Lead acid battery

Abstract

SOLUTION: A lead acid battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator interposed between the positive electrode plate and the negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material contains lead and barium sulfate particles. The number of barium sulfate particles included in 1 g of the negative electrode material is 1.0×109 or more, and the chemical oxygen demand in the electrolyte is less than 170 mg / L.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 proposes "a lead-acid battery having a negative electrode plate containing barium sulfate as a negative electrode active material, characterized in that the barium sulfate has a primary particle size of 0.1 μm or less and equal to or larger than the smallest particle size that can be formed" and "a method for manufacturing a lead-acid battery having a negative electrode plate containing barium sulfate as a negative electrode active material, characterized in that barium sulfate having a primary particle size of 0.1 μm or less and equal to or larger than the smallest particle size that can be formed is added in a slurry state to the negative electrode active material." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-355942 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the way lead-acid batteries are used has been changing. For example, in the case of automotive lead-acid batteries, it is expected that they will increasingly be used as auxiliary batteries for electric vehicles, hybrid vehicles, etc. In such cases, they are expected to be used under light loads.

[0005] The light-load life test specified in JIS D5301 (2019) is suitable as a charge-discharge cycle test that simulates the use of auxiliary batteries. The main mode of deterioration of the negative plate in the light-load life test is shrinkage of the negative electrode material. Shrinkage of the negative electrode material can be suppressed by adding barium sulfate as an additive to the negative electrode material.

[0006] On the other hand, the inventors have discovered that changes in chemical oxygen demand (COD), which is an index of the concentration of organic components in the electrolyte, change the charging efficiency and significantly affect the light-load life performance.

[0007] When there is a lot of COD, there are many organic components on the surfaces of the positive and negative plates that inhibit the charging reaction, resulting in low charging efficiency.The light-load life test is conducted under conditions that make it difficult for lead-acid batteries to be overcharged, and low charging efficiency causes the charging current to drop rapidly as charging progresses during constant-voltage charging, resulting in insufficient charging and shortening the life of the lead-acid battery.

[0008] On the other hand, when COD is low, charging efficiency improves. Therefore, it is expected that light-load life performance will improve. However, contrary to expectations, when COD is low, light-load life performance hardly improves at all. This is thought to be because, as a result of improved charging efficiency, it becomes difficult for the charging reaction to proceed uniformly across the entire negative plate, making it more likely that localized shrinkage of the negative electrode material will occur. [Means for solving the problem]

[0009] One aspect of the present disclosure provides a 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, the negative electrode plate including a negative electrode current collector and a negative electrode material, the negative electrode material including lead and barium sulfate particles, and the number of the barium sulfate particles contained per gram of the negative electrode material is 1.0×10 9 and the chemical oxygen demand in the electrolyte is less than 170 mg / L. [Effects of the Invention]

[0010] According to the present disclosure, the light load life performance of a lead-acid battery can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a partially cutaway perspective view showing the appearance and internal structure of a lead-acid battery according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present disclosure using 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 are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more of the materials may be used in combination.

[0013] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0014] The lead acid battery according to the present disclosure may be a valve regulated battery (VRLA battery), but is preferably a flooded battery (vented battery) in that it can effectively utilize the effects of reducing COD.

[0015] A lead-acid battery includes positive and negative electrode plates, a separator interposed between the positive and negative electrode plates, and an electrolyte. The electrolyte contains sulfuric acid. Charging and discharging proceeds as sulfate ions move between the positive and negative electrode plates and the electrolyte. During discharging, sulfate ions move to the positive and negative electrode plates, decreasing the density of the electrolyte. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte, increasing the density of the electrolyte.

[0016] The positive electrode plates, negative electrode plates, and separator constitute an electrode plate group. The electrode plate group, together with an electrolyte, constitutes a cell. One electrode plate group constitutes one cell. A lead-acid battery comprises one or more electrode groups, thereby comprising one or more cells. There is no particular limit to the number of positive electrode plates and negative electrode plates contained in one electrode plate group. The electrode plate group provided in the lead-acid battery according to the present disclosure includes, for example, a total of 12 or more positive electrode plates and negative electrode plates. Multiple electrode plate groups are usually housed in individual cell chambers and connected to each other in series.

[0017] The positive electrode plate includes a positive electrode material including lead dioxide. More specifically, the positive electrode material includes at least lead dioxide during charging and at least lead sulfate during discharging as a positive electrode active material that exhibits capacity through an oxidation-reduction reaction.

[0018] The negative electrode plate includes a negative electrode material including lead and barium sulfate particles. More specifically, the negative electrode material includes at least lead as a negative electrode active material that exhibits capacity through an oxidation-reduction reaction during charging and at least lead sulfate during discharging, and further includes barium sulfate (BaSO4) as an additive that suppresses shrinkage of the negative electrode material.

