lead-acid batteries

Abstract

SOLUTION: A lead acid battery includes a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material, and the negative electrode plate includes a negative electrode material. The negative electrode material contains a Bi element, and the content of the Bi element in the negative electrode material is 100 ppm or more and 300 ppm or less based on mass. A chemical oxygen demand in the electrolyte is 160 mg / L or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial use. A lead-acid battery consists of a positive electrode plate, a negative electrode plate, a separator interposed between them, and an electrolyte.

[0003] Patent Document 1 proposes a lead-acid battery characterized by comprising a group of electrode plates in which a positive electrode plate having a positive electrode active material containing lead dioxide and a negative electrode plate having a negative electrode active material containing metallic lead are alternately stacked with a separator in between, the group of electrode plates being immersed in an electrolyte to form a cell, the flatness of the positive electrode plate after chemical formation being 4.0 mm or less, and the bismuth content in the negative electrode active material being 0.5 ppm or more and 250 ppm or less.

[0004] Patent Document 2 proposes a lead-acid battery comprising "a negative electrode plate made of a negative electrode grid that does not contain Sb, a positive electrode plate made of a positive electrode grid that does not contain Sb and has a layer containing 0.01 to 0.20 wt% of the positive electrode active material amount of Sb on at least a part of the surface that is in contact with the positive electrode active material, and a separator interposed between the positive electrode and negative electrode plates, wherein the entire surface of the electrode plates of the positive electrode and negative electrode plates is immersed in an electrolyte, and the negative electrode active material contains 0.02 to 0.10 wt% of Bi relative to the amount of negative electrode active material."

[0005] Patent Document 3 proposes a lead-acid battery comprising a negative electrode plate having a non-Sb negative electrode grid and a negative electrode active material containing 0.1 to 3% by weight of Ba and 0.1 to 2.5% by weight of graphite or carbon, wherein the negative electrode active material contains at least one selected from the group consisting of Sb, Sn, Bi, Zn, Se, Mn, Ca, Mg, and Sr.

[0006] Patent document 4 proposes a lead-acid battery characterized by containing a reducing organic substance in an electrolyte solution of 0.5 mg / L to 3 mg / L. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-163612 [Patent Document 2] Japanese Patent Publication No. 2006-079973 [Patent Document 3] Japanese Patent Publication No. 2003-142085 [Patent Document 4] Japanese Patent Publication No. 2005-251394 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Recent lead-acid batteries, particularly those used in vehicles with idle stop-start (ISS) control, are operated under different conditions than conventional lead-acid batteries. Such batteries are used, for example, in a partially charged state (PSOC). If the lead-acid battery continues to discharge without being charged while the engine is stopped from PSOC, the depth of discharge (hereinafter referred to as "DOD") deepens. In recent years, the number of vehicles with ISS control, such as taxis, buses, and delivery vehicles, has been increasing. These commercial ISS vehicles have longer engine stop times compared to owner-operated ISS vehicles. In other words, commercial ISS vehicles have a higher electrical load, and the amount of electricity discharged from the lead-acid battery has increased. To cope with this increased load, the conditions for charge-discharge cycle tests are becoming stricter than before. Therefore, there is a need to improve the lifespan in charge-discharge cycle tests (heavy load life tests) that assume use at a deep DOD (e.g., 20% to 50%).

[0009] One of the factors contributing to the degradation of lead-acid batteries when used in deep dead-end environments (DODs) is the decrease in the charge acceptance of the negative electrode material and the increase in impedance due to the formation of a high-resistance layer at the positive electrode material / positive electrode lattice interface.

[0010] When Bi is added to the negative electrode material, the charge acceptance of the negative electrode is improved, but it may be difficult to sufficiently improve the life in the heavy load life test only by this.

[0011] By the way, the chemical oxygen demand (COD) in the electrolytic solution is considered to affect the charge acceptance.

Means for Solving the Problems

[0012] One aspect of the present disclosure includes a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolytic solution. The positive electrode plate includes a positive electrode material, the negative electrode plate includes a negative electrode material, the negative electrode material includes a Bi element, and the content of the Bi element in the negative electrode material is 100 ppm or more and 300 ppm or less based on mass. The chemical oxygen demand in the electrolytic solution is 160 mg / L or less, and relates to a lead storage battery.

Effects of the Invention

[0013] According to the present disclosure, the life in the heavy load life test of the lead storage battery is improved.

Brief Description of the Drawings

[0014] [Figure 1] It is a partially cut-away perspective view showing the appearance and internal structure of a lead storage battery according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit of a numerical value regarding a specific physical property or condition are exemplified, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0016] In addition, the present disclosure includes combinations of matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims. That is, as long as no technical contradiction occurs, matters described in two or more claims arbitrarily selected from a plurality of claims described in the appended claims can be combined.

[0017] In this specification, the up-down direction of a lead-acid battery or a component of a lead-acid battery (such as a plate electrode, a battery case, a separator, etc.) means the up-down direction in the vertical direction of the lead-acid battery arranged in the used state. Each of the positive electrode plate and the negative electrode plate has an ear portion for connection to an external terminal. For example, in a liquid-type battery, the ear portion is provided at the upper part of the plate electrode so as to protrude upward.

[0018] The lead-acid battery according to the present disclosure may be a controlled valve type battery (VRLA type battery), but a liquid-type battery (vent type battery) is preferable in that the action effect by the Bi element can be effectively utilized.

[0019] 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, causing the density of the electrolyte to decrease. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte, causing the density of the electrolyte to increase.

[0020] A positive electrode plate, a negative electrode plate, and a separator constitute an electrode group. The electrode group, together with the electrolyte, constitutes a cell. One electrode group constitutes one cell. A lead-acid battery comprises one or more cells by comprising one or more electrode groups. There is no particular limit to the number of positive and negative electrode plates included in one electrode group. An electrode group comprising a lead-acid battery according to this disclosure may, for example, include a total of 12 or more positive and negative electrode plates. Multiple electrode groups are typically housed in separate cell chambers and connected in series with one another.

[0021] The positive electrode plate includes a positive electrode material. The positive electrode material, as a positive electrode active material that exhibits capacity through oxidation-reduction reactions, contains at least lead dioxide during charging and at least lead sulfate during discharge.

