Lead-acid battery

Abstract

DEPCT64 A lead-acid battery consists of a positive electrode plate, a negative electrode plate, and a separator. Placed between the positive and negative electrode plates and the electrolyte solution, the separator will have a section... It is the first ridge on the shore of the negative electrode plate, at least; the negative electrode plate will have the negative electrode material and... The material that acts as the negative electrode contains graphite particles. -----------------------------------------------------------

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 an electrode plate assembly including a negative electrode plate, a positive electrode plate, and 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, etc.

[0003] Patent Document 1 proposes adding flake graphite to the negative electrode active material. On the other hand, separators having ribs are sometimes used (for example, Patent Documents 1 and 2).

[0004] International Publication No. 2011 / 142072 Pamphlet Japanese Patent Application Laid-Open No. 2015-216125

[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] It has been known for some time that adding graphite to a negative electrode material improves PSOC life performance and charge acceptance to some extent, but in recent years, there has been a demand for further improvement in PSOC life performance.

[0007] One aspect of the present invention relates to a lead-acid battery including 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 includes a first rib on at least the negative electrode plate side, and the negative electrode plate includes a negative electrode material, and the negative electrode material includes graphite particles.

[0008] In a lead-acid battery using a negative electrode material containing graphite particles, the PSOC life performance can be significantly improved.

[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 one aspect of 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, and the negative electrode material includes graphite particles.

[0011] Conventionally, conductive carbon particles such as carbon black and graphite particles have been added to negative electrode materials to enhance their conductivity. However, it has been found that the use of graphite particles can inhibit the supply of ions necessary for electrode reactions to and from the negative electrode material during charge and discharge, resulting in insufficient improvement in PSOC life performance. This is thought to be because the particle size of graphite particles is larger than that of carbon black, acting as a barrier to the supply of ions to and the discharge of ions from the negative electrode material. Furthermore, when a PSOC is continuously used in an undercharged state, such as in a PSOC, if the distance between the separator and the negative electrode plate is small, the area between the separator and the negative electrode plate may become locally overdischarged, resulting in a localized decrease in the amount of ions in the electrolyte between the separator and the negative electrode plate. Therefore, when graphite particles are used as the negative electrode material, if the distance between the separator and the negative electrode plate is small, the supply of ions to the negative electrode material and the discharge of ions from the negative electrode material are significantly reduced, and it is thought that the effect of improving PSOC life performance cannot be sufficiently obtained.

[0012] According to the above aspect of the present invention, graphite particles are used as the negative electrode material, and a separator having a first rib on the negative electrode plate side is used. This combination ensures high ion supply to and high ion discharge from the negative electrode material, and also ensures a conductive network in the negative electrode material for a long period of time. Therefore, PSOC life performance can be significantly improved.

[0013] More specifically, according to the above aspect, the first rib is provided on the negative electrode plate side of the separator, thereby ensuring the presence of electrolyte near the negative electrode plate. This ensures the amount of ions in the electrolyte between the separator and the negative electrode plate and further improves the ion exchange rate required for electrode reactions during charge and discharge. Therefore, even in cases where ion supply and discharge are likely to be hindered by graphite particles, the efficiency of ion supply to and ion discharge from the negative electrode material is improved, ensuring high ion supply and discharge properties in the negative electrode material. Second, compared to carbon black, graphite particles are less likely to leak into the electrolyte during charge and discharge, ensuring a long-term conductive network in the negative electrode material. Furthermore, the first rib improves the diffusibility of the electrolyte near the negative electrode plate. These factors suppress the accumulation of lead sulfate. These mechanisms are believed to ensure high PSOC life performance.

[0014] The average height of the first rib is preferably 0.05 mm or more. In this case, the electrolyte can be easily secured near the negative electrode plate, which further enhances the effect of improving the ion exchange rate and the effect of suppressing the accumulation of lead sulfate. This is advantageous in improving the PSOC life performance.

[0015] The separator preferably has a region where the average pitch of the first ribs is 0.2 mm or more and 12 mm or less, which makes it easier to secure the electrolyte near the negative electrode plate, thereby further improving the ion exchange rate and suppressing the accumulation of lead sulfate.