[0019] The present disclosure provides the following techniques. (1) A lead-acid battery according to an embodiment of the present disclosure includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material includes lead and barium sulfate particles, and the number of the barium sulfate particles contained per gram of the negative electrode material is 1.0×10 9 or more, and the chemical oxygen demand (COD) in the electrolyte is less than 170 mg / L.

[0020] COD is the amount of oxygen required to oxidize oxidizable substances in the electrolyte. The COD in the electrolyte can be considered an index of the concentration of organic components contained in the electrolyte. In this specification, the COD is the COD in the electrolyte collected from a lead-acid battery in a fully charged state at the beginning of use.

[0021] The lead-acid battery described in (1) above has excellent light load life performance.

[0022] (2) In the lead-acid battery described in (1) above, the chemical oxygen demand may be 120 mg / L or less.

[0023] The lead-acid battery described in (2) above is further excellent in light load life performance.

[0024] (3) In the lead-acid battery according to any one of (1) to (2), the number of the barium sulfate particles contained per gram of the negative electrode material is 1.2 × 10 9 There may be more than one.

[0025] The lead-acid battery described in (3) above is further excellent in light load life performance.

[0026] By reducing the COD in the electrolyte, side reactions such as oxidation of organic components are reduced, and the charging reaction between the positive and negative plates is facilitated, improving charging efficiency. Reducing the COD in the electrolyte to less than 170 mg / L significantly improves charging efficiency.

[0027] On the other hand, increasing the charging efficiency may not improve the battery life in light-load life tests. When charging efficiency is improved by reducing the COD, rapid charging occurs at high currents, resulting in localized charging reactions in areas of the negative plate that are easily charged, such as near the lugs of the negative electrode current collector, resulting in uneven charging across the entire negative plate. This is thought to shorten the battery life due to localized contraction of the negative electrode material in areas of the negative plate that are easily charged. In other words, when the COD in the electrolyte is 170 mg / L or higher, the life degradation mode due to insufficient charging changes to a life degradation mode due to contraction of the negative electrode material when the COD in the electrolyte is less than 170 mg / L. Furthermore, when the COD in the electrolyte is 170 mg / L or higher, the charging efficiency is low, so in light-load life tests, the lead-acid battery reaches the end of its life due to insufficient charging before contraction of the negative electrode material begins.

[0028] In contrast, the number of barium sulfate particles contained in 1 g of the negative electrode material is 1.0 × 10 9 It was found that when the number of barium sulfate particles per gram of negative electrode material is 100 or more, reducing the COD in the electrolyte to less than 170 mg / L significantly improves the light-load life performance. This is presumably due to the following reasons: When the number of barium sulfate particles contained per gram of negative electrode material increases to a certain extent, the barium sulfate particles become more widely distributed throughout the negative electrode plate. As a result, lead sulfate, a discharge product generated using these barium sulfate particles as crystal nuclei, also becomes more widely distributed throughout the negative electrode plate. This improves the charging efficiency throughout the negative electrode plate. As a result, the state of charge of the negative electrode plate becomes uniform throughout the negative electrode plate, extending the period until the negative electrode material shrinks, thereby improving the light-load life performance of the lead-acid battery.

[0029] Furthermore, the number of barium sulfate particles contained in 1 g of the negative electrode material is 1.2 × 10 9 When the COD in the electrolyte is reduced to less than 170 mg / L, the light load life performance improves significantly. This is because the period until the shrinkage of the negative electrode material progresses becomes longer, and the lead-acid battery rarely reaches the end of its life due to the shrinkage of the negative electrode material.

[0030] The lead-acid battery according to the present disclosure is also suitable for use in vehicles with start-stop control. Start-stop control is sometimes called idling stop-start (ISS). ISS control is also called idling reduction control.

[0031] In this specification, the fully charged state of a flooded lead-acid battery is defined by JIS D5301:2019. More specifically, the fully charged state is defined as a state in which a lead-acid battery is charged at a current 2I20 (unit: A), which is twice the 20-hour rate current I20, until the terminal voltage (unit: V) during charging or the electrolyte density converted to 20°C temperature, measured every 15 minutes in a water bath at 25°C ± 2°C, shows a constant value to three significant digits three times consecutively. Note that the 20-hour rate current I20 is a current (A) that is 1 / 20 of the value in Ah listed in the rated capacity. The value listed as the rated capacity is in Ah (ampere-hour). The unit of current set based on the value listed as the rated capacity is A (ampere). In addition, for valve-regulated lead-acid batteries, a fully charged state is defined as the state when charging is completed in a gas tank at 25°C ± 2°C, at a constant current and constant voltage of 2.67 V / cell (16.00 V for lead-acid batteries with a rated voltage of 12 V) at a current of 5I20 (unit: A), which is five times the 20-hour rate current I20, and when charging is completed after a total charging time of 24 hours.

