lead-acid batteries

Abstract

SOLUTION: A lead acid battery includes at least one plate group and an electrolyte, in which the electrode plate group includes a positive electrode plate containing a positive electrode material, a negative electrode plate, and a bag-shaped separator interposed between the positive electrode plate and the negative electrode plate, and the separator accommodates the positive electrode plate, and a ratio (=A / B) of the pore volume A (mL) of the positive electrode material to the volume B (mL) in the separator excluding the positive electrode plate is 0.13 or more and 0.75 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. Lead-acid batteries include negative and positive plates, separators (or mats), and electrolytes. Each plate includes a current collector and an electrode material.

[0003] Patent Document 1 proposes a lead-acid battery comprising a positive electrode and a negative electrode facing each other with a separator interposed therebetween, and an electrolyte, the separator containing polyolefin and silica, and the electrolyte containing aluminum ions.

[0004] Patent Document 2 discloses a flooded lead-acid battery comprising an electrode plate assembly in which positive and negative electrode plates, each having a positive active material or a negative active material supported on a current collector, are stacked, a flowable electrolyte in which the electrode plate assembly is immersed, and a battery case in which these are housed; wherein the volume Ve of the electrode plate assembly is calculated by the following formula (1), and the ratio (Vp+Vn) / Ve of the total volume Vp+Vn of the total pore volume Vp of the positive electrode active material and the total pore volume Vn of the negative electrode active material contained in the electrode plate assembly to the volume Ve of the electrode plate assembly is 0.27 to 0.32, and the ratio Vp / Ve of the total pore volume Vp of the positive electrode active material to the volume Ve of the electrode plate assembly is 0.13 to 0.15. Ve = (Sp + Sn) × D / 2 Equation (1) In the formula (1), Sp represents the electrode plate area of ​​the positive electrode plate, Sn represents the electrode plate area of ​​the negative electrode plate, and D represents the inner dimension of the battery case in the electrode plate stacking direction of the electrode plate group.

[0005] Patent Document 3 proposes a lead-acid battery characterized by using a positive electrode plate in which a conductive oxide layer, a dense PbO2 layer, and a positive electrode active material layer are provided on a substrate made of titanium or a titanium alloy.

[0006] Patent Document 4 proposes a lead-acid battery containing a metal or metal compound other than lead in the positive electrode active material, characterized in that the theoretical capacity A of the electrolyte and the theoretical capacity B of the positive electrode active material satisfy the relationship 0.2≦A / B≦0.4. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 139855 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-38860 [Patent Document 3] Japanese Patent Application Publication No. 7-65821 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-142147 Summary of the Invention [Problem to be solved by the invention]

[0008] In lead-acid batteries, repeated charge and discharge cycles tend to cause stratification, in which the electrolyte density gradually decreases in the upper part of the battery and increases in the lower part. As stratification progresses, the reaction distribution in the electrode plates becomes uneven, and lead sulfate accumulates significantly in the lower part of the electrode plates, making sulfation, in which lead sulfate crystals form, more likely to occur. This leads to a decrease in capacity and uneven charge and discharge reactions, which deteriorate the electrode plates and shorten the life of the lead-acid battery. In particular, during deep discharge cycles, reaction variations are likely to occur, and as stratification progresses, the deterioration of life performance tends to become more pronounced. In this specification, life performance during deep discharge cycles is sometimes referred to as deep discharge cycle performance. [Means for solving the problem]

[0009] A first aspect of the present disclosure is a lead-acid battery, The lead-acid battery includes at least one electrode plate group and an electrolyte, the electrode plate group includes a positive electrode plate including a positive electrode material, a negative electrode plate, and a pouch-shaped separator interposed between the positive electrode plate and the negative electrode plate, The separator accommodates the positive electrode plate, The lead-acid battery relates to a ratio (=A / B) of a pore volume A (mL) of the positive electrode material to a volume B (mL) of the separator excluding the positive electrode plate, of 0.13 or more and 0.75 or less. [Effects of the Invention]

[0010] In lead-acid batteries, the deep discharge cycle performance can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 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. [Figure 2] FIG. 2 is a conceptual diagram of a positive electrode plate for explaining a method for measuring the thickness of the positive electrode plate. DETAILED DESCRIPTION OF THE INVENTION

[0012] In general, in lead-acid batteries, sulfate is released from the electrodes during charging and absorbed into the electrodes during discharging. During charging, a large amount of sulfate is released from the positive and negative electrodes. Therefore, with repeated charge / discharge cycles, sulfate not absorbed by the electrodes settles in the electrolyte, gradually increasing the specific gravity of the electrolyte in the lower part of the battery, leading to stratification. During deep discharge cycles, the deep discharge depth makes it easy for many sulfates to be absorbed into the positive electrodes during discharge, while the large charging current facilitates softening of the positive electrode material. Depending on the balance between the amount of sulfate released from the electrodes and the amount of sulfate absorbed, stratification may progress during deep discharge cycles. When stratification becomes pronounced after the positive electrode material has softened, the softening of the positive electrode material in the upper part of the positive plate becomes extremely likely. Therefore, the softened positive electrode material is particularly prone to falling off in the upper part of the positive plate, resulting in reduced life performance. Furthermore, stratification makes it difficult for charge-discharge reactions to proceed in the lower part of the electrode plate, resulting in significant accumulation of lead sulfate and facilitating sulfation. This also reduces the battery life. Thus, during deep discharge cycles, significant variations in charge-discharge reactions in the electrode plate make it difficult to ensure a long battery life.

[0013] In view of the above, (1) a lead-acid battery according to one aspect of the present invention includes at least one electrode plate assembly and an electrolyte. The electrode plate assembly includes a positive electrode plate including a positive electrode material, a negative electrode plate, and a pouch-shaped separator interposed between the positive electrode plate and the negative electrode plate. The separator houses the positive electrode plate. The ratio (=A / B) of the pore volume A (mL) of the positive electrode material to the volume B (mL) of the separator excluding the positive electrode plate is 0.13 or more and 0.75 or less.

[0014] By housing the positive electrode in a pouch-shaped separator, sulfate radicals released from the positive electrode plate during charging are more likely to remain within the separator. This reduces the settling of sulfate radicals below the bottom of the separator, thereby mitigating stratification. In addition, by having an A / B ratio in the range of 0.13 to 0.75, sulfate radicals released from the positive electrode plate during charging are prevented from moving away from the positive electrode plate and near the negative electrode plate, and are also prevented from being released outside the separator. Therefore, sulfate radicals released from the positive electrode plate are more likely to return to the positive electrode plate during discharge. This also reduces the settling of sulfate radicals and the progression of stratification. In other words, according to the above-described aspect of the present invention, the volume of the free space within the separator is optimized according to the amount of sulfate radicals that can be released from the positive electrode plate during charge. As a result, even if sulfate radicals are released from the positive electrode plate during charge, they can be retained near the positive electrode plate, making it easier for the sulfate radicals to return to the positive electrode plate during discharge.

[0015] During deep discharge cycles, the discharge depth is deep, so many sulfate radicals are easily absorbed into the positive electrode plate during discharge, making it susceptible to softening and shedding. If stratification becomes pronounced in this state, reaction variability, such as excessive softening of the upper part of the positive electrode plate, is likely to become significant. In a lead-acid battery according to one aspect of the present invention, as described above, stratification can be effectively suppressed, thereby making the reaction distribution in the electrode plate more uniform, even during deep discharge cycles where reaction variability is likely to occur, and suppressing lead sulfate accumulation and sulfation in both the negative and positive electrode plates (particularly in the lower parts of the electrode plates). This more uniform reaction distribution in the electrode plate prevents charge / discharge reactions from concentrating in the upper parts of the electrode plates, thereby enhancing the effectiveness of suppressing softening and shedding of the positive electrode material even during deep discharge cycles. These factors contribute to improved life performance during deep discharge cycles (deep discharge cycle performance).

