Valve-regulated lead acid battery

Abstract

Provided is a valve-regulated lead acid battery comprising a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein: the separator is a nonwoven fabric containing glass fibers and an oxygen-containing organic compound; the ratio (Vp / Vt) of the volume (Vp) of the electrolyte impregnated in the positive electrode plate to the total volume (Vt) of the electrolyte is 0.20-0.30; the LC / MS spectrum of the oxygen-containing organic compound measured by using chloroform as a solvent has a plurality of peaks in a region in which the m / z value is 400-2000; the plurality of peaks are present with intervals of 20-25 or 40-50 in the m / z value; all oxygen atoms contained in the oxygen-containing organic compound are contained in at least one of an ether bond and a hydroxy group; and the ratio of the total mass of oxygen atoms contained in the oxygen-containing organic compound to the mass of the oxygen-containing organic compound is less than 0.320.

Description

Valve-regulated lead-acid battery

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

[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 percent relative to the total pore volume of the negative electrode plate, the positive electrode plate, and the mat separator.

[0003] Patent Document 2 describes a valve-regulated lead-acid battery, the lead-acid battery comprising at least one cell comprising an electrode plate group and an electrolyte, the electrode plate group comprising a negative electrode plate, a positive electrode plate, and a separator interposed between the negative electrode plate and the positive electrode plate, the negative electrode plate comprising a negative electrode material, the negative electrode material comprising a polymer compound having a peak in the range of 3.2 ppm to 3.8 ppm in the chemical shift of the 1H-NMR spectrum measured using deuterated chloroform as a solvent, the positive electrode plate comprising a positive electrode material, the density of the positive electrode material being 3.70 g / cm³. ３ 4.65g / cm or more ３ The following is proposed: a lead-acid battery.

[0004] Japanese Patent Publication No. 2015-018628, International Publication No. 2022-113635

[0005] When float charging of a valve-regulated lead-acid battery continues in a high-temperature environment, the amount of electrolyte held by the positive electrode increases, and consequently, the amount of electrolyte held by the negative electrode and separator decreases. When the amount of electrolyte held by the negative electrode decreases, the capacity at low-rate discharge decreases. This is because low-rate discharge performance is more significantly affected by the amount of electrolyte held inside the negative electrode.

[0006] One aspect of the present invention relates to a valve-regulated lead-acid battery comprising a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein the separator is a nonwoven fabric containing glass fibers and an oxygen-containing organic compound, the ratio (Vp / Vt) of the volume of the electrolyte impregnated in the positive electrode plate to the total volume (Vt) of the electrolyte is 0.20 or more and 0.30 or less, the LC / MS spectrum of the oxygen-containing organic compound measured with chloroform as a solvent has a plurality of peaks in the region of m / z value 400 or more and 2000 or less, the plurality of peaks are spaced apart with m / z values ​​of 20 or more and 25 or less, or 40 or more and 50 or less, all oxygen atoms contained in the oxygen-containing organic compound are contained in at least one of an ether bond and a hydroxyl group, and the ratio of the total mass of the oxygen atoms contained in the oxygen-containing organic compound to the mass of the oxygen-containing organic compound is less than 0.320.

[0007] The valve-regulated lead-acid battery according to the present invention can maintain low-rate discharge performance even when float charging is continued in a high-temperature environment.

[0008] 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.

[0009] 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.

[0010] Furthermore, this disclosure encompasses any combination of matters described in two or more claims 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 arbitrarily selected from the multiple claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency.

[0011] 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.

[0012] 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 one 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.

[0013] 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.

[0014] 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.

[0015] 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 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.

[0016] (1) A valve-regulated lead-acid battery according to an embodiment of the present disclosure comprises a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein the separator is a nonwoven fabric containing glass fibers and an oxygen-containing organic compound, the ratio (Vp / Vt) of the volume of the electrolyte impregnated in the positive electrode plate to the total volume (Vt) of the electrolyte is 0.20 or more and 0.30 or less, the LC / MS spectrum of the oxygen-containing organic compound measured with chloroform as a solvent has a plurality of peaks in the region of m / z value 400 or more and 2000 or less, the plurality of peaks are spaced apart with m / z values ​​of 20 or more and 25 or less, or 40 or more and 50 or less, all oxygen atoms contained in the oxygen-containing organic compound are contained in at least one of an ether bond and a hydroxyl group, and the ratio of the total mass of the oxygen atoms contained in the oxygen-containing organic compound to the mass of the oxygen-containing organic compound is less than 0.320.

[0017] Valve-regulated lead-acid batteries are also known as VRLA batteries or sealed batteries.