[0016] The average particle size of the graphite particles is preferably 50 μm or more and 300 μm or less. When the average particle size is 50 μm or more, the excellent electronic conductivity of graphite makes it easier to obtain the effect of suppressing the accumulation of lead sulfate. When the average particle size is 300 μm or less, the first rib can ensure higher ion supply and discharge properties. Therefore, the PSOC life performance can be further improved.

[0017] The content of the graphite particles in the negative electrode material is preferably 0.2% by mass to 3% by mass, which facilitates ensuring high ion supply and discharge properties and also facilitates the spread of a conductive network in the negative electrode material, thereby further enhancing the effect of improving PSOC life performance.

[0018] The separator preferably also has a rib (second rib) on the positive electrode plate side, which is advantageous in improving the PSOC life because it increases the diffusibility of the electrolyte even near the positive electrode plate and suppresses oxidation degradation of the separator.

[0019] The average height of the first ribs is preferably 0.30 mm or less. When the average height of the first ribs is in this range, it is easy to ensure a certain level of height for the second ribs, which makes it easier to ensure electrolyte near the positive electrode plate and further enhances the effect of suppressing oxidation degradation of the separator.

[0020] The separator may be bag-shaped. While a bag-shaped separator tends to retain the electrolyte, providing ribs on the separator can improve the electrolyte's diffusibility. When a positive electrode plate is housed in a bag-shaped separator, sulfuric acid discharged from the positive electrode plate during charging is less likely to escape outside the bag-shaped separator, thereby enhancing the effectiveness of suppressing stratification due to sulfuric acid precipitation, thereby further improving PSOC life performance. When a negative electrode plate is housed in a bag-shaped separator, forming a first rib within the bag facilitates increasing the electrolyte's diffusibility within the bag, thereby improving the ion exchange rate and enhancing the effectiveness of suppressing lead sulfate accumulation. Furthermore, unlike a positive electrode current collector, a negative electrode current collector exhibits little expansion during charging and discharging. Therefore, when a negative electrode plate is housed in a bag-shaped separator, separator tearing due to expansion of the current collector is suppressed, thereby suppressing short circuits.

[0021] Hereinafter, a lead-acid battery according to one embodiment of the present invention will be described in detail with respect to each of its main constituent elements, but the present invention is not limited to the following embodiment.

[0022] (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.

[0023] 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.

[0024] The negative electrode material includes graphite particles (first carbonaceous material). The negative electrode material also includes a negative electrode active material (lead or lead sulfate) that generates capacity through an oxidation-reduction reaction. The negative electrode material may include a shrinkage inhibitor, a carbonaceous material other than graphite particles (second carbonaceous material), barium sulfate, or the like, and may also include other additives as needed. The negative electrode active material in a charged state is spongy lead, but unformed negative electrode plates are typically made using lead powder.

[0025] The graphite particles may be any carbonaceous material having a graphite-type crystal structure, and may be either artificial graphite or natural graphite. Examples of the shape of the graphite particles include spherical, oval, flaky, and thin-film shapes. Although flat-shaped graphite particles, such as flaky and thin-film shapes, tend to impede the supply and discharge of ions in the negative electrode material, the first rib can increase the ion exchange rate. Therefore, even when such graphite particles are used, excellent PSOC life performance can be ensured.

[0026] The average particle diameter of the graphite particles is, for example, 5 μm or more, preferably 50 μm or more. The average particle diameter of the graphite particles is, for example, 1 mm or less, preferably 500 μm or less (e.g., 400 μm or less), and more preferably 300 μm or less. These lower and upper limits can be arbitrarily combined. Graphite particles of this size tend to hinder the supply and discharge of ions in the negative electrode material, but the first rib can increase the ion exchange rate. Therefore, even when graphite particles of this size are used, excellent PSOC life performance can be ensured. In particular, when the negative electrode material contains graphite particles with an average particle diameter of 50 μm or more and 300 μm or less, the effect of suppressing lead sulfate accumulation can be enhanced and a high ion exchange rate can be more easily ensured. Therefore, PSOC life performance can be further improved.

[0027] The content of graphite particles in the negative electrode material is, for example, 0.1% by mass to 5% by mass, preferably 0.2% by mass to 5% by mass, and more preferably 0.2% by mass to 3% by mass. When the content of graphite particles is within this range, the supply of ions to the negative electrode material and the discharge of ions from the negative electrode material can be prevented from being hindered, and a conductive network can easily spread within the negative electrode material. This is therefore more advantageous in ensuring a high PSOC life performance.

[0028] Examples of the other carbonaceous material (second carbonaceous material) include carbon black. Examples of carbon black include acetylene black, furnace black, channel black, and lamp black. The negative electrode material may contain one type of second carbonaceous material, or two or more types of second carbonaceous materials.

[0029] The content of graphite particles contained in the negative electrode material and the average particle size of the graphite particles can be determined as follows.

[0030] 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 collected 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 further added, and heating was continued to dissolve the soluble components. The sample recovered by filtration was then passed through a 1000 μm sieve to remove large components such as reinforcing materials, and the components that passed through the sieve were collected as carbonaceous material.

[0031] The liquid containing the recovered carbonaceous material is sieved through a 32 μm mesh sieve and then through a 5 μm mesh sieve to remove small carbon particles, mainly consisting of a second carbonaceous material such as carbon black. The material remaining on the 32 μm and 5 μm mesh sieves is collected and dried at a temperature of 110° C. for 2 hours. The Raman spectrum of the dried carbon particles shows a peak at 1300 cm －１ More than 1400cm －１ Intensity I of the peak (D band) appearing in the following range Ｄ and 1550 cm －１ 1620cm or more －１ Intensity I of the peak (G band) appearing in the following range Ｇ Intensity ratio I Ｄ / I Ｇ is 0 or more and 0.9 or less, the obtained carbon particles are referred to as graphite particles (first carbonaceous material) in the above aspect of the present invention.

[0032] The content of graphite particles in the negative electrode material is determined by measuring the mass of the graphite particles separated by the above procedure and calculating the proportion (mass %) of this mass in 5 g of the pulverized sample.

[0033] The average particle size of the graphite particles is determined from the volumetric particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. The laser diffraction / scattering particle size distribution analyzer used is the "SALD-2000J" manufactured by Shimadzu Corporation. The average particle size of the graphite particles is measured after drying the graphite particles and dispersing them in water.

[0034] To specifically explain the procedure for calculating the average particle size of graphite particles, first, 250 mL of ion-exchanged water is placed in a stirring tank, 20 mg of dried graphite particles are added, and the pump speed is set to maximum to apply ultrasonic vibrations to suppress aggregation of the graphite particles. Then, in this state, the particle size distribution is measured 7 minutes after the start of stirring. The particle size distribution is expressed based on volume frequency. It can be said that the particle size distribution is stable 7 minutes after the start of stirring.

[0035] In measurements using the SALD-2000J, the measurement intervals for particle size distribution are intervals obtained by dividing the measured particle size range on a logarithmic scale. In this case, the average particle size is calculated by dividing the average particle size by 10 using the respective average values ​​μ on the logarithmic scale shown in the following formula: μ (i.e., 10 μ power). The unit of the measured particle size and 10 μ For example, if the measured particle diameter is in μm, then 10 μ The average primary particle diameter expressed by is also in μm units.

[0036]

[0037] (where n is the number of divisions in the range of particle diameters to be measured, j is a natural number, and χ ｊ : particle diameter to be measured (χ ｊ : Maximum particle diameter, χ ｎ＋１ : minimum particle size), q ｊ : Particle size interval [χ ｊ , χ ｊ＋１ ] and the relative particle size (difference %) in each

[0038] The lower limit of the measurement particle size range is 0.05 μm or less, and the upper limit is 700 μm or more. The number of divisions n of the measurement particle size range is 40 or more. The particle size distribution is measured at equally divided measurement intervals on a logarithmic scale.

[0039] In this specification, the fully charged state of a lead-acid battery refers to a state in which, in the case of a flooded lead-acid battery, the battery is charged at a constant current of 0.2 CA in a water tank at 25°C until a voltage of 2.5 V / cell is reached, followed by a further constant current charge of 0.2 CA for two hours. In the case of a valve-regulated battery, the fully charged state refers to a state in which the battery is charged at a constant current and constant voltage of 0.2 CA to 2.23 V / cell in an air tank at 25°C, and charging is terminated when the charging current during constant voltage charging drops to 1 mCA or less. In this specification, 1 CA refers to 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.

[0040] 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.

[0041] 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.

[0042] (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 a 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 a second rib. The first rib ensures electrolyte near the negative electrode plate, thereby increasing the ion exchange rate, and by increasing the diffusibility of the electrolyte near the negative electrode plate, the accumulation of lead sulfate can be suppressed, thereby further improving PSOC life performance.

[0043] The separator is formed of a polymer material (but different from fibers). At least the base portion is a porous sheet, which may also be called a porous film. 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 the 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.

[0044] The average thickness of the base, the average height of the ribs, and the average pitch of the ribs described below are determined for separators that have been removed from fully charged lead-acid batteries, washed, and vacuum-dried (dried under a pressure lower than atmospheric pressure), as described above.

[0045] 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 charge-discharge characteristics. 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.

[0046] The first ribs are formed on the surface of the separator facing the negative electrode plate. The average height of the first ribs is preferably 0.05 mm or more, more preferably 0.06 mm or more, and may be 0.10 mm or more. When the average height of the first ribs is within this range, it is easier to secure electrolyte near the negative electrode plate, thereby further enhancing the effect of improving the ion exchange rate and the effect of suppressing the accumulation of lead sulfate. From the viewpoint of ensuring charge / discharge characteristics and easily ensuring the height of the second ribs, the average height of the first ribs is, for example, 0.40 mm or less, preferably 0.30 mm or less, and more preferably 0.25 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 separator facing the negative electrode plate.

[0047] 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.

[0048] 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 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.

[0049] 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.

[0050] The average pitch of the striped or grid-shaped first ribs is preferably 0.2 mm to 12 mm, and more preferably 0.3 mm to 10 mm. When the separator includes a region where the first ribs are formed at an average pitch within this range, it becomes easier to secure electrolyte near the negative electrode plate, thereby further improving the ion exchange rate and suppressing lead sulfate accumulation. This is therefore more advantageous in improving PSOC life performance. In the separator, the first ribs are preferably formed at such an average pitch 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 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 regions where the negative electrode material is not present, first ribs may or may not be formed. Alternatively, multiple first ribs may be formed densely (e.g., at an average pitch of 0.5 mm to 5 mm).

[0051] 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.

[0052] The improvement in ion velocity is particularly significantly affected by the average height and average pitch of the first ribs and the content of graphite particles in the negative electrode material. From the viewpoint of ensuring a greater improvement in ion velocity, it is preferable that the average height of the first ribs be 0.06 mm or more and 0.25 mm or less, the average pitch of the first ribs be 0.3 mm or more and 10 mm or less, and the content of graphite particles in the negative electrode material be 0.2 mass % or more and 3 mass % or less.

[0053] 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, 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 and electrolyte is easily maintained near the positive electrode plate. From the viewpoint of ensuring high capacity, the average height of the second ribs may be, for example, 1.0 mm or less, or 0.7 mm or less. These lower and upper limits can be arbitrarily combined. When the separator has second ribs, it is preferable that the second ribs are formed with such an average height at least in the region 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 facing the positive electrode plate of the separator.

[0054] 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.

[0055] 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 the region facing the positive electrode plate (preferably the region where 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 the region where 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).

[0056] 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.

[0057] A sheet-shaped separator may be sandwiched between the negative and positive electrode plates, or the negative or positive electrode plates may be housed in a bag-shaped separator, thereby interposing the separator between the negative and positive electrode plates. When a bag-shaped separator is used, the electrolyte is less likely to diffuse, but providing a first rib and a second rib improves diffusion. Housing the positive electrode plate in a bag-shaped separator tends to suppress stratification, further improving PSOC life performance. When a bag-shaped separator houses the negative electrode plate, the first rib facilitates improving the ion exchange rate near the negative electrode plate and suppressing the accumulation of lead sulfate. Furthermore, it suppresses separator tearing due to elongation of the current collector, thereby preventing short circuits.

[0058] 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.

[0059] (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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] (Electrolyte) An aqueous solution containing sulfuric acid is used as the electrolyte. The electrolyte may be gelled as needed. The electrolyte may contain additives used in lead-acid batteries as needed. The additives include, for example, metal salts (sodium salts such as sodium sulfate, aluminum salts such as aluminum sulfate, etc.). The specific gravity of the electrolyte at 20°C in a lead-acid battery in a fully charged state after chemical formation is, for example, 1.10 g / cm. ３ 1.35g / cm or more ３ The following is the result.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Lead-acid batteries A1-1 to A1-34 (1) Preparation of negative electrode plate: Lead powder, water, dilute sulfuric acid, graphite particles, 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, aged, and dried to obtain an unformed negative electrode plate. Sodium lignin sulfonate was used as the organic shrinkage preventer. The graphite particles were blended into the negative electrode paste in amounts adjusted to the contents per 100% by mass of the negative electrode material shown in Table 1. The carbon black and organic shrinkage preventer were blended into the negative electrode paste in amounts adjusted to 0.3% by mass and 0.2% by mass, respectively, per 100% by mass of the negative electrode material. The average particle diameter of the graphite particles was as shown in Table 1. The graphite particle content and average particle size in the table are values ​​determined from the fabricated lead-acid batteries using the procedures described above. The graphite particle content is approximately the same as the amount of graphite particles added when preparing the negative electrode paste. The average particle size of the graphite particles is approximately the same as the value determined for the graphite particles before preparing the negative electrode paste.

[0068] (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.

[0069] (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 seven unformed positive electrode plates per cell formed an electrode plate assembly. The separator had a first rib on the outside of the pouch and a second rib on the inside 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 and positive electrode plates, respectively. The average height of the first ribs was as shown in Table 1, and the average thickness of the separator base was 0.2 mm. The total thickness of the separator, corresponding to the sum of the average heights of the first and second ribs and the average thickness of the base, was 0.7 mm, and the average height of the second ribs was varied depending on the average height of the first ribs and the average thickness of the base. The pitch of the first ribs in the region facing the negative electrode plate was the value shown in Table 1, and the average pitch of the second ribs in the region facing the positive electrode plate was 1 mm. The average height of the ribs, the average thickness of the base portion, and the average pitch of the ribs of the separator were values ​​obtained for the separator before the lead-acid battery was fabricated, but were approximately the same as the values ​​measured by the above-mentioned procedure for the separator removed from the fabricated lead-acid battery.

[0070] 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 A1-1 to A1-34 with a nominal voltage of 12 V and a nominal capacity of 30 Ah (5-hour rate). The electrolyte used was a sulfuric acid aqueous solution with a specific gravity of 1.28 at 20°C.

[0071] <<Lead-acid battery B1-1>> A negative electrode plate was produced without using graphite particles. A pouch-shaped separator without a first rib was used. Except for these, a lead-acid battery B1-1 was produced in the same manner as the lead-acid battery A1-1.

[0072] Lead-acid batteries B1-2 and B1-3: A pouch-shaped separator without a first rib was used. The graphite particle content, average particle diameter, and average aspect ratio were the values ​​shown in Table 1. Other than these, lead-acid batteries B1-2 and B1-3 were produced in the same manner as lead-acid battery A1-1.

[0073] Lead-acid batteries B1-4 and B1-5: A negative electrode plate was produced without using graphite particles. The average height of the first ribs of the separator and the pitch of the first ribs in the region facing the positive electrode plate were set to the values ​​shown in Table 1. Other than these, lead-acid batteries B1-4 and B1-5 were produced in the same manner as lead-acid battery A1-1.

[0074] <<Lead-acid batteries B2-1 to B2-5>> Each unformed positive electrode plate was housed in a pouch-shaped separator. In the lead-acid batteries B2-1 to B2-3, the pouch-shaped separator had a second rib on the inside. In the lead-acid batteries B2-4 to B2-5, the pouch-shaped separator had a second rib on the inside of the pouch and a first rib on the outside of the pouch. Other than these, the lead-acid batteries B2-1 to B2-5 were fabricated in the same manner as the lead-acid batteries B1-1 to B1-5, respectively. Note that,

[0075] Lead-acid batteries A2-1 to A2-12: Each unformed positive electrode plate was housed in a pouch-shaped separator. The pouch-shaped separator had a second rib on the inside of the pouch and a first rib on the outside of the pouch. Other than these, lead-acid batteries A2-1 to A2-12 were fabricated in the same manner as lead-acid batteries A1-1 to A1-4, A1-13 to A1-16, and A1-25 to A1-28, respectively.

[0076] [Evaluation: 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 the cycle count was determined until the end-of-discharge voltage reached 7.2 V or less. The PSOC life performance was evaluated as a ratio, assuming the number of cycles for lead-acid battery B1-1 to be 100. Note that during charging and discharging, a 40- to 48-hour pause was performed 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 14.0 V for 60 seconds. The evaluation results are shown in Tables 1 and 2.

[0077]

[0078]

[0079] As shown in Tables 1 and 2, when a separator without a first rib is used, even if graphite particles are added to the negative electrode material, the PSOC life performance is improved by only 5% (comparison between lead-acid batteries B1-1 and B1-2 and B1-3, and comparison between lead-acid batteries B2-1 and B2-2 and B2-3). Also, when a separator with a first rib is used but does not contain graphite particles, the PSOC life performance is improved by only 5% (comparison between lead-acid batteries B1-1 and B1-4 and B1-5, and comparison between lead-acid batteries B2-1 and B2-4 and B2-5).

[0080] In contrast, when a negative electrode material containing graphite particles is combined with a separator having a first rib, the PSOC life performance is significantly improved compared to when either one is used alone. Specifically, when the negative electrode plate is wrapped with a separator, the PSOC life performance is improved by 15% to 55% (comparison between lead-acid batteries B1-2 to B1-4 and lead-acid batteries A1-1 to A1-34), and when the positive electrode plate is wrapped with a separator, the PSOC life performance is improved by 35% to 55% (comparison between lead-acid batteries B2-2 to B2-4 and lead-acid batteries A2-1 to A2-12).

[0081] Compared to when the negative electrode plate is wrapped in a separator, when the positive electrode plate is wrapped in a separator, a higher PSOC life performance can be obtained. Furthermore, when the average particle diameter of the graphite particles is 50 μm or more and 300 μm or less, a higher PSOC life performance can be obtained.

[0082] The lead-acid battery according to one aspect of the present invention is applicable to valve-regulated and flooded lead-acid batteries, and is suitable for use in applications where charging and discharging is performed under PSOC conditions, such as deep cycle batteries and cycle-use batteries, and is particularly useful as a charge-controlled lead-acid battery and an IS lead-acid battery. It may also be used as an emergency or backup power source, as well as a starting power source for automobiles, motorcycles, etc.

[0083] 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 consisting of: a positive electrode plate; a negative electrode plate; a separator placed between the positive and negative electrode plates; and an electrolyte solution, where the separator has at least one ridge on the negative electrode side, the negative electrode plate contains an electrode material, and the electrode material contains graphite particles.

2. A lead-acid battery according to claim 1 where the first ridge has an average height of 0.05 mm or more.

3. A lead-acid battery according to claim 1.

1. A lead-acid battery under either Reservation 1 or 2, where the separator has an area with an average pitch interval between each first ridge of 0.2 mm or more and 12 mm or less.

4. A lead-acid battery under either Reservation 1 to 3, where the average particle size of graphite particles is 50 micrometers or more and 300 micrometers or less.

5. A lead-acid battery under either Reservation 1 to 4, where the amount of graphite particles in the negative electrode material is 0.2% by mass or more and 3% by mass or less. 6.

7. Lead-acid battery under any one of claims 1 through 5 where the separator has a second ridge on the positive electrode side.

8. Lead-acid battery under claim 6 where the first ridge has an average height of 0.30 mm or less.

9. Lead-acid battery under claim 6 or 7 where the separator is bag-shaped and stores the positive electrode.

10. Lead-acid battery under any one of claims 1 through 7 where the separator is bag-shaped and stores the negative electrode.