[0016] On the other hand, even when the positive electrode plate is housed in a pouch-shaped separator, deep discharge cycle performance is poor when the A / B ratio is less than 0.13 or greater than 0.75. For example, when the A / B ratio is less than 0.13, the space within the separator is too large for the amount of sulfate released during charging, leading to sulfate diffusing away from the positive electrode plate and toward the negative electrode plate. Sulfate diffusing toward the negative electrode plate is less likely to return to the positive electrode plate during discharge, leading to stratification. In addition to the increased accumulation of lead sulfate at the negative electrode plate, the uneven distribution of reactions within the electrode plate is thought to significantly accelerate the softening and shedding of the positive electrode material. Furthermore, when the A / B ratio is greater than 0.75, the free space within the separator is too small for the amount of sulfate released during charging. In this case, the sulfate concentration inside the separator increases, resulting in a large difference in concentration between the inside and outside of the separator. This is thought to facilitate sulfate diffusing from the inside to the outside of the separator. The barrier of the separator makes it difficult for sulfate radicals that diffuse outside the separator to return to the vicinity of the positive electrode plate. In addition, when sulfate radicals that diffuse outside the separator approach the negative electrode plate, they are easily absorbed by the negative electrode plate, making it difficult for sulfate radicals to return to the vicinity of the positive electrode plate. Therefore, in this case, stratification is also likely to progress. In addition to the tendency for lead sulfate to accumulate in the lower part of the electrode plate, the uneven distribution of reaction in the electrode plate is thought to result in significant softening and shedding of the positive electrode material in the upper part of the positive electrode plate.

[0017] Furthermore, when the separator contains a negative electrode plate, even when the ratio of the pore volume of the negative electrode material to the volume of the free space in the separator (corresponding to the A / B ratio for a positive electrode plate) is between 0.13 and 0.75, stratification suppression is difficult to achieve. This is thought to be because, since the positive electrode plate is not contained in the separator, sulfate radicals released from the positive and negative electrodes during charging settle below the electrodes and are less available for subsequent charge / discharge reactions. In other words, stratification is likely to progress. Stratification increases the variability of reactions in the electrodes, which accelerates the rate at which softening and shedding occurs, at least in the upper part of the positive electrode plate. These factors are thought to result in poor deep discharge cycle performance.

[0018] (2) In the above (1), the ratio A / B may be 0.2 or more, which tends to provide higher deep discharge cycle performance.

[0019] (3) In the above (1) or (2), the thickness of the positive electrode plate may be 1.2 mm or more and 2.5 mm or less, which makes it easier to adjust the A / B ratio to a range of 0.13 or more (preferably 0.2 or more) and 0.75 or less, and thus makes it easier to obtain higher deep discharge cycle performance.

[0020] (4) In any one of the above (1) to (3), the positive electrode plate may contain Sb. In this case, the effect of suppressing softening and falling off of the positive electrode material is further enhanced. This suppression of softening and falling off, combined with the suppression of stratification by the A / B ratio, can further improve deep discharge cycle performance.

[0021] (5) In the above (4), the Sb content in the positive electrode plate may be 100 ppm or more and 1000 ppm or less. When the Sb content is in this range, it is easy to ensure higher deep discharge cycle performance.

[0022] In this specification, the pore volume A (mL) of the positive electrode material is the pore volume of the positive electrode material per positive electrode plate. The pore volume A is expressed as the porosity (mL / g) of the positive electrode material multiplied by the mass (g) of the positive electrode material per positive electrode plate. When the electrode plate group includes multiple positive electrode plates, the pore volume A (mL) is the average value of the pore volumes determined for all or some of the positive electrode plates, as described later in the measurement method.

[0023] The volume B (mL) of the separator excluding the positive electrode plate is calculated by 2 × {distance between the opposing positive and negative electrode plates (mm) – thickness of the separator base (mm)} × separator width (mm) × separator height (mm) × 10 -3The inter-electrode distance is the average value obtained for all positive and negative plates included in the electrode plate group. The separator size is the average value obtained for multiple separators (e.g., 10) removed from a lead-acid battery. If the separator has a rib (second rib, described below) that protrudes toward the negative electrode plate, the part in {} in the above formula is {inter-electrode distance between the opposing positive and negative electrode plates (mm) - thickness of the separator base (mm) - height of the second rib (mm)}.

[0024] In this specification, the up-down direction of a lead-acid battery or its components (such as plates, a battery case, and a separator) refers to the up-down direction in the vertical direction of the lead-acid battery when the battery is in use. Each of the positive and negative plates has a lug for connecting to an external terminal. In some cases, such as horizontally placed valve-regulated lead-acid batteries, the lug is provided on the side of the plate so as to protrude laterally, but in most lead-acid batteries, the lug is usually provided on the top of the plate so as to protrude upward.

[0025] The lead-acid battery according to one aspect of the present invention is suitable as a flooded (vented) lead-acid battery.

[0026] In this specification, the A / B ratio, the thickness of the positive electrode plate, and the Sb content are each determined using a positive electrode plate, a negative electrode plate, or a separator taken out of a fully charged lead-acid battery.

[0027] In this specification, the fully charged state of a flooded lead-acid battery is defined by JIS D 5301:2019. More specifically, the fully charged state is defined as a state in which a lead-acid battery is charged in a water tank at 25°C ± 2°C at a current (A) that is 0.2 times the value (unit: Ah) listed as the rated capacity, until the terminal voltage (V) during charging or the electrolyte density converted to a temperature of 20°C shows a constant value to three significant digits three times consecutively.

[0028] In this specification, a fully charged lead-acid battery refers to a lead-acid battery that has already been chemically formed and is fully charged. The lead-acid battery may be fully charged immediately after chemical formation, or after a certain period of time has passed since chemical formation (for example, a lead-acid battery that has been in use (preferably in the early stages of use) after chemical formation may be fully charged). A battery in the early stages of use refers to a battery that has not been in use for very long and has hardly deteriorated.

[0029] Hereinafter, a lead-acid battery according to one aspect of the present invention will be described in terms of each of its main constituent elements. However, the present invention is not limited to the constituent elements described below. The constituent elements described in this specification can be combined in any manner. The constituent elements described in this specification may be combined with any one of the above (1) to (5).

[0030] [Lead acid battery] A lead-acid battery includes at least one electrode plate group, a negative electrode plate, a positive electrode plate, and a pouch-shaped separator interposed between the negative electrode plate and the positive electrode plate, and an electrolyte.

[0031] (electrode group) (positive electrode plate) The positive electrode plate may be, for example, a paste-type positive electrode plate. The paste-type positive electrode plate includes a positive electrode material. In addition to the positive electrode material, the positive electrode plate typically includes a positive electrode current collector.

[0032] The positive electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead sheet or a lead alloy sheet. Examples of processing methods include expanding and punching. A lattice-shaped current collector is preferably used as the positive electrode current collector because it is easy to support the positive electrode material.

[0033] Examples of lead alloys used for the positive electrode current collector include Pb-Sb based alloys, Pb-Ca based alloys, Pb-Ca-Sn based alloys, etc. The lead alloy may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc.

