lead-acid batteries

Abstract

This invention provides a lead-acid battery that achieves both low-rate and high-rate discharge performance when float charging is continued in a high-temperature environment. [Solution] The device comprises an electrode group 11, an electrolyte, and a battery case 10 that houses the electrode group and the electrolyte. The electrode group includes 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 includes a positive electrode material and a positive electrode current collector. The negative electrode plate includes a negative electrode material and a negative electrode current collector. The separator is a nonwoven fabric containing inorganic fibers. The surface area of ​​the separator is 0.2 m² per unit volume of the space where the separator is housed in the battery case. 2 / cm 3 ~0.6m 2 / cm 3 A lead-acid battery wherein the Ca content in the positive electrode current collector is 0.04 mass% or less, and the negative electrode material contains an organic shrinkage inhibitor, with the sulfur element content in the organic shrinkage inhibitor being 3000 μmol / g to 9000 μmol / g.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 proposes "a sealed lead-acid battery including a plate group configured by interposing an electrolyte holding body between a positive electrode plate and a negative electrode plate, wherein the side of the electrolyte holding body that contacts the positive electrode plate is composed of (1) fibers of a single diameter with an average fiber diameter of 1.4 μm or less, and (2) has a density of 0.12 to 0.18 g / cm 2 when pressurized at 20 kgf / dm 3 and is characterized by such a sealed lead-acid battery."

[0003] Patent Document 2 proposes "a sealed lead-acid battery in which a positive electrode plate, a negative electrode plate, and a separator made of glass fiber are laminated to form a plate group, and the plate group is housed in an electrolytic cell in such a state that the lamination direction is the vertical direction, wherein the separator has a glass fiber density of 0.16 g / cm 3 or less, a maximum pore diameter of 19 μm or more, an average pore diameter of 4.3 μm or more, and a specific surface area of 2.2 m 2 / g or less, and is characterized by such a sealed lead-acid battery."

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, continuous float charging of lead-acid batteries in high-temperature environments gradually reduces their low-rate discharge performance. The main cause of this decrease in low-rate discharge performance is corrosion of the positive electrode current collector. Therefore, to improve low-rate discharge performance, it is considered effective to reduce the Ca content in the positive electrode current collector to enhance its corrosion resistance.

[0006] On the other hand, in recent float charging applications, not only low-rate discharge performance but also high-rate discharge performance is required. To improve high-rate discharge performance, it is effective to suppress the decrease in the specific surface area of ​​the negative electrode material, and it is considered effective to add organic shrinkage inhibitors other than lignin (e.g., organic condensates) to the negative electrode material.

[0007] However, adding organic condensates to the negative electrode material can unexpectedly reduce low-rate discharge performance, even when using a positive electrode current collector with a low Ca content. Furthermore, adding organic condensates to the negative electrode material may not sufficiently improve high-rate discharge performance. [Means for solving the problem]

[0008] One aspect of the present invention comprises a group of electrode plates, an electrolyte, and a battery case containing the group of electrode plates and the electrolyte, wherein the group of electrode plates 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 electrode material and a positive electrode current collector, the negative electrode plate includes a negative electrode material and a negative electrode current collector, the separator is a nonwoven fabric containing inorganic fibers, and the surface area of ​​the separator is 0.2 m³ per unit volume of the space in which the separator is housed within the battery case. 2 / cm 3 ~0.6m 2 / cm 3 The present invention relates to a lead-acid battery wherein the Ca content in the positive electrode current collector is 0.04% by mass or less, and the negative electrode material contains an organic shrinkage inhibitor, with the sulfur element content in the organic shrinkage inhibitor being 3000 μmol / g to 9000 μmol / g. [Effects of the Invention]

[0009] The lead-acid battery according to the present invention can achieve both low-rate discharge performance and high-rate discharge performance when float charging is continued in a high-temperature environment. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing the structure of an example of a valve-regulated lead-acid battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are 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 "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0012] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0013] A lead-acid battery comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte. The electrolyte contains sulfuric acid. Charging and discharging proceed through the movement of sulfate ions between the positive and negative electrode plates and the electrolyte. During discharge, sulfate ions move to the positive and negative electrode plates. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte.

[0014] A positive electrode plate, a negative electrode plate, and a separator constitute an electrode plate group. An electrode plate 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 plate group, together with the electrolyte, constitutes a cell. One electrode plate group constitutes one cell. A lead-acid battery comprises one or more cells by comprising one or more electrode plate groups. There is no particular limit to the number of positive and negative electrode plates included in a single electrode plate group. An electrode plate group comprising a lead-acid battery according to this disclosure may, for example, include a total of 12 or more positive and negative electrode plates. Multiple electrode plate groups are typically housed in separate cell chambers and connected in series with one another.