[0032] A fully charged lead-acid battery is a lead-acid battery that has already been formed and charged to a fully charged state. The timing for charging a lead-acid battery to a fully charged state may be immediately after formation, or after a certain time (e.g., 720 hours or less) has passed since formation. For example, a lead-acid battery that has been formed and is in use (preferably in the early stages of use) may be charged.

[0033] In this specification, a battery in its early stages of use is a battery that has not been in use for a long time and has hardly deteriorated (for example, a battery that has been in use for only 720 hours or less since formation).

[0034] Hereinafter, lead-acid batteries according to embodiments of the present invention will be described in more detail with reference to the drawings, although the present invention is not limited to the following embodiments.

[0035] Examples of components of a lead-acid battery will be described below.

[0036] (positive electrode plate) The positive electrode plate includes a positive electrode collector and a positive electrode material. The positive electrode material is held by the positive electrode collector. The positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector. An attachment member such as a conductive layer, mat, or pasting paper may be attached to the positive electrode plate. The attachment member is used integrally with the positive electrode plate, and is therefore included as a component of the positive electrode plate. When the positive electrode plate includes an attachment member, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector and the attachment member.

[0037] 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, expanding or punching. When a grid-shaped current collector is used as the positive electrode current collector, it is easy to support the positive electrode material.

[0038] The lead alloy used for the positive electrode current collector is preferably a Pb-Ca alloy or a Pb-Ca-Sn alloy, which have excellent corrosion resistance and mechanical strength. The positive electrode current collector may have metal layers with different compositions, and the metal layer may be a single layer or multiple layers.

[0039] The positive electrode material includes a positive electrode active material that generates capacity through an oxidation-reduction reaction. Examples of the positive electrode active material include lead dioxide and lead sulfate. The positive electrode material may include additives as needed. The additives may include reinforcing materials, antimony compounds, and the like. Examples of reinforcing materials include inorganic fibers and organic fibers.

[0040] An unformed positive electrode plate is obtained by aging and drying a positive electrode paste filled on a 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. The additives may include reinforcing materials, antimony compounds, etc. Such positive electrode plates are also called paste-type positive electrode plates.

[0041] A positive electrode plate can be obtained by chemically forming an unformed positive electrode plate. Chemical formation may be performed by immersing an electrode plate assembly including the unformed positive electrode plate in an electrolyte containing sulfuric acid in a battery container of a lead-acid battery and charging the electrode plate assembly. Chemical formation may also be performed before assembling the lead-acid battery or the electrode plate assembly.

[0042] (negative plate) The negative electrode plate includes 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. An adhesive member such as a conductive layer, mat, or pasting paper may be attached to the negative electrode plate. The adhesive member is included as a component of the negative electrode plate. When the negative electrode plate includes an adhesive member, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive member.

[0043] 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 expanding or punching. If a grid-shaped current collector is used as the negative electrode current collector, it is easy to support the negative electrode material.

[0044] The lead alloy used for the negative electrode current collector may be any of a Pb-Sb alloy, a Pb-Ca alloy, and a Pb-Ca-Sn alloy. The lead alloy used for the negative electrode current collector may 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 with different compositions, and the metal layer may be a single layer or multiple layers.

[0045] The negative electrode plate is obtained by chemically converting an unformed negative electrode plate. The unformed negative electrode plate is obtained by aging and drying a negative electrode current collector and a negative electrode paste filled in the negative electrode current collector. The aging is preferably performed in an atmosphere that is higher than room temperature and has high humidity. The negative electrode paste is prepared by kneading a mixture containing lead powder or lead oxide, barium sulfate particles, water, and sulfuric acid.

[0046] The formation may be performed by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery container of a lead-acid battery and charging the electrode plate assembly. The formation may be performed before assembling the lead-acid battery or the electrode plate assembly. The negative electrode active material in the charged state contains spongy lead.

[0047] The negative electrode material contains a negative electrode active material that generates capacity through an oxidation-reduction reaction. The negative electrode active material includes lead, lead sulfate, etc. The negative electrode material contains barium sulfate particles. The number of barium sulfate particles contained per gram of the negative electrode material is 1.0 x 10 9 1.2 x 10 or more 9 The number of barium sulfate particles contained in 1 g of the negative electrode material may be 1.5 × 10 9 or more or 2.3 x 10 9 It can be more than 5.0 × 10 11 When the number of barium sulfate particles contained per gram of the negative electrode material is equal to or greater than the above lower limit, the barium sulfate particles are uniformly distributed in the negative electrode material, and the light load life can be improved. The number of barium sulfate particles contained per gram of the negative electrode material is 5.0 × 10 15 It can be less than 1.0 x 10 15 It can be less than 5.0 x 10 14 When the number of barium sulfate particles contained per gram of the negative electrode material is equal to or less than the above upper limit, the barium sulfate particles can be easily dispersed in a dispersion medium, thereby improving productivity.