[0022] The negative electrode plate includes a negative electrode material. The negative electrode material is a negative electrode active material that exhibits capacity through an oxidation-reduction reaction, and contains at least lead during charging and at least lead sulfate during discharging.

[0023] The chemical oxygen demand (COD) in an electrolyte is the amount of oxygen required to oxidize oxidizable substances in the electrolyte. The COD in an electrolyte can be considered an indicator of the concentration of organic components in the electrolyte. In this specification, COD refers to the COD in the electrolyte sampled from a fully charged lead-acid battery in its initial state of use. An initial-use lead-acid battery is one that has not been in use for very long and has shown little degradation.

[0024] (1) A lead-acid battery according to one embodiment of the present disclosure comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein the positive electrode plate contains a positive electrode material, the negative electrode plate contains a negative electrode material, the negative electrode material contains Bi element, the Bi element content in the negative electrode material is 100 ppm or more and 300 ppm or less by mass, and the chemical oxygen demand (COD) in the electrolyte is 160 mg / L or less. The lead-acid battery described in (1) above exhibits excellent lifespan in heavy load life tests.

[0025] (2) In the lead-acid battery described in (1) above, the COD in the aqueous electrolyte may be 120 mg / L or less. According to the lead-acid battery described in (2) above, a better lifespan can be obtained in heavy load life tests.

[0026] (3) In the lead-acid battery described in (1) or (2) above, the COD in the electrolyte may be 1 mg / L or more. According to the lead-acid battery described in (3) above, deterioration of the upper part of the positive electrode plate is suppressed in the heavy load life test, so a better lifespan can be obtained.

[0027] (4) In the lead-acid battery described in any one of (1) to (3) above, the COD in the electrolyte may be 5 mg / L or more. According to the lead-acid battery described in (4) above, an even better lifespan can be obtained in the heavy load life test.

[0028] (5) In the lead-acid battery described in any one of (1) to (4) above, the ratio of the mass of the positive electrode material to the mass of the negative electrode material may be 1.2 or more and 1.4 or less. The lead-acid battery described in (5) above not only provides excellent lifespan in heavy load life tests, but also reduces the amount of negative electrode material used, making it suitable for weight reduction and cost reduction.

[0029] (6) Any of the lead-acid batteries described in (1) to (5) above may be for vehicles controlled by ISS. In recent years, the number of vehicles controlled by ISS has been increasing, including taxis, buses, and delivery vehicles, and there is a great need to improve the lifespan of the lead-acid batteries installed in these vehicles in heavy load life tests.

[0030] Generally, cycle tests that discharge to a deep DOD tend to cause non-uniformity of the reaction in the vertical direction. This is because, during discharge, the negative electrode plate tends to discharge relatively uniformly overall, but during charging, it tends to become undercharged depending on the charging conditions (charging voltage, charging time). When charging from a deep discharge, PbSO4 + 2e is formed at the top of the negative electrode plate. - →Pb+SO4 2- The reaction and 2H + +2e - →Because the H2 reaction proceeds competitively, the number of electrons that can be supplied to the lower part of the negative electrode plate decreases. As a result, the upper part of the negative electrode plate, which is more easily charged, is selectively charged, while the lower part of the negative electrode plate is less likely to be charged. In other words, lead sulfate tends to remain in the lower part of the negative electrode plate. If similar charge and discharge cycles are repeated, lead sulfate accumulates in the lower part of the negative electrode plate, causing non-uniformity of the reaction in the vertical direction of the negative electrode plate. When Bi is included in the negative electrode material, the upper part of the negative electrode plate becomes more easily charged due to improved charge acceptance caused by the Bi element's effect of reducing hydrogen generation overpotential. On the other hand, the effect of adding Bi element on improving charge acceptance is limited in the lower part of the negative electrode plate. In other words, the non-uniformity of the reaction in the vertical direction of the negative electrode plate becomes more pronounced when Bi element is added.

[0031] On the other hand, if the chemical oxygen demand (COD) in the electrolyte exceeds a predetermined range, a side reaction occurs in which organic matter in the electrolyte is oxidized and decomposed on the surface of the positive electrode plate. This reduces the charge acceptance of the positive electrode plate, and the charge acceptance of the opposing negative electrode plate also tends to decrease. For this reason, in heavy load life tests where discharge is performed to a deep DOD, non-uniformity of the reaction is likely to occur in the vertical direction. This is because, during discharge, the amount of discharged electricity is large (e.g., DOD 20-50%), so the positive and negative electrodes tend to discharge relatively uniformly overall. However, during charging, the amount of charge is almost the same as the amount of discharged electricity, so the amount of charge is consumed by the side reaction due to the decomposition of organic matter, which tends to result in insufficient charging. In particular, this side reaction is more pronounced in the upper part of the electrode plate where the concentration of organic matter is relatively higher because the density of organic matter is lower than the density of the electrolyte.

[0032] In contrast, when the COD in the electrolyte is controlled to 160 mg / L or less, the concentration of organic matter in the electrolyte is reduced, which decreases the proportion of side reactions relative to the charging reaction and makes it less likely for reaction heterogeneity to occur due to insufficient charging.

[0033] The lower the COD in the electrolyte, the lower the concentration of organic matter in the electrolyte, and the less side reactions occur during charging. Therefore, it is assumed that lower COD in the electrolyte improves charging efficiency and extends the lifespan in heavy-load life tests. However, in reality, if charging efficiency improves excessively, the charging reaction tends to proceed locally. Specifically, the charging reaction tends to proceed more easily at the top of the positive and negative electrodes, so the tops of these electrodes are selectively charged, while the bottoms are less likely to be charged. As a result, the top of the positive electrode is prone to overcharging, which accelerates the deterioration of the positive electrode material and corrosion of the positive electrode current collector. In other words, it is not undercharging of the negative electrode, but rather non-uniformity of the positive electrode reaction due to excessive charging. To suppress such non-uniformity of the reaction and achieve a longer lifespan, it is preferable to control the COD in the electrolyte to 1 mg / L or higher. In other words, by controlling not only the Bi element content in the negative electrode material but also the COD in the electrolyte, a significant improvement in lifespan in heavy-load life tests is possible.