[0015] 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.

[0016] 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 discharging.

[0017] 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 wall. The battery case has one or more cell chambers. The inside of the battery case may be divided into multiple spaces (cell chambers) by partitions. For example, 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.

[0018] (1) The lead-acid battery according to an embodiment of the present disclosure includes a plate group, an electrolyte, and a battery case that houses the plate group and the electrolyte. The 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 electrode active material and a positive electrode current collector. The negative electrode plate includes a negative electrode active material and a negative electrode current collector. The separator is a non-woven fabric containing inorganic fibers, and the surface area of the separator is 0.2 m 2 / cm 3 ~0.6 m 2 / cm 3 per unit volume of the accommodation space of the separator in the battery case, and the Ca content in the positive electrode current collector is 0.04% by mass or less. The negative electrode active material contains an organic shrinkage inhibitor, and the content of sulfur element in the organic shrinkage inhibitor is 3000 μmol / g to 9000 μmol / g.

[0019] In the lead-acid battery (hereinafter, also referred to as "lead-acid battery (LA)") described in (1) above, when continuous float charging is performed in a high-temperature environment, it is possible to achieve both low-rate discharge performance and high-rate discharge performance. That is, the capacity in low-rate discharge and the capacity in high-rate discharge are both less likely to decrease. For example, in a float test in which float charging is performed in a high-temperature environment (for example, 60°C), when low-rate discharge and high-rate discharge are performed once a month, the lead-acid battery (LA) can ensure an excellent capacity retention rate.

[0020] As described above, the lead-acid battery described in (1) above satisfies the following conditions (A) to (C).

[0021] (A) The Ca content in the positive electrode current collector is 0.04% by mass or less.

[0022] (B) The negative electrode active material contains an organic shrinkage inhibitor, and the content of sulfur element in the organic shrinkage inhibitor is 3000 μmol / g to 9000 μmol / g.

[0023] (C) The separator is a nonwoven fabric containing inorganic fibers, and the surface area of ​​the separator is 0.2 m² per unit volume of the space where the separator is housed within the battery case. 2 / cm 3 ~0.6m 2 / cm 3 That is the case.

[0024] For example, lead alloys containing calcium (Ca) and tin (Sn) are used for positive electrode current collectors. Ca improves the mechanical strength of the lead alloy, and Sn improves its corrosion resistance. From the viewpoint of mechanical strength, lead alloys with a Ca content of 0.04 mass% or more are often used for positive electrode current collectors. On the other hand, it has been found that even if the Ca content of the lead alloy is 0.04 mass% or less (for example, 0.01 mass% or less), it is possible to sufficiently improve the mechanical strength of the lead alloy and also improve the corrosion resistance of the positive electrode current collector. Therefore, adopting condition (A) is considered an effective means of improving low-rate discharge performance.

[0025] However, when a positive electrode current collector with a low Ca content is used, and an organic shrinkage inhibitor other than lignin (e.g., an organic condensate) is added to the negative electrode material, the low-rate discharge performance may unexpectedly decrease, or the high-rate discharge performance may not improve sufficiently. One reason for this is that organic shrinkage inhibitors other than lignin have a high sulfur content and are easily eluted into the electrolyte. The organic shrinkage inhibitor that has eluted into the electrolyte is oxidized and decomposed on the positive electrode plate, and this decomposition reaction causes a structural change in the positive electrode material, leading to a decrease in density. As a result, the movement of electrolyte to the positive electrode plate is promoted, increasing the amount of electrolyte held by the positive electrode plate, and consequently decreasing the amount of electrolyte held by the negative electrode plate and separator.

[0026] When the amount of electrolyte held by the negative electrode plate decreases, the low-rate discharge performance deteriorates. This is because the low-rate discharge performance is affected by the amount of electrolyte held inside the negative electrode plate. Furthermore, when the amount of electrolyte held by the separator decreases, the separator shrinks and its resistance increases, thus limiting the effect of using organic shrinkage inhibitors with a high sulfur content to improve high-rate discharge performance.

[0027] In contrast, when conditions (A) to (C) are met, it becomes possible to achieve both low-rate and high-rate performance. Specifically, when condition (A) is met, the corrosion resistance of the positive electrode current collector is improved, and when conditions (B) and (C) are met, the reduction in density of the positive electrode material is suppressed, thereby improving both low-rate and high-rate performance.

[0028] When conditions (B) and (C) are met, the amount of electrolyte held by the positive electrode material is limited, and organic shrinkage inhibitors dissolved in the electrolyte are trapped in the separator with a high probability. As a result, the amount of organic shrinkage inhibitor reaching the positive electrode material is reduced, the decrease in density of the positive electrode material caused by the oxidative decomposition reaction of the organic shrinkage inhibitor on the positive electrode plate is suppressed, the amount of electrolyte held by the positive electrode plate is less likely to increase, and the amount of electrolyte held by the negative electrode plate and separator is less likely to decrease. In other words, the uneven distribution of electrolyte on the positive electrode plate is suppressed.

[0029] Specifically, if condition (B) is met, that is, if the surface area of ​​the separator per unit volume of the separator containment space is 0.2 m² 2 / cm 3 When the value is greater than the above, the separator's ability to retain electrolyte for a longer period is high, thus limiting the movement of electrolyte to the positive electrode plate. As a result, the separator and negative electrode plate can hold more electrolyte. By ensuring a sufficient amount of electrolyte is held in the separator, the shrinkage of the separator is suppressed and the increase in resistance is limited, thus increasing the effect of organic shrinkage inhibitors with a high sulfur content on improving high-rate discharge performance. Furthermore, the decrease in low-rate discharge performance is also less likely to occur.

[0030] Furthermore, when condition (C) is met, that is, when the sulfur content in the organic shrinkage inhibitor is 3000 μmol / g or more, the colloidal diameter of the organic shrinkage inhibitor dissolved in the electrolyte becomes significantly smaller. The degree of adsorption of the organic shrinkage inhibitor to the separator varies greatly depending on the colloidal diameter of the organic shrinkage inhibitor. When the sulfur content in the organic shrinkage inhibitor is 3000 μmol / g or more, the colloidal diameter of the organic shrinkage inhibitor dissolved in the electrolyte becomes significantly smaller, and much of the organic shrinkage inhibitor dissolved in the electrolyte is adsorbed and trapped by the separator, preventing it from reaching the positive electrode plate. Therefore, the decrease in density of the positive electrode material caused by the oxidative decomposition reaction of the organic shrinkage inhibitor on the positive electrode plate is significantly suppressed. As a result, the movement of the electrolyte to the positive electrode plate is further significantly restricted, and the increase in resistance due to the shrinkage of the separator is further significantly suppressed. While the sulfur content in the organic condensate may exceed 9000 μmol / g, particularly good high-rate performance tends to be obtained when it is 9000 μmol / g or less.

[0031] Furthermore, the surface area per unit volume of the separator's containment space is 0.6 m². 2 / cm 3 If the size exceeds this limit, the high-rate discharge performance actually decreases. This is thought to be because the diffusivity of the electrolyte within the battery case decreases. The surface area per unit volume of the separator's containment space is 0.2 m². 2 / cm 3 Anything above that is fine, but 0.25m 2 / cm 3 The above is preferable, 0.3m 2 / cm 3 Anything above that is also acceptable, 0.4m 2 / cm 3 Anything above that is also acceptable, 0.5m 2 / cm 3 The above is also acceptable. The surface area per unit volume of the separator's containment space is 0.25 m². 2 / cm 3 ~0.6m 2 / cm 3 But often, 0.3m 2 / cm 3 ~0.6m 2 / cm 3 But often, 0.4m 2 / cm3 ~0.6m 2 / cm 3 But often, 0.5m 2 / cm 3 ~0.6m 2 / cm 3 But that's fine.

[0032] (2) In the lead-acid battery described in (1) above, the organic shrinkage inhibitor is preferably a condensate of a bisphenol compound.

[0033] In the lead-acid battery described in (2) above, it is easy to increase the sulfur element content in the organic shrinkage inhibitor and to easily control the colloidal diameter of the organic shrinkage inhibitor.

[0034] (3) In the lead-acid battery described in (1) or (2) above, the surface area of ​​the separator is 0.3 m² per unit volume of the space in which the separator is housed within the battery case. 2 / cm 3 ~0.6m 2 / cm 3 It is preferable that this be the case.

[0035] According to the lead-acid battery described in (3) above, both low-rate and high-rate performance can be improved to a higher level.

[0036] (4) In the lead-acid battery described in any one of (1) to (2) above, the sulfur element content in the organic shrinkage inhibitor is preferably 5000 μmol / g to 9000 μmol / g.

[0037] According to the lead-acid battery described in (4) above, both low-rate and high-rate performance can be improved to an even higher level.

[0038] While the present invention is suitable for application to valve-regulated lead-acid batteries, it may also be applied to liquid-type lead-acid batteries. Valve-regulated lead-acid batteries are also called VRLA (Valve-regulated lead-acid battery) or sealed batteries. The applications of valve-regulated lead-acid batteries are not particularly limited, but the above effects can be particularly clearly obtained in stationary batteries. This is because stationary batteries are often subjected to continuous float charging in high-temperature environments.

[0039] In this specification, a fully charged state of a valve-regulated lead-acid battery means a constant voltage charge of 2.275V / cell (13.65V for a lead-acid battery with a nominal voltage of 12V) in an air chamber at 25℃±2℃ (maximum current is the 20-hour rate current 1 20 Five times the current 5I 20 The charging process (in A) was performed, and the charging was terminated when the total charging time reached 24 hours. Note that the n-hour rate current I n This refers to a current (A) that is 1 / n of the Ah value listed in the rated capacity. n This is the current value (in A) that corresponds to the value obtained by dividing the battery's rated n-hour rate capacity (in Ah) by n. Therefore, the 20-hour rate current I 20 This refers to a current (A) that is 1 / 20th of the Ah value listed in the rated capacity. Hereafter, the value listed as the rated capacity, with the unit Ah (ampere-hour), will simply be referred to as "rated capacity."

[0040] 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.

[0041] In this specification, a battery in its initial use is a battery that is unused or has not been used for a long time and has not deteriorated much (for example, a battery that has been in use for less than 720 hours, including the time since chemical preparation).

[0042] The following explains how to determine various parameters or physical properties. These parameters or physical properties are determined for components extracted from a fully charged lead-acid battery.

[0043] <Ca content in positive electrode current collector> Prior to the quantitative analysis of Ca, the positive electrode material is removed from the positive electrode plate taken from the lead-acid battery, the positive electrode current collector is removed, and a portion of the positive electrode current collector is taken to prepare a sample for analysis. Specifically, the positive electrode material is detached from the positive electrode current collector by vibrating the positive electrode plate, and then the remaining positive electrode material around the positive electrode current collector is removed using a ceramic knife, and a portion of the metallic luster part of the positive electrode current collector is taken as a sample. After measuring the mass of the taken sample, an aqueous solution is obtained by mixing it with tartaric acid and dilute nitric acid. Hydrochloric acid is added to the aqueous solution to precipitate lead chloride, and the solution is filtered and the filtrate is collected. Using this filtrate, the Ca content in the positive electrode current collector is analyzed in accordance with the lead separation inductively coupled plasma emission spectroscopy described in JIS H2105:1955. Specifically, the Ca concentration in the above filtrate is analyzed using an ICP emission spectrometer by the calibration curve method. The Ca content in the positive electrode current collector is determined from the obtained concentration and the mass of the taken sample. For example, the ICPS-8000 manufactured by Shimadzu Corporation can be used as an ICP emission spectrometer.

[0044] Furthermore, the content of elements other than Ca (e.g., Sn) in the positive electrode current collector can be analyzed in the same way as the Ca content. For example, the Sn content can be analyzed by replacing Ca with Sn in the method described above.

[0045] <Sulfur element content in organic shrinkage inhibitors> Using a powder sample of an organic shrinkage inhibitor, the sulfur element in 0.1 g of the organic shrinkage inhibitor is converted to sulfuric acid by the oxygen combustion flask method. During this process, the powder sample is burned in a flask containing an adsorbent to obtain an eluate in which sulfate ions are dissolved in the adsorbent. Next, the sulfur element content (C1) in 0.1 g of the organic shrinkage inhibitor is determined by titrating the eluate with barium perchlorate using thorin as an indicator. Then, C1 is multiplied by 10 to calculate the sulfur element content per gram of organic shrinkage inhibitor (μmol / g).

[0046] Powder samples of organic shrinkage inhibitors can be collected by the following method. First, 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. Washing is continued until a pH test paper is pressed against the surface of the washed negative electrode plate and the color of the test paper does not change. However, the washing time should be no more than 2 hours. The washed negative electrode plate is dried under reduced pressure at 60°C ± 5°C for about 6 hours. If adhesive material is present on the negative electrode plate after drying, the adhesive material is removed by peeling. The mass of the dried material (negative electrode plate) is measured. Next, the negative electrode material is scraped off and separated from the negative electrode current collector, and a pulverized sample of the negative electrode material is obtained by pulverizing it.

[0047] A predetermined amount of the pulverized sample is taken and weighed, then immersed in a 1 mol / L NaOH aqueous solution to extract the organic shrinkage inhibitor. Next, insoluble components are removed from the extract by filtration, the resulting solution is desalted, concentrated, and dried. Desalting is performed using a desalting column, by passing the solution through an ion exchange membrane, or by placing the solution in a dialysis tube and immersing it in distilled water. By drying the desalted solution, a powdered sample of the organic shrinkage inhibitor is obtained.

[0048] Furthermore, the structure of organic shrinkage inhibitors can be identified by combining information obtained from methods such as infrared spectroscopy of powder samples, ultraviolet-visible absorption spectroscopy of solutions obtained by dissolving powder samples in distilled water or the like, nuclear magnetic resonance (NMR) spectroscopy of solutions obtained by dissolving powder samples in solvents such as heavy water, or gas chromatography-mass spectroscopy (GC-MS).

[0049] <Surface area of ​​separators per unit volume of the separator's containment space> First, the fully charged lead-acid battery, after the chemical treatment is complete, is disassembled to remove the electrode plates. The separator, positive electrode, and negative electrode are then washed with water to remove sulfuric acid, and after that, they are dried.

[0050] Next, the surface area of ​​the separator is measured using the BET method with a dried sample of the separator. Specifically, the mass W of the separator after drying is determined, and the total surface area St(m²) of all the separators contained in the battery case is calculated from the BET specific surface area S and the separator mass W. 2 ) is calculated from the thickness Tp, length L, width W, and number of separators compressed in the battery case, which gives the total volume Vt (cm³) of the separators in the battery case. 3 ) is calculated, and from St / Vt, the surface area of ​​the separator per unit volume of the separator's containment space (m 2 / cm 3 )

[0051] The thickness Tp of the separator within the battery case is calculated by subtracting the total dimensions of the positive and negative plates, and any other components (e.g., spacers) included in the plate group from the internal dimensions of the cell chamber of the battery case where the plate group was housed, determining the space occupied by the separator within the battery case, and then dividing this by the number of separators.

[0052] The surface area of ​​the separator is determined by cutting a sample of the required mass from near the center of a dried separator, pre-treating it in a nitrogen flow at an appropriate temperature for 1 hour, and then determining the BET specific surface area by measurement using the gas adsorption method and calculation using the BET formula. The pre-treatment temperature is, for example, around 150°C. If the separator contains a low melting point material (e.g., organic fiber), pre-treatment may be performed at a temperature below the melting point for a longer period (e.g., 24 hours). For example, the BET specific surface area is determined by measurement using the following apparatus and conditions, and calculation using the following calculation method. Measurement device: TriStar3000 manufactured by Micromerities Corporation Adsorption gas: Nitrogen gas with a purity of 99.99% or higher. Adsorption temperature: Boiling point temperature of liquid nitrogen (77K) Method for calculating BET specific surface area: Conforms to JIS Z 8830:2013, section 7.2.

[0053] 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.

[0054] This section describes examples of components in a valve-regulated lead-acid battery.

[0055] (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.

[0056] 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.

[0057] The composition of the lead alloy used in the positive electrode current collector is determined considering corrosion resistance and mechanical strength. For example, Pb-Ca alloys and Pb-Ca-Sn alloys are preferred.

[0058] The Ca content of the lead alloy used for the positive electrode current collector may be 0.04 mass% or less, 0.03 mass% or less, 0.02 mass% or less, or 0.01 mass% or less. The lead alloy used for the positive electrode current collector does not necessarily have to contain Ca, but considering the mechanical strength of the lead alloy, the Ca content of the lead alloy is preferably 0.005 mass% or more, and may also be 0.01 mass% or more. A preferred range for the Ca content of the lead alloy can be set by combining any of the above upper and lower limits. A preferred range for the Ca content of the lead alloy is, for example, 0.005 mass% to 0.04 mass%, but may also be 0.01 mass% to 0.04 mass%, 0.005 mass% to 0.03 mass%, or 0 mass% to 0.01 mass%.

[0059] The Sn content of the lead alloy used for the positive electrode current collector is, for example, 3% by mass or less, but may also be 2% by mass or less, 1.5% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less. The lead alloy used for the positive electrode current collector does not necessarily have to contain Sn, but considering corrosion resistance and overvoltage of the positive electrode plate, the Sn content of the lead alloy is preferably 0.1% by mass or more, may also be 0.5% by mass or more, or 1% by mass or more. A preferred range for the Sn content of the lead alloy can be set by combining any of the above upper and lower limits. A preferred range for the Sn content of the lead alloy is, for example, 0.1% by mass to 3% by mass, but may also be 0.1% by mass to 2% by mass, 0.1% by mass to 1% by mass, or 0% by mass to 1% by mass.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] (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.

[0064] 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.

[0065] The lead alloy used for the negative electrode current collector may be any of the following: a Pb-Sb alloy, 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.

[0066] The negative electrode material contains a negative electrode active material that exhibits capacity through an oxidation-reduction reaction. The negative electrode active material includes lead, lead sulfate, and the like.

[0067] The negative electrode material may contain an organic shrinkage inhibitor as an additive, and may optionally contain carbonaceous materials, barium sulfate, etc.

[0068] As an organic shrinkage inhibitor, an organic shrinkage inhibitor with a sulfur element content of 3000 μmol / g to 9000 μmol / g is used. The sulfur element content in the organic shrinkage inhibitor may also be 4000 μmol / g to 9000 μmol / g, 5000 μmol / g to 9000 μmol / g, 5000 μmol / g to 7000 μmol / g, or 7000 μmol / g to 9000 μmol / g.

[0069] As an organic shrinkage inhibitor with a sulfur element content of 3000 μmol / g to 9000 μmol / g, for example, a synthetic organic shrinkage inhibitor can be used. The synthetic organic shrinkage inhibitor is an organic condensate. The organic condensate may be a condensate of a bisphenol compound. Note that the condensate of a bisphenol compound may contain compounds other than bisphenol compounds. The condensate of a bisphenol compound may be, for example, a condensate of a bisphenol compound and an aldehyde compound (e.g., formaldehyde), a condensate of a bisphenol compound, a phenol compound and an aldehyde compound, or a condensate of a bisphenol compound, a sulfite compound and / or an amino acid compound and an aldehyde compound. The negative electrode material may contain one type of organic shrinkage inhibitor, or two or more types.

[0070] 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.

[0071] 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.

[0072] As phenolic compounds, phenol, phenolsulfonic acid (or its substituted derivatives) can be used. Organic condensates containing a phenolsulfonic acid unit have a phenolic hydroxyl group and a sulfonic acid group. Both the phenolic hydroxyl group and the sulfonic acid group are strongly negatively polar and have high affinity for metals. Therefore, organic condensates containing a phenolsulfonic acid unit dissolve in small amounts into the electrolyte and tend to remain in the negative electrode material. Note that the phenolic hydroxyl group also includes the salt of the phenolic hydroxyl group (-OMe). It is thought that phenolic compounds inhibit the formation of intramolecular bonds due to the interaction between the π electrons of the aromatic ring of bisphenol compounds, imparting flexibility to the linear chain of the molecule and making it easier to expose more strongly negatively polar functional groups on the surface.

[0073] In a condensate of a bisphenol compound, a phenol compound, and an aldehyde compound, the molar ratio of the bisphenol compound to the phenol compound may be in the range of, for example, 1:9 to 9:1, and preferably in the range of 2:8 to 8:2.

[0074] Sodium salts such as sodium sulfite, sodium bisulfite, and sodium pyrosulfite can be used as sulfite compounds.

[0075] Suitable amino acid compounds include glutamic acid, glycine, alanine, iminodiacetic acid, aspartic acid, serine, aminobutyric acid, glutathione, 6-aminohexanoic acid, valine, methionine, and leucine. Among these, glutamic acid, glycine, alanine, and iminodiacetic acid are preferred.

[0076] Suitable aldehyde compounds include formaldehyde, paraformaldehyde, formaldehyde derivatives such as hexamethylenetetramine, and acetaldehyde. Among these, formaldehyde derivatives are preferred, and formaldehyde is more preferred in terms of reactivity and cost.

[0077] The weight-average molecular weight (Mw) of the organic condensate is preferably, for example, 7,000 or more. The Mw of the organic condensate may be, for example, 100,000 or less, or 20,000 or less.

[0078] The Mw of organic shrinkage inhibitors is determined by GPC (Geometry Proof-Conductivity). Sodium polystyrene sulfonate is used as the standard substance when determining Mw. Mw is measured using the following equipment under the following conditions. GPC equipment: Build-up GPC system SD-8022 / DP-8020 / AS-8020 / CO-8020 / UV-8020 (manufactured by Tosoh Corporation) Column: TSKgel G4000SWXL, G2000SWXL (7.8mm I.D. × 30cm) (Manufactured by Tosoh Corporation) Detector: UV detector, λ=210nm Eluent: Mixed solution of 1 mol / L NaCl aqueous solution and acetonitrile (volume ratio = 7:3) Flow rate: 1mL / min. Concentration: 10mg / mL Injection volume: 10μL Standard substance: Sodium polystyrene sulfonate (Mw = 275,000, 35,000, 12,500, 7,500, 5,200, 1,680)

[0079] Carbonaceous materials that can be used as additives for the negative electrode material 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. The carbonaceous material content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0080] 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, additives, water, and sulfuric acid.

[0081] 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.

[0082] (Separator) A nonwoven fabric containing inorganic fibers is used as the separator. Glass fibers are preferred as the inorganic fibers. A nonwoven fabric containing glass fibers is also called AGM (Absorbed Glass Mat (Absorbent Glass Mat)) or AGM separator. A nonwoven fabric containing glass fibers (hereinafter also referred to as "glass fiber nonwoven fabric") 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 a glass fiber nonwoven fabric is made up of glass fibers. A glass fiber nonwoven fabric may also contain components other than glass fibers, such as acid-resistant inorganic powders (e.g., silica powder, glass powder, diatomaceous earth), polymers as binders, etc.

[0083] The separator or AGM may contain inorganic fibers (glass fibers) and organic fibers. Preferably, the proportion of glass fibers in the total number of fibers constituting the separator or AGM is 60% by mass or more.

[0084] 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.

[0085] 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.

[0086] (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.

[0087] 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 may also be acceptable. The density of the electrolyte at 20°C is, for example, 1.35 g / cm³. 3 The following is the result: 1.32 g / cm³ 3 The following is preferable:

[0088] 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 12A. The electrode plate group 11 is composed of multiple negative electrode plates 2 and positive electrode plates 3 stacked with separators 4 in between.

[0089] 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.

[0090] The battery case 10 is divided into multiple (three in the illustrated example) independent cell chambers 10R, and one electrode plate group 11 is housed in each cell chamber 10R. The lid 12 is equipped with an independent exhaust valve 13 for each cell chamber 10R. When the internal pressure of a 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 a 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.

[0091] The structure of the lead-acid battery is not limited to the above. For example, the battery case 10 may be divided into six independent cell chambers 10R, or it may have only one cell chamber. Also, although Figure 1 shows the case where there are three cells in the cell chamber 10R, 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).

[0092] The following describes the evaluation method for valve-regulated lead-acid batteries.

[0093] <Float Test> Under a temperature of 60°C, float charging is performed at 2.23V / cell, and low-rate discharge and high-rate discharge are repeated every 30 days for 12 months, and the predetermined discharge time is measured.

[0094] <Low-rate discharge performance> For a fully charged lead-acid battery, the discharge current I at a 10-hour rate (0.1C) is 10 (A) Discharge in a 25°C air chamber until the terminal voltage reaches 1.8V / cell, and determine the discharge time (h) at this time. Then, I 10 (A) Charge the battery to 120% of its discharge capacity. Then, perform a high-rate discharge.

[0095] <High-rate discharge performance> For a fully charged lead-acid battery, the discharge current I at a 1 / 3 hour rate (3C) is 1 / 3(A) Discharge in a 25°C air chamber until the terminal voltage reaches 1.0V / cell, and determine the discharge time (min). Then, I 10 (A) Charge the battery to 120% of its discharged capacity. Then, continue float charging at 2.23V / cell.

[0096] [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. Here, a lead-acid battery (nominal voltage 2V) with a rated 10-hour rate capacity of 200Ah is used, which comprises one cell containing a group of electrodes comprising eight positive electrodes and nine negative electrodes.

[0097] 《Lead acid batteries R1~R6, E1~E16, C1~C38》 (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 an expanded grid made of a Pb-Ca-Sn alloy, which serves as the positive electrode current collector. The grid is then aged and dried to obtain an unformed positive electrode plate. The Ca content of the Pb-Ca-Sn alloy is as shown in Tables 1-3, and the Sn content is 1.0% by mass.

[0098] (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 an expanded grid made of a Pb-Ca-Sn alloy, which serves as 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 0.2% by mass, 0.4% by mass, and 0.2% by mass, respectively, when measured in the fully charged state after formation.

[0099] Here, the following organic shrinkage inhibitors shown in Tables 1-3 are used. VN: Natural organic shrinkage inhibitor (lignin) with a sulfur content of 600 μmol / g S1000: A synthetic organic shrinkage inhibitor with a sulfur content of 1000 μmol / g (a condensate of bisphenol and formaldehyde). S5000: A synthetic organic shrinkage inhibitor with a sulfur content of 5000 μmol / g (a condensate of bisphenol and formaldehyde). For bisphenol, sulfonated bisphenol A, F, or S is used, and their ratios and sulfonation rates are adjusted as appropriate.

[0100] (3) Separator AGM with a glass fiber content of 90% by mass is used as the separator.

[0101] (4) Preparation of electrolyte Prepare an aqueous sulfuric acid solution as the electrolyte. The density of the electrolyte after chemical conversion is 1.12 to 1.32 g / cm³. 3 It is within the range.

[0102] (5) Manufacturing of lead-acid batteries Eight unformed positive electrode plates and nine unformed negative electrode plates are stacked alternately with an AGM (Automated Magnetium) in between to form an electrode plate group. The tabs of the positive electrode plates and the tabs of the negative electrode plates are welded to the positive and negative electrode straps, respectively, using the cast-on-strap (COS) method. The electrode plate group is inserted into a polypropylene battery case, electrolyte is poured in, and the deposition process is carried out inside the battery case to assemble a valve-regulated lead-acid battery with a nominal voltage of 2V and a rated 10-hour rate capacity of 200Ah as described above.