[0048] The average particle size of the barium sulfate particles may be 0.4 μm or less, or 0.1 μm or less. Controlling the average particle size in this manner facilitates controlling the number of barium sulfate particles contained per gram of the negative electrode material within the above range. Furthermore, when dispersing barium sulfate particles in the negative electrode paste, it is believed that pre-crushing the barium sulfate particle agglomerates suppresses the aggregation of the barium sulfate particles, resulting in more uniform fine dispersion in the negative electrode paste. The average particle size of the barium sulfate particles may be 0.01 μm or more. This further suppresses the aggregation of the barium sulfate particles, allowing the barium sulfate particles to be dispersed with high dispersibility in the negative electrode paste.

[0049] The higher the barium sulfate particle content, the more barium sulfate particles can be contained per gram of the negative electrode material. On the other hand, from the viewpoint of maintaining a high capacity of the negative electrode material and suppressing aggregation of the barium sulfate particles, the lower the barium sulfate particle content, the more preferable. Considering the balance between capacity and light-load life performance, the barium sulfate particle content in the negative electrode material is preferably, for example, 0.1% by mass or more and 2.0% by mass or less, and may be 0.5% by mass or more and 1.0% by mass or less.

[0050] The lower limit of the cumulative volume ratio of particles having a particle diameter of 0.1 μm or less in the volume-based particle size distribution of barium sulfate particles may be 0.6% or 1%. By having the cumulative volume ratio of particles having a particle diameter of 0.1 μm or less equal to or greater than this lower limit, it becomes easy to control the number of barium sulfate particles contained per gram of negative electrode material within the above range, thereby improving light-load life. The upper limit of the cumulative volume ratio of particles having a particle diameter of 0.1 μm or less in the volume-based particle size distribution of barium sulfate particles is not particularly limited, but may be, for example, 70%, 50%, or 25%, and is preferably 10% or less from the viewpoint of improving manufacturability.

[0051] The number, average particle size, and content of barium sulfate particles contained per gram of negative electrode material can be measured by dismantling a fully charged lead-acid battery after chemical formation, extracting the negative electrode material, pulverizing it, dissolving all lead and lead compounds using a reagent such as nitric acid or ammonium acetate, and separating the barium sulfate particles from other additives such as carbonaceous materials by centrifugation.

[0052] The content of barium sulfate particles in the negative electrode material can be calculated from the mass of barium sulfate particles separated from a given mass of the negative electrode material. In addition, by measuring the particle size distribution of the barium sulfate particles contained in a given mass of the negative electrode material, the number of barium sulfate particles contained per gram of the negative electrode material and the average particle size can be measured.

[0053] The particle size distribution of barium sulfate particles can be measured using a laser diffraction / scattering particle size analyzer. An example of such a particle size analyzer is the Mastersizer 3000 manufactured by Malvern Panalytical. The particle size distribution can also be measured using a dispersion obtained by adding barium sulfate particles to an aqueous solution of sodium hexametaphosphate (NaHMP) (NaHMP concentration: 0.05% by mass) and ultrasonically dispersing for 1 minute. The number of barium sulfate particles contained per gram of negative electrode material can be calculated from the particle size distribution based on the number of particles. The average particle size is a weighted average value, and can be calculated as follows: Average particle size = (particle diameter X1 × particle number Y1 + particle diameter X2 × particle number Y2 + ··· + particle diameter Xn × particle number Yn) / (Y1 + Y2 + ··· + Yn), where Yn is the number of particles with particle diameter Xn.

[0054] The negative electrode material (negative electrode paste) may contain other additives as needed, such as an organic shrinkage inhibitor and a carbonaceous material.

[0055] Examples of the organic shrink-preventing agent include lignin, lignin sulfonic acid, and synthetic organic shrink-preventing agents. Examples of the synthetic organic shrink-preventing agent include formaldehyde condensates of phenolic compounds. One type of organic shrink-preventing agent may be used alone, or two or more types may be used in combination. The content of the organic shrink-preventing agent in the negative electrode material is, for example, 0.01% by mass or more and 1% by mass or less.

[0056] Examples of the carbonaceous material include carbon black, artificial graphite, natural graphite, hard carbon, and soft carbon. The carbonaceous material may be used alone or in combination of two or more. The content of the carbonaceous material in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0057] An example of a method for manufacturing a negative electrode plate (hereinafter also referred to as "manufacturing method M") will be described below. Manufacturing method M includes a first step of preparing a dispersion, a second step of preparing a negative electrode paste, and a third step of fabricating a negative electrode plate using the negative electrode paste. Each step will be described in more detail below.