[0034] The positive electrode current collector may have a surface layer. The surface layer and the inner layer of the positive electrode current collector may have different compositions. The surface layer may be formed on a part of the positive electrode current collector. For example, the surface layer may be formed only on the grid portion, the lug portion, or the frame portion of the positive electrode current collector.

[0035] 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 additives (reinforcing materials (e.g., resin fibers)) as needed.

[0036] The pore volume A of the positive electrode material may be 7.3 mL or more, or 8 mL or more. The pore volume A of the positive electrode material may be 17 mL or less, 16 mL or less, or 15.5 mL or less. When the pore volume A is in this range, it is easy to adjust the A / B ratio to an appropriate range. Furthermore, when the pore volume A is in this appropriate range, a relatively large amount of sulfate radicals can be retained in the positive electrode plate and it is easy to suppress the excessive release of sulfate radicals during charging, which would cause stratification. As described above, the pore volume A is the pore volume of the positive electrode material per positive electrode plate. The pore volume A can be adjusted by adjusting the amounts of water and sulfuric acid used when preparing the positive electrode paste, the amount of additives (carbonaceous material, red lead, etc.), etc.

[0037] The pore volume A of the positive electrode material may be 7.3 mL or more (or 8 mL or more) to 17 mL or less, 7.3 mL or more (or 8 mL or more) to 16 mL or less, or 7.3 mL or more (or 8 mL or more) to 15.5 mL or less.

[0038] The thickness of the positive electrode plate may be 1.2 mm or more, or 1.3 mm or more. The thickness of the positive electrode plate may be 2.5 mm or less, or 2.4 mm or less. When the thickness of the positive electrode plate is within this range, it is easy to adjust the A / B ratio to an appropriate range. When the thickness of the positive electrode plate is within this appropriate range, a relatively large amount of sulfate radicals can be retained in the positive electrode plate, making it easy to suppress the progression of stratification. Therefore, higher deep discharge cycle performance can be ensured.

[0039] In lead-acid batteries, the density of the positive electrode material is 3.6 g / cm 3 It may be 3.65 g / cm or more. 3 or more than 3.67 g / cm 3 The density of the positive electrode material may be 4.5 g / cm or more. 3 It may be less than 4.30 g / cm 3 or less than 4.20g / cm 3 It may be the following:

[0040] The density of the positive electrode material is 3.6 g / cm 3 or more (or 3.65g / cm 3 or more)4.5g / cm 3 Below, 3.67g / cm 3 More than 4.5g / cm 3 Below, 3.6g / cm 3 or more (or 3.65g / cm 3 or more)4.30g / cm 3 Below, 3.6g / cm 3 or more (or 3.65g / cm 3 or more)4.20g / cm 3 Below, 3.67g / cm 3 More than 4.30g / cm 3 or less (or 4.20g / cm 3 (See below) may also be used.

[0041] The density of the positive electrode material is the bulk density (unit: g / cm 3 The bulk density is calculated by dividing the mass (unit: g) of the positive electrode material by the bulk volume (unit: cm 3 ) The bulk volume is determined by mercury porosimetry. The bulk density is determined for a sample of uncrushed positive electrode material taken from the positive electrode plate removed from a fully charged lead-acid battery. The uncrushed sample is taken from near the center of the electrode plate in the surface direction.

[0042] From the viewpoint of enhancing the effect of suppressing softening and falling off of the positive electrode material and making it easier to ensure higher deep discharge cycle performance, the positive electrode plate (specifically, at least one of the positive electrode current collector and the positive electrode material) may contain Sb element.

[0043] The Sb content in the positive electrode plate may be 100 ppm or more, 200 ppm or more, or 300 ppm or more. When the Sb content is within this range, a higher softening suppression effect of the positive electrode material can be obtained, ensuring higher deep discharge cycle performance. When the Sb content is too high, the softening suppression effect tends to plateau. The Sb content in the positive electrode plate may be 1000 ppm or less.

[0044] An unformed paste-type positive electrode plate can be obtained, for example, by applying or filling a positive electrode paste onto a positive electrode current collector, followed by aging and drying. The positive electrode paste is prepared, for example, by kneading lead powder, additives (such as a reinforcing material), water, and sulfuric acid. A positive electrode plate can be obtained by forming the unformed positive electrode plate.

[0045] The formation of the unformed positive plate may be carried out, for example, by placing a plate assembly including the unformed positive plate and an electrolyte containing sulfuric acid in a battery case of a lead-acid battery, and charging the plate assembly in a state in which the electrolyte has permeated the plate assembly. However, the formation may also be carried out before assembling the lead-acid battery or the plate assembly.

[0046] (Analysis or measurement of positive electrode plate) Analysis or measurement of the positive plate or positive electrode material is carried out on a positive plate removed from a fully charged lead-acid battery.

[0047] (1) Pore volume A of the positive electrode material The pore volume A can be calculated from the porosity of the positive electrode material, which is calculated by the following procedure, and the mass of the positive electrode material, using the above definition (formula).

[0048] (a) Sample preparation A fully charged lead-acid battery is disassembled to obtain the positive electrode plate to be analyzed. The obtained positive electrode plate is washed with water and dried to remove the electrolyte from the positive electrode plate. The washing is continued until a pH test paper is pressed against the washed surface of the positive electrode plate and no color change is confirmed. The washed positive electrode plate is dried at 50±5°C for approximately 24 hours. After drying, if the positive electrode plate contains an adhesive material, the adhesive material is removed from the positive electrode plate by peeling. The mass (g) of the obtained dried material (A) is measured. Next, the positive electrode material is separated from near the center of the surface of the positive electrode plate to obtain an unpulverized sample (Sample B).

[0049] (b) Porosity of the positive electrode material A predetermined amount of unpulverized sample B is collected and its mass (g) is measured. Next, the total pore volume (mL) of sample B is measured using a mercury porosimeter. The porosity (mL / g) of the positive electrode material is calculated by dividing the total pore volume by the mass of sample B. The measurement pressure range is 0.5 psia to 33,000 psia (≒ 3.447 kPa to 227,528 kPa). An automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation is used as the mercury porosimeter.

[0050] When the electrode plate assembly includes one positive electrode plate, the porosity of the positive electrode material is determined for the positive electrode material sampled from that positive electrode plate. When the electrode plate assembly includes two positive electrode plates, the porosity of the positive electrode material is the average of the values ​​determined for the positive electrode material sampled from each of the two positive electrode plates. When the electrode plate assembly includes three or more positive electrode plates, the porosity of the positive electrode material is the average of the values ​​determined for the positive electrode material sampled from two positive electrode plates arbitrarily selected from the positive electrode plates other than the plates at the ends of the electrode plate assembly. However, when two of the three positive electrode plates are the plates at the ends of the electrode plate assembly, the porosity of the positive electrode material is determined for the positive electrode material sampled from the remaining positive electrode plate.

[0051] (c) Mass of the positive electrode material For dried material A, the positive electrode material is removed from the positive electrode current collector, and then the positive electrode current collector is treated with mannitol to remove the positive electrode material adhering to the positive electrode current collector. The resulting positive electrode current collector is washed with water, dried, and then its mass is measured. The mass (g) of the positive electrode material per positive electrode plate is calculated by subtracting the mass of the positive electrode current collector from the mass of dried material A (positive electrode plate). The mass of the positive electrode material is calculated for the positive electrode plate for which porosity is to be determined.