[0018] The valve-regulated lead-acid battery described in (1) above can maintain low-rate discharge performance even when float charging is continued in a high-temperature environment. In other words, the capacity does not easily decrease during low-rate discharge. For example, in a float test in a high-temperature environment (e.g., 60°C), the rate of maintenance of discharge capacity when low-rate discharge is performed once every month is excellent.

[0019] The valve-regulated lead-acid battery described in (1) above satisfies the following conditions (A) to (C), as previously stated.

[0020] (A) The separator is a nonwoven fabric containing glass fibers and oxygen-containing organic compounds.

[0021] (B) The ratio (Vp / Vt) of the volume of electrolyte impregnated in the positive electrode plate to the total volume of electrolyte (Vt) is 0.20 or more and 0.30 or less.

[0022] (C) Oxygen-containing organic compounds satisfy the following conditions. Note that oxygen-containing organic compounds that satisfy the following conditions (C1) to (C4) are also referred to as "oxygen-containing organic compounds (P)".

[0023] (C1) The LC / MS spectra of oxygen-containing organic compounds measured with chloroform as the solvent have multiple peaks in the region where the m / z value (m is the mass of the ionic species and Z is the charge number of the ionic species) is between 400 and 2000.

[0024] (C2) Multiple peaks exist at intervals of m / z values ​​between 20 and 25, or between 40 and 50. Note that peaks with m / z values ​​between 20 and 25 and peaks with m / z values ​​between 40 and 50 may coexist. Multiple peaks may exist at equal intervals. Such oxygen-containing organic compounds may be polymer compounds.

[0025] (C3) All oxygen atoms in an oxygen-containing organic compound are contained in at least one of an ether bond and a hydroxyl group.

[0026] (C4) The ratio of the total mass of oxygen atoms contained in the oxygen-containing organic compound to the mass of the oxygen-containing organic compound (hereinafter also referred to as "oxygen content (PO)") is less than 0.320.

[0027] In conventional valve-regulated lead-acid batteries, if float charging is continued in a high-temperature environment, the pores of the positive electrode plate become smaller, and consequently, electrolyte is drawn up from the separator to the positive electrode plate. This reduces the amount of electrolyte held by the negative electrode plate, resulting in a decrease in low-rate discharge performance.

[0028] In contrast, when conditions (A) to (C) are met, the oxygen-containing organic compound (P) present in the separator (for example, on the surface of the glass fibers) has a moderate hydrophilicity. As a result, some of the oxygen-containing organic compound (P) gradually dissolves from the glass fibers into the electrolyte and moves to the positive electrode plate, while some remains in the separator. The oxygen-containing organic compound (P) that moves to the positive electrode plate acts on the positive electrode material to suppress the refinement of the pores in the positive electrode plate. The moderate amount of hydrophilic oxygen-containing organic compound (P) remaining in the separator has the effect of keeping the electrolyte in the separator, suppressing excessive movement to the positive electrode plate. These phenomena work synergistically to suppress excessive movement of the electrolyte to the positive electrode plate during float charging, thereby maintaining low-rate discharge performance.

[0029] When the ratio (Vp / Vt) of the volume of electrolyte impregnated in the positive electrode plate to the total volume of electrolyte (Vt) is less than 0.20, the separator retains more electrolyte, resulting in less oxygen-containing organic compound (P) remaining in the separator. As a result, the effect of retaining the electrolyte in the separator is reduced, and the movement of electrolyte to the positive electrode plate cannot be sufficiently suppressed.

[0030] On the other hand, if the Vp / Vt ratio is greater than 0.30, the amount of electrolyte held by the separator decreases, resulting in a reduction in the amount of oxygen-containing organic compounds (P) that dissolve from the separator and move to the positive electrode plate. Consequently, the effect of oxygen-containing organic compounds (P) in suppressing the miniaturization of the pores in the positive electrode plate is not sufficiently obtained, and the movement of electrolyte to the positive electrode plate during float charging cannot be adequately suppressed.

[0031] The oxygen-containing organic compound (P) requires a moderate degree of hydrophilicity. Conditions (C1) and (C2) are derived from the repeating structure containing oxygen. The repeating structure containing oxygen is typically a polyoxyalkylene, but other repeating structures may be used as long as conditions (C1) and (C2) are met. The manifestation of hydrophilicity is derived from the oxygen atoms contained in the repeating structure. For example, oxygen-containing organic compounds that do not meet conditions (C1) and (C2) have low hydrophilicity and therefore cannot be expected to exhibit the effects described above. Note that, due to the repeating structure, multiple peaks may appear substantially equally spaced under condition (C2).

