Lead-acid battery

Abstract

DEPCT64 A lead-acid battery consists of a positive electrode plate, a negative electrode plate, and a separator. The separator, situated between the positive and negative electrode plates and the electrolyte solution, will have a portion... At least the ridges on the negative electrode plate will have a portion of the electrode material. The negative and negatively electrode material will contain carbon particles; these carbon particles will include one carbon particle. These have particle sizes smaller than 32 micrometers, and the first carbon particle includes a second carbon particle which has... The particle size is smaller than the pore size of the separator, on average the amount of carbon particles in the material. The negative electrode will be 0.2% by mass or more and 2% by mass or less. -----------------------------------------------------------

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 electrode plates, and an electrolyte. The negative electrode plate includes a current collector and a negative electrode material. The negative electrode material includes a negative electrode active material, a carbon material, and the like.

[0003] Patent Document 1 proposes adding 0.1 to 3 mass % of carbon black to the negative electrode active material. On the other hand, separators having ribs are sometimes used (Patent Document 2).

[0004] International Publication No. 2015 / 087749 Pamphlet Japanese Patent Application Laid-Open No. 2014-203678

[0005] 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 in charge-controlled vehicles and idle-stop (IS) vehicles. Therefore, lead-acid batteries are required to have excellent life performance in cycle tests under PSOC conditions (hereinafter referred to as PSOC life performance).

[0006] Adding carbon to the negative electrode material can suppress sulfation and improve PSOC life performance to some extent, but the carbon that leaks into the electrolyte can block the pores of the separator, resulting in a decrease in low-temperature high-rate performance.

[0007] One aspect of the present invention relates to a lead-acid battery comprising: a positive electrode plate; a negative electrode plate; a separator interposed between the positive electrode plate and the negative electrode plate; and an electrolyte; wherein the separator has a rib on at least the negative electrode plate side; the negative electrode plate includes a negative electrode material, and the negative electrode material includes carbon particles; 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 an average pore diameter of the separator; and the content of the first carbon particles in the negative electrode material is 0.2 mass % or more and 2 mass % or less.

[0008] In a lead-acid battery, excellent PSOC life performance can be ensured and degradation of low-temperature high-rate performance can be suppressed.

[0009] 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.

[0010] A lead-acid battery according to the present invention includes a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolyte. The separator includes a rib (first rib) on at least the negative electrode plate side. The negative electrode plate includes a negative electrode material, which includes carbon particles. 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 content of the first carbon particles in the negative electrode material is 0.2% by mass or more and 2% by mass or less.

[0011] It was found that when the negative electrode material contains first carbon particles, the PSOC life performance is improved to some extent, but the low-temperature high-rate performance (more specifically, the retention rate of low-temperature high-rate performance) is reduced. This is thought to be because when the first carbon particles contain second carbon particles whose particle diameter (primary particle diameter) is smaller than the average pore diameter of the separator, these second carbon particles flow into the electrolyte and clog the pores of the separator. Furthermore, in lead-acid batteries, sulfuric acid is released from the negative and positive electrode plates during charging, but if the diffusibility of the electrolyte near the negative electrode plate is low, sulfuric acid remains near the negative electrode plate, resulting in a high sulfuric acid concentration.

[0012] According to the above aspects of the present invention, by providing a first rib on the negative electrode plate side of the separator, the diffusibility of the electrolyte near the negative electrode plate is improved, thereby reducing stratification of the electrolyte. This improved diffusibility can further improve PSOC life performance in addition to the effect of improving PSOC life performance due to the first carbon particles. Furthermore, even if the second carbon particles contained in the first carbon particles leak into the electrolyte, the provision of the first rib on the separator prevents the separator and the negative electrode plate from coming into close contact, thereby preventing the pores of the separator from being blocked by the second carbon particles. This can prevent a decrease in low-temperature high-rate performance (more specifically, the retention rate of low-temperature high-rate performance). Furthermore, by reducing stratification of the electrolyte even with a longer life, a decrease in the specific gravity of the upper part of the electrolyte is suppressed, and the occurrence of permeation short circuits can be suppressed even at the end of life. The first rib improves the diffusibility of the electrolyte near the negative electrode plate, which prevents sulfuric acid from accumulating near the negative electrode plate, thereby preventing an increase in the specific gravity of the electrolyte near the negative electrode plate and improving charging efficiency. Therefore, it is possible to prevent the loss of electrolyte due to charging.