[0052] (2) Thickness of the positive electrode plate The calculation of the thickness of the positive electrode plate will be described in more detail below with reference to the drawings. Note that FIG. 2 described below is a conceptual diagram shown as an example to explain the calculation of the thickness of the positive electrode plate. FIG. 2 does not correspond to a specific embodiment of the lead-acid battery according to the present disclosure, and the description after FIG. 2 is not limited to only FIG. 2.

[0053] A plate assembly is removed from a fully charged lead-acid battery, and all positive plates are removed from the plate assembly. As shown in Figure 2, the shape of the positive plate 2, excluding the lug portions, is approximately rectangular. The portion of the positive plate 2 containing the positive electrode material is divided into three equal parts along the x-direction of the positive plate 2 by lines L1 and L2, and into three equal parts along the y-direction by lines L3 and L4, resulting in nine roughly equal-sized sections, 3 rows and 3 columns. The maximum thickness of the positive plate 2 is measured with a vernier caliper in a 5 mm x 7.5 mm rectangular area A1 to A9 (short sides parallel to L1 and L2, long sides parallel to L3 and L4) in the center of each section. The thickness of each positive plate is calculated as the average of the nine measurements. The thickness of each positive plate in the plate assembly is then calculated using the above procedure, and the average thickness is then calculated. In a lead-acid battery having multiple electrode plate groups, the thickness of the positive plate is determined using the above procedure for one electrode plate group located at the end and one electrode plate group located near the center, and the thickness (average value) of the positive plate is determined by averaging the thicknesses for both electrode plate groups.

[0054] (3) Density of the positive electrode material (Dp) The density (bulk density) of unpulverized sample A is determined by mercury intrusion porosimetry using a mercury porosimeter. More specifically, a predetermined amount of unpulverized sample A is first collected and its mass is measured. This sample A is placed in a measurement vessel of the mercury porosimeter, evacuated under reduced pressure, and then filled with mercury at a pressure of 0.5 psia to 0.55 psia (≒ 3.45 kPa to 3.79 kPa). The bulk volume of sample A is measured, and the measured mass of sample A is divided by the bulk volume to determine the density of the positive electrode material. The bulk volume is determined by subtracting the injected volume of mercury from the volume of the measurement vessel. An automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation is used as the mercury porosimeter. When the electrode plate assembly includes one positive electrode plate, the density Dp of the positive electrode material is determined for the positive electrode material collected from that positive electrode plate. When the electrode plate assembly contains two positive electrodes, the density Dp of the positive electrode material is the average of the values ​​obtained for the positive electrode material sampled from each of the two positive electrodes. When the electrode plate assembly contains three or more positive electrodes, the density Dp of the positive electrode material is the average of the values ​​obtained for the positive electrode material sampled from two positive electrodes arbitrarily selected from the positive electrodes other than the electrodes at both ends of the electrode plate assembly. However, if two of the three positive electrodes are at both ends of the electrode plate assembly, the density Dp of the positive electrode material is obtained for the positive electrode material sampled from the remaining positive electrode plate.

[0055] (4) Positive plate pitch The pitch of the positive electrode plates is the average value of the center-to-center distance between the lugs of a pair of adjacent positive electrode plates. More specifically, the pitch is the average value of the center-to-center distance between the lugs of all pairs of adjacent positive electrode plates included in the electrode plate group. The pitch of the positive electrode plates is determined by the following procedure.

[0056] For a plate assembly removed from a fully charged lead-acid battery, the lugs of multiple positive plates and the straps connecting these lugs in parallel are removed, washed with water, and dried. The dried material is impregnated with epoxy resin and cured. The cured material is cut to expose the cross-section of the plate assembly lugs, and the cut surface is polished. The cross-section of the exposed lugs is observed under a microscope, and the center-to-center distance between the lugs of adjacent pairs of positive plates is measured. The positive plate pitch is determined by measuring and averaging the center-to-center distances for all adjacent pairs of positive plates in the plate assembly. For a lead-acid battery with multiple plate groups, the pitch is determined by measuring and averaging the pitch of the positive plates in one plate group located at the edge and one plate group located near the center. The determined positive plate pitch is used to calculate the inter-electrode distance to determine the volume B of the separator excluding the positive plates.

[0057] (5) Sb content in the positive electrode plate The quantitative determination of elements other than lead contained in the positive electrode current collector is performed using lead separation inductively coupled plasma atomic emission spectroscopy as specified in JIS H2105:1955. A portion of the metallic luster of the positive electrode current collector obtained when determining the mass of the positive electrode material is collected as a sample and its mass is measured. The collected sample is dissolved in tartaric acid and dilute nitric acid to obtain an aqueous solution. Hydrochloric acid is added to the resulting aqueous solution to precipitate lead chloride, and the solution is filtered to collect the filtrate. The luminescence intensity of Sb in the filtrate is measured using an inductively coupled plasma (ICP) atomic emission spectrometer. The mass of Sb contained in the filtrate is then determined using a previously prepared calibration curve. The percentage of the resulting Sb mass relative to the mass of the portion of the positive electrode current collector used for analysis is calculated as the Sb content in the positive electrode current collector.

[0058] Quantitative analysis of Sb in the positive electrode material is performed using ICP atomic emission spectrometry. Specifically, a predetermined amount of pulverized sample B is first collected and its mass is measured. The collected sample B is then completely dissolved in a mixed aqueous solution containing tartaric acid, nitric acid, and hydrogen peroxide. The resulting solution is diluted with ion-exchange water as needed to a constant volume, and the emission intensity of Sb in the solution is then measured using an ICP atomic emission spectrometer. The mass of Sb contained in the solution is then determined using a previously prepared calibration curve. The percentage of the resulting Sb mass relative to the mass of sample B of the positive electrode material used for analysis is calculated as the Sb content in the positive electrode material.

[0059] The Sb content (mass%) in the positive electrode plate is calculated from the mass ratio of the positive electrode current collector to the positive electrode material in the positive electrode plate, the Sb content in the positive electrode current collector, and the Sb content in the positive electrode material. The Sb content is calculated for the positive electrode plate whose porosity is being calculated. The ICP optical emission spectrometer used is an ICPS-8000 manufactured by Shimadzu Corporation.

[0060] (negative plate) The negative electrode plate includes, for example, a negative electrode current collector and a negative electrode material.

[0061] The negative electrode current collector may be formed in the same manner as the positive electrode current collector, for example. A lattice-shaped current collector may also be used as the negative electrode current collector.

[0062] 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 additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, and Cu.

[0063] The negative electrode current collector may have a surface layer. The surface layer and the inner layer of the negative electrode current collector may have different compositions. The surface layer may be formed on a part of the negative electrode current collector. For example, the surface layer may be formed only on the grid portion, the edge portion, or the frame portion of the negative electrode current collector.

[0064] The negative electrode material contains a negative electrode active material (lead or lead sulfate) that generates capacity through an oxidation-reduction reaction. The negative electrode material may contain additives as needed. Preferred additives include organic shrinkage inhibitors, carbonaceous materials, and barium sulfate. In addition to these additives, the negative electrode material may also contain other additives (e.g., reinforcing materials such as resin fibers).

[0065] Examples of organic shrinkage inhibitors include lignin compounds and synthetic organic shrinkage inhibitors. Examples of lignin compounds include lignin and lignin derivatives (e.g., lignin sulfonic acid or its salts (e.g., alkali metal salts such as sodium salts)). However, the organic shrinkage inhibitors are not limited to these specific examples. The negative electrode material may contain one type of organic shrinkage inhibitor or a combination of two or more types.