[0034] The Bi element content in the negative electrode material must be limited to 100 ppm to 300 ppm by mass. Although the detailed mechanism is not fully understood, if the Bi element content is less than 100 ppm by mass, it is not affected by COD, and sufficient heavy-load life performance cannot be obtained, as shown in the examples described later. This is presumed to be because the upper part of the negative electrode plate, which is easily charged, is selectively charged, and the upper part of the opposing positive electrode plate is also selectively charged, making it easy for the charging reaction to become non-uniform in the vertical direction of the electrodes. However, if the Bi element content is 100 ppm to 300 ppm by mass, and the COD is 1 mg / L to 160 mg / L, the oxidation reaction of organic matter on the upper part of the positive electrode plate can suppress the selective charging reaction on the upper parts of the positive and negative electrodes, and the entire electrode plate can be charged relatively uniformly.

[0035] If the Bi element content in the negative electrode material exceeds 300 ppm, even if the COD in the electrolyte is sufficiently reduced, the electrolyte decomposition reaction (side reaction) is more likely to occur throughout the negative electrode plate, leading to a tendency for undercharging. On the other hand, on the positive electrode plate, the charging reaction is concentrated in the upper part of the plate where charging is easily performed, leading to deterioration of the positive electrode material and corrosion of the positive electrode current collector in the upper part of the positive electrode plate. Conversely, if the Bi element content in the negative electrode material is too high, the COD in the electrolyte becomes excessive. During charging, the electrolyte decomposition reaction on the negative electrode plate and the decomposition reaction of organic matter on the positive electrode plate proceed, making the difference between the amount of discharged electricity during discharge and the amount of charged electricity during charging more pronounced, leading to an extremely undercharged state at an early stage.

[0036] The Bi content in the negative electrode material may be 100 ppm or more by mass, but may also be 150 ppm or more. The Bi content in the negative electrode material may be 250 ppm or less by mass, or 230 ppm or less. A preferred range for the Bi content in the negative electrode material may be, for example, 100 ppm to 250 ppm by mass, or 150 ppm to 230 ppm by mass.

[0037] The COD in the electrolyte should be 160 mg / L or less, but it may also be 120 mg / L or less. From the viewpoint of obtaining higher charge acceptance, the COD in the electrolyte may be 100 mg / L or less, 50 mg / L or less, 30 mg / L or less, or 25 mg / L or less. The COD in the electrolyte may be 1 mg / L or more, 5 mg / L or more, or 8 mg / L or more. A preferred range for the COD in the electrolyte is, for example, 1 mg / L or more and 160 mg / L or less, 1 mg / L or more and 120 mg / L or less, 5 mg / L or more and 160 mg / L or less, or 5 mg / L or more and 120 mg / L or less.

[0038] The COD in the electrolyte can be controlled, for example, by the following methods. One of these methods may be used, or a combination of several may be used. (1) Adjust the concentration of organic additives in the electrolyte. (2) Adjust the content of organic components in components other than the electrolyte. "Components other than the electrolyte" include separators, current collectors for positive or negative electrode plates, and positive or negative electrode materials. In other words, the method in (2) can be broadly classified into the following three methods. (2-1) Control the content of relatively low molecular weight organic additives in the separator. Examples of organic additives include penetrants and oils. (2-2) Control the degree to which cutting oil is cleaned from the current collector of the positive or negative electrode plate, or from the metal plate before it is processed into a current collector. (2-3) Control the content of at least one of the organic component and carbonaceous material contained in the positive electrode material or the negative electrode material. The organic component contained in the electrode material also includes organic shrinkage inhibitors.

[0039] Organic solvents may be used to clean current collectors or metal plates. Examples of organic solvents include at least one selected from alcohols, ketones, esters, ethers, amides, and sulfoxides. An example of an alcohol is ethanol. Examples of ketones are acetone and ethyl methyl ketone. An example of an ester is ethyl acetate. An example of an ether is tetrahydrofuran. Examples of amides are dimethylformamide and N-methyl-2-pyrrolidone. An example of a sulfoxide is dimethyl sulfoxide.

[0040] To avoid increasing the COD in the electrolyte, it is desirable to use an organic solvent that is easily removed by washing with water, or an organic solvent that is miscible with water, as the organic solvent used to clean the current collector or metal plate. The cleaning time is preferably 3 seconds or more in an organic solvent that is miscible with water. There is no particular upper limit to the cleaning time, and it may be 60 seconds or less, for example.

[0041] The electrolyte is an aqueous solution in which at least sulfuric acid is dissolved as a solute. The electrolyte may be gelled as needed. The electrolyte may further contain at least one metal ion selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0042] The electrolyte used in the assembly of lead-acid batteries may contain organic additives. Examples of organic additives include surfactants. However, if the COD in the electrolyte of the lead-acid battery is to be kept low, it is not necessary to include organic additives in the electrolyte used in the assembly of the lead-acid battery.

[0043] In lead-acid batteries, the density of the electrolyte at 20°C is, for example, 1.10 or higher. The density of aqueous electrolytes at 20°C may be 1.35 or lower. These densities are for the electrolyte of a fully charged lead-acid battery.

[0044] The COD of the electrolyte is measured in accordance with JIS K 0102-1:2021, "17.2 Oxygen consumption by acidic potassium permanganate (CODMn)". COD (CODMn) is calculated using the following formula. In this calculation, CODMn is calculated with 2 significant figures, 1 decimal place, and a lower limit of <0.5. CODMn=(titration value-BL)×F×1000 / V×0.2 Titration value: The volume (mL) of 5 mmol / L potassium permanganate aqueous solution required to titrate the sample prepared from the electrolyte. Blank (BL): The volume (mL) of 5 mmol / L potassium permanganate aqueous solution required for titration in a test using distilled water. F: Factor of potassium permanganate aqueous solution with a concentration of 5 mmol / L V: Volume (mL) of sample prepared from the electrolyte (sample used for titration) Oxygen equivalent (mg) in 1 mL of 0.2:5 mmol / L potassium permanganate aqueous solution

[0045] The titration sample is prepared using the following procedure: First, the electrolyte is taken from a fully charged lead-acid battery into a 300 mL Erlenmeyer flask. The amount of electrolyte taken should be a maximum of 100 mL, and adjusted so that the titration volume is in the range of 3.5 mL to 5.5 mL. If the amount taken is less than 100 mL, the amount is measured and distilled water is added until the diluted volume reaches 100 mL. In this way, the electrolyte sample is prepared. In addition, 100 mL of distilled water is prepared in a separate 300 mL Erlenmeyer flask as a sample for BL (Body Line). BL measurement is performed each time the sample prepared from the electrolyte is titrated.