[0032] Condition (C3), in other words, means that the oxygen-containing functional groups that can be contained in the oxygen-containing organic compound (P) are limited to ether bonds and / or hydroxyl groups, and that it does not contain oxygen atoms found in other functional groups (e.g., ester bonds). Since oxygen-containing groups, such as ester bonds, are hydrolyzed in sulfuric acid aqueous solution, even if the oxygen-containing organic compound (P) remains in the separator, it does not have the effect of keeping the electrolyte in the separator. Similarly, even if the oxygen-containing organic compound (P) dissolves into the electrolyte and moves to the positive electrode plate, it cannot be expected to have a sufficient effect in suppressing the refinement of the pores in the positive electrode plate.

[0033] Condition (C4) means that the oxygen-containing organic compound (P) contains an appropriate amount of oxygen atoms. Oxygen atoms have lone pairs of electrons that enable hydrogen bonding, and the presence of lone pairs of electrons in the oxygen-containing organic compound (P) results in good hydrophilicity. If the oxygen content (PO) is 0.320 or higher, the hydrophilicity of the oxygen-containing organic compound (P) is too high, causing an excessive amount of the oxygen-containing organic compound (P) to dissolve from the separator into the electrolyte, thus preventing the electrolyte from remaining in the separator.

[0034] As described above, only specific oxygen-containing organic compounds (P) that satisfy conditions (A) to (C) can exist stably in an aqueous sulfuric acid solution and possess appropriate hydrophilicity, thus exhibiting the effects described. In other words, oxygen-containing organic compounds (P) have the effect of suppressing the decrease in low-rate discharge performance and improving the maintenance rate of discharge capacity when float charging of a valve-regulated lead-acid battery is continued in a high-temperature environment.

[0035] While the applications of valve-regulated lead-acid batteries are not particularly limited, the above effects can be particularly pronounced in stationary batteries. This is because stationary batteries are often subjected to continuous float charging in high-temperature environments.

[0036] (2) In the valve-regulated lead-acid battery described in (1) above, it is preferable that the LC / MS spectrum of the oxygen-containing organic compound (P) measured with chloroform as the solvent has 10 or more peaks in the region where the m / z value is 400 or more and 1200 or less.

[0037] According to the control valve type lead-acid battery described in (2) above, since the balance between the hydrophilicity and hydrophobicity of the oxygen-containing organic compound (P) is particularly good, the effect of suppressing the excessive movement of the electrolyte to the positive electrode plate is enhanced. The hydrophilicity mainly contributes to the elution of the oxygen-containing organic compound (P) into the electrolyte, and the hydrophobicity mainly contributes to the adsorption of the oxygen-containing organic compound (P) to the glass fiber.

[0038] (3) In the control valve type lead-acid battery described in (1) or (2) above, the ratio of the mass of the oxygen-containing organic compound contained in the separator to the mass of the electrolyte may be 0.01% by mass or more and 0.15% by mass or less.

[0039] According to the control valve type lead-acid battery described in (3) above, when continuous float charging is performed in a high-temperature environment, higher low-rate discharge performance can be ensured.

[0040] (4) In the control valve type lead-acid battery described in any one of (1) to (3) above, the oxygen-containing organic compound (P) may be an ether having a polyoxyethylene group and a terminal alkyl group or a terminal alkenyl group (hereinafter, also referred to as "polyoxyethylene-alkyl / alkenyl ether").

[0041] In the control valve type lead-acid battery described in (4) above, the polyoxyethylene-alkyl / alkenyl ether is stable to sulfuric acid, is difficult to decompose, and has appropriate hydrophilicity and hydrophobicity. Therefore, the quantitative balance between the oxygen-containing organic compound (P) adsorbed on the glass fiber and the oxygen-containing organic compound (P) that moves away from the glass fiber and moves to the positive electrode plate is improved.

[0042] (5) In the control valve type lead-acid battery described in (4) above, the carbon number of the terminal alkyl group or the terminal alkenyl group is preferably 10 or more and 20 or less.

[0043] In the control valve type lead-acid battery described in (5) above, it is considered that the polyoxyethylene-alkyl / alkenyl ether having a terminal alkyl group or a terminal alkenyl group with a carbon number of 10 to 20 exhibits suitable hydrophobicity for adsorbing an appropriate amount on the glass fiber.

[0044] (6) In the valve-regulated lead-acid battery described in (4) or (5) above, the number N of oxyethylene units in the polyoxyethylene group is preferably 5 or more and 35 or less.

[0045] In the valve-regulated lead-acid battery described in (6) above, when the number of oxyethylene units N is 5 to 35, more favorable hydrophilicity is exhibited due to the lone pairs of electrons of the oxygen atoms. Furthermore, since the oxygen content (PO) of the oxygen-containing organic compound (P) is limited to a favorable range, the amount of oxygen-containing organic compound (P) that dissolves from the separator into the electrolyte is also limited to a favorable range.

[0046] (7) In the valve-regulated lead-acid battery described in any one of (1) to (6) above, the oxygen-containing organic compound (P) may be at least one selected from the group consisting of, for example, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, and polyoxyethylene cetyl ether.

[0047] In the valve-regulated lead-acid battery described in (7) above, the decrease in low-rate discharge performance can be suppressed more reliably, and the rate of maintaining discharge capacity can be significantly improved.

[0048] A fully charged valve-regulated lead-acid battery is defined as a state where, in an air chamber at 25°C ± 2°C, charging is performed at a constant current and voltage of 2.23 to 2.30 V / cell with a current (A) equal to 0.2 times the value (A) indicated for the rated capacity (a value expressed in Ah), and charging is terminated when the charging current during constant voltage charging reaches 0.005 times the value (A) indicated for the rated capacity (a value expressed in Ah).

[0049] 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 some time has passed since chemical formation (for example, 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.

[0050] 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).

[0051] The time rate specified for the rated capacity of a lead-acid battery may differ from the time rate specified in the experimental method. In such cases, the converted value of the rated capacity (CW) can be calculated using the time rate specified for the rated capacity, the time rate to be used in the test, and a coefficient. CW = Cx × (W / x) ｙ　　 (y is the exponent of the power) Conversion formula 1 W: Time rate to be converted (time rate to be actually used) Cx: Rated capacity at X time rate X: Time rate for which the rated capacity is specified (different from the time rate specified in the test method) Note that y = 0.1545 can also be used when converting from any of the 3-hour, 5-hour, 10-hour, or 20-hour rates.

[0052] The following explains how to determine various parameters and material properties.

[0053] <Ratio of the mass of oxygen-containing organic compounds in the separator to the mass of the electrolyte> After disassembling a fully charged battery immediately after compounding or in the initial stages of use, the separator is washed with water and dried. The mass W1 of the dried separator is measured. The separator with mass W1 is immersed in chloroform to extract oxygen-containing organic compounds (P), and the mass W2 of oxygen-containing organic compounds (P) contained in the separator is quantified by analysis using liquid chromatography. At this time, 1 g of separator is immersed in 5 mL of chloroform, subjected to ultrasound at 20 ± 5 °C for 1 hour, and then left overnight (approximately 18 hours) for extraction. The ratio of the mass of oxygen-containing organic compounds in the separator to the mass of the electrolyte is calculated as "100 × W2 / (mass of electrolyte)".

[0054] Liquid chromatography is performed under the following conditions. The LC / MS spectrum of the extract is measured, and the concentration of the oxygen-containing organic compound (P) in the dilution is determined by a calibration curve method based on the intensity of the characteristic peak of the oxygen-containing organic compound (P). The calibration curve is prepared in advance using the oxygen-containing organic compound (P) that has been identified by qualitative analysis. Identification of the oxygen-containing organic compound (P) is possible by qualitative analysis, and information can be obtained from at least one of the following for the extract: IR, UV-VIS, NMR, LC / MS, and GC / MS. By identifying the oxygen-containing organic compound (P), the number of carbon atoms in the terminal alkyl group or terminal alkenyl group of the oxygen-containing organic compound (P) and the number of oxyethylene units N in the polyoxyethylene group can be determined.

[0055] LC / MS Spectrometer Measurement Conditions Equipment: LC section (Agilent Technologies 1100 Series), MS section (Bruker Ductonics microOTOF focus type) Column: Unison UK-C8 (3 μm, 2 × 50 mm) Column temperature: 40°C Mobile phase: A mixture of solutions A and B is used, with the mixing ratio of A and B gradually changed from 90:10 to 0:100 over 20 minutes, and only B is used from 20 to 30 minutes. Solution A: 10 mM ammonium formate aqueous solution Solution B: Acetonitrile Flow rate: 0.3 mL / min Detection method: ESI (Pos.) Injection volume: 1 μL

[0056] <Vp / Vt Ratio> The ratio of Vp to Vt (Vp / Vt) is calculated as follows: To determine the total volume of the electrolyte (Vt), disassemble a fully charged battery after chemical formation, and then wash and dry the positive electrode plate, negative electrode plate, and separator with water. The difference in total mass of the positive electrode plate, negative electrode plate, and separator before and after washing and drying is used to determine the electrolyte density (g / cm³). ３ The total volume Vt (mL) of the electrolyte is calculated from the following: Similarly, the volume (Vp) of the electrolyte impregnated in the positive electrode plate is calculated from the difference in mass of the positive electrode plate before and after washing and drying and the electrolyte density (g / cm³). ３ It is calculated from ). Then, the ratio of Vp to Vt (Vp / Vt) is calculated.

[0057] <Identification of oxygen atoms in oxygen-containing organic compounds> The presence of oxygen atoms in oxygen-containing organic compounds (P) in at least one of the ether bond and the hydroxyl group can be confirmed, for example, by FT-IR.

[0058] <Oxygen Content (PO)> The ratio of the total mass of oxygen atoms contained in an oxygen-containing organic compound (P) to the mass of the oxygen-containing organic compound (P) (oxygen content (PO)) can be measured by the following method. The concentrated extract is burned in a quartz tube filled with carbon particles and heated to 1150°C, using nitrogen as the carry gas. By thermal decomposition by the carbon particles, all oxygen atoms in the resulting decomposition gas are converted to carbon monoxide. The resulting carbon monoxide is oxidized by reacting with copper monoxide to produce carbon dioxide, which is then collected by adsorption by passing it through an absorption tube filled with sodium hydroxide and magnesium perchlorate. The amount of carbon dioxide collected can be determined from the change in mass of the absorption tube at this time. The amount of oxygen in the extract can be determined by converting the amount of carbon dioxide to the amount of oxygen. The oxygen content (PO) can be determined from the amount of oxygen in the extract and the mass W2 of the oxygen-containing organic compound (P) contained in the separator.

[0059] 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.

[0060] The following describes examples of components of a valve-regulated lead-acid battery.

[0061] (Positive electrode 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. Note that 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.

[0062] 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. The processing method may be, 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.

[0063] 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 with different compositions, and the metal layers may be one layer or multiple layers.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] (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.

[0068] 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.

[0069] 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. The negative electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers.

[0070] 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.

[0071] The negative electrode material may contain additives as needed. Such additives may include organic shrinkage inhibitors, carbonaceous materials, barium sulfate, and the like.

[0072] 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.

[0073] 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 also be 0.03% by mass or more and 0.6% by mass or less.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The carbonaceous material content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0078] The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0079] 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. The negative electrode paste is prepared by kneading a mixture containing lead powder, water, and sulfuric acid. The negative electrode paste may optionally contain organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc.

[0080] 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.

[0081] (Separator) A nonwoven fabric containing glass fibers is used as the separator. The nonwoven fabric containing glass fibers is also called AGM (Absorbed Glass Mat) or AGM separator. The 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 the glass fiber nonwoven fabric is made up of glass fibers. The 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.

[0082] The separator further contains an oxygen-containing organic compound (P). The method for incorporating the oxygen-containing organic compound (P) into the separator is not particularly limited. For example, the separator may be immersed in a concentrated solution of the oxygen-containing organic compound (P), or the oxygen-containing organic compound (P) may be mixed into the raw material slurry of the glass fiber nonwoven fabric during the preparation of the separator. In the former method, the concentration of the concentrated solution of the oxygen-containing organic compound (P) may be, for example, 30% to 90% by mass. In the latter method, for example, a raw material slurry containing a high concentration of glass fibers may be prepared, the raw material slurry may be diluted with water containing the oxygen-containing organic compound (P), and the diluted slurry may be used for papermaking.

[0083] Furthermore, simply adding an appropriate amount of oxygen-containing organic compound (P) to the electrolyte, in a quantity that does not affect battery performance, does not produce the same effect as when oxygen-containing organic compound (P) is included in the separator, which is necessary to maintain low-rate discharge performance. In that case, oxygen-containing organic compound (P) is either not detectable in the separator, or if detected, it is in a very small amount. If the ratio of the mass of oxygen-containing organic compound contained in the separator to the mass of the electrolyte is less than 0.01% by mass (and even less than 0.005% by mass), the separator cannot be said to substantially contain oxygen-containing organic compound (P).

[0084] The oxygen-containing organic compound (P) only needs to satisfy the previously described condition (C) (i.e., conditions (C1) to (C4)). However, the LC / MS spectrum of the oxygen-containing organic compound measured with chloroform as the solvent preferably has multiple peaks in the region where the m / z value is between 400 and 1200, and preferably has 10 or more, and more preferably 15 or more peaks.