[0066] The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more, and may be, for example, 1% by mass or less, or 0.5% by mass or less.

[0067] Examples of the carbonaceous material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, etc. The negative electrode material may contain one type of carbonaceous material or two or more types of carbonaceous materials.

[0068] The content of the carbonaceous material in the negative electrode material is, for example, 0.05 mass % or more, or may be 0.1 mass parts or more, and the content of the carbonaceous material is, for example, 5 mass % or less.

[0069] The content of barium sulfate in the negative electrode material is, for example, 0.05% by mass or more, or may be 0.1% by mass or more, and the content of barium sulfate is, for example, 3% by mass or less.

[0070] The thickness of the negative electrode plate is adjusted in consideration of the balance of capacity with the positive electrode plate, and also so as to easily adjust the A / B ratio within an appropriate range.

[0071] An unformed negative electrode plate is produced, for example, by applying or filling a negative electrode paste onto a negative electrode current collector, followed by aging and drying. The negative electrode active material in a charged state is sponge lead, but an unformed negative electrode plate is usually produced using lead powder. More specifically, the negative electrode paste used to produce an unformed negative electrode plate is prepared, for example, by adding water and sulfuric acid (or an aqueous sulfuric acid solution) to lead powder and, if necessary, various additives (such as an organic shrinkage inhibitor or a carbonaceous material), and kneading the mixture. When aging, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and at high humidity. A negative electrode plate is produced, for example, by chemically converting an unformed negative electrode plate.

[0072] The formation may be performed, for example, by placing a plate assembly including unformed negative plates and an electrolyte containing sulfuric acid in a lead-acid battery container, and charging the plate assembly while the electrolyte is permeated into the plate assembly. However, the formation may also be performed before assembling the lead-acid battery or the plate assembly. The formation produces spongy lead.

[0073] (Analysis or measurement of negative electrode plate) Analysis or measurement of the negative plate or negative electrode material is carried out on a negative plate removed from a fully charged lead-acid battery.

[0074] (1) Thickness of the negative electrode plate The thickness of the negative plate is determined in the same manner as the thickness of the positive plate. The thickness of the negative plate is determined by measuring and averaging the thicknesses of all the negative plates included in the plate group. In a lead-acid battery with multiple plate groups, the thickness of the negative plates in one plate group located at the end and one plate group located near the center is determined and averaged to determine the negative plate thickness (average). The determined negative plate thickness is used to calculate the inter-electrode distance to determine the volume B excluding the positive plate in the separator.

[0075] (2) Electrode distance The inter-electrode distance is calculated from the pitch of the positive electrode plates, the thickness of the positive electrode plates, and the thickness of the negative electrode plates, which are calculated by the above-described procedure, using the following formula: Distance between electrodes = (positive electrode pitch - positive electrode thickness - negative electrode thickness) / 2 The inter-electrode distance is the average value of the distance between opposing positive and negative electrode plates. More specifically, the inter-electrode distance corresponds to the average value of the shortest distance between opposing surfaces of all pairs of adjacent positive and negative electrode plates included in the electrode plate group.

[0076] (3) Analysis of the components in the negative electrode material (a) Sample preparation A fully charged lead-acid battery is disassembled to obtain the negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative electrode plate and no color change is confirmed. However, the washing time should be within 2 hours. The washed negative electrode plate is dried in a reduced pressure environment at 50±5°C for approximately 24 hours. If an adhesive material is contained in the negative electrode plate after drying, the adhesive material is removed from the negative electrode plate by peeling. The negative electrode material is separated from the center of the obtained negative electrode plate in the surface direction to obtain an uncrushed sample (Sample C). Sample C is crushed as necessary and subjected to analysis.

[0077] (b) Quantitative determination of organic shrinkage inhibitor The crushed sample C is collected, its mass is measured, and it is immersed in a 1 mol / L NaOH aqueous solution to extract the organic shrink-preventing agent. Insoluble components are removed by filtration from the NaOH aqueous solution containing the extracted organic shrink-preventing agent, and the filtrate (hereinafter also referred to as filtrate D) is recovered.

[0078] A predetermined amount of filtrate D is measured, desalted, concentrated, and dried to obtain a powder of the organic shrinkage preventer (hereinafter also referred to as sample E). Desalting can be performed using a desalting column, by passing filtrate D through an ion exchange membrane, or by placing filtrate D in a dialysis tube and immersing it in distilled water.

[0079] The organic shrinkage preventer is identified by combining information obtained from the infrared spectrum of sample E, the ultraviolet-visible absorption spectrum of a solution obtained by dissolving sample E in distilled water or the like, the nuclear magnetic resonance (NMR) spectrum of a solution obtained by dissolving sample E in a solvent such as heavy water, or pyrolysis gas chromatography mass spectrometry (Py-GC / MS), which can obtain information on the individual compounds that make up the substance.

[0080] The ultraviolet-visible absorption spectrum of the filtrate D is measured. The content of the organic shrinkage inhibitor in the negative electrode material is quantified from the spectral intensity, the calibration curve prepared in advance, the measured amount of filtrate D, and the mass of the collected sample C. If the structural formula of the organic shrinkage inhibitor to be analyzed cannot be precisely identified and a calibration curve for the same organic shrinkage inhibitor cannot be used, a calibration curve is prepared using an available organic shrinkage inhibitor that exhibits a similar ultraviolet-visible absorption spectrum, infrared spectrum, NMR spectrum, etc. to the organic shrinkage inhibitor to be analyzed.

[0081] (c) Quantitative determination of carbonaceous materials and barium sulfate 50 mL of 20% by mass nitric acid was added to 10 g of crushed sample C, and the mixture was heated for approximately 20 minutes to dissolve the lead components as lead ions. The resulting solution was filtered to separate out the carbonaceous material, barium sulfate, and other solids.

[0082] The obtained solid content is dispersed in water to form a dispersion, and then components other than the carbonaceous material and barium sulfate (e.g., reinforcing material) are removed from the dispersion using a sieve. Next, the dispersion is subjected to suction filtration using a membrane filter whose mass has been measured in advance, and the membrane filter together with the filtered sample is dried in a dryer at 110°C ± 5°C. The filtered sample is a mixed sample of the carbonaceous material and barium sulfate. The mass of the membrane filter is subtracted from the total mass of the dried mixed sample (hereinafter referred to as sample F) and the membrane filter to determine the mass of sample F (M m) is measured. Then, sample F is placed in a crucible together with the membrane filter and burnt at 1300°C or higher to be incinerated. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate to determine the mass of barium sulfate (M B ) to find the mass M m to mass M B The mass of the carbonaceous material is calculated by subtracting the mass of the barium sulfate obtained from the carbonaceous material. The ratio (percentage) of the mass of the obtained barium sulfate and the mass of the carbonaceous material to the mass of the sample C is calculated. In this way, the content of barium sulfate and the content of the carbonaceous material in the negative electrode material are calculated.

[0083] (separator) The separator is bag-shaped and houses the positive electrode plate. By stacking the positive electrode plate and the negative electrode plate housed in the bag-shaped separator, the separator is interposed between the negative electrode plate and the positive electrode plate.

[0084] The separator may be, for example, a microporous membrane. The microporous membrane is a porous sheet mainly composed of components other than fiber components. The microporous membrane can be obtained, for example, by extruding a composition containing a pore-forming agent into a sheet, and then removing the pore-forming agent to form pores.