[0013] When the content of the first carbon particles in the negative electrode material is 0.2 mass % or more (up to 2 mass %), the small-sized second carbon particles contained in the first carbon particles are likely to leak into the electrolyte during charging and discharging. However, according to the above aspect of the present invention, the separator including the first rib is used, so even if the second carbon particles contained in the first carbon particles leak out, the second carbon particles are prevented from blocking the pores of the separator. This makes it possible to suppress a decrease in low-temperature high-rate performance. Furthermore, the presence of the first rib increases the diffusibility of the electrolyte near the negative electrode plate, ensuring high PSOC life performance. Furthermore, by extending the life, stratification is reduced and permeation short circuits are suppressed, even under conditions where permeation short circuits are likely to occur, thereby extending the life.

[0014] The ratio R (= d1 / d2) of the average particle size d1 of the second carbon particles to the average pore size d2 of the separator is preferably 0.8 or less. When the ratio R is in this range, the second carbon particles tend to flow into the electrolyte and clog the pores of the separator. According to the above aspect of the present invention, the separator is provided with first ribs, so that even if the second carbon particles contained in the first carbon particles flow into the electrolyte, the action of the first ribs can prevent the pores of the separator from being clogged with the second carbon particles. Therefore, even when the ratio R is in the above range, a decrease in the retention rate of low-temperature high-rate performance can be more effectively prevented.

[0015] The average particle diameter d1 of the second carbon particles is, for example, 10 nm or more and 100 nm or less. When the second carbon particles contained in the first carbon particles have such an average particle diameter, the second carbon particles are likely to flow out of the negative electrode plate into the electrolyte. According to the above aspect of the present invention, since the separator is provided with the first rib, even if the second carbon particles flow out into the electrolyte, the action of the first rib can prevent the second carbon particles from blocking the pores of the separator. Therefore, a decrease in low-temperature high-rate performance can be more effectively prevented.

[0016] In the above aspect of the present invention, the second carbon particles preferably contain carbon black. Carbon black tends to leak from the negative electrode plate into the electrolyte. According to the above aspect of the present invention, the separator is provided with the first rib. Therefore, even if the carbon black leaks into the electrolyte, the action of the first rib can prevent the pores of the separator from being blocked by the carbon black. Therefore, deterioration of low-temperature high-rate performance can be more effectively prevented.

[0017] The separator preferably further includes a rib (second rib) on the positive electrode plate side, which can suppress oxidation degradation of the separator.

[0018] The separator may be bag-shaped. When a bag-shaped separator is used, the electrolyte tends to stagnate, but providing a first rib and a second rib increases the diffusibility of the electrolyte, further improving PSOC life performance. The effect of suppressing permeation short circuits is also further enhanced. When a bag-shaped separator houses a positive electrode plate, stratification of the electrolyte is easily suppressed. When a bag-shaped separator houses a negative electrode plate, forming a first rib inside the bag makes it easier to increase the diffusibility of the electrolyte within the bag. Furthermore, unlike a positive electrode current collector, a negative electrode current collector elongates less during charge and discharge. Therefore, when a negative electrode plate is housed in a bag-shaped separator, separator tearing due to the elongation of the current collector is suppressed, thereby suppressing short circuits.

[0019] The lead-acid battery may include a fiber mat interposed between the positive electrode plate and the negative electrode plate. When the fiber mat is provided, the electrode plate is compressed by the fiber mat, reducing the amount of electrolyte around the electrode plate. In the above aspect of the present invention, by providing a first rib at least on the negative electrode plate side of the separator, even when the fiber mat is provided, it is possible to retain the electrolyte near the negative electrode plate and improve the diffusibility of the electrolyte.

[0020] 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.