[0085] The ratio of the mass of oxygen-containing organic compounds contained in the separator to the mass of the electrolyte may be, for example, 0.01% by mass or more, but may also be 0.05% by mass or more, or 0.07% by mass or more. The ratio of the mass of oxygen-containing organic compounds contained in the separator to the mass of the electrolyte may be, for example, 0.15% by mass or less, but may also be 0.12% by mass or less, or 0.10% by mass or less. The ratio of the mass of oxygen-containing organic compounds contained in the separator to the mass of the electrolyte may be, for example, in the range of 0.01% by mass to 0.15% by mass, or in the range of 0.05% by mass to 0.12% by mass (or 0.15% by mass).

[0086] The oxygen-containing organic compound (P) may be an ether compound. The ether compound may have a polyoxyalkylene group and a terminal alkyl group or terminal alkenyl group. The polyoxyalkylene group is typically a polyoxyethylene group.

[0087] The number of carbon atoms in the terminal alkyl group or terminal alkenyl group is, for example, 10 or more, and may be 13 or more. The number of carbon atoms in the terminal alkyl group or terminal alkenyl group is, for example, 20 or less, and may be 18 or less, and may be 17 or less. The number of carbon atoms in the terminal alkyl group is, for example, in the range of 10 to 20, and may be 13 to 18, with a preferred range of 13 to 17.

[0088] The number of oxyethylene units N in the polyoxyethylene group is, for example, 5 to 35, and may be 7 to 25, with 10 to 20 being preferred. This results in a more favorable hydrophilicity.

[0089] Specific examples of the oxygen-containing organic compound (P) include, for example, at least one selected from the group consisting of polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, and polyoxyethylene cetyl ether, but are not limited thereto.

[0090] The glass fiber nonwoven fabric or AGM may contain glass fibers and organic fibers. The proportion of glass fibers in the total fibers constituting the glass fiber nonwoven fabric or AGM is preferably 60% by mass or more.

[0091] As the organic fiber, a fiber material insoluble in the electrolytic solution is used. Examples of the organic fiber include polymer fibers (such as polyolefin fibers, acrylic fibers, polyester fibers (such as polyethylene terephthalate fibers, etc.)), pulp fibers, and the like.

[0092] The thickness of the separator interposed between the negative electrode plate and the positive electrode plate may be selected according to the interelectrode distance. The number of separators may be selected according to the number of interelectrodes.

[0093] (Electrolytic solution) The electrolytic solution is an aqueous solution containing sulfuric acid and may be gelled if necessary. The electrolytic solution may contain cations (for example, metal cations) and / or anions (for example, anions other than sulfate anions (such as phosphate ions)) if necessary. Examples of the metal cations include at least one selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0094] The density of the electrolytic solution in the fully charged lead storage battery at 20°C is, for example, 1.20 g / cm ３ or more, and may be 1.25 g / cm ３ or more. The density of the electrolytic solution at 20°C is, for example, 1.35 g / cm ３ or less, and preferably 1.32 g / cm ３ or less.

[0095] 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.

[0096] Each of the multiple negative electrode plates 2 is provided with upward-projecting current-collecting tabs (not shown) on its upper surface. Each of the multiple positive electrode plates 3 is also provided with upward-projecting current-collecting tabs (not shown) on its upper surface. 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.

[0097] The battery case 10 is divided into a plurality of (three in the illustrated example) independent cell chambers 10R, and one electrode plate group 11 is housed in each cell chamber 10R. The lid 12A 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.

[0098] 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, and 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).

[0099] The evaluation method for valve-regulated lead-acid batteries is described below. For evaluation, a lead-acid battery (nominal voltage 12V) with six cells, each consisting of three positive plates and four negative plates, 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.

[0100] <Float Test> The battery is float charged at 2.23V in an environment of 60°C, and the discharge capacity is measured by performing a low-rate discharge every 30 days (one month).

[0101] <Low-rate discharge performance> For a fully charged lead-acid battery, the discharge current I at a 10-hour rate １０ (A) Discharge in a 25°C air chamber until the terminal voltage reaches 10.8V (1.8V / cell), and determine the discharge time (minutes). Then, I １０ (A) Charge the battery to 120% of the discharged amount. Then, continue the float charging described above.

[0102] [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.

[0103] 《Lead-acid batteries R1, E1-E15, C1-C8》 (1) Preparation of 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 is the positive electrode current collector, and then aged and dried to obtain an unformed positive electrode plate. The volume of electrolyte impregnated into the positive electrode plate (Vp) can be controlled by changing the state of the lead oxide used when preparing the positive electrode paste, the water and sulfuric acid content in the paste, etc.

[0104] (2) Preparation of the negative electrode plate A negative electrode paste is prepared by mixing lead oxide, carbon black, barium sulfate, 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 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 when measured in the fully charged state after formation, they are 0.2 mass%, 0.4 mass%, and 0.1 mass%, respectively.

[0105] (3) AGM with a glass fiber content of 90% by mass is used as the separator. The Vp / Vt ratio is controlled by changing the type of oxygen-containing organic compound (P) included in the separator, the content of oxygen-containing organic compound (P) in the separator, the state of the lead oxide used when preparing the positive electrode paste and negative electrode paste, the water and sulfuric acid content in the paste, and the density of the AGM separator.

[0106] <Oxygen-containing organic compound (P)> As the oxygen-containing organic compound (P), the following polyoxyethylene alkyl / alkenyl ethers that satisfy condition (C) are used.

[0107] (a) POE / TDE (Polyoxyethylene Tridecyl Ether) Number of carbon atoms in the terminal alkyl group = 13 Number of oxyethylene units N = 5 to 22 Number of peaks in the m / z region = 400 to 1200 = 18 Peak interval (m / z) = 20 to 25 or 40 to 50 Oxygen content (PO) = 0.309

[0108] (b) POE / STE (Polyoxyethylene cetyl ether) Number of carbon atoms in the terminal alkyl group = 16 Number of oxyethylene units N = 6 to 33 Number of peaks in the m / z region = 400 to 1200 = 45 Peak interval (m / z) = 20 to 25 or 40 to 50 Oxygen content (PO) = 0.318

[0109] (c) POE / OLE (Polyoxyethylene Oleyl Ether) Number of carbon atoms in terminal alkylene group = 18 Number of oxyethylene units N = 5-20 Number of peaks in the m / z range = 400-1200 = 32 Peak interval (m / z) = 20-25 or 40-50 Oxygen content (PO) = 0.209

[0110] The oxygen-containing organic compound (P) is incorporated into the separator by one of the following methods: Method (X): Immerse the separator in an aqueous solution of the oxygen-containing organic compound (P) and dry it.

[0111] Method (Y): A method for producing a separator by diluting a raw material slurry containing glass fibers at a high concentration with an aqueous solution of an oxygen-containing organic compound (P), and then using the diluted slurry to make paper.

[0112] Method (Z): A method of adding an oxygen-containing organic compound (P) to the electrolyte at a concentration of 0.25% by mass.

[0113] (4) Preparation of the electrolyte A sulfuric acid aqueous solution is prepared 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 of [the specified range].

[0114] (5) Manufacturing of a lead-acid battery A valve-regulated lead-acid battery that satisfies the various parameters shown in Table 1 is manufactured. Specifically, four unformed negative plates and three unformed positive plates are 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 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 battery is reformed inside the battery case to assemble a valve-regulated lead-acid battery with a nominal voltage of 12V and a rated 20-hour rate capacity of 40Ah as described above.

[0115] When an oxygen-containing organic compound (P) is used, "Yes" is indicated in Table 1; when an oxygen-containing organic compound (P) is not used, "No" is indicated in Table 1. If "Yes" is indicated in Table 1, the oxygen-containing organic compound (P) is included in the separator by method (X). In the case of "Yes," the ratio of the mass of the oxygen-containing organic compound contained in the separator to the mass of the electrolyte is within the range of 0.05 to 0.15% by mass.

[0116] (6) Evaluation The prepared lead-acid battery is fully charged, and a float test is performed using the method described above to evaluate the low-rate discharge performance. The Vp / Vt ratio at the initial stage and after 10 months, and the ratio of the low-rate discharge capacity after 10 months to the initial discharge capacity (low-rate discharge capacity maintenance rate) are shown in Table 1.

[0117]

[0118] Table 1 shows that when the initial Vp / Vt ratio falls outside the range of 0.20 to 0.30, the low-rate discharge capacity maintenance rate after 10 months is significantly lower, regardless of whether or not an oxygen-containing organic compound (P) is used. Furthermore, when an oxygen-containing organic compound (P) is not used, the low-rate discharge capacity maintenance rate after 10 months is significantly lower, even if the initial Vp / Vt ratio is within the range of 0.20 to 0.30. On the other hand, when an oxygen-containing organic compound (P) that satisfies condition (C) is used, the low-rate discharge capacity maintenance rate after 10 months is significantly improved.

[0119] Lead-acid batteries C9-C20: Batteries were fabricated and evaluated in the same manner as the previously described batteries (e.g., battery E1), except that the following compounds were used instead of oxygen-containing organic compounds (P). The results are shown in Table 2.