[0058] (1st step) In the first step, a dispersion liquid is prepared by mixing barium sulfate particles with a liquid. The liquid may be an aqueous sulfuric acid solution, but is preferably pure water.

[0059] When an aqueous sulfuric acid solution is used, the average particle size (D50) of the barium sulfate particles used as the raw material for preparing the dispersion may be, for example, 0.4 μm or less, 0.3 μm or less, or 0.1 μm or less. The average particle size of the barium sulfate particles may be 0.01 μm or more. The maximum particle size of the barium sulfate particles is, for example, 2.5 μm or less, preferably 2 μm or less. The average particle size and maximum particle size of the barium sulfate particles are measured using a laser diffraction / scattering particle size distribution analyzer.

[0060] The density of the sulfuric acid aqueous solution is not particularly limited, but for example, it is 1 g / cm 3 Larger, 1.03g / cm 3In this case, the dispersibility of the barium sulfate particles in the dispersion is improved. The upper limit of the density of the aqueous sulfuric acid solution is not particularly limited, and is, for example, 1.4 g / cm. 3 The density of the aqueous sulfuric acid solution is the density at 20°C.

[0061] The dispersion is obtained by mixing barium sulfate particles with a liquid dispersion medium. Barium sulfate particles have good affinity for water. Therefore, the mixing method is not particularly limited, but it is desirable to perform intensive stirring to sufficiently increase the number of barium sulfate particles contained per gram of negative electrode material. It is preferable to disperse the barium sulfate particles until a significant amount of the barium sulfate particles in the dispersion is crushed to the primary particle level. For example, it is preferable to disperse the barium sulfate particles until the cumulative volume ratio of particles with a particle diameter of 0.1 μm or less in the volume-based particle size distribution of the barium sulfate particles is 0.6% or more (preferably until the ratio of the first particles constituting the first peak in the cumulative volume V1 is 3% or more). As long as the number of barium sulfate particles can be sufficiently increased, the mixing device is not particularly limited, and known devices such as agitators, mixers, and ball mills may be used.

[0062] By dispersing barium sulfate particles in a liquid dispersion medium to a much higher level than conventional levels, the number of barium sulfate particles contained per gram of negative electrode material can be significantly increased. The smaller the particle size of barium sulfate particles, the more likely they are to aggregate due to van der Waals forces. However, by dispersing barium sulfate particles to a level exceeding conventional levels, the particle size of the barium sulfate particles becomes extremely small, for example, 0.1 μm or less, allowing them to exist more stably, and the number of particles is thought to increase.

[0063] The mixing of the barium sulfate particles and the liquid may be carried out at a temperature at which the liquid does not solidify, for example, at 10° C. or higher, or at 20° C. or higher. The mixing may be carried out at a temperature of 60° C. or lower, or at 40° C. or lower. The mixing time of the barium sulfate particles and the liquid is not particularly limited and is adjusted depending on the scale of mixing, the mixing method, etc.

[0064] The barium sulfate particles and the liquid may be mixed in an inert gas atmosphere (such as nitrogen gas) or in the air, or may be mixed under reduced pressure or atmospheric pressure.

[0065] The content of barium sulfate particles in the dispersion is preferably 55% by mass or less, more preferably 40% by mass or less, and may be 30% by mass or less or 25% by mass or less. When the content of barium sulfate particles is within this range, the dispersibility of the barium sulfate particles in the dispersion is further improved. As a result, the number of barium sulfate particles in the negative electrode paste increases. The content of barium sulfate in the dispersion may be, for example, 0.1% by mass or more, 1% by mass or more, or 5% by mass or more.

[0066] (2nd process) In the second step, the dispersion liquid is mixed with lead powder or lead oxide to prepare a negative electrode paste. If necessary, carbonaceous materials, organic shrinkage inhibitors, reinforcing materials, and other known additives may be added to the negative electrode paste.

[0067] The order of mixing is not particularly limited. For example, all components may be mixed at once, or some components may be mixed in advance and then mixed with the remaining components. For example, components other than the dispersion may be mixed in advance, and the resulting mixture may be mixed with the dispersion. In addition to the dispersion, a liquid component (such as at least one of pure water and an aqueous sulfuric acid solution) may be added and mixed. Components other than the dispersion may be mixed in advance, pure water may be added and further mixed, and a dispersion using an aqueous sulfuric acid solution may be added and further mixed. Alternatively, components other than the dispersion may be mixed in advance, a dispersion using pure water may be added and further mixed, and an aqueous sulfuric acid solution may be added and further mixed.

[0068] The mixing is not particularly limited and can be carried out using, for example, a kneader. The mixing can be carried out, for example, at 10°C or higher, or may be carried out at 20°C or higher. The mixing can be carried out, for example, at 40°C or lower. The mixing can be carried out in the air. The mixing is usually carried out under atmospheric pressure.