[0021] (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.

[0022] 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.

[0023] As the lead alloy used for the positive electrode current collector, a Pb—Ca-based alloy or a Pb—Ca—Sn-based alloy is preferred in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, or the number of alloy layers may be multiple. A Pb—Ca-based alloy or a Pb—Sb-based alloy is preferably used for the core metal. 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.

[0024] 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. Clad-type positive plates are formed by filling a tube with a core metal inserted with lead powder or lead powder slurry and connecting multiple tubes together.

[0025] (Negative Electrode Plate) The negative electrode plate of a lead-acid battery contains a negative electrode material. Typically, the negative electrode plate 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.

[0026] 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.

[0027] The negative electrode material contains carbon particles. The carbon particles are usually electrically conductive. The negative electrode material also contains a negative electrode active material (lead or lead sulfate) that exhibits capacity through an oxidation-reduction reaction. The negative electrode material may contain a shrinkage inhibitor, barium sulfate, etc., and may also contain other additives as needed.

[0028] The negative electrode active material in the charged state is sponge lead, but the unformed negative electrode plate is usually made using lead powder.

[0029] 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. 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.

[0030] The carbon particles include first carbon particles having a particle size of less than 32 μm, and the first carbon particles 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.

[0031] The second carbon particles preferably contain carbon black. The second carbon particles, such as carbon black, contained in the first carbon particles tend to leak into the electrolyte, but even if they do leak into the electrolyte, the first ribs prevent the separator pores from being blocked by the second carbon particles, such as carbon black. 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.

[0032] 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.

[0033] 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.

[0034] The content of the first carbon particles in the negative electrode material is 0.2% by mass or more and 2% by mass or less. By using a negative electrode plate including a negative electrode material with a content of the first carbon particles in this range in combination with a separator including a first rib, the diffusibility of the electrolyte near the negative electrode plate is increased, ensuring high PSOC life performance. Furthermore, when the content of the first carbon particles in the negative electrode material is 0.2% by mass or more (up to 2% by mass), the second carbon particles contained in the first carbon particles tend to leak into the electrolyte during charging and discharging. However, the presence of the first rib prevents the leaked second carbon particles from blocking the pores of the separator. This prevents 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 the deterioration of 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. As the content of the first carbon particles in the negative electrode material increases, the amount of liquid loss during charging tends to increase. However, even in such a case (for example, when the content is 1% by mass or more and 2% by mass or less), the amount of liquid loss can be reduced by using a separator including the first rib. 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 (for example, 0.2% by mass or more and 1% by mass or 0.3% by mass or more and 1% by mass or less).

[0035] The average particle diameter d1 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 second carbon particles is within this range, the second carbon particles contained in 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.

[0036] The ratio of the second carbon particles contained in the first carbon particles is preferably 60% by volume or more. When the ratio of the second carbon particles is in this range, higher PSOC life performance can be ensured and high low-temperature high-rate performance can be more easily ensured. Furthermore, the ratio of the second carbon particles contained in the first carbon particles is preferably 80% by volume or more. When the ratio of the second carbon particles is in this range, the effects of improving PSOC life performance and low-temperature high-rate performance can be further enhanced.

[0037] The third carbon particles preferably contain carbon particles other than carbon black among the above carbon particles, and particularly preferably contain graphite.

[0038] The ratio R (= d1 / d2) of the average particle size (d1) of the second carbon particles to the average pore size (d2) 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. Therefore, a high PSOC life performance can be ensured and a decrease in low-temperature high-rate performance can be further prevented.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The first carbon particles that have passed through the sieve contain many second carbon particles having a small primary particle diameter. The average particle diameter of such primary particles corresponds to the average particle diameter d1 of the second carbon particles, as described below. Since the particle diameter of such second carbon particles contained in the first carbon particles is smaller than the average pore diameter d2 of the separator, they flow into the electrolyte and cause blockage of the pores of the separator.

[0044] 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 d1 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.

[0045] 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.