[0046] Prepare titration samples from 100 mL of electrolyte solution and distilled water for BL using the following procedure. First, add 10 mL of 5 mmol / L potassium permanganate aqueous solution to the above sample using a volumetric pipette and stir. Next, heat each Erlenmeyer flask in a boiling water bath for 30 minutes. During this time, ensure that the water in the bath is always boiling and that the liquid level in the bath does not fall below the liquid level in the Erlenmeyer flask. After 30 minutes of heating, remove the Erlenmeyer flask and immediately add 10 mL of 12.5 mmol / L sodium oxalate aqueous solution to the liquid in the Erlenmeyer flask using a volumetric pipette. Prepare the titration sample by cooling the liquid to a temperature within the range of 50°C to 60°C. If the sample contains chloride ions, add 2 mL of 500 g / L silver nitrate aqueous solution using a volumetric pipette and stir the resulting mixture well until no precipitate remains and the liquid becomes clear. If the cloudiness persists, continue adding silver nitrate solution little by little while stirring until the cloudiness disappears. The amount of silver nitrate solution added should be such that the total amount of silver nitrate is 1g more than the equivalent amount of chloride ions contained in each sample. The silver nitrate solution is then added to the sample described above.

[0047] Each prepared sample for titration is titrated with a 5 mmol / L potassium permanganate aqueous solution. During titration, when the liquid in the Erlenmeyer flask turns slightly red, stop the titration and let it stand for about 30 seconds to check if the red color has disappeared. If the red color disappears, repeat the titration and standing process until the red color disappears. For samples prepared from the electrolyte and samples prepared from distilled water, use the amount of potassium permanganate aqueous solution (mL) required for titration as the titration value and BL in the above formula to determine the COD of the electrolyte. If the electrolyte is diluted with distilled water during sample preparation, calculate the COD of the electrolyte before dilution, taking the dilution into account.

[0048] The ratio of the mass of the positive electrode material to the mass of the negative electrode material (hereinafter also referred to as the "Mp / Mn ratio") is, for example, 1.2 or higher, and may also be 1.3 or higher. The Mp / Mn ratio may also be 1.4 or lower. The preferred range for the Mp / Mn ratio is, for example, 1.2 or higher and 1.4 or lower, and may also be 1.3 or higher and 1.4 or lower. The mass of the positive electrode material is the mass of the positive electrode material contained in one positive electrode plate. The mass of the negative electrode material is the mass of the negative electrode material contained in one negative electrode plate. Increasing the Mp / Mn ratio to 1.2 or higher means reducing the amount of negative electrode material used. In other words, by increasing the Mp / Mn ratio to 1.2 or higher, the lead-acid battery can be made lighter and less expensive.

[0049] On the other hand, when the Mp / Mn ratio is 1.2 or higher, the load on the negative electrode plate becomes considerably large, and the charge acceptance capacity tends to decrease. In this embodiment, since the negative electrode material contains a predetermined amount of Bi element, the charge acceptance capacity of the negative electrode plate is improved, so even if the Mp / Mn ratio is increased to 1.2 or higher, sulfation of the negative electrode plate does not progress easily, and the heavy load life performance does not decrease easily.

[0050] The lead-acid battery described herein is suitable for use in vehicles with idle stop-start (ISS) control. Lead-acid batteries installed in ISS-controlled vehicles are often used in PSOCs (Power Storage Operations Centers) and require excellent deep discharge cycle life. Furthermore, excellent heavy-load life performance is also required.

[0051] The lead-acid battery according to an embodiment of the present invention will be described in more detail below with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0052] The following describes examples of components of a lead-acid battery.

[0053] (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.

[0054] 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.

[0055] As the lead alloy used for the positive electrode current collector, Pb-Ca alloys and Pb-Ca-Sn alloys, which have excellent corrosion resistance and mechanical strength, are preferred. The positive electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers.

[0056] The positive electrode material includes a positive electrode active material that exhibits capacity through a redox reaction. The positive electrode active material includes lead dioxide, lead sulfate, etc. The positive electrode material may also include additives as needed. Additives may include reinforcing materials, antimony compounds, etc. Examples of reinforcing materials include inorganic fibers and organic fibers.

[0057] Unformed positive electrode plates are obtained by maturing and drying a positive electrode current collector and a positive electrode paste filled in the positive electrode current collector. The positive electrode paste is prepared by kneading a mixture containing lead powder, water, and sulfuric acid. The positive electrode paste may contain additives as needed. These additives may include reinforcing materials, antimony compounds, etc. Such positive electrode plates are also called paste-type positive electrode plates.

[0058] A positive electrode plate can be obtained by forming an unformed positive electrode plate. The forming may be performed by immersing a group of electrode plates including the unformed positive electrode plate in an electrolytic solution containing sulfuric acid in the battery case of a lead-acid battery and charging the group of electrode plates. The forming may also be performed before assembling the lead-acid battery or the group of electrode plates.

[0059] (Negative electrode plate) The negative electrode plate includes a negative electrode current collector and a negative electrode electrode material. The negative electrode electrode material is held by the negative electrode current collector. The negative electrode electrode material is the part of the negative electrode plate excluding the negative electrode current collector. Note that, a conductive layer, a mat, a pasting paper, or the like may be attached to the negative electrode plate. The attached member is included in the components of the negative electrode plate. When the negative electrode plate includes the attached member, the negative electrode electrode material is the part of the negative electrode plate excluding the negative electrode current collector and the attached member.

[0060] The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. The processing method may be expansion processing or punching processing. When a grid-like current collector is used as the negative electrode current collector, it is easy to carry the negative electrode electrode material.

[0061] The lead alloy used for the negative electrode current collector may be any of a Pb-Sb-based alloy, a Pb-Ca-based alloy, and a Pb-Ca-Sn-based alloy. The lead alloy used for the negative electrode current collector may contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element. The negative electrode current collector may have metal layers with different compositions, and the metal layer may be one layer or multiple layers.

[0062] The negative electrode electrode material includes a negative electrode active material that exhibits capacitance by an oxidation-reduction reaction. The negative electrode active material includes lead, lead sulfate, etc. The negative electrode electrode material contains Bi element at 100 ppm or more and 300 ppm or less on a mass basis. The negative electrode electrode material may contain other additives as required. The additives may include an organic anti-shrinkage agent, a carbonaceous material, barium sulfate, etc.

[0063] <Analysis of the content rate of Bi element> For the analysis of the content rate of Bi element in the negative electrode material, a negative electrode plate taken from a lead-acid battery in an unused or initial-use fully charged state is used. The negative electrode plate taken from the lead-acid battery is washed and dried prior to analysis or measurement.

[0064] After washing and drying the negative electrode plate taken from the lead-acid battery, the negative electrode material is sampled and a sample of the pulverized negative electrode material is prepared. The sample is dissolved in a (1+3) nitric acid solution heated to about 100°C, and after filtering the insoluble matter, the Bi content rate is determined by performing ICP (Inductively Coupled Plasma) emission analysis on the solution.

[0065] In this specification, the fully charged state of a flooded lead-acid battery is defined according to JIS D 5301:2019. More specifically, in a water tank at 25°C±2°C, the lead-acid battery is charged with a current 2I which is twice the 20-hour rate current I 20 until the terminal voltage (V) during charging measured every 15 minutes or the electrolyte density converted to 20°C shows a constant value with three significant figures for three consecutive times. The state where charging is completed is the fully charged state. Note that the 20-hour rate current I 20 refers to a current (A) that is 1 / 20 of the numerical value of Ah described in the rated capacity. The numerical value described as the rated capacity is a value with the unit of Ah (ampere-hour). The unit of the current set based on the numerical value described as the rated capacity is A (ampere). Also, in the case of a lead-acid battery with a control valve, the fully charged state means that in an air tank at 25°C±2°C, with a current 5I which is five times the 20-hour rate current I 20 constant current constant voltage charging is performed at 2.67 V / cell (in a lead-acid battery with a rated voltage of 12 V, it is 16.00 V), and the charging is terminated when the total charging time reaches 24 hours. 20 20 20 A fully charged lead-acid battery is a lead-acid battery that has been charged to the fully charged state from a preformed lead-acid battery. Charging the lead-acid battery to the fully charged state may be done immediately after formation if it is after formation, or it may be done after a period of time has elapsed since formation. For example, it is also possible to charge a lead-acid battery during use (preferably in the initial stage of use) after formation.

[0066] ​

[0067] In this specification, a "battery in its initial use" refers to a battery that has not been in use for very long and has shown little to no degradation.

[0068] Examples of organic shrinkage inhibitors include lignin, lignin sulfonic acid, and synthetic organic shrinkage inhibitors. Synthetic organic shrinkage inhibitors may be, for example, formaldehyde condensates of phenolic compounds. Organic shrinkage inhibitors may be used individually or in combination of two or more. The content of organic shrinkage inhibitors in the negative electrode material is, for example, 0.01% by mass or more and 1% by mass or less.

[0069] As carbonaceous materials, carbon black, artificial graphite, natural graphite, hard carbon, soft carbon, etc., can be used. One type of carbonaceous material may be used alone, or two or more types 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.

[0070] The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0071] Unformed negative electrode plates are obtained by aging and drying a negative electrode current collector and a negative electrode paste filled in the negative electrode current collector. Aging is preferably carried out in an atmosphere with a temperature higher than room temperature and high humidity. The negative electrode paste is prepared by kneading a mixture containing lead powder, water, and sulfuric acid. The negative electrode paste may contain additives as needed. Additives may include bismuth compounds (e.g., bismuth sulfate), organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc.

[0072] A negative electrode plate can be obtained by chemically treating an untreated negative electrode plate. Chemical treatment may be carried out by immersing a group of electrode plates, including the untreated negative electrode plate, in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery, 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. The charged negative electrode active material contains spongy lead.

[0073] (Separator) The separator is a porous membrane having pores. The polymer material constituting the porous membrane (hereinafter also referred to as the base polymer) may include a crystalline polymer. Crystalline polymers include, for example, polyolefins. A polyolefin is a polymer that contains at least olefin units (monomer units derived from olefins).

[0074] Polyolefins may be used in combination with other base polymers as the base polymer. The ratio of polyolefins to the total base polymer contained in the porous membrane is, for example, 50% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. The ratio of polyolefins is, for example, 100% by mass or less. The base polymer may also be composed solely of polyolefins.

[0075] Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefin units, and copolymers containing olefin units and copolymerizable monomer units other than olefins. Examples of polyolefins include, for example, at least C 2-3 Examples include polymers containing olefins as monomer units. 2-3 Examples of olefins include at least one selected from the group consisting of ethylene and propylene.

[0076] To improve the oxidation resistance of the separator, it is desirable to provide ribs on the surface of the separator facing the positive electrode plate. The ribs create a gap between the separator and the positive electrode plate, thereby reducing oxidative degradation of the separator.

[0077] A separator with ribs comprises, for example, a base portion and ribs erected from the surface of the base portion. The ribs may be provided only on the surface of the base portion on the positive electrode side, or on both the positive electrode side and the negative electrode side. The base portion of the separator refers to the part of the separator's components excluding protrusions such as ribs, and is a sheet-like portion that defines the outer shape of the separator.

[0078] The height of the ribs may be between 0.05 mm and 1.20 mm. The height of the ribs is the height of the portion that protrudes from the surface of the base (protrusion height). The height of the ribs provided in the region of the separator that faces the positive electrode plate may be between 0.40 mm and 1.20 mm.

[0079] The separator preferably contains oil. Since oil has the effect of suppressing oxidative degradation of the separator, including oil in the separator leads to a more significant improvement in lifespan during heavy load life tests.

[0080] The oil content in the separator is preferably 11% by mass or more, and may also be 13% by mass or more. The oil content in the separator is preferably 18% by mass or less. The preferred range for the oil content in the separator is, for example, 11% by mass or more and 18% by mass or less, or 13% by mass or more and 18% by mass or less. When the oil content is within this range, the effect of suppressing oxidative degradation of the separator is further enhanced. Furthermore, the resistance of the separator can be kept relatively low.

[0081] An oil is a hydrophobic substance that is liquid at room temperature (between 20°C and 35°C) and separates from water. Oils include naturally derived oils, mineral oils, and synthetic oils, with mineral oils and synthetic oils being preferred. For example, paraffin oil and silicone oil can be preferably used. The separator may contain one type of oil or a combination of two or more types.

[0082] The separator may contain inorganic particles. For example, ceramic particles are preferred as the inorganic particles. Examples of ceramics constituting the ceramic particles include at least one selected from the group consisting of silica, alumina, and titania.

[0083] The inorganic particle content in the separator may be, for example, 40% by mass or more. The inorganic particle content may be, for example, 80% by mass or less, or 70% by mass or less. A preferred range for the inorganic particle content is, for example, 40% by mass or more and 80% by mass or less, or 40% by mass or more and 70% by mass or less.

[0084] The separator may be in the form of a sheet, or a sheet folded into an accordion shape may be used as the separator. The separator may also be formed into a bag shape. Either the positive electrode plate or the negative electrode plate may be wrapped in the bag-shaped separator.

[0085] A separator can be obtained, for example, by extruding a resin composition containing a base polymer and a pore-forming agent into a sheet, stretching it, and then removing at least a portion of the pore-forming agent. The resin composition may also contain a penetrating agent (surfactant), etc. By removing at least a portion of the pore-forming agent, micropores are formed in the matrix of the base polymer. After the removal of the pore-forming agent, the sheet-shaped separator is dried as needed. The stretching process may be carried out by biaxial stretching, but is usually carried out by uniaxial stretching. The sheet-shaped separator may be processed into a bag shape as needed.

[0086] In separators having ribs, the ribs may be formed when the resin composition is extruded into a sheet. Alternatively, the ribs may be formed after the resin composition has been formed into a sheet or after the pore-forming agent has been removed, by pressing the sheet with a roller having grooves corresponding to each rib.

[0087] Examples of pore-forming agents include liquid pore-forming agents that are liquid at room temperature (20°C to 35°C) and solid pore-forming agents. Oil may also be used as a liquid pore-forming agent. In this case, if some of the oil is left behind, an oil-containing separator can be obtained. When extracting and removing the oil, the oil content in the separator can be adjusted by adjusting the type and composition of the solvent, the extraction conditions (extraction time, extraction temperature, solvent supply rate, etc.). A single pore-forming agent may be used alone, or two or more may be used in combination. Oil may be used in combination with other pore-forming agents. A liquid pore-forming agent and a solid pore-forming agent may be used in combination. As a solid pore-forming agent, for example, polymer powder may be used.

[0088] The surfactant used as a penetrating agent may be either an ionic surfactant or a nonionic surfactant. The surfactant may be used alone or in combination of two or more types.

[0089] The content of the penetrant in the separator is, for example, 0.01% by mass or more, and may be 0.1% by mass or more. The content of the penetrant in the separator may be 10% by mass or less. From the viewpoint of keeping the COD in the electrolyte low and improving charge acceptance, the content of the penetrant in the separator may be 3% by mass or less, or 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.2% by mass or less.

[0090] The thickness of the separator may be 0.10 mm or more, or 0.15 mm or more. The thickness of the separator may be 0.30 mm or less, or 0.25 μm or less, or 0.20 mm or less. A preferred range for the thickness of the separator may be, for example, 0.10 mm or more and 0.30 mm or less, 0.10 mm or more and 0.25 mm or less, or 0.15 μm or more and 0.20 mm or less.

[0091] <Analysis or measurement of separators> (Preparing the separator) For separator analysis or size measurement, unused separators or separators removed from fully charged lead-acid batteries in their early stages of use are used. Separators removed from lead-acid batteries are washed and dried prior to analysis or measurement.

[0092] The separators removed from lead-acid batteries are cleaned and dried using the following procedure: The separators are immersed in pure water for 1 hour to remove sulfuric acid from them. Then, the separators are removed from the liquid and allowed to stand at 25°C ± 5°C for at least 16 hours to dry.

[0093] (Thickness of the separator and height of the ribs) The thickness of the separator can be determined by measuring the thickness at five arbitrarily selected points in a cross-sectional photograph of the separator and averaging the results. The thickness of the conductive layer in a separator with a conductive layer can be determined using the same method.

[0094] The height of the rib can be determined by the following procedure. First, select 10 arbitrary points on the rib in a cross-sectional photograph of the separator. Next, measure the height of the rib (height from the surface of the base) at each of the 10 selected points. Then, the height of the rib can be determined by averaging the heights of the 10 measured points.

[0095] (Oil content in the separator) A sample (hereinafter referred to as Sample A) is prepared by processing the portion of the separator facing the electrode material into a strip shape. If a conductive layer is provided on the surface of the separator, the conductive layer is polished off to prepare the sample. In the case of a separator with ribs, Sample A is prepared by processing the base portion into a strip shape so as not to include the ribs.