[0069] The lead or lead oxide powder contains lead monoxide. The proportion of lead oxide in the powder is greater than 50% by mass, typically 70% by mass or greater. Lead or lead oxide is also commonly referred to as "lead powder." The powder may be a common lead powder used in the manufacture of electrode materials for lead-acid batteries.

[0070] The mixing ratio of the dispersion liquid and the lead powder is adjusted so that the amount of barium sulfate particles per 100 parts by mass of lead powder is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, or 1 part by mass or more. By using the dispersion liquid, high dispersibility of the barium sulfate particles in the negative electrode material can be ensured. Furthermore, the mixing ratio of the dispersion liquid and the lead powder is adjusted so that the amount of barium sulfate particles per 100 parts by mass of lead powder is, for example, 7 parts by mass or less, preferably 5 parts by mass or less. In this case, a high initial capacity can be ensured.

[0071] Examples of the carbonaceous material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, etc. The negative electrode paste may contain one type of carbonaceous material or two or more types.

[0072] The amount of the carbonaceous material is, for example, 0.1 parts by mass or more relative to 100 parts by mass of the lead powder, and 3.5 parts by mass or less relative to 100 parts by mass of the lead powder.

[0073] Examples of the organic shrinkage inhibitor include lignin, lignin sulfonic acid or its salt, synthetic organic shrinkage inhibitor (such as a formaldehyde condensate of a phenol compound), etc. The negative electrode paste may contain one type of organic shrinkage inhibitor or two or more types.

[0074] The amount of the organic shrinkage inhibitor is, for example, 0.01 parts by mass or more relative to 100 parts by mass of the lead powder, and 1.2 parts by mass or less relative to 100 parts by mass of the lead powder.

[0075] (3rd step) In the third step, a negative electrode plate is produced using the negative electrode paste prepared in the second step. More specifically, the negative electrode paste is filled into a negative electrode current collector, and the negative electrode current collector is aged and dried to produce an unformed negative electrode plate. The unformed negative electrode plate is then formed by forming the negative electrode plate. The formed negative electrode plate comprises a negative electrode material and a negative electrode current collector that holds the negative electrode material.

[0076] The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead sheet or a lead alloy sheet. Examples of processing methods include expanding and punching. A lattice-shaped current collector is preferably used as the negative electrode current collector because it is easy to support the negative electrode material.

[0077] In the aging step, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature (for example, 20° C. or higher and 35° C. or lower) and at high humidity.

[0078] The formation can be carried out by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery jar of a lead-acid battery and then charging the electrode plate assembly. However, the formation can also be carried out before assembling the lead-acid battery or the electrode plate assembly. The formation produces spongy lead.

[0079] 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 more, and may be 1.3 or more. The Mp / Mn ratio may be 1.4 or less. A preferred range of the Mp / Mn ratio is, for example, 1.2 or more and 1.4 or less, and may be 1.3 or more and 1.4 or less. 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 more means reducing the amount of negative electrode material used. In other words, an Mp / Mn ratio of 1.2 or more can reduce the weight and cost of lead-acid batteries. Furthermore, an Mp / Mn ratio of 1.2 or more can reduce the load on the positive electrode plate, making it easier to suppress softening and detachment of the positive electrode material.

[0080] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. The electrolyte may be gelled as necessary. 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. The specific gravity of the electrolyte at 20°C is, for example, 1.10 or more. The specific gravity of the electrolyte at 20°C may be 1.35 or less. Note that these specific gravities are values ​​for the electrolyte of a fully charged lead-acid battery.

[0081] To ensure high charging efficiency and improve light-load life performance, the COD in the electrolyte should be less than 170 mg / L, but it may also be 160 mg / L or less, 120 mg / L or less, 100 mg / L or less, or 80 mg / L or less. The COD in the electrolyte may also be 15 mg / L or more, 20 mg / L or more, 25 mg / L or more, or 30 mg / L or more. A preferred range of the COD in the electrolyte is, for example, 15 mg / L or more but less than 170 mg / L, 20 mg / L or more but less than 160 mg / L, or 25 mg / L or more but less than 120 mg / L.

[0082] The COD amount in the electrolyte solution can be controlled, for example, by the following methods. The following methods may be adopted alone or in combination. (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 the separator, the positive or negative electrode current collector, and the positive or negative electrode material. In other words, method (2) can be broadly divided into the following three methods: (2-1) The content of relatively low molecular weight organic additives contained in the porous film used as the separator is controlled. Examples of organic additives include penetrants and oils. (2-2) At least a part of the cutting oil adhering to the current collector of the positive or negative electrode plate or to the metal plate before being processed into the current collector is removed by washing or the like. (2-3) The content of at least one of the organic component and the carbonaceous material contained in the positive electrode material or the negative electrode material is controlled. The organic component contained in the electrode material also includes an organic shrinkage preventer.