[0046] The ratio (volume %) 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 in 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 d2 of the separator are designated as second carbon particles, and particles with a primary particle diameter equal to or greater than the average pore diameter d2 are designated 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 sum of the areas of the second carbon particles (total area) and the sum of the areas of the first carbon particles other than the second carbon particles (total area) are determined. The ratio (area %) of the total area of ​​the second carbon particles to the sum of the total area of ​​the second carbon particles and the total area of ​​the first carbon particles other than the second carbon particles is calculated. This area-based ratio is considered to be the volume-based ratio (volume %) of the second carbon particles contained in the first carbon particles.

[0047] 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.

[0048] 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.

[0049] (Separator) The separator includes a base portion made of a microporous membrane and a rib protruding from at least one main surface of the base portion. The separator may include a rib protruding from one main surface of the base portion and a rib protruding from the other main surface of the base portion. The separator includes at least a rib protruding from one main surface, and this rib is arranged so as to be located on the negative electrode plate side. The rib located on the negative electrode plate side is referred to as the first rib. If the separator includes a rib protruding from the other main surface of the base portion, this rib is arranged on the positive electrode plate side (i.e., facing the positive electrode plate). The 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. Furthermore, by suppressing an increase in the specific gravity of the electrolyte near the negative electrode plate, charging efficiency is improved, thereby suppressing loss of electrolyte during charging.

[0050] 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.

[0051] The average pore diameter of the separator, the average thickness of the base portion, the average height of the ribs, and the average pitch of the ribs described below are determined for the separator that has been removed from the battery, washed, and dried in the same manner as above.

[0052] The average pore diameter d2 of the separator is, for example, 0.03 μm or more and 0.5 μm or less, preferably 0.05 μm or more and 0.3 μm or less, and more preferably 0.07 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.

[0053] The average pore diameter d2 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 d2 is determined from this pore distribution. An automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation is used to measure the average pore diameter.

[0054] 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.

[0055] The first ribs are formed on the surface of the separator facing the negative electrode plate. The average height of the first ribs is, for example, 0.05 mm or more, preferably 0.07 mm or more. When the average height of the first ribs is within this range, the electrolyte is more easily diffused. From the viewpoint of ensuring high capacity, the average height of the first ribs is, for example, 0.40 mm or less, preferably 0.20 mm or less. These lower and upper limits can be arbitrarily combined. In the separator, it is preferable that the first ribs are formed with such an average height at least in the region facing the negative electrode plate (preferably the region where the negative electrode material is present). For example, it is preferable that the first ribs with such an average height are formed on at least 70% of the area of ​​the region facing the negative electrode plate of the separator.

[0056] The height of the first rib refers to the distance from one main surface of the base portion at a predetermined position on the first rib to the top of the first rib. If the main surface of the base portion is not flat, the height of the first rib is the distance from the highest point on one main surface of the base portion to 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. The average height of the first rib is calculated by averaging the heights of the first rib measured at 10 arbitrarily selected positions on the first rib on one main surface of the base portion.

[0057] 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.

[0058] 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.

[0059] The average 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 an average pitch in this range, the effect of improving the diffusion of the electrolyte near the negative electrode plate is easily achieved. In the separator, the first ribs are preferably formed at such an average pitch in a region facing the negative electrode plate (preferably a region where the negative electrode material is present). For example, it is preferable that the first ribs are formed at such an average 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, or in regions where the negative electrode material is not present, first ribs may or may not be formed, or multiple first ribs may be formed densely (for example, at an average pitch of 0.5 mm to 5 mm).

[0060] 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 a region of the separator that does not face the negative electrode plate or in a region of the negative electrode plate that faces a region where no negative electrode material is present, the average pitch can be calculated excluding this region. The average pitch of such partially densely formed first ribs can be calculated for this region in the same manner as described above.

[0061] The second ribs are formed on the surface of the separator facing the positive electrode plate. The average height of the second ribs is, for example, 0.3 mm or more, and preferably 0.4 mm or more. When the average height of the second ribs is within this range, oxidation degradation of the separator is easily suppressed. From the viewpoint of ensuring high capacity, the average height of the second ribs may be, for example, 1.0 mm or less, and may be 0.7 mm or less. These lower and upper limits can be arbitrarily combined. It is preferable that the second ribs are formed with such an average height in at least the region of the separator facing the positive electrode plate (preferably the region where the positive electrode material is present). For example, it is preferable that the second ribs with such an average height are formed on at least 70% of the area of ​​the region of the separator facing the positive electrode plate.

