Valve-regulated lead-acid battery

Abstract

This invention provides a valve-regulated lead-acid battery that can ensure a high discharge capacity even when performing high-rate discharge after float charging in a high-temperature environment. [Solution] The electrode plate group 11 and an electrolyte are provided, the electrode plate group comprising a positive electrode plate 3, a negative electrode plate 2, and a separator 4 interposed between the positive electrode plate and the negative electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode material, the negative electrode plate comprising a negative electrode current collector and a negative electrode material, the separator being a nonwoven fabric containing glass fibers, the ratio of the volume of the electrolyte to the pore volume of the electrode plate group being 108% or more and 130% or less, and the inter-electrode density of the separator being 0.15 g / cm³ 3 More than 0.28g / cm 3 A valve-regulated lead-acid battery 1, wherein, in the pore size distribution of the positive electrode material, the ratio of the volume of pores with a diameter of 1 μm or more to the total pore volume is 50% or more and 70% or less.

Description

[Technical Field]

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

[0002] Patent Document 1 proposes a valve-regulated lead-acid battery comprising a negative electrode plate and a positive electrode plate each containing an active material, a mat separator interposed between the negative electrode plate and the positive electrode plate, and an electrolyte, characterized in that the electrolyte is contained in an amount of 100.0 to 106.5 volume% relative to the total pore volume of the negative electrode plate, the positive electrode plate, and the mat separator. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-018628 [Overview of the project] [Problems that the invention aims to solve]

[0004] Because valve-regulated lead-acid batteries require the gas absorption reaction to proceed, the amount of electrolyte is limited. For example, in stationary batteries, the ratio of the electrolyte volume to the pore volume of the electrode group is usually around 100% to 104%.

[0005] When a valve-regulated lead-acid battery is float-charged in a high-temperature environment, the discharge capacity tends to decrease after a high-rate discharge. This decrease in discharge capacity is thought to be due to the electrolyte level decreasing during float charging, leading to the following phenomena.

[0006] Firstly, valve-regulated lead-acid batteries use a nonwoven fabric containing glass fibers as a separator. This nonwoven fabric containing glass fibers tends to shrink in a high-temperature environment inside a lead-acid battery during float charging. When the nonwoven fabric containing glass fibers (separator) shrinks, the compressive force applied to the electrode group decreases, and the contact resistance between the positive and negative electrode plates and the separator increases.

[0007] Second, during float charging of a lead-acid battery in a high-temperature environment, the electrolyte volatilizes to the outside, so the amount of electrolyte retained by the positive and negative electrode plates decreases, and the amount of electrolyte diffusion from the separator to the positive and negative electrode plates also decreases during high-rate discharge.

[0008] Third, during high-rate discharge, on the positive electrode plate, the discharge reaction preferentially occurs on the surface of the electrode plate, and the generated lead sulfate tends to block the pores. Due to such pore blockage, it becomes difficult for the electrolyte to diffuse into the interior of the positive electrode plate, and the discharge reaction at high rates is restricted.

Means for Solving the Problems

[0009] One aspect of the present invention includes an electrode plate group and an electrolyte. The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode material. The negative electrode plate includes a negative current collector and a negative electrode material. The separator is a non-woven fabric containing glass fibers. The ratio of the volume of the electrolyte to the pore volume of the electrode plate group is 108% or more and 130% or less. The inter-pole density of the separator is 0.15 g / cm 3 or more and 0.28 g / cm 3 or less. In the pore size distribution of the positive electrode material, the ratio of the pore volume with a pore diameter of 1 μm or more to the total pore volume is 50% or more and 70% or less. The present invention relates to a controlled valve type lead-acid battery.

Effects of the Invention

[0010] The controlled valve type lead-acid battery according to the present invention can ensure a high discharge capacity even when performing high-rate discharge after float charging in a high-temperature environment.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing an example of the structure of a controlled valve type lead-acid battery according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit of a numerical value regarding a specific physical property or condition are exemplified, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0013] In addition, the present disclosure includes combinations of matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims. That is, as long as no technical contradiction occurs, matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims can be combined.

[0014] A lead-acid battery 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 electrolyte contains sulfuric acid. Charging and discharging proceed by the movement of sulfate ions between the positive electrode plate and the negative electrode plate and the electrolyte. During discharging, sulfate ions move to the positive electrode plate and the negative electrode plate. During charging, sulfate ions move from the positive electrode plate and the negative electrode plate into the electrolyte.

[0015] A positive electrode plate, a negative electrode plate, and a separator constitute an electrode group. An electrode group typically includes multiple positive electrode plates, multiple negative electrode plates, and a separator interposed between the positive and negative electrode plates. The positive and negative electrode plates are stacked alternately via the separator. The electrode group, together with the electrolyte, constitutes a cell. One electrode group constitutes one cell. A lead-acid battery comprises one or more cells by comprising one or more electrode groups. There is no particular limit to the number of positive and negative electrode plates included in one electrode group. An electrode group comprising a lead-acid battery according to this disclosure, for example, includes a total of seven or more positive and negative electrode plates. Multiple electrode groups are typically housed in separate cell chambers and connected in series with one another.

[0016] The positive electrode plate includes a positive electrode current collector and a positive electrode material. The positive electrode material is a positive electrode active material that exhibits capacity through oxidation-reduction reactions, and contains at least lead dioxide during charging and at least lead sulfate during discharge.

[0017] The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material is a negative electrode active material that exhibits capacity through oxidation-reduction reactions, and contains at least lead during charging and at least lead sulfate during discharge.

[0018] The battery case has a bottom, side walls rising from the periphery of the bottom, and a lid that closes the open end of the side walls. The inside of the battery case is usually divided into multiple spaces by partitions. The inside of the battery case may be divided into multiple (e.g., six) cell chambers by partitions that are parallel to each other. Multiple partitions may intersect with each other to divide into multiple (e.g., four or more) cell chambers.

[0019] (1) A valve-regulated lead-acid battery according to an embodiment of the present disclosure comprises an electrode group and an electrolyte, the electrode group comprising a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode material, the negative electrode plate comprising a negative electrode current collector and a negative electrode material, the separator being a nonwoven fabric containing glass fibers, the ratio of the volume of the electrolyte to the pore volume of the electrode group being 108% or more and 130% or less, and the inter-electrode density of the separator being 0.15 g / cm³ 3 More than 0.28g / cm 3 The following conditions apply to the pore size distribution of the positive electrode material: the ratio of the volume of pores with a diameter of 1 μm or more to the total pore volume is 50% or more and 70% or less.

[0020] Valve-regulated lead-acid batteries are also known as VRLA (Valve-regulated lead-acid battery) or sealed batteries.

[0021] In the valve-regulated lead-acid battery described in (1) above, a high discharge capacity can be secured even when high-rate discharge is performed after float charging in a high-temperature environment. For example, in a float test in a high-temperature environment (e.g., 60°C), the retention rate of discharge capacity improves when high-rate discharge is performed once every month.

[0022] The valve-regulated lead-acid battery described in (1) above satisfies the following conditions (a) to (c), as previously stated.

[0023] Condition (a) The ratio of the electrolyte volume to the pore volume of the electrode plate group is between 108% and 130%.

[0024] Condition (b) The separator is a nonwoven fabric containing glass fibers, and the inter-electrode density of the separator is 0.15 g / cm³. 3 More than 0.28g / cm 3 The following applies:

[0025] Condition (c) In the pore size distribution of the positive electrode material, the ratio of the volume of pores with a diameter of 1 μm or larger to the total pore volume is between 50% and 70%.

[0026] When condition (a) is met, the large amount of electrolyte ensures that even if the electrolyte level decreases, a sufficient amount of electrolyte remains in the separator, maintaining a high compressive force on the electrode group. Therefore, when using a valve-regulated lead-acid battery in a high-temperature environment, contact between the positive and negative electrodes and the separator is maintained over a long period, keeping the contact resistance low, and during high-rate discharge, the electrolyte diffuses more easily from the separator to the positive and negative electrodes.

[0027] Furthermore, when condition (b) is met, the contact area between glass fibers within the separator is large, and the entanglement of the fibers is significant. As a result, even when the glass fibers are wetted with the electrolyte, shrinkage of the separator due to surface tension is less likely to occur, and the compressive force of the electrode group is more easily maintained at a high level.

[0028] Furthermore, if condition (c) is met, the positive electrode plate has many large pores with a diameter of 1 μm or more. Therefore, even if the electrode plate surface discharges preferentially and lead sulfate is generated on the electrode plate surface, the pores are less likely to become blocked, and the electrolyte can easily diffuse into the interior of the positive electrode plate.

[0029] It is believed that the organic interaction of the phenomena described above significantly improves the maintenance rate of high-rate discharge capacity over the long term, even when using valve-regulated lead-acid batteries in high-temperature environments.

[0030] While there are no particular limitations on the applications of valve-regulated lead-acid batteries, the above effects can be particularly pronounced in stationary batteries. Since increasing the electrolyte volume is not typically anticipated in stationary batteries, even if conditions (b) and (c) are met, it is not predictable that the maintenance rate of high-rate discharge capacity will change significantly by further satisfying condition (a).

[0031] The inter-electrode density of the separator is 0.28 g / cm³. 3If the voltage exceeds a certain level, the amount of electrolyte contained in the separator decreases, and the amount of electrolyte diffusing from the separator to the positive and negative electrode plates decreases. As a result, the amount of positive electrode material and the amount of electrolyte that can react with the positive electrode material decreases, which actually reduces the discharge capacity.

[0032] (2) In the valve-regulated lead-acid battery described in (1) above, the ratio (Y / X) of the volume-central pore diameter Y in the pore diameter distribution of the negative electrode material to the volume-central pore diameter X in the pore diameter distribution of the positive electrode material may be 3 or more and 6 or less.

[0033] According to the valve-regulated lead-acid battery described in (2) above, even if the electrolyte held by the electrode plate group decreases (for example, when the ratio of the volume of electrolyte to the pore volume of the electrode plate group falls below 100%), the amount of electrolyte moving into the positive electrode plate increases due to capillary action caused by differences in pore size. Therefore, the capacity retention rate at low-rate discharge, which is often limited by the positive electrode plate, is also improved.

[0034] The reason why capacity retention improves with low-rate discharge is thought to be that a larger amount of sulfuric acid can react with the positive electrode active material, allowing for sufficient discharge not only on the surface of the positive electrode plate but also into the positive electrode active material inside.

[0035] More specifically, the amount of electrolyte moving from the separator to the positive electrode increases. Since the pore size of the negative electrode is smaller than that of the separator, electrolyte also moves from the separator to the negative electrode, which has smaller pores. However, since the pore size of the positive electrode is even smaller, more electrolyte ultimately moves to the positive electrode via the separator. As a result, the capacity retention rate at low discharge improves.

[0036] As described above, by setting the Y / X ratio to 3 or higher, the amount of electrolyte transferred to the positive electrode plate can be increased. Furthermore, when the Y / X ratio is 6 or lower, the amount of electrolyte on the negative electrode plate does not decrease excessively, and the capacity is less limited by the negative electrode plate.

[0037] (3) In the controlled valve type lead-acid battery according to (1) or (2) above, the ratio of the volume of the electrolyte to the pore volume of the electrode plate group may be 115% or more and 130% or less.

[0038] According to the controlled valve type lead-acid battery described in (3) above, when high-rate discharge is performed after floating charge in a high-temperature environment, a higher discharge capacity can be ensured.

[0039] (4) In the controlled valve type lead-acid battery according to any one of (1) to (3) above, the inter-pole density of the separator is 0.23 g / cm 3 or more and 0.28 g / cm 3 or less.

[0040] According to the controlled valve type lead-acid battery described in (4) above, since the inter-pole density of the separator is 0.23 g / cm 3 or more, the contact area between the glass fibers in the separator further increases, and the shrinkage of the separator due to the surface tension when the fibers are wetted by the electrolyte is further less likely to occur, and the compression force of the electrode plate group is likely to be maintained high.

[0041] In this specification, the fully charged state of the controlled valve type lead-acid battery means that in an air bath at 25°C ± 2°C, constant voltage charging at 2.275 V / cell (in a lead-acid battery with a nominal voltage of 12 V, 13.65 V) (the maximum current is 5 times the 20-hour rate current I 20 of 5I 20 (unit: A)) is performed, and charging is terminated when the total charging time reaches 24 hours. Here, the n-hour rate current I n means a current (A) that is 1 / n of the numerical value of Ah described in the rated capacity. I n corresponds to a current value (unit: A) obtained by dividing the rated n-hour rate capacity (unit: Ah) of the battery by n. Therefore, the 20-hour rate current I 20 means a current (A) that is 1 / 20 of the numerical value of Ah described in the rated capacity. Hereinafter, the numerical value described as the rated capacity and having the unit of Ah (ampere-hour) is simply referred to as the "rated capacity".

[0042] A fully charged lead-acid battery is a lead-acid battery that has been charged to its full capacity after chemical formation. The timing for charging a lead-acid battery to its full capacity can be immediately after chemical formation, or after a certain amount of time has passed since formation (e.g., 720 hours or less). For example, a lead-acid battery that has been chemically formed and is in use (preferably in the early stages of use) may be charged.

[0043] In this specification, a battery in its initial use refers to a battery that has not been used for very long and has not deteriorated much (for example, a battery that has been in use for less than 720 hours, including the time elapsed since chemical preparation).

[0044] The following explains how to determine various parameters and material properties.

[0045] <The ratio of the volume of electrolyte to the pore volume of the electrode group (hereinafter also referred to as the "L / P ratio")> The electrolyte volume is determined by disassembling a fully charged battery after chemical conversion, washing and drying the positive electrode plate, negative electrode plate, and separator with water. The electrolyte volume (mL) (=A) is calculated from the difference in mass before and after washing and drying.

[0046] The pore volume of the electrode group is determined as the sum of the pore volumes of the positive electrode, the negative electrode, and the separator.

[0047] The pore volume (mL) (=B1) of the positive electrode plate is calculated by washing and drying the positive electrode plate, taking a sample of the positive electrode material from the dried plate, measuring the mass (g) of the sampled positive electrode material, determining the total pore volume (mL / g) using the mercury intrusion method, and then calculating the pore volume (mL / g) from the total pore volume (mL / g) and the mass of the positive electrode material.

[0048] The pore volume (mL) (=B2) of the negative electrode plate is calculated by washing and drying the negative electrode plate, taking a sample of the negative electrode material from the dried negative electrode plate, measuring the mass (g) of the sampled negative electrode material, determining the total pore volume (mL / g) by the mercury intrusion method, and then calculating the B2 from the total pore volume (mL / g) and the mass of the negative electrode material.

[0049] In the mercury intrusion method, the unground sample is placed in a measuring container, evacuated, and then the log differential pore volume distribution in the region of pore diameters of 5.5 nm or more and 333 μm or less is measured by mercury intrusion at a pressure of 0.05 psia to 33000 psia (≒ 0.345 kPa to 22700 kPa) for both the positive and negative electrodes.

[0050] For the separator, the separator is compressed to the inter-electrode dimensions, impregnated with sulfuric acid having the same specific gravity as the disassembled battery, and the maximum volume of electrolyte it can hold is determined as the pore volume (mL) (=C).

[0051] The ratio of the volume of electrolyte to the pore volume of the electrode group is calculated using the L / P ratio (%) = A × 100 ÷ (B1 + B2 + C).

[0052] The L / P ratio (%) should be 108% or higher, preferably 115% or higher, and may be 120% or higher. The L / P ratio (%) should be 130% or lower, but may be 125% or lower.

[0053] The L / P ratio (%) may be 108% or more and 130% or less, 115% or more and 130% or less (for example, 125% or less), or 120% or more and 130% or less (for example, 125% or less).

[0054] <Inter-electrode density of the separator (hereinafter also referred to as "D(AGM)")> After disassembling a fully charged battery following chemical conversion, the separators are washed and dried. The mass (g) (=M) of one separator (the separator between one electrode) after drying is measured.

[0055] From the measurement results of the length and width of the positive electrode plate, the electrode plate area (cm²) can be calculated. 2 Calculate (=S).

[0056] The distance between the electrodes (cm) (=d) is calculated from the internal dimensions of the battery case and the thickness of the positive and negative electrode plates. The internal dimensions of the battery case are measured at a height of half the height of the positive and negative electrode plates from the bottom of the battery case.

[0057] D(AGM)(g / cm 3 The inter-pole density of the separator is calculated using the formula: ) = M ÷ (S × d).

[0058] D(AGM) is 0.15 g / cm³ 3 Anything above that is acceptable, but 0.19 g / cm³ is acceptable. 3 The above is also acceptable, 0.23 g / cm³ 3 The above is also acceptable. D(AGM) is 0.28 g / cm³. 3 The following is acceptable, but 0.27 g / cm³ is acceptable. 3 The following is also acceptable.

[0059] D(AGM) is 0.15 g / cm³ 3 More than 0.28g / cm 3 The following is acceptable, but 0.19 g / cm³ is acceptable. 3 More than 0.28g / cm 3 (For example, 0.27 g / cm³) 3 The following is also acceptable: 0.23 g / cm³ 3 More than 0.28g / cm 3 Below (0.27g / cm 3 The following is also acceptable.

[0060] <The ratio of the volume of pores with a diameter of 1 μm or more to the total pore volume in the pore size distribution of the positive electrode material (hereinafter also referred to as "Rp(≧1μm)")> After disassembling a fully charged battery following chemical conversion, the positive electrode plate is washed and dried with water. The positive electrode material is then collected from the dried positive electrode plate, and the pore size distribution of the collected positive electrode material is measured using the mercury intrusion method. The percentage of the total pore volume to which the volume of pores with a diameter of 1 μm or larger is calculated.

[0061] Rp(≧1μm) should be 50% or higher, but it can also be 55% or higher, 60% or higher, or 65% or higher. Rp(≧1μm) should be 70% or lower, but it can also be 65% or lower, or 60% or lower.

[0062] Rp (≧1μm) can be between 50% and 70%, but it can also be between 50% and 65%, or between 50% and 60%.

[0063] <The ratio of the volume-central pore diameter Y in the pore size distribution of the negative electrode material to the volume-central pore diameter X in the pore size distribution of the positive electrode material (hereinafter also referred to as the "Y / X ratio")> The volume-based median pore diameters X and Y are measured and calculated from the pore size distribution of the positive electrode material and the negative electrode material, respectively.

[0064] Hereinafter, a valve-regulated lead-acid battery according to an embodiment of the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0065] The following describes examples of components of a valve-regulated lead-acid battery.

[0066] (Positive plate) The positive electrode plate comprises a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. The positive electrode material is the portion of the positive electrode plate excluding the positive electrode current collector. Adhesive members such as conductive layers, mats, and pasting paper may be attached to the positive electrode plate. Since the adhesive members are used integrally with the positive electrode plate, they are included as components of the positive electrode plate. When the positive electrode plate includes adhesive members, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode current collector and the adhesive members.

[0067] The positive electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. Processing methods may include, for example, expansion or punching. Using a grid-like current collector as the positive electrode current collector makes it easier to support the positive electrode material.

[0068] As the lead alloy used for the positive electrode current collector, Pb-Ca alloys and Pb-Ca-Sn alloys, which have excellent corrosion resistance and mechanical strength, are preferred. The positive electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers.

[0069] The positive electrode material contains a positive electrode active material that exhibits capacity through a redox reaction. The positive electrode active material includes lead dioxide, lead sulfate, and the like.

[0070] Positive electrodes are obtained by chemically converting unconverted positive electrodes. Unconverted positive electrodes are obtained by filling a positive electrode current collector with positive electrode paste, allowing it to mature, and drying. Positive electrode paste is prepared, for example, by kneading a mixture containing lead powder, water, and sulfuric acid. Such positive electrodes are also called paste-type positive electrodes.

[0071] Chemical treatment may be carried out by immersing the electrode plate group, including the untreated positive electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and charging the electrode plate group. Chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group.

[0072] (Negative electrode plate) The negative electrode plate comprises a negative electrode current collector and a negative electrode material. The negative electrode material is held by the negative electrode current collector. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. Note that adhesive members such as conductive layers, mats, and pasting paper may be attached to the negative electrode plate. The adhesive members are included as components of the negative electrode plate. When the negative electrode plate includes adhesive members, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive members.

[0073] The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. The processing method may be expansion or punching. Using a grid-like current collector as the negative electrode current collector makes it easier to support the negative electrode material.

[0074] The lead alloy used for the negative electrode current collector may be either a Pb-Ca alloy or a Pb-Ca-Sn alloy. The lead alloy used for the negative electrode current collector may also contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. The negative electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers.

[0075] The negative electrode material contains a negative electrode active material that exhibits capacity through oxidation-reduction reactions. The negative electrode active material includes lead, lead sulfate, etc. The negative electrode material also contains an organic shrinkage inhibitor. Organic shrinkage inhibitors are known to improve the lifespan of lead-acid batteries and enhance low-temperature high-rate discharge performance.

[0076] Organic shrinkage inhibitors that can be used include lignin, lignin derivatives, and synthetic organic shrinkage inhibitors (such as formaldehyde condensates of phenol compounds). Examples of lignin derivatives include lignin sulfonic acid or its salts (such as alkali metal salts). The negative electrode material may contain one organic shrinkage inhibitor or two or more.

[0077] The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more and 1% by mass or less, and may be 0.03% by mass or less and 0.6% by mass or less.

[0078] As the formaldehyde condensate of the phenol compound, a condensate of a bisphenol compound with at least one selected from the group consisting of sulfite compounds and amino acid compounds and an aldehyde compound is preferred.

[0079] Examples of bisphenol compounds that can be used include 4,4'-dihydroxydiphenylmethane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)hexafluoropropane (bisphenol F), 4,4'-dihydroxydiphenylsulfone (bisphenol S), 4,4'-bis(4-hydroxyphenyl)valeric acid, 4,4'-bis(4-hydroxyphenyl)butyric acid, and their isomers.

[0080] The negative electrode material may contain other additives as needed. Such additives may include carbonaceous materials, barium sulfate, and the like.

[0081] Carbonaceous materials that can be used include carbon black, artificial graphite, natural graphite, hard carbon, and soft carbon. A single carbonaceous material may be used, or two or more may be used in combination.

[0082] The carbonaceous material content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0083] The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0084] The negative electrode plate is obtained by chemically converting an unconverted negative electrode plate. The unconverted negative electrode plate is obtained by filling a negative electrode current collector with negative electrode paste, allowing it to mature, and drying it. The negative electrode paste is prepared by kneading a mixture containing lead powder, water, an organic shrinkage inhibitor, and sulfuric acid. The negative electrode paste may optionally contain carbonaceous materials, barium sulfate, etc.

[0085] The chemical treatment may be carried out by immersing the electrode plate group, including the untreated negative electrode plate, in an electrolyte containing sulfuric acid in the lead-acid battery case, thereby charging the electrode plate group. The chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group. The charged negative electrode active material contains spongy lead.

[0086] (Separator) A nonwoven fabric containing glass fibers is used as a separator. This nonwoven fabric containing glass fibers is also called AGM (Absorbed Glass Mat (Absorbent Glass Mat)) or AGM separator. The nonwoven fabric (AGM) is a mat in which glass fibers are intertwined without weaving, and is mainly composed of glass fibers. For example, 60% or more by mass of the nonwoven fabric is made up of glass fibers. The nonwoven fabric may also contain components other than glass fibers, such as acid-resistant inorganic powders (e.g., silica powder, glass powder, diatomaceous earth), and polymers as binders.

[0087] AGM may contain glass fibers and organic fibers. Preferably, the proportion of glass fibers in the total number of fibers constituting the AGM is 60% by mass or more.

[0088] As organic fibers, fibrous materials insoluble in the electrolyte are used. Examples of organic fibers include polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (such as polyethylene terephthalate fibers)), pulp fibers, etc.

[0089] The thickness of the separator placed between the negative and positive electrodes should be selected according to the distance between the electrodes. The number of separators should be selected according to the number of electrodes.

[0090] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, which may be gelled if necessary. The electrolyte may optionally contain cations (e.g., metal cations) and / or anions (e.g., anions other than sulfate anions (e.g., phosphate ions)). Examples of metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0091] The density of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 g / cm³. 3 The above is 1.25 g / cm³. 3 The above is also acceptable. The density of the electrolyte at 20°C is 1.35 g / cm³. 3 The following is the result: 1.32 g / cm³ 3 The following is preferable:

[0092] Figure 1 is a schematic cross-sectional view showing the structure of an example of a valve-regulated lead-acid battery. In Figure 1, the lead-acid battery 1 comprises a battery case 10 that houses an electrode plate group 11 and an electrolyte (not shown). The upper opening of the battery case 10 is closed with a lid 12. The electrode plate group 11 is composed of multiple negative electrode plates 2 and positive electrode plates 3 stacked with separators 4 in between.

[0093] Each of the multiple negative electrode plates 2 has an upward-projecting current-collecting tab (not shown) on its upper part. Each of the multiple positive electrode plates 3 also has an upward-projecting current-collecting tab (not shown) on its upper part. The tabs of the negative electrode plates 2 are connected and integrated by negative electrode straps (not shown). Similarly, the tabs of the positive electrode plates 3 are connected and integrated by positive electrode straps (not shown). The negative electrode straps are connected to negative electrode posts (not shown) which serve as external terminals, and the positive electrode straps are connected to positive electrode posts (not shown) which serve as external terminals.

[0094] A single electrode plate group 11 is housed in the cell chamber 10R of the battery case 10. The cell chamber 10R is equipped with an exhaust valve 13 on its lid 12. When the internal pressure of the cell chamber 10R exceeds a predetermined upper limit, the exhaust valve 13 opens, and gas is directly released from the cell chamber 10R to the outside. When the internal pressure of the cell chamber 10R is below the upper limit, the oxygen generated on the positive electrode plate 3 is reduced on the negative electrode plate 2 inside the cell chamber 10R to produce water.

[0095] The structure of a lead-acid battery is not limited to the above. For example, Figure 1 shows a case where the cell chamber 10R is a single cell, but the battery case 10 may have multiple independent cell chambers, each cell chamber may be equipped with an exhaust valve 13, or the lid may have a central exhaust chamber that communicates with each cell chamber. The central exhaust chamber is equipped with fewer exhaust valves than the number of cell chambers (for example, one).

[0096] The following describes the evaluation method for valve-regulated lead-acid batteries. For evaluation, a lead-acid battery (nominal voltage 2V) with one cell containing a plate group comprising three positive electrodes and four negative electrodes is used. Here, a stationary valve-regulated lead-acid battery with a rated 20-hour rate capacity of 40Ah is used. The evaluation method is described below.

[0097] <Float Test> Float charging is performed at 2.23V / cell in an environment of 60°C, and the discharge capacity is measured by high-rate discharge every month. Low-rate discharge is measured every month.

[0098] <High-rate discharge performance> For a fully charged lead-acid battery, discharge it at a discharge current of 15 × I5 (A) in an air chamber at 25°C until the terminal voltage reaches 1.0V / cell, and determine the discharge time (minutes). A longer discharge duration indicates better low-temperature high-rate discharge performance. Subsequently, charge 120% of the discharged amount at 0.5 × I5 (A). Then, continue the float charging described above.

[0099] <Low-rate discharge performance> For a fully charged lead-acid battery, discharge it in an air chamber at 25°C at a discharge current of 1.25 × I5 (A) until the terminal voltage reaches 1.6V / cell, and determine the discharge time (minutes). Then, charge it to 120% of the discharged amount at a current of 0.5 × I5 (A). After that, continue the float charging described above.

[0100] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0101] 《Lead acid batteries R1~R7》 (1) Fabrication of the positive electrode plate A positive electrode paste is prepared by mixing lead oxide, water, and sulfuric acid. The positive electrode paste is filled into the mesh of a cast grid made of a Pb-Ca-Sn alloy, which is the positive electrode current collector, and then aged and dried to obtain an unformed positive electrode plate. Rp (≧1μm) is controlled by changing the water and sulfuric acid content in the paste when preparing the positive electrode paste, the sulfuric acid concentration of the electrolyte injected into the electrolytic cell during formation, and the degree of impregnation into the unformed positive electrode plate ((volume of sulfuric acid held by the unformed positive electrode plate) ÷ (pore volume of the unformed positive electrode plate)).

[0102] (2) Fabrication of the negative electrode plate A negative electrode paste is prepared by mixing lead oxide, carbon black, barium sulfate, an organic shrinkage inhibitor, water, and sulfuric acid. The negative electrode paste is filled into the mesh of a cast grid made of a Pb-Ca-Sn alloy, which is the negative electrode current collector, and then aged and dried to obtain an unformed negative electrode plate. The amounts of carbon black, barium sulfate, and organic shrinkage inhibitor are adjusted so that they are 0.3 mass%, 2.1 mass%, and 0.1 mass%, respectively, when measured in the fully charged state after formation. The Y / X ratio is controlled by changing the water and sulfuric acid content in the pastes when preparing the positive and negative electrode pastes, the sulfuric acid concentration of the electrolyte injected into the battery case during formation, and the degree of impregnation into the unformed negative electrode plate ((volume of sulfuric acid held by the unformed negative electrode plate) ÷ (pore volume of the unformed negative electrode plate)).

[0103] (3) Separator An AGM with a glass fiber content of 80% by mass is used as the separator. The inter-electrode density of the separator (D(AGM)) is controlled by changing the thickness of the AGM, the density of the glass fibers, and the spacing between the electrode groups.

[0104] (4) Preparation of electrolyte Prepare an aqueous sulfuric acid solution as the electrolyte. The density of the electrolyte after chemical conversion is 1.24-1.35 g / cm³. 3 It is within the range.

[0105] (5) Manufacturing of lead-acid batteries A valve-regulated lead-acid battery satisfying the various parameters shown in Table 1 will be manufactured. Specifically, four unformed negative plates and three unformed positive plates will be alternately stacked with an AGM in between to form an electrode plate group. The tabs of the positive plates and the tabs of the negative plates will be welded to the positive and negative electrode straps, respectively, using a burner welding method. The electrode plate group will be inserted into an ABS resin battery case, electrolyte will be poured in, and the plate formation process will be carried out inside the battery case to assemble a stationary valve-regulated lead-acid battery with a nominal voltage of 2V and a rated 20-hour rate capacity of 40Ah, as described above. The L / P ratio will be controlled by the amount of electrolyte poured into the battery case.

[0106] (6) Evaluation The fabricated lead-acid batteries were fully charged, and a float test was performed using the method described above to evaluate their high-rate discharge performance. The results are shown in Table 1.

[0107] [Table 1]

[0108] Table 1 shows that when the L / P ratio is 100%, the high-rate discharge performance deteriorates quickly even when D(AMG), Rp(≧1μm), and Y / X ratio are changed. This is thought to be because the AGM shrinks, reducing the compressive force on the electrode group, increasing the contact resistance between the positive and negative electrodes and the AGM, and because the amount of electrolyte held by the positive and negative electrodes decreases, reducing the amount of electrolyte diffusing from the AGM to the positive and negative electrodes during discharge.

[0109] Lead-acid batteries C1-C4 and E1-E4 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 2 will be fabricated and evaluated in the same manner as described above.

[0110] [Table 2]

[0111] From Table 2, D(AGM) is 0.23 g / cm³. 3 When Rp (≧1μm) is fixed at 60% and the Y / X ratio at 4, and the L / P ratio is set to 108-130%, high-rate discharge performance can be maintained for a long time. This is thought to be because, due to the large amount of electrolyte, sufficient electrolyte is retained in the separator even when the electrolyte is reduced, thereby maintaining contact between the positive and negative electrodes and the AGM, maintaining a high compressive force between the electrode group, maintaining a low contact resistance, and facilitating the diffusion of electrolyte from the AGM to the positive and negative electrodes during discharge. In addition, even if lead sulfate is generated as the discharge reaction proceeds on the electrode surface of the positive electrode, the pores are less likely to be blocked, and the electrolyte is more likely to diffuse into the interior of the positive electrode, which also plays a role. Note that when the L / P ratio was 140%, the electrolyte overflowed during the chemical conversion, so a float test was not performed.

[0112] 《Lead acid battery C5~C10》 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 3 will be fabricated and evaluated in the same manner as described above.

[0113] [Table 3]

[0114] Table 3 shows that when the L / P ratio is 95% or 100%, the high-rate discharge performance deteriorates quickly regardless of how D(AGM) is changed.

[0115] Lead-acid batteries C17-C22 and E5-E16 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 4 will be fabricated and evaluated in the same manner as described above.

[0116] [Table 4]

[0117] Table 4 shows that when the L / P ratio is 108-130%, D(AGM) is 0.15-0.28 g / cm³. 3 Within this range, high-rate discharge performance can be maintained for a long period. This is because D(AGM) is 0.15 g / cm³. 3 When D(AGM) is large, it is thought that the increased contact area and entanglement of glass fibers within the AGM makes it less likely for the AGM to shrink due to surface tension even when the fibers are wetted with electrolyte, thus maintaining a high compressive force on the electrode group. In this case, even if the electrolyte level decreases, the AGM is less likely to shrink, and the contact state between the positive and negative electrodes and the AGM is maintained well. On the other hand, when D(AGM) is 0.32 g / cm³, 3 If the value becomes excessively large, the amount of electrolyte held by the AGM decreases, which is thought to actually reduce the discharge time.

[0118] 《Lead acid battery C23~C34》 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 5 will be fabricated and evaluated in the same manner as described above.

[0119] [Table 5]

[0120] Table 5 shows that when the L / P ratio is 95% or 100%, the high-rate discharge performance deteriorates quickly regardless of how Rp (≧1μm) is changed.

[0121] Lead-acid batteries C35-C40 and E17-E28 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 6 is fabricated and evaluated in the same manner as described above.

[0122] [Table 6]

[0123] Table 6 shows that when the L / P ratio is 108-130%, high-rate discharge performance can be maintained for a long time when Rp (≧1μm) is in the range of 50-70%. This is because a large proportion of pores with a diameter of 1μm or more in the positive electrode material makes it difficult for lead sulfate to clog the pores even if it is formed on the surface of the positive electrode plate, and the electrolyte can easily diffuse into the interior of the positive electrode plate. On the other hand, if the proportion of pores with a diameter of 1μm or more in the positive electrode material is too large, such as 75%, the reaction area of ​​the positive electrode material decreases, which is thought to reduce the high-rate discharge performance.

[0124] 《Lead acid battery E29~E31》 A valve-regulated lead-acid battery satisfying the various parameters shown in Table 7 is fabricated and evaluated in the same manner as described above.

[0125] [Table 7]

[0126] Table 7 shows the effect of the Y / X ratio on low-rate discharge performance. From Table 7, it can be seen that low-rate discharge performance is particularly good when the Y / X ratio is between 3 and 6. This is because, due to capillary action caused by the pore size of the positive and negative electrodes, the amount of electrolyte moving into the positive electrode increases as the Y / X ratio increases, which is advantageous for low-rate discharge, which is easily limited by the positive electrode. When the Y / X ratio is greater than 6, the amount of electrolyte held in the negative electrode decreases, and low-rate discharge performance tends to decline. However, compared to battery C2, the low-rate discharge time can also be maintained for a longer period. [Industrial applicability]

[0127] The valve-regulated lead-acid battery according to the present invention is suitable, for example, as a stationary power supply, but its applications are not particularly limited. [Explanation of Symbols]

[0128] 1:Lead acid battery 2: Negative plate 3: Positive plate 4: Separator 11: Plate group 10:Battery container 10R: Cell chamber 12: Lid 13: Exhaust valve

Claims

1. It comprises a group of electrode plates and an electrolyte, The electrode plate group comprises a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode material. The negative electrode plate includes a negative electrode current collector and a negative electrode material. The separator is a nonwoven fabric containing glass fibers. The ratio of the volume of the electrolyte to the pore volume of the electrode plate group is 108% or more and 130% or less. The inter-electrode density of the separator is 0.15 g / cm³. ３ 0.28g / cm or more ３ The following: A valve-regulated lead-acid battery in which, in the pore size distribution of the positive electrode material, the ratio of the volume of pores with a diameter of 1 μm or more to the total pore volume is 50% or more and 70% or less.

2. The valve-controlled lead-acid battery according to claim 1, wherein the ratio (Y / X) of the volume-central pore diameter Y in the pore size distribution of the negative electrode material to the volume-central pore diameter X in the pore size distribution of the positive electrode material is 3 or more and 6 or less.

3. The valve-regulated lead-acid battery according to claim 1, wherein the ratio of the volume of the electrolyte to the pore volume of the electrode plate group is 115% or more and 130% or less.

4. The inter-electrode density of the separator is 0.23 g / cm³. ３ 0.28g / cm or more ３ The valve-regulated lead-acid battery according to claim 1, which is as follows:

Images