[0120] (d) Oleic acid oxygen content (PO) = 0.113

[0121] (e) PPG (Polyoxypropylene Glycol) Peak interval (m / z) = 58 Oxygen content (PO) = 0.283

[0122] (f) PEG oleate (polyoxyethylene oleate) Peak interval (m / z) = 44 Oxygen content (PO) = 0.240

[0123] (g) PEG distearate (polyoxyethylene distearate) Peak interval (m / z) = 44 Oxygen content (PO) = 0.345

[0124] (h) PEG (polyoxyethylene glycol) Peak interval (m / z) = 44 Oxygen content (PO) = 0.371

[0125] (i) POE lauryl ether (polyoxyethylene laurate) Peak interval (m / z) = 22, 44 Oxygen content (PO) = 0.320

[0126]

[0127] Table 2 shows that when using compounds that do not meet condition (C), it is not possible to significantly improve the low-rate discharge capacity maintenance rate after 10 months.

[0128] Lead-acid batteries E16-E18, C21-C23: Batteries are prepared and evaluated in the same manner as the previously described batteries (e.g., battery E1), except that an oxygen-containing organic compound (P) is added to the separator using method Y or Z. The results are shown in Table 3.

[0129]

[0130] Table 3 shows that even if oxygen-containing organic compounds (P) are included in the electrolyte at a considerable concentration, it is not possible to include a sufficient amount of oxygen-containing organic compounds in the separator, and therefore no effect on improving the low-rate discharge capacity maintenance rate after 10 months can be expected.

[0131] 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.

[0132] 1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 11: Electrode plate group 10: Battery case 10R: Cell chamber 13: Exhaust valve

Claims

1. A valve-regulated lead-acid battery comprising: a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, wherein the separator is a nonwoven fabric containing glass fibers and an oxygen-containing organic compound, the ratio (Vp / Vt) of the volume of the electrolyte impregnated in the positive electrode plate to the total volume (Vt) of the electrolyte is 0.20 or more and 0.30 or less, the LC / MS spectrum of the oxygen-containing organic compound measured with chloroform as a solvent has multiple peaks in the region of m / z value 400 or more and 2000 or less, the multiple peaks are spaced apart with m / z values ​​of 20 or more and 25 or less, or 40 or more and 50 or less, all oxygen atoms contained in the oxygen-containing organic compound are contained in at least one of an ether bond and a hydroxyl group, and the ratio of the total mass of the oxygen atoms contained in the oxygen-containing organic compound to the mass of the oxygen-containing organic compound is less than 0.

320.

2. The LC / MS spectrum of the oxygen-containing organic compound measured with chloroform as a solvent has 10 or more peaks in the region where the m / z value is 400 or more and 1200 or less, according to claim 1.

3. The ratio of the mass of the oxygen-containing organic compound contained in the separator to the mass of the electrolyte is 0.01% by mass or more and 0.15% by mass or less, according to claim 1.

4. The ratio of the mass of the oxygen-containing organic compound contained in the separator to the mass of the electrolyte is 0.05% by mass or more and 0.12% by mass or less, according to claim 1, the valve-regulated lead-acid battery.

5. The valve-regulated lead-acid battery according to claim 1, wherein the oxygen-containing organic compound is an ether having a polyoxyethylene group and a terminal alkyl group or terminal alkenyl group.

6. The valve-regulated lead-acid battery according to claim 5, wherein the number of carbon atoms in the terminal alkyl group or terminal alkenyl group is 10 or more and 20 or less.

7. The valve-regulated lead-acid battery according to claim 5, wherein the number of carbon atoms in the terminal alkyl group or terminal alkenyl group is 13 or more and 18 or less.

8. The valve-regulated lead-acid battery according to claim 5, wherein the number of carbon atoms in the terminal alkyl group or terminal alkenyl group is 13 or more and 17 or less.

9. The valve-regulated lead-acid battery according to claim 5, wherein the number N of oxyethylene units in the polyoxyethylene group is 5 or more and 35 or less.

10. The valve-regulated lead-acid battery according to claim 5, wherein the number N of oxyethylene units in the polyoxyethylene group is 7 or more and 25 or less.

11. The valve-regulated lead-acid battery according to claim 5, wherein the number N of oxyethylene units in the polyoxyethylene group is 10 or more and 20 or less.

12. The valve-regulated lead-acid battery according to claim 5, wherein the oxygen-containing organic compound is at least one selected from the group consisting of polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, and polyoxyethylene cetyl ether.

Images