[0103] Here, we will fabricate a valve-regulated lead-acid battery in which various parameters, such as the surface area per unit volume of the separator housing space within the battery case (indicated as "Spv" in the table), satisfy the values ​​shown in Tables 1-3. Spv is controlled by changing the fiber diameter and density of the AGM separator.

[0104] (6) Evaluation The fabricated lead-acid batteries were fully charged, and a float test was performed using the method described above to evaluate the low-rate discharge performance. The Vs / Vt ratio, low-rate discharge time (h), and high-rate discharge time (min) were measured after 12 months. The results are shown in Tables 1-3. Batteries R1-R6 are conventional examples, batteries E1-E16 are examples, and batteries C1-C38 are comparative examples.

[0105] Here, the Vs / Vt ratio is the ratio of the mass Vs of electrolyte impregnated in the separator to the total mass Vt of electrolyte in the cell. A low Vs / Vt ratio means that during float charging, the density of the positive electrode material decreases, and more electrolyte moves to the positive electrode plate. The less electrolyte impregnated in the separator, the more the separator shrinks, negatively affecting the discharge performance. The Vs / Vt ratio is calculated by disassembling the battery, measuring the masses wp1, wn1, and ws1 of the positive electrode plate, negative electrode plate, and separator while they are wet with electrolyte, and then measuring the masses wp2, wpn, and ws2 of the positive electrode plate, negative electrode plate, and separator after washing and drying, and using the following formula. Vt=(wp1+wn1+ws1)-(wp2+wpn+ws2) Vs = ws1 - ws2

[0106] Furthermore, after the float test in December, the battery was disassembled, the positive electrode plate was washed with water to remove sulfuric acid, and then the positive electrode material was removed, leaving only the positive electrode current collector. This positive electrode current collector was immersed in an alkaline mannitol solution for approximately 12 hours to remove the corrosion layer present on the surface of the positive electrode current collector. The corrosion rate was calculated from the weight change before and after the float test. A higher corrosion rate indicates more advanced corrosion. The results are shown in Tables 1-3.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] Table 1 shows that when conditions (A) to (C) are met, the Vs / Vt ratio is large, and both low-rate discharge performance and high-rate discharge performance after 12 months can be achieved.

[0111] 《Lead acid battery R7~R30, E17~E28, C39~C74》 As shown in Tables 4 and 5, a lead-acid battery was fabricated in the same manner as in the above example, except that the Ca and Sn content in the Pb-Ca-Sn alloy constituting the positive electrode current collector was changed, and the surface area per unit volume (Spv) of the separator housing space in the battery case was changed to 0.4 m2 / cm3. The low-rate discharge performance and high-rate discharge performance after 12 months were evaluated. The results for the low-rate discharge performance are shown in Table 4, and the results for the high-rate discharge performance are shown in Table 5.

[0112] [Table 4]

[0113] [Table 5]

[0114] From Tables 4 and 5, it can be seen that in order to achieve both low-rate and high-rate discharge performance, the Ca content in the positive electrode current collector must be 0.04 mass% or less, regardless of the Sn content. [Industrial applicability]

[0115] 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]

[0116] 1:Lead acid battery 2: Negative plate 3: Positive plate 4: Separator 11: Plate group 10:Battery container 10R: Cell chamber 13: Exhaust valve

Claims

1. A group of electrode plates, an electrolyte, and a battery case containing the group of electrode plates and the electrolyte, It is equipped with, 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 electrode material and a positive electrode current collector. The negative electrode plate includes a negative electrode material and a negative electrode current collector. The separator is a nonwoven fabric containing inorganic fibers. The surface area of ​​the separator is 0.2 m³ per unit volume of the space in which the separator is housed within the battery case. ２ / cm ３ ~0.6m ２ / cm ３ And, The Ca content in the positive electrode current collector is 0.04% by mass or less. The negative electrode material contains an organic shrinkage inhibitor. A lead-acid battery in which the sulfur element content in the organic shrinkage inhibitor is 3000 μmol / g to 9000 μmol / g.

2. The lead-acid battery according to claim 1, wherein the organic shrinkage inhibitor is a condensate of a bisphenol compound.

3. The surface area of ​​the separator is 0.3 m³ per unit volume of the space in which the separator is housed within the battery case. ２ / cm ３ ~0.6m ２ / cm ３ The lead-acid battery according to claim 1.

4. The lead-acid battery according to any one of claims 1 to 3, wherein the sulfur element content in the organic shrinkage inhibitor is 5,000 μmol / g to 9,000 μmol / g.

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