[0085] The microporous membrane is preferably made of an acid-resistant material, and is preferably a microporous membrane mainly made of a polymer component. The polymer component is preferably a polyolefin (polyethylene, polypropylene, etc.). The pore-forming agent may be at least one selected from the group consisting of polymer powder and oil.

[0086] The microporous membrane may have a single-layer structure or a multi-layer structure (or laminate structure). In a multi-layer separator, two adjacent layers may be interlocked with each other via the unevenness at their interfaces.

[0087] The separator preferably includes at least a microporous membrane. The separator may be, for example, composed of only a microporous membrane, or may be composed of a laminate of a microporous membrane and a nonwoven fabric.

[0088] A nonwoven fabric is a mat of intertwined fibers, and is primarily composed of fibers. For example, 60% or more by mass of a nonwoven fabric is made of fibers. Examples of fibers include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (polyethylene terephthalate fibers, etc.)), and pulp fibers. A nonwoven fabric may contain components other than fibers (for example, acid-resistant inorganic powder, polymers as binders, etc.).

[0089] The separator may have a base portion and a rib protruding from the base portion toward the electrode plate. Having a rib (first rib) protruding from the base portion toward the positive electrode plate helps to suppress oxidative degradation of the separator. The separator may also have a rib (second rib) protruding from the base portion toward the negative electrode plate, as necessary. The separator does not necessarily have a second rib. The separator base portion refers to the separator's constituent parts, excluding protrusions such as ribs, and is the sheet-like portion that defines the separator's outer shape. The main surface of the separator facing the positive electrode plate is sometimes referred to as the first main surface, and the main surface facing the negative electrode plate is sometimes referred to as the second main surface. The separator may have one or more ribs on each of its main surfaces. The first rib and the second rib may be formed at least in the area facing the electrode material.

[0090] The average thickness of the base portion is, for example, 0.1 mm or more, and may be 0.15 mm or more. When the average thickness of the base portion is in this range, high strength of the separator is easily obtained. From the viewpoint of easily ensuring a higher capacity, the average thickness of the base portion is, for example, 0.3 mm or less.

[0091] The average height of the first ribs may be 0.3 mm or more, or may be 0.4 mm or more. When the average height of the first ribs is in this range, high oxidation degradation of the base portion can be ensured. From the viewpoint of ensuring high capacity, the average height of the first ribs may be 0.7 mm or less.

[0092] The average height of the second rib may be 0.1 mm or less. The average height of the second rib may be, for example, 0.02 mm or more.

[0093] In the lead-acid battery according to one aspect of the present invention, high deep discharge cycle performance can be ensured by setting the A / B ratio within an appropriate range. The A / B ratio is 0.13 or more. From the viewpoint of easily ensuring higher deep discharge cycle performance, the A / B ratio may be 0.2 or more. The A / B ratio is 0.75 or less.

[0094] The volume B of the separator excluding the positive electrode plate is preferably 20 mL or more. Alternatively, the volume B may be 65 mL or less, or may be 63 mL or less. When the volume B is in this range, it is easy to adjust the A / B ratio to an appropriate range.

[0095] (Separator size measurement) A separator sample for measurement (hereinafter also referred to as Sample G) was prepared by removing the sulfuric acid from a separator removed from a fully charged lead-acid battery by rinsing with water. The size of the separator was measured within 10 minutes after rinsing while the separator was still wet with water.

[0096] For sample G, the thickness of the base portion is measured using a vernier caliper. The base thickness of sample G is measured for multiple (e.g., 10) separators removed from the lead-acid battery, and the measurements are averaged to determine the base thickness (average). If the separator has a second rib, the base thickness and height of the second rib of sample G are measured in the same manner as for the base thickness described above, and the average is determined. The average height of the second rib is determined by subtracting the average base thickness from this average. The thickness of the base portion and the height of the second rib are measured at the portion facing the negative electrode material. If the thickness of the base portion and the height of the second rib cannot be determined using a vernier caliper, the pouch-shaped separator is observed under a microscope from the opening side with the opening closed, and the height of the second rib is determined. The height of the second rib is measured at the portion facing the negative electrode material.

[0097] Sample G is laid flat on a flat surface, and the height and width of the separator are measured. The height of the separator is the length (distance) between the opening of the bag and the bottom on the opposite side of the opening. The width of the separator is the length of the separator in a direction perpendicular to the height of the separator when laid flat. The height and width of sample G are measured for multiple separators (e.g., 10) removed from the lead-acid battery, and the height and width of the separator are calculated by averaging the measurements.

[0098] The thickness of the base portion of the separator (and the height of the second rib), height, and width thus determined are used to calculate the volume B of the separator excluding the positive electrode plate.

[0099] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled if necessary.

[0100] The electrolytic solution may contain cations (e.g., metal cations) and / or anions (e.g., anions other than sulfate anions (e.g., phosphate ions)) as needed. Examples of metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0101] The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 or more, and may be 1.25 or more. The specific gravity of the electrolyte at 20°C is 1.35 or less, and may be 1.32 or less.

[0102] The specific gravity of the electrolyte at 20° C. may be 1.20 or more and 1.35 or less, 1.20 or more and 1.32 or less, 1.25 or more and 1.35 or less, or 1.25 or more and 1.32 or less.

[0103] (others) A lead-acid battery may include one cell or two or more cells. When a lead-acid battery includes multiple cells (in other words, multiple electrode plate groups), the multiple electrode plate groups may be connected in series.

[0104] The number of each electrode plate in the electrode plate group may be 1 or 2 or more. From the viewpoint of ensuring higher capacity, the number of negative electrode plates included in the electrode plate group is preferably 2 or more, and may be 4 or more or 6 or more. If the number of negative electrode plates included in the electrode plate group is m, the number of positive electrode plates is (m-1) or more and (m+1) or less when m≧2, and is 1 or 2 when m=1.

[0105] (evaluation) The deep discharge cycle performance of a lead-acid battery is evaluated by the following procedure. In accordance with EN 50342-6:2015, a deep discharge cycle test is performed at a 50% depth of discharge (DOD), and the life performance is evaluated based on the end-of-discharge voltage. Specifically, the deep discharge cycle test is performed in a water tank at 40°C ± 2°C in accordance with the 40°C test specified in EN 50432-6:2015 (Endurance in cycle test with 50% depth of discharge at 40°C and preceded deep discharge test). More specifically, the deep discharge cycle test is performed according to the following procedure.

[0106] First, using a fully charged lead-acid battery, the following steps 1 to 4 are carried out at 40°C ± 2°C until the end of life is determined. At this time, the end-of-discharge voltage at 50% DOD discharge in each cycle is measured and monitored. The end of life is determined when the voltage at 50% DOD discharge reaches 1.67V / cell. Life performance is evaluated based on the number of cycles at which the end of life is reached. The higher the number of cycles, the better the life performance in the deep discharge cycle test. 20 is the 20-hour rate current (A), which is 1 / 20 of the value (unit: Ah) listed as the rated capacity. Step 1: Insert the lead acid battery into the 20 Discharge at a constant current five times that of (A) for 2 hours (DOD 50%). Step 2: Charge the lead-acid battery at a constant voltage of 2.6 V / cell and I 20Charge for 5 hours at a maximum current five times that of (A). If the charge quantity reaches 108% of the discharge quantity in step 1, proceed to step 4; if not, proceed to step 3. Step 3: Charge the lead-acid battery at a constant voltage of 3.0 V / cell and I 20 Charge for up to 1 hour under the maximum current condition of (A). When the total amount of charge electricity in steps 2 and 3 reaches 108% of the amount of discharge electricity in step 1, proceed to step 4. Step 4: Repeat steps 1 to 3 until the end of the service life.