[0096] Approximately 0.5 g of sample A is taken, accurately weighed, and the initial mass of sample A (m0) is determined. The weighed sample A is placed in a glass beaker of appropriate size, and 50 mL of n-hexane is added. Next, the beaker and sample A are subjected to ultrasound for approximately 30 minutes to dissolve the oil contained in sample A into the n-hexane. Then, sample A is removed from the n-hexane, dried in the air at room temperature (temperature between 20°C and 35°C), and weighed to determine the mass of sample A after oil removal (m1). The oil content is then calculated using the following formula. The oil content is determined for 10 samples of sample A, and the average value is calculated. The resulting average value is taken as the oil content in the separator. Oil content (mass %) = 100 × (m0 - m1) / m0

[0097] (Content of inorganic particles in the separator) A portion of sample A, prepared in the same manner as described above, is taken, accurately weighed, placed in a platinum crucible, and heated with a Bunsen burner until no more white smoke is emitted. Next, the resulting sample is heated in an electric furnace (in an oxygen stream, 550°C ± 10°C) for approximately 1 hour to ash, and the ashed material is weighed. The ratio (percentage) of the mass of the ashed material to the mass of sample A is calculated and used as the inorganic particle content (mass %). The inorganic particle content is determined for 10 samples of sample A, and the average value is calculated. The resulting average value is used as the inorganic particle content (inorganic particles other than carbon material) in the separator.

[0098] (Percentage of penetrating agent contained in the separator) A portion of sample A, prepared in the same manner as described above, is taken, accurately weighed, and dried at room temperature (20°C to 35°C) under reduced pressure below atmospheric pressure for at least 12 hours. The dried material is placed in a platinum cell and set in a thermogravimetric analyzer, and the temperature is raised from room temperature to 800°C ± 1°C at a heating rate of 10 K / min. The weight loss when the temperature is raised from room temperature to 250°C ± 1°C is taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of sample A is calculated and taken as the penetrant content (mass %). A Q5000IR manufactured by TA Instruments is used as the thermogravimetric analyzer. The penetrant content is determined for 10 samples of sample A and the average value is calculated. The obtained average value is taken as the penetrant content in the separator.

[0099] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte may be gelled if necessary. The chemical oxygen demand (COD) of the electrolyte is 160 mg / L or less.

[0100] The electrolyte may further contain at least one metal ion selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0101] The density of the electrolyte at 20°C is, for example, 1.10 or higher. The density of the electrolyte at 20°C may also be 1.35 or lower. These densities are values ​​for the electrolyte of a fully charged lead-acid battery.

[0102] Figure 1 shows the external appearance of an example of a lead-acid battery according to an embodiment of the present invention. The lead-acid battery 1 comprises a battery case 12 that houses an electrode plate group 11 and an electrolyte (not shown). The inside of the battery case 12 is divided into a plurality of cell chambers 14 by a partition wall 13. Each cell chamber 14 houses one electrode plate group 11. The opening of the battery case 12 is closed with a lid 15 equipped with a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a liquid inlet plug 18 for each cell chamber. When replenishing water, the liquid inlet plug 18 is removed and the water is replenished. The liquid inlet plug 18 may also have a function of discharging gas generated in the cell chamber 14 to the outside of the battery.

[0103] Each electrode plate group 11 is constructed by stacking multiple negative electrode plates 2 and positive electrode plates 3 via separators 4. Here, a bag-shaped separator 4 that houses the negative electrode plates 2 is shown, but the shape of the separator is not particularly limited. In the cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects multiple negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode shelf 5 that connects multiple positive electrode plates 3 in parallel is connected to a positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 on the outside of the lid 15. In the cell chamber 14 located at the other end of the battery case 12, a negative electrode column 9 is connected to the negative electrode shelf 6, and a through connector 8 is connected to the positive electrode shelf 5. The negative electrode column 9 is connected to a negative electrode terminal 16 on the outside of the lid 15. Each through connector 8 passes through a through hole provided in the partition wall 13 and connects the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0104] The following describes the heavy load life test. The heavy-load life test is evaluated in accordance with JIS D5301:2019, based on the number of cycles required to reach the end of life in the following charge-discharge cycle test. A fully charged lead-acid battery with a rated voltage of 12V is subjected to repeated discharge and charging under the following conditions. Here, (a) and (b) are performed in a water bath at 40℃±2℃.

[0105] The heavy load life test measures the 20-hour rate capacity C of the test battery. 20 The discharge current and charging current are specified based on the difference, and the procedure is carried out in steps (a) to (f). Here, the 20-hour rate capacity C 20 This refers to the capacity when the battery is discharged to the discharge termination voltage at a current (A) that is 1 / 20th of the Ah value listed in the rated capacity.

[0106] (a) Discharge: Discharge at a current of 20A or 40A for 1 hour. (b) Charging: Charge for 5 hours at a current of 5A or 10A. (c) Repeat: Repeat steps (a) and (b) above 24 times, with each step counting as one cycle. (d) Discharge for judgment: After (c) above, perform continuous discharge at 20A or 40A until the voltage reaches 10.2V, and record the discharge duration. (e) Charging: Charge the lead-acid battery at a current of 5A or 10A until the terminal voltage or electrolyte density (at 25°C) measured every 15 minutes shows a constant value for three consecutive times.

[0107] Here, the number of cycles until the end of the lifespan is the capacity (Ah) obtained from the product of the discharge duration and discharge current measured in (d) above, which is the 20-hour rate capacity C 20 This is the number of cycles that is less than or equal to 50% of the value obtained by dividing by 1.155.

[0108] Furthermore, the discharge and charge cycles described in (d) and (e) above are also added to the number of cycles. Also, the 20-hour rate capacity C 20 When evaluating lead-acid batteries between 55Ah and 81Ah, a discharge current of 20A and a charge current of 5A are used, and the 20-hour rate capacity C is used. 20 When evaluating lead-acid batteries with a capacity exceeding 81Ah but not exceeding 205Ah, a discharge current of 40A and a charging current of 10A shall be used.

[0109] The matters described herein can be combined in any way.

[0110] [Examples] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples.

[0111] (Examples 1-24 and Comparative Examples 1-15) (1) Fabrication of the positive electrode plate A positive electrode paste was prepared by mixing lead oxide, reinforcing material (synthetic resin fiber), water, and sulfuric acid. The positive electrode paste was filled into the mesh of an expanded grid made of an antimony-free Pb-Ca-Sn alloy, and aged and dried to obtain an unformed positive electrode plate with a width of 137.5 mm, a height of 110 mm, and a thickness of 1.6 mm.