[0062] The average height of the second rib is determined in the same manner as for the first rib. The height of the second rib is the distance from the other main surface of the base at a predetermined position of the second rib to the top of the second rib.

[0063] 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 average 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 an average 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 an average pitch in a region facing the positive electrode plate (preferably a region in which the positive electrode material is present). For example, it is preferable that the second ribs are formed at such an average 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 end of the separator, or regions facing a region in which the positive electrode material is not present, second ribs may or may not be formed, or multiple second ribs may be formed densely (for example, at an average pitch of 0.5 mm to 5 mm).

[0064] The pitch of the second ribs is the distance between the tops of adjacent second ribs (more specifically, the distance between the centers of adjacent second ribs in a direction crossing the second ribs). The average pitch of the second ribs can be calculated based on the average pitch of the first ribs.

[0065] A sheet-like separator may be sandwiched between the negative and positive electrode plates, or the negative or positive electrode plates may be housed in a bag-like separator, thereby interposing the separator between the negative and positive electrode plates. 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 facilitates the improvement of the diffusibility of the electrolyte near the negative electrode plate and also prevents the separator from breaking due to the extension of the current collector, thereby preventing short circuits. When the positive electrode plate is housed in a bag-like separator, stratification of the electrolyte can be suppressed.

[0066] 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.

[0067] (Electrolyte) An aqueous solution containing sulfuric acid is used as the electrolyte, which may be gelled as necessary.

[0068] The negative electrode material contains first carbon particles, and second carbon particles having a smaller particle size contained in the first carbon particles flow out into the electrolyte, thereby causing the second carbon particles to be contained in the electrolyte. The second carbon particles may be contained in the electrolyte even in an initial state (for example, a pre-formed, fully charged state), but the flow out of the second carbon particles becomes more noticeable with repeated charge and discharge.

[0069] The electrolyte may contain additives used in lead-acid batteries as needed. 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.

[0070] (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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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 active material, the fiber mat is preferably disposed so as to be in contact with the positive electrode plate. From the viewpoint of enhancing 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 negative electrode plate side of the separator, 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] Lead-acid batteries A1 to A6 and C1 (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 of an expanded lattice made of a Pb—Ca—Sn alloy as a negative electrode current collector, aged, and dried to obtain an unformed negative electrode plate. Sodium lignin sulfonate was used as the organic shrinkage preventer. The amount of carbon black added was adjusted so that the content of carbon black in 100% by mass of the negative electrode material was the value shown in Table 1. The amount of each organic shrinkage preventer added to the negative electrode paste was adjusted so that the content of each organic shrinkage preventer in 100% by mass of the negative electrode material was 0.2% by mass.

[0079] (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.

[0080] (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 a first rib on the inside of the pouch and a second rib on the outside of the pouch. The separator had a plurality of striped first ribs and a plurality of striped second ribs, which were formed along the height direction of the negative electrode plate and the positive electrode plate, respectively. The average 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 average height of the second ribs was 0.4 mm, and the average pitch of the second ribs in the region facing the positive electrode plate was 10 mm. The average thickness of the separator base was 0.2 mm. The average height of the separator ribs, the average thickness of the base portion, and the average pitch of the ribs were values ​​obtained for the separator before the lead-acid battery was fabricated, but were almost the same as the values ​​measured by the above-mentioned procedure for the separator removed from the fabricated lead-acid battery.

[0081] The electrode plate group was inserted into a polypropylene battery case, an electrolyte was poured into the battery case, and chemical formation was performed inside the battery case to assemble flooded lead-acid batteries A1 to A6 and C1 with a nominal voltage of 12 V and a nominal capacity of 40 Ah (20-hour rate). The electrolyte used was an aqueous solution containing sulfuric acid and having a specific gravity of 1.28 at 20°C.

[0082] For a fully charged lead-acid battery manufactured using a chemical process, the average particle diameter d1 of the second carbon particles (carbon black) contained in the negative electrode material and the average pore diameter d2 of the separator were determined using the procedure described above and found to be 50 nm and 0.1 μm, respectively, with a ratio R = d1 / d2 of 0.5. The content of the first carbon particles in the negative electrode material determined using the procedure described above was approximately the same as the amount of carbon black added when preparing the negative electrode paste. The average pore diameter d2 of the separator was also approximately the same as the average pore diameter of the separator before assembly into the battery. The ratio of the second carbon particles to the first carbon particles determined using the procedure described above was approximately 100% by volume.

[0083] Lead-acid batteries B1 to B7 were assembled in the same manner as lead-acid batteries C1 and A1 to A6, except that a pouch-shaped separator without a first rib was used.

[0084] [Evaluation 1: PSOC Life Performance] 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 (a) to (c) were counted as one cycle, and repeated until the end-of-discharge voltage reached 7.2 V or less. The number of cycles was determined. However, the charge-discharge cycle was temporarily stopped at 18,000 cycles, and a low-temperature high-rate performance discharge test (described below) was performed. The battery was then charged at a constant voltage of 14.5 V for 16 hours, and the following (a) to (c) charge-discharge cycles were repeated. PSOC life performance was evaluated as a ratio, assuming the number of cycles for lead-acid battery B1 to be 100. During charge and discharge, a 40- to 48-hour pause was performed every 3,600 cycles. (a) Discharge 1: Discharge at a current value of 32 A for 59 seconds. (b) Discharge 2: Discharge at a current value of 300 A for 1 second. (c) Charging: charging at a limited current of 100 A and a voltage of 14.0 V for 60 seconds.

[0085] [Evaluation 2: Low-Temperature High-Rate Discharge Test] Before and during the charge-discharge cycle test of Evaluation 1, a high-rate discharge test at -15°C was conducted in accordance with JIS D 5301:2006. Specifically, in the high-rate discharge test, the lead-acid battery was placed in a cooling chamber at a temperature of -15°C ± 1°C for at least 16 hours. The battery was then discharged at a discharge current (150 A) specified in JIS D 5301:2006 at -15°C until the terminal voltage reached 1.0 V per cell, and the discharge time (seconds) was determined. The discharge times before and after the PSOC life test were designated t0 and t1, respectively, and the ratio t1 / t0 was calculated to determine the low-temperature high-rate performance retention rate. The ratio of the retention rates was calculated based on the retention rate of lead-acid battery B1, which was set to 100, and the low-temperature high-rate performance retention rate was evaluated based on this ratio.

[0086] [Evaluation 3: Penetration Short Circuit] The lead-acid battery after evaluation in Evaluation 1 was disassembled, the separator was removed, and the presence or absence of a lead penetration mark was confirmed.

[0087] [Evaluation 4: Amount of Liquid Loss] A light-load life test was conducted in accordance with JIS D 5301:2006, and the amount of liquid loss of the electrolyte after the test was determined compared to the amount before the test. However, the test temperature was 75°C. Specifically, the lead-acid batteries were discharged at 75°C for 4 minutes at a discharge current (25 A) specified in JIS D 5301:2006, and then charged at 75°C for 10 minutes at a voltage of 14.8 V. This discharge-charge cycle was repeated 480 times and left for 56 hours, after which the above discharge-charge cycle was repeated another 480 times and left for 56 hours. The mass of the lead-acid batteries after the test was measured and subtracted from the mass before the test to determine the amount of liquid loss of the electrolyte. The amount of liquid loss was expressed as a ratio, with the amount of liquid loss in lead-acid battery B1 set to 100. The results for lead-acid batteries A1 to A6, C1, and B1 to B7 are shown in Table 1.

[0088]

[0089] As shown in Table 1, in the lead-acid battery C1 in which the content of the first carbon particles in the negative electrode material is 0.1% by mass and which uses a separator provided with a first rib, the effect of improving PSOC life performance due to the presence of the first rib is small compared to the lead-acid battery B1, and no effect of improving low-temperature high-rate performance is obtained at all.

[0090] In contrast, in the lead-acid batteries A1 to A6, in which the content of the first carbon particles in the negative electrode material is 0.2 mass % or more and 2 mass % or less and which use a separator with a first rib, the presence of the first rib significantly improves the PSOC life performance compared to the lead-acid batteries B2 to B7. In particular, the PSOC life performance of the lead-acid batteries A2 to A7 is even higher than that of the lead-acid battery A1, which has a lower content of the first carbon particles.

[0091] When the content of the first carbon particles in the negative electrode material is 0.2% by mass or more (up to 2% by mass), the retention rate of low-temperature high-rate performance tends to decrease (lead-acid batteries B2 to B7). This is thought to be because when the content of the first carbon particles is 0.2% by mass or more, the outflow of second carbon particles, which have a smaller particle size, into the electrolyte becomes significant. In contrast, by providing the first rib, even at this content of the first carbon particles, the decrease in the retention rate of low-temperature high-rate performance is suppressed (lead-acid batteries A1 to A6). This is thought to be because the first rib suppresses blockage of separator pores by the second carbon particles. The effect of suppressing the decrease in the retention rate of low-temperature high-rate performance is particularly significant when the content of the first carbon particles in the negative electrode material is 0.3% by mass or more.

[0092] Furthermore, in lead-acid batteries C1 and B1, no penetration marks were observed, and the first rib did not have the effect of suppressing permeation short circuits when the content of the first carbon particles was 0.1% by mass. On the other hand, when the content of the first carbon particles in the negative electrode material was 0.2% by mass or more, penetration marks were observed when a separator without a first rib was used (lead-acid batteries B2 to B7). In contrast, in lead-acid batteries A1 to A6, even when the content of the first carbon particles was within the same range, the provision of the first rib suppressed lead penetration and precipitation into the separator.

[0093] Furthermore, the lead-acid batteries A1 to A6 exhibit a significantly reduced amount of liquid loss during charging compared to the lead-acid batteries B2 to B7. In particular, when the content of the first carbon particles in the negative electrode material is 1% by mass or less, the amount of liquid loss can be reduced to less than 100%. Furthermore, as shown in Table 1, the amount of liquid loss tends to increase as the content of the first carbon particles in the negative electrode material increases. However, even when the content of the first carbon particles is high (e.g., 1% by mass or more), the presence of the first rib can reduce the amount of liquid loss during charging (comparison of lead-acid batteries B5 to B7 with A4 to A6).

[0094] 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.

[0095] 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: a positive electrode plate; a negative electrode plate; a separator placed between the positive and negative electrode plates; and an electrolyte solution. The separator has at least ridges on the negative electrode side, the negative electrode plate contains negative electrode material, and the negative electrode material contains carbon particles. These carbon particles include primary carbon particles smaller than 32 micrometers, and secondary carbon particles of a smaller size...

1. A lead-acid battery under claim 1 where the ratio R(=d1 / d2) of the average particle size d1 of the second carbon particle to the average hole size (d2) of the separator is 0.8 or less.

2. A lead-acid battery under claim 1 or 2 where the average particle size d1 of the second carbon particle is 10 nm or more and 100 nm or less.

3. A lead-acid battery under claim 1 or 2 where the average particle size d1 of the second carbon particle is 10 nm or more and 100 nm or less. 4.

5. Lead-acid battery under any of the claims 1-3 where the second carbon particle includes carbon black.

6. Lead-acid battery under any of the claims 1-4 where the separator is in the shape of a bag.

7. Lead-acid battery under claim 5 where the separator stores the negative electrode plate.

8. Lead-acid battery under claim 5 where the separator stores the positive electrode plate.

9. Lead-acid battery under any of the claims 1-7 where the ridges are created along the height direction of the negative electrode plate.

10. Lead-acid battery under any of the claims 1-8 where a fibrous composite material is placed between the positive and negative electrode plates.