[0107] A lead-acid battery according to one aspect of the present invention will be summarized below.

[0108] (1) A lead-acid battery, The lead-acid battery includes at least one electrode plate group and an electrolyte, the electrode plate group includes a positive electrode plate including a positive electrode material, a negative electrode plate, and a pouch-shaped separator interposed between the positive electrode plate and the negative electrode plate, The separator accommodates the positive electrode plate, A lead-acid battery, wherein the ratio (=A / B) of the pore volume A (mL) of the positive electrode material to the volume B (mL) of the separator excluding the positive electrode plate is 0.13 or more and 0.75 or less.

[0109] (2) In the above (1), the ratio A / B may be 0.2 or more.

[0110] (3) In the above (1) or (2), the pore volume A may be 7.3 mL or more or 8 mL or more.

[0111] (4) In any one of the above (1) to (3), the pore volume A may be 17 mL or less, 16 mL or less, or 15.5 mL or less.

[0112] (5) In any one of the above (1) to (4), the thickness of the positive electrode plate may be 1.2 mm or more or 1.3 mm or more.

[0113] (6) In any one of the above (1) to (5), the thickness of the positive electrode plate may be 2.5 mm or less or 2.4 mm or less.

[0114] (7) In any one of the above (1) to (6), the density of the positive electrode material in the lead-acid battery is 3.6 g / cm 3 More than 3.65g / cm 3 or more, or 3.67 g / cm 3 It may be more than that.

[0115] (8) In any one of the above (1) to (7), the density of the positive electrode material in the lead-acid battery is 4.5 g / cm 3 Below 4.30g / cm 3 or less, or 4.20 g / cm 3 It may be the following:

[0116] (9) In any one of the above (1) to (8), the positive electrode plate may contain Sb.

[0117] (10) In the above (9), the content of Sb in the positive electrode plate may be 100 ppm or more, 200 ppm or more, or 300 ppm or more.

[0118] (11) In the above (9) or (10), the content of Sb in the positive electrode plate may be 1000 ppm or less.

[0119] (12) In any one of the above (1) to (11), the negative electrode plate may contain a negative electrode material, and the negative electrode material may contain an organic shrinkage preventer.

[0120] (13) In the above (12), the content of the organic shrinkage preventer in the negative electrode material may be 0.01% by mass or more.

[0121] (14) In the above (12) or (13), the content of the organic shrinkage preventer in the negative electrode material may be 1% by mass or less or 0.5% by mass or less.

[0122] (15) In any one of the above (1) to (14), the negative electrode plate may include a negative electrode material, and the negative electrode material may include a carbonaceous material.

[0123] (16) In the above (15), the content of the carbonaceous material in the negative electrode material may be 0.05 mass % or more or 0.1 mass parts or more.

[0124] (17) In the above (15) or (16), the content of the carbonaceous material in the negative electrode material may be 5% by mass or less.

[0125] (18) In any one of the above (1) to (17), the negative electrode plate may contain a negative electrode material, and the negative electrode material may contain barium sulfate.

[0126] (19) In the above (18), the content of the barium sulfate in the negative electrode material may be 0.05% by mass or more, or 0.1% by mass or more.

[0127] (20) In the above (18) or (19), the content of the barium sulfate in the negative electrode material may be 3 mass % or less.

[0128] (21) In any one of the above (1) to (20), the separator may include a base portion, and the average thickness of the base portion may be 0.1 mm or more or 0.15 mm or more.

[0129] (22) In any one of the above (1) to (21), the separator may include a base portion, and the average thickness of the base portion may be 0.3 mm or less.

[0130] (23) In any one of the above (1) to (22), the separator may include a base portion and a first rib protruding from the base portion toward the positive electrode plate.

[0131] (24) In the above (23), the average height of the first rib may be 0.3 mm or more or 0.4 mm or more.

[0132] (25) In the above (23) or (24), the average height of the first rib may be 0.7 mm or less.

[0133] (26) In any one of the above (1) to (25), the separator may include a base portion and a second rib protruding from the base portion toward the negative electrode plate.

[0134] (27) In the above (26), the average height of the second rib may be 0.1 mm or less.

[0135] (28) In the above (26) or (27), the average height of the second rib may be 0.02 mm or more.

[0136] (29) In any one of the above (1) to (28), the volume B may be 20 mL or more.

[0137] (30) In any one of the above (1) to (29), the volume B may be 65 mL or less or 63 mL or less.

[0138] (31) In any one of the above (1) to (30), the specific gravity of the electrolyte at 20° C. in the lead-acid battery in a fully charged state may be 1.20 or more or 1.25 or more.

[0139] (32) In any one of the above (1) to (31), the specific gravity of the electrolyte at 20° C. in the lead-acid battery in a fully charged state may be 1.35 or less or 1.32 or less.

[0140] (33) In any one of the above (1) to (32), the lead-acid battery may include two or more cells (or the electrode plate group).

[0141] (34) In any one of the above (1) to (33), the lead-acid battery may include a plurality of the electrode plate groups, and the plurality of the electrode plate groups may be connected in series.

[0142] (35) In any one of the above (1) to (34), the number of the positive electrode plate and the negative electrode plate in the electrode plate group may each be one or two or more.

[0143] (36) In any one of the above (1) to (35), the number of the negative electrode plates included in the electrode plate group may be two or more, four or more, or six or more.

[0144] (37) In the above (36), when the number of negative electrode plates included in the electrode plate group is m, the number of positive electrode plates may be (m-1) or more and (m+1) or less when m≧2, and may be 1 or 2 when m=1.

[0145] An external appearance of an example of a lead-acid battery according to one embodiment of the present disclosure is shown in Fig. 1. However, the lead-acid battery according to one aspect of the present disclosure is not limited to the following embodiment. The lead-acid battery 1 includes a battery case 12 that contains a plate group 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 group 11. The opening of the battery case 12 is closed by a lid 15 that has a positive electrode terminal 16 and a negative 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 liquid 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.

[0146] The electrode plate group 11 is formed by alternately stacking multiple negative electrode plates 3 and multiple positive electrode plates 2 with separators 4 interposed between them. The separators 4 are bag-shaped and individually package the positive electrode plates 2. In a cell chamber 14 located at one end of the battery case 12, a positive electrode shelf 6, which connects the ears 2a of multiple positive electrode plates 2 in parallel, is connected to a through-connector 8, and a negative electrode shelf 5, which connects the ears 3a of multiple negative electrode plates 3 in parallel, is connected to a negative electrode column 7. The negative electrode column 7 is connected to a negative electrode terminal 17 outside the lid 15. In a cell chamber 14 located at the other end of the battery case 12, a positive electrode column 9 is connected to the positive electrode shelf 6, and a through-connector 8 is connected to the negative electrode shelf 5. The positive electrode column 9 is connected to a positive 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.

[0147] The positive electrode shelf 6 is formed by welding together the ears 2a provided on the top of each positive electrode plate 2 by a cast-on-strap method or a burning method. The negative electrode shelf 5 is also formed by welding together the ears 3a provided on the top of each negative electrode plate 3 in the same manner as the positive electrode shelf 6.

[0148] The lid 15 of the lead-acid battery has a single structure (single lid), but this is not limited to the illustrated example. The lid 15 may have a double structure, for example, including an inner lid and an outer lid (or top lid). A lid having a double structure may have a reflux structure between the inner lid and the outer lid for returning the electrolyte to the battery (inside the inner lid) from a reflux port provided in the inner lid.

[0149] [Example] Hereinafter, a lead-acid battery according to one aspect of the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

[0150] Lead-acid batteries E1 to E5 and C1 to C4 (1) Preparation of the positive electrode plate Lead powder, antimony trioxide, water, and dilute sulfuric acid are mixed to obtain a positive electrode paste. The positive electrode paste is applied to an expanded grid made of a Pb-Ca-Sn alloy as a positive electrode current collector. The applied positive electrode paste is filled into the mesh of the grid and aged and dried. In this manner, an unformed positive electrode plate is obtained. The density of the positive electrode material or the thickness of the positive electrode plate is changed as shown in Table 1 so that the A / B ratio obtained by the above-mentioned procedure becomes the value shown in Table 1. When preparing the positive electrode paste, the amount of antimony trioxide is adjusted so that the Sb content in the positive electrode plate obtained by the above-mentioned procedure becomes 380 ppm to 690 ppm for E1 to E5 and 360 ppm to 480 ppm for C1 to C4.

[0151] (2) Preparation of the negative electrode plate A negative electrode paste is prepared by mixing lead powder, water, dilute sulfuric acid, sodium lignosulfonate as an organic shrinkage preventer, barium sulfate, and carbon black. The amounts of each component are adjusted so that the organic shrinkage preventer, barium sulfate, and carbon black contents in the negative electrode material obtained by the previously described procedures are 0.2 mass%, 0.6 mass%, and 0.3 mass%, respectively. The negative electrode paste is applied to an expanded grid made of a Pb-Ca-Sn alloy. The applied negative electrode paste is filled into the mesh of the grid and aged and dried. In this way, an unformed negative electrode plate is obtained.

[0152] (3) Preparation of test battery The unformed positive electrode plate is housed in a pouch-shaped separator. However, in C1, the unformed negative electrode plate is housed in a pouch-shaped separator. The unformed positive electrode plate and the unformed negative electrode plate are stacked with a separator between them to form an electrode plate assembly. The number of positive electrode plates and negative electrode plates included in one electrode plate assembly is shown in Table 1. The pouch-shaped separator is made of a microporous polyethylene film and has a first rib (average height 0.6 mm) that protrudes toward the positive electrode plate. The average thickness of the base portion of the pouch-shaped separator is 0.25 mm.

[0153] The electrode plate group is inserted into a battery case, and a predetermined amount of sulfuric acid aqueous solution is poured in as the electrolyte. Chemical formation is performed inside the battery case to prepare a wet lead-acid battery (test battery). The specific gravity of the electrolyte in a fully charged lead-acid battery at 20°C is 1.285. The above chemical formation brings the lead-acid battery into a fully charged state. In this way, a lead-acid battery (test battery) is prepared with a rated voltage of 2V / cell and a rated 20-hour rate capacity as shown in Table 1.

[0154] The test batteries prepared as described above were evaluated for deep discharge cycle performance (50% DOD life) using the method described above. Table 1 shows the evaluation results of the lead-acid batteries as relative values, with the evaluation result of lead-acid battery C1 set at 100. The evaluation of deep discharge cycle performance indicates that the higher the value, the greater the effect.

[0155] The results are shown in Table 1. Lead acid batteries E1 to E5 are examples, and lead acid batteries C1 to C4 are comparative examples.

[0156] [Table 1]

[0157] As shown in Table 1, E1 to E5, in which the positive electrode plate is housed in a pouch-shaped separator and the A / B ratio is 0.13 to 0.75, exhibit high deep discharge cycle performance. This is thought to be because stratification inside and outside the separator is suppressed, reducing the accumulation of lead sulfate and allowing the reaction to occur more uniformly throughout the electrode plate. In addition, the more uniform reaction is thought to reduce the variability in the progress of softening and shedding.

[0158] On the other hand, in C2, where A / B<0.13, deep discharge cycle performance is significantly reduced. This is thought to be because the amount of sulfate released during charging is compared to the amount of free space in the separator, causing sulfate to leave the positive plate and diffuse to the vicinity of the negative plate. Sulfate that diffuses to the vicinity of the negative plate is unlikely to return to the positive plate during discharge, which is thought to promote stratification. In addition to the tendency for lead sulfate to accumulate on the negative plate, the uneven distribution of reactions on the plate tends to lead to significant softening and shedding of the positive electrode material. These factors are thought to be the cause of the significant reduction in cycle performance in C2.

[0159] Even in C3 and C4, where A / B is greater than 0.75, deep discharge cycle performance is significantly reduced. This is thought to be because the amount of free space in the separator is very small compared to the amount of sulfate released during charging, making it easy for sulfate to diffuse out of the separator, which facilitates stratification. In addition, lead sulfate tends to accumulate on the negative electrode plate, and the reaction distribution on the electrode plate becomes uneven, making the softening and shedding of the positive electrode material more likely to occur in certain areas. These factors are thought to be the cause of the significant reduction in deep discharge cycle performance in C3 and C4.

[0160] When the negative electrode is housed in a pouch-shaped separator, the deep discharge cycle performance is low even when the ratio of the pore volume of the negative electrode material to the volume of the free space in the separator (corresponding to A / B in the case of a positive electrode plate) is in the range of 0.13 to 0.75 (C1). This is thought to be because it is difficult to achieve the stratification suppression effect, and the reaction in the electrode plate becomes more uneven, which increases the rate at which softening and falling off occurs in the upper part and other areas. [Industrial Applicability]

[0161] A lead-acid battery according to one aspect of the present invention is suitable for use in a vehicle equipped with an idle-stop system (also called start-stop or idle reduction system) as a lead-acid battery for idle-stop systems. Furthermore, the lead-acid battery can be suitably used as a starting power source for vehicles (cars, motorcycles, etc.) and an industrial power storage device (for example, a power source for an electric vehicle (forklift, etc.)). These are merely examples, and the uses of the lead-acid battery are not limited to these. [Explanation of symbols]

[0162] 1:Lead acid battery 2: Positive electrode plate 2a: ears 3: Negative electrode plate 3a: ears 4: Separator 5: Negative electrode shelf 6: Positive electrode shelf 7: Negative pole 8: Through-connector 9: Positive pole 11: Plate group 12:Battery container 13: Bulkhead 14: Cell Room 15: Lid 16: Positive terminal 17: Negative terminal 18: Liquid vent plug

Claims

1. A lead-acid battery, The lead-acid battery includes at least one electrode plate group and an electrolyte, the electrode plate group includes a positive electrode plate including a positive electrode material, a negative electrode plate, and a pouch-shaped separator interposed between the positive electrode plate and the negative electrode plate, the separator accommodates the positive electrode plate, a ratio (=A / B) of a pore volume A (mL) of the positive electrode material to a volume B (mL) of the separator excluding the positive electrode plate is 0.13 or more and 0.75 or less.

2. 2. The lead-acid battery according to claim 1, wherein the ratio A / B is 0.2 or more.

3. 3. The lead-acid battery according to claim 1, wherein the positive electrode plate has a thickness of 1.2 mm or more and 2.5 mm or less.

4. The lead-acid battery according to claim 1 or 2, wherein the positive electrode plate contains Sb.

5. The lead-acid battery according to claim 4, wherein the Sb content in the positive electrode plate is 100 ppm or more and 1000 ppm or less.

Images