[0112] (2) Fabrication of the negative electrode plate A negative electrode paste was prepared by mixing lead oxide, bismuth sulfate (Bi2(SO4)3), carbon black, barium sulfate, lignin, water, and sulfuric acid. The negative electrode paste was filled into the mesh of an expanded grid made of Pb-Ca-Sn alloy that did not contain antimony, and aged and dried to obtain an unformed negative electrode plate with a width of 137.5 mm, a height of 110 mm, and a thickness of 1.3 mm. The amount of bismuth sulfate used was adjusted so that the Bi element content of the negative electrode plate taken from a fully charged lead-acid battery was the value shown in Table 1 by mass. The amounts of carbon black, barium sulfate, and lignin used were adjusted so that the content of each component was 0.3 mass%, 2.1 mass%, and 0.1 mass%, respectively, of the negative electrode plate taken from a fully charged lead-acid battery.

[0113] (3) Fabrication of separators A resin composition containing 100 parts by mass of polyethylene, 160 parts by mass of silica particles, a predetermined amount of paraffin-based oil as a pore-forming agent, and a predetermined amount of a penetrating agent was extruded into a sheet, stretched, and then a portion of the pore-forming agent was removed to obtain a separator having ribs on one side.

[0114] The oil content of the separator determined by the procedure described above was 11-18% by mass, and the silica particle content was 60% by mass. The rib height determined by the procedure described above was 0.60 mm. The thickness of the separator (base thickness) determined by the procedure described above was 0.20 mm.

[0115] The sheet-like separator obtained using the above procedure was folded in half so that ribs were positioned on the outer surface to form a bag. Next, the overlapping ends were crimped together to obtain a bag-shaped separator.

[0116] The oil content, silica particle content, thickness, and rib height of the separator were determined for the separator before the lead-acid battery was manufactured. These values ​​are approximately the same as those measured using the previously described procedure for separators removed from the manufactured lead-acid battery.

[0117] (4) Manufacturing of lead-acid batteries Untreated negative electrode plates were placed in a bag-shaped separator and stacked with positive electrode plates to form an electrode plate group consisting of 7 untreated negative electrode plates and 6 untreated positive electrode plates. The ratio of the mass of the positive electrode material to the mass of the negative electrode material (Mp / Mn) was set to 1.3.

[0118] The tabs of the positive electrode plate and the tabs of the negative electrode plate were welded to the positive and negative electrode trays, respectively, using the cast-on-strap (COS) method. The electrode plates were inserted into a polypropylene battery case, electrolyte was poured in, and a chemical conversion was performed inside the case to assemble a liquid lead-acid battery with a rated voltage of 12V and a 5-hour rate capacity of 30Ah. Here, the 5-hour rate capacity is the capacity when discharged at a current (A) of 1 / 5 of the Ah value stated in the rated capacity. Six electrode plate groups are connected in series inside the battery case.

[0119] A sulfuric acid aqueous solution was used as the electrolyte. The density of the electrolyte after chemical conversion at 20°C was 1.285. The COD of the electrolyte extracted from a fully charged lead-acid battery was adjusted to the values ​​shown in Table 1 on a mass basis. The COD was controlled by factors such as the amount of penetrant used in the separator during separator fabrication and the cleaning condition of the expanded grids of the positive and negative electrodes.

[0120] The obtained lead-acid batteries are used to perform heavy-load life tests according to the procedure described above, and their life performance is evaluated. Life performance is evaluated as a relative value of the number of cycles N until the end of life. The relative value of the number of cycles N is the value when the number of cycles N of battery CA4 in Comparative Example 4 is set to 100. The results for batteries A1 to A24 and CA1 to CA15 of Examples 1 to 24 and Comparative Examples 1 to 15 are shown in Table 1.

[0121] [Table 1]

[0122] As shown in Table 1, when the Bi element content of the negative electrode material is 100-300 ppm and the COD is 160 mg / L or less, the lifespan in the heavy load life test is good, and when the COD is 15 mg / L or more, or 8 mg / L or more, the lifespan is significantly improved. Furthermore, when the COD in the electrolyte is 120 mg / L or less, or 100 mg / L or less, or 50 mg / L or less, the lifespan is significantly improved.

[0123] (Examples 25-28) Except for changing the Mp / Mn ratio as shown in Table 2, batteries A25 to A28 of Examples 25 to 28 were fabricated and evaluated in the same manner as in Example 12. [Table 2]

[0124] As shown in Table 2, when the Mp / Mn ratio was between 1.2 and 1.4, the lifetime performance was significantly improved. [Industrial applicability]

[0125] This disclosure is particularly applicable to liquid-type lead-acid batteries. The lead-acid battery according to this disclosure is suitable as a lead-acid battery for vehicles controlled by an ISS (Integrated Stability Control) system. The lead-acid battery can also be suitably used as a power source for industrial energy storage devices such as electric vehicles (forklifts, etc.). These applications are merely examples. The applications of the lead-acid battery according to the present invention are not limited to these. [Explanation of Symbols]

[0126] 1: Lead-acid battery, 2: Negative electrode plate, 3: Positive electrode plate, 4: Separator, 5: Positive electrode shelf, 6: Negative electrode shelf, 7: Positive electrode column, 8: Through connector, 9: Negative electrode column, 11: Electrode plate group, 12: Battery case, 13: Partition wall, 14: Cell chamber, 15: Cover, 16: Negative electrode terminal, 17: Positive electrode terminal, 18: Electrode cap

Claims

1. The device comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive electrode plate and the negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode material, The aforementioned negative electrode plate includes a negative electrode material, The aforementioned negative electrode material contains the element Bi, The content of the element Bi in the negative electrode material is 100 ppm or more and 300 ppm or less by mass. A lead-acid battery in which the chemical oxygen demand in the electrolyte is 1 mg / L or more and 160 mg / L or less.

2. The lead-acid battery according to claim 1, wherein the chemical oxygen demand in the electrolyte is 120 mg / L or less.

3. The lead-acid battery according to claim 1, wherein the chemical oxygen demand in the electrolyte is 5 mg / L or more.

4. The lead-acid battery according to claim 1, wherein the ratio of the mass of the positive electrode material to the mass of the negative electrode material is 1.2 or more and 1.4 or less.

5. A lead-acid battery according to any one of claims 1 to 4, for use in a vehicle with idle stop / start control.

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