[0083] An organic solvent can be used to clean the current collector or metal plate. Examples of the organic solvent include at least one selected from alcohols, ketones, esters, ethers, amides, and sulfoxides. Examples of the alcohol include ethanol. Examples of the ketone include acetone and ethyl methyl ketone. Examples of the ester include ethyl acetate. Examples of the ether include tetrahydrofuran. Examples of the amide include dimethylformamide and N-methyl-2-pyrrolidone. Examples of the sulfoxide include dimethyl sulfoxide.

[0084] To avoid excessive increase in COD in the electrolyte, it is desirable to use an organic solvent that is easily removed by washing with water or that is miscible with water as the organic solvent used to wash the current collector or metal plate. The washing time is preferably, for example, 3 seconds or more in a water-miscible organic solvent. The upper limit of the washing time is not particularly limited and may be, for example, 60 seconds or less.

[0085] The electrolyte used in the assembly of a lead-acid battery may contain an organic additive. Examples of the organic additive include a surfactant. However, from the viewpoint of keeping the COD amount in the electrolyte contained in the lead-acid battery low, it is preferable that the electrolyte used in the assembly of a lead-acid battery does not contain an organic additive.

[0086] 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: CODMn is calculated to two significant figures, one decimal place, and a lower limit of <0.5. CODMn=(titration value-BL)×F×1000 / V×0.2 Titration value: The amount (mL) of 5mmol / L potassium permanganate solution required to titrate the sample prepared from the electrolyte. Blank (BL): The amount (mL) of 5mmol / L potassium permanganate solution required for titration in a test using distilled water F: Factor of potassium permanganate solution with a concentration of 5mmol / L V: Volume (mL) of sample prepared from the electrolyte (sample used for titration) 0.2: The oxygen equivalent (mg) of 1 mL of 5 mmol / L potassium permanganate solution

[0087] The titration sample is prepared using the following procedure. First, electrolyte is collected from an initial, fully charged lead-acid battery into a 300 mL Erlenmeyer flask. The amount of electrolyte collected is limited to a maximum of 100 mL, and is adjusted so that the titration volume is in the range of 3.5 mL to 5.5 mL. If the amount collected is less than 100 mL, measure the collected volume and add distilled water 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 BL sample. BL measurement is performed each time a sample prepared from the electrolyte is titrated.

[0088] Prepare titration samples from 100 mL of electrolyte and BL distilled water samples using the following procedure. First, add 10 mL of 5 mmol / L potassium permanganate solution to the sample using a volumetric pipette and stir. Next, place each Erlenmeyer flask in a boiling water bath and heat for 30 minutes. Ensure that the water in the bath is always boiling and that the water level does not drop 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 solution using a volumetric pipette to the liquid in the Erlenmeyer flask. Cool the liquid to a temperature between 50°C and 60°C to prepare the titration sample. If the sample contains chloride ions, add 2 mL of 500 g / L silver nitrate solution using a volumetric pipette and stir the resulting mixture thoroughly until no precipitate remains and the liquid becomes clear. If the cloudiness does not disappear, add more silver nitrate solution little by little while stirring until the cloudiness disappears. Add the silver nitrate solution in such an amount that the total amount of silver nitrate is 1 g in excess of the equivalent amount of chloride ions contained in each sample. Add the silver nitrate solution to the above samples.

[0089] Each of the prepared titration samples is titrated with a 5 mmol / L potassium permanganate aqueous solution. When the liquid in the Erlenmeyer flask turns slightly red during titration, stop the titration and let it stand for about 30 seconds to check whether the red color has disappeared. If the red color has disappeared, repeat the titration and leaving process until the red color no longer disappears. For samples prepared from electrolyte and distilled water, use the amount of potassium permanganate aqueous solution (mL) required for titration as the titration value and BL in the above equation to calculate 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 into account the dilution amount.

[0090] (separator) Lead-acid batteries typically include a separator between the negative and positive electrodes, which may be a microporous membrane or an absorbed glass mat (AGM).

[0091] A microporous membrane is a porous sheet whose main component is a material other than a fiber component. The material other than a fiber component preferably accounts for, for example, 60% by mass or more. A microporous membrane can be obtained, for example, by extruding a resin composition containing a pore-forming agent into a sheet and then removing the pore-forming agent to form pores. A microporous membrane is preferably composed of an acid-resistant polymer component. A polyolefin is preferred as the polymer component. A microporous membrane may also contain inorganic particles. On the other hand, a glass fiber mat preferably contains, for example, 60% by mass or more of glass fibers.

[0092] The thickness of the separator interposed between the negative and positive electrode plates may be selected depending on the distance between the positive and negative electrode plates.

[0093] [Evaluation method] (Light load life test) Light load life is evaluated based on the number of cycles required to reach the end of its life in the following charge / discharge cycle test in accordance with JIS D5301 (2019). A fully charged lead-acid battery with a rated voltage of 12V is repeatedly discharged and charged under the following conditions:

[0094] In the light load life test, the 20-hour rate capacity C of the test battery 20 Regardless of the difference, the following steps (a) to (e) are followed. 20 This refers to the capacity when discharged to the discharge end voltage at a current (A) that is 1 / 20 of the Ah value listed in the rated capacity. Here, the following steps (a) to (e) are carried out in a gas phase at 40°C ± 2°C.

[0095] (a) Discharge: Discharge for 240 seconds at a current of 25A. (b) Charging: Charging for 600 seconds at a constant voltage of 14.8V (however, the upper limit current is 100A). (c) Repetition: (a) and (b) above constitute one cycle and are repeated 480 times. (d) Rest for 40 to 60 hours. (e) Judgment discharge: After (d) above, discharge for 30 seconds at the rated cold cranking current Icc specified in JIS D5301 (2019). The point at which the voltage drops to 7.2 V 30 seconds after the start of discharge is considered the end of life, and the number of cycles until the end of life is considered the number of life cycles.

[0096] Since discharge at the rated cold cranking current Icc occurs every 480 cycles, the number of cycles at which the voltage at 30 seconds becomes 7.2 V can be calculated by linear interpolation from a graph in which the vertical axis represents the voltage at 30 seconds in the Icc discharge and the horizontal axis represents the number of cycles, and this can be used as the lifespan.

[0097] The items described in this specification can be combined in any manner.

[0098] FIG. 1 shows the appearance of an example of a lead-acid battery according to an embodiment of the present invention. The lead-acid battery 1 includes a battery case 12 that contains a plate group 11 and an electrolyte (not shown). The battery case 12 is divided into multiple cell chambers 14 by partition walls 13. Each cell chamber 14 contains one plate group 11. The opening of the battery case 12 is closed by a lid 15 that has a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a vent plug 18 for each cell chamber. When rehydrating, the vent plug 18 is removed and rehydration liquid is added. The vent plug 18 may have the function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0099] Each electrode plate group 11 is formed by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 interposed therebetween. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects a plurality of negative electrode plates 2 in parallel is connected to a feedthrough connector 8, and a positive electrode shelf 5 that connects a plurality of 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 outside the lid 15. In a 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 feedthrough connector 8 is connected to the positive electrode shelf 5. The negative electrode column 9 is connected to a negative electrode terminal 16 outside the lid 15. Each feedthrough connector 8 passes through a through hole provided in the partition wall 13, connecting the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0100] [Example] The present invention will be specifically described below based on examples and reference examples, but the present invention is not limited to the following examples.

[0101] 《Battery R1》 (1) Preparation of the negative electrode plate A dispersion of barium sulfate particles was prepared in pure water, and the dispersion was mixed with lead powder, a carbonaceous material, an organic shrinkage inhibitor, and an aqueous sulfuric acid solution or pure water to prepare a negative electrode paste. At this time, the number of barium sulfate particles per gram of the negative electrode material was 7.3 × 10 8 The preparation conditions for the dispersion and the negative electrode paste were controlled so that the number of barium sulfate particles per gram of the negative electrode material in the negative electrode paste was approximately the same as the number of barium sulfate particles per gram of the negative electrode material separated and analyzed from the negative electrode plate of a lead-acid battery in a fully charged state after chemical formation, as described below. The content of barium sulfate particles in the negative electrode material provided in the negative electrode plate of a lead-acid battery in a fully charged state after chemical formation, as described below, was 0.5 mass%.

[0102] The average particle size of the barium sulfate particles in the negative electrode paste was 0.2 μm. The content of sodium lignin sulfonate as an organic shrinkage inhibitor in the negative electrode material of the negative electrode plate in the lead-acid battery in a fully charged state after chemical formation, which will be described later, was adjusted to 0.1 mass % and the content of carbon black was adjusted to 0.3 mass %.

[0103] The negative electrode paste was filled into the mesh of an expanded grid made of a Pb-Ca-Sn alloy, aged, and dried to obtain an unformed negative electrode plate (width 100 mm, height 115 mm, thickness 1.2 mm).

[0104] (2) Preparation of the positive electrode plate A positive electrode paste was prepared by mixing lead powder, water, and sulfuric acid. The positive electrode paste was filled into the mesh of a Pb-Ca-Sn alloy expanded grid, aged, and dried to obtain an unformed positive electrode plate (width 100 mm, height 115 mm, thickness 1.6 mm).

[0105] (3) Preparation of lead-acid battery The unformed negative electrode plates were housed in a pouch-shaped microporous membrane separator. The negative electrode plates and positