of the second carbon particles contained in the first carbon particles can be determined from a scanning electron microscope (SEM) photograph of the first carbon particles separated above as follows. First, an arbitrary region measuring 100 μm in length and 100 μm in width is selected from the SEM photograph. Of the carbon particles contained in this region and with a clear outer periphery, particles with a primary particle diameter smaller than the average pore diameter a2 of the separator are determined as second carbon particles, and particles with a primary particle diameter equal to or greater than the average pore diameter a2 are determined as first carbon particles other than the second carbon particles. Then, for each carbon particle, the area of ​​the region surrounded by the outer periphery of the particle is calculated, and the particle volume is calculated from this area and the primary particle diameter of the particle. Then, the total volume of the second carbon particles and the total volume of the first carbon particles other than the second carbon particles are determined, and the ratio (volume %) of the total volume of the second carbon particles to the sum of both total volumes is calculated.

[0080] The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying the paste to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is produced by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed, and kneading them. In the aging process, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature and at a high humidity.

[0081] The formation can be carried out by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery jar of a lead-acid battery and then charging the electrode plate assembly. However, the formation can also be carried out before assembling the lead-acid battery or the electrode plate assembly. The formation produces spongy lead.

[0082] (Fiber Mat) The lead-acid battery may further include a fiber mat interposed between the positive electrode plate and the negative electrode plate. When the fiber mat is disposed, the electrode plate is compressed by the fiber mat, making it difficult to retain the electrolyte around the electrode plate. In the above aspect of the present invention, the first rib is provided on the separator, making it easier to retain the electrolyte near the negative electrode plate and ensuring high diffusibility of the electrolyte.

[0083] Unlike separators, fiber mats are composed of a sheet-like fiber assembly. Examples of such fiber assembly include a sheet of entangled fibers that are insoluble in the electrolyte. Examples of such sheets include nonwoven fabrics, woven fabrics, and knitted fabrics.

[0084] Examples of fibers that can be used include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers such as polyethylene terephthalate fibers, etc.), pulp fibers, etc. Among the polymer fibers, polyolefin fibers are preferred.

[0085] The fiber mat may contain components other than fibers, such as an acid-resistant inorganic powder and a polymer as a binder. Examples of inorganic powder that can be used include silica powder, glass powder, and diatomaceous earth. However, the fiber mat is primarily composed of fibers. For example, 60% by mass or more of the fiber mat is made up of fibers.

[0086] The fiber mat may be disposed between the negative electrode plate and the positive electrode plate. Because a separator is also disposed between the negative electrode plate and the positive electrode plate, the fiber mat may be disposed between the negative electrode plate and the positive electrode plate, for example, between the negative electrode plate and the separator and / or between the separator and the positive electrode plate. From the viewpoint of suppressing stratification of the electrolyte, the fiber mat is preferably disposed so as to be in contact with the negative electrode plate. Furthermore, from the viewpoint of suppressing softening and shedding of the positive electrode material, the fiber mat is preferably disposed so as to be in contact with the positive electrode plate. To enhance the effect of suppressing softening and shedding, the fiber mat is preferably disposed in a state where it is pressed against the positive electrode plate. However, in this case, the electrolyte near the negative electrode plate is likely to be insufficient. In this embodiment, the first rib is provided on the surface of the separator facing the negative electrode plate, so that the electrolyte can be secured near the negative electrode plate even when the fiber mat is disposed on the positive electrode plate side.

[0087] FIG. 1 shows the external appearance of an example of a lead-acid battery according to an embodiment of the present invention. The lead-acid battery 1 includes a battery case 12 that contains a plate pack 11 and an electrolyte (not shown). The battery case 12 is divided into multiple cell chambers 14 by partition walls 13. Each cell chamber 14 contains one plate pack 11. The opening of the battery case 12 is closed by a lid 15 that includes 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 rehydrating, the vent plug 18 is removed and rehydration solution is added. The vent plug 18 may have the function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0088] Each electrode plate group 11 is formed by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 interposed therebetween. Here, a bag-shaped separator 4 is shown housing the negative electrode plates 2, but the shape of the separator is not particularly limited. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects a plurality of negative electrode plates 2 in parallel is connected to a through-connector 8, and a positive electrode shelf 5 that connects a plurality of positive electrode plates 3 in parallel is connected to a positive electrode pole 7. The positive electrode pole 7 is connected to a positive electrode terminal 17 outside the lid 15. In a cell chamber 14 located at the other end of the battery case 12, a negative electrode pole 9 is connected to the negative electrode shelf 6, and a through-connector 8 is connected to the positive electrode shelf 5. The negative electrode pole 9 is connected to a negative electrode terminal 16 outside the lid 15. Each through-connector 8 passes through a through-hole provided in the partition wall 13 to connect the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0089] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0090] Lead acid battery A1 (1) Preparation of negative electrode plate: Lead powder, water, dilute sulfuric acid, carbon black, and an organic shrinkage preventer were mixed to obtain a negative electrode paste. The negative electrode paste was filled into the mesh portion of an expanded lattice made of a Pb—Ca—Sn alloy as a negative electrode current collector, and the resulting mixture was aged and dried to obtain an unformed negative electrode plate. Sodium lignin sulfonate was used as the organic shrinkage preventer. The amounts of carbon black and the organic shrinkage preventer added were adjusted to 0.3% by mass and 0.2% by mass, respectively, based on 100% by mass of the negative electrode material.

[0091] (2) Preparation of Positive Electrode Plate: Lead powder, water, and sulfuric acid were mixed to prepare a positive electrode paste. The positive electrode paste was filled into the mesh of a Pb—Ca—Sn alloy expanded lattice as a positive electrode current collector, and the resulting mixture was aged and dried to obtain an unformed positive electrode plate.

[0092] (3) Preparation of Lead-Acid Battery: Each unformed negative electrode plate was housed in a pouch-shaped separator made of a polyethylene microporous membrane, and seven unformed negative electrode plates and six unformed positive electrode plates per cell formed an electrode plate assembly. The separator had multiple striped second ribs on the outside of the pouch. The separator used did not have a first rib on the inside of the pouch. The multiple second ribs were formed along the height direction of the positive electrode plate, each with a height of 0.4 mm, and the pitch of the second ribs in the region facing the positive electrode plate was 10 mm. The average thickness of the base portion of the separator was 200 μm. The average pore diameter of the separator was 0.1 μm.

[0093] The electrode assembly was inserted into a polypropylene container, an electrolyte was poured into the container, and chemical formation was performed inside the container to assemble a flooded lead-acid battery A1 with a nominal voltage of 2 V and a nominal capacity of 30 Ah (5-hour rate). The electrolyte used was an aqueous solution containing sulfuric acid with a specific gravity of 1.28 at 20°C. The electrode gap W was determined to be 0.2 mm.

[0094] For a fully charged lead-acid battery manufactured using a chemical process, the average particle diameter a1 of the second carbon particles (carbon black) contained in the negative electrode material and the average pore diameter a2 of the separator were determined using the procedures described above and found to be 50 nm and 0.1 μm, respectively, with a ratio R = a1 / a2 of 0.5. The content of the first carbon particles was approximately the same as the amount of carbon black added when preparing the negative electrode material. The average pore diameter of the separator was also approximately the same as the average pore diameter of the separator before assembly into the battery.

[0095] <<Lead-acid batteries A2 to A26>> As the electrolyte, the above-mentioned aqueous solution containing sulfuric acid is dissolved in sodium sulfate (Na ２ SO ４) was added, and five types of lead-acid batteries were fabricated with different Na contents of 0.02 mol / L, 0.03 mol / L, 0.1 mol / L, 0.3 mol / L, and 0.35 mol / L. In addition, when inserting the electrode plate assembly into the battery case, the height of the ribs provided on the battery case was adjusted, and five types of lead-acid batteries were fabricated with different inter-electrode gaps W of 0.2 mm, 0.15 mm, 0.1 mm, 0 mm, and −0.1 mm.

[0096] Other than this, 25 types of lead-acid batteries A2 to A26 were produced in the same manner as lead-acid battery A1, but with different combinations of the inter-electrode gap W and the Na content in the electrolyte. Table 1 shows the inter-electrode gap W and the Na content in the electrolyte of lead-acid batteries A1 to A26.

[0097] Lead-acid battery B1: A separator having a first rib on the inside of the bag was used. The separator had a plurality of striped first ribs on the inside of the bag, each extending along the height of the negative electrode plate. The height of the first ribs was 0.1 mm, and the pitch of the first ribs in the region facing the negative electrode plate was 1 mm. The height and pitch of the second ribs and the average thickness of the separator base were the same as those of lead-acid battery A1.

[0098] A lead-acid battery B1 was assembled in the same manner as the lead-acid battery A1, except that a separator provided with ribs on both the positive and negative electrode plate sides was used.

[0099] <<Lead-acid batteries B2 to B26>> Using the same method as for the lead-acid batteries A2 to A26, 25 types of lead-acid batteries were produced using different combinations of the electrode gap W and the Na content in the electrolyte compared to the lead-acid battery B1, to produce lead-acid batteries B2 to B26. Table 2 shows the electrode gap W and the Na content in the electrolyte for the lead-acid batteries B1 to B26.

[0100] [Evaluation 1: Amount of Lead Sulfate Accumulation] In accordance with SBA S 0101:2014, the lead-acid battery was charged and discharged under idle-stop conditions. Specifically, at 25°C, the following cycles (a) to (c) were repeated until the end-of-discharge voltage fell to 1.2 V or less per cell, and the number of cycles was calculated. Note that during charging and discharging, a 40- to 48-hour pause was applied every 3,600 cycles. (a) Discharge 1: Discharge at a current of 32 A for 59 seconds. (b) Discharge 2: Discharge at a current of 300 A for 1 second. (c) Charge: Charge at a limited current of 100 A and a voltage of 2.33 V per cell for 60 seconds.

[0101] After the charge-discharge test, one negative electrode plate (excluding the end plate) was removed from the lead-acid battery, washed with water, dried, and then the entire electrode material was collected and pulverized. The sulfur content of the pulverized sample was measured using a sulfur analyzer to determine the amount of lead sulfate accumulation. The amount of lead sulfate accumulation per cycle was calculated by dividing the amount by the number of PSOC life cycles.

[0102] The amount of lead sulfate accumulated per cycle was expressed as a relative ratio, with the amount of lead sulfate accumulated in lead-acid battery A1 being set at 100, and evaluated. Tables 1 and 2 show the evaluation results.

[0103] [Evaluation 2: Discharge Performance] The RC (Reserve Capacity) discharge capacity was measured in accordance with JIS D 5301. The measured discharge capacity was expressed as a relative ratio, with the discharge capacity of lead-acid battery A1 set to 100, and evaluated. Tables 1 and 2 show the evaluation results. A higher evaluation value indicates better discharge performance.

[0104] As can be seen from Tables 1 and 2, the amount of lead sulfate accumulation increases and the discharge capacity tends to decrease as the Na content increases. In lead-acid batteries A2 to A26, which do not have a first rib on the negative electrode side, narrowing the inter-electrode gap W and compressing the electrode plate assembly, as shown in Table 1, can suppress the increase in the amount of lead sulfate accumulation. However, in lead-acid batteries A2 to A26, the effect of suppressing lead sulfate accumulation is insufficient. When the Na content is high, at 0.3 mol / L or more, it is difficult to reduce the amount of lead sulfate accumulation compared to lead-acid battery A1, which does not contain Na, even by controlling the inter-electrode gap W. Furthermore, compressing the electrode plate assembly significantly reduces the discharge capacity.

[0105] In contrast, in the lead-acid batteries B2 to B26, which have the first rib on the negative electrode side, the increase in the amount of accumulated lead sulfate is significantly suppressed by narrowing the inter-electrode gap W and compressing the electrode plate pack, as shown in Table 2. This makes it possible to reduce the amount of accumulated lead sulfate to nearly half that of the lead-acid battery A1, even while containing Na in the electrolyte. In addition, the decrease in discharge capacity due to compression of the electrode plate pack is also suppressed.

[0106] In addition, the separators were removed after the charge-discharge test and visually inspected for the presence or absence of penetration marks. Penetration marks were confirmed in lead-acid batteries A1, A2, A7, A12, A17, and A22, which had a Na content of 0.02 mol / L or less and did not have a first rib on the negative electrode side. In contrast, no penetration marks were observed in the lead-acid batteries with a first rib on the negative electrode side, except for lead-acid battery B1, whose electrolyte did not contain Na. This is thought to be because the provision of the first rib on the negative electrode side improved the diffusion of the electrolyte near the negative electrode plate.

[0107] When the Na content was 0.02 to 0.3 mol / L and the electrode gap W was −0.1 to 0.15 mm (lead-acid batteries B7 to B10, B12 to B15, B17 to B20, and B22 to B25), the discharge capacity was maintained at 97% or more of that of lead-acid battery A1, while the amount of lead sulfate accumulation was reduced to 95% or less of that of lead-acid battery A1. No penetration marks were observed. However, in order to further suppress penetration short circuits, a Na content of 0.03 mol / L or more is preferred.

[0108] Therefore, lead-acid batteries B8 to B10, B13 to B15, B18 to B20, and B23 to B25, each having a Na content of 0.03 to 0.3 mol / L and an inter-electrode gap W of −0.1 to 0.15 mm, are excellent in discharge performance, suppress the accumulation of lead sulfate, and also have excellent resistance to penetration short circuits.

[0109]

[0110]

[0111] A lead-acid battery according to one aspect of the present invention is applicable to valve-regulated and flooded lead-acid batteries, and can be suitably used as a power source for starting automobiles, motorcycles, and the like.

[0112] 1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 5: Positive electrode shelf 6: Negative electrode shelf 7: Positive electrode column 8: Through-connector 9: Negative electrode column 11: Plate group 12: Battery case 13: Partition wall 14: Cell chamber 15: Lid 16: Negative electrode terminal 17: Positive electrode terminal 18: Vent plug

Claims

DEPCT641. A lead-acid battery consists of: an electrode group with multiple positive and negative electrode plates separated by a separator; a cell compartment containing the electrode group; and an electrolyte solution containing 0.03 to 0.3 mol / L of Na. When the first end plate, which is one of the multiple positive electrode plates or one of the multiple negative electrode plates located at one end of the electrode group, is placed close to one inner wall of the cell compartment with the inner walls facing each other, and the second end plate, which is one of the multiple positive electrode plates or one of the multiple negative electrode plates located at the other end of the electrode group, is placed close to the other inner wall, the gap between the electrodes W will be -0.1 to +0.15mm is obtained from the following equation: W={(L–d1) / N}-d2, where the distance between the end plates, which is the maximum separation distance between the surface of the first end plate facing the inner wall and the surface of the second end plate facing the inner wall, is equal to L; the total thickness of the positive and negative electrode plates in the electrode group is equal to d1; and the number of gaps between electrodes, which is the number of regions where each positive and each negative electrode plate faces each other in each cell region, is equal to g. The total thickness of one separator placed between the positive and negative electrode plates is equal to d2, and the separator has a first ridge on the negative electrode side.

2. Lead-acid battery under claim 1, where the separator has a second ridge on the positive electrode side.

3. Lead-acid battery under claim 1 or 2, where the separator is bag-shaped.

4. Lead-acid battery under claim 3, where the separator holds the negative electrode. 5.A lead-acid battery under Reputation 3 where the separator stores the positive electrode plate.

6. A lead-acid battery under Reputation 1 through 5 where the negative electrode plate contains a portion of anionic material, the anionic material contains conductive carbon particles, the carbon particles include primary carbon particles smaller than 32 micrometers, and the primary carbon particles include secondary carbon particles smaller than the average pore size of the separator.

7. A lead-acid battery under Reputation 6 where the amount of primary carbon particles in the anionic material is 0.2% by mass or more and 2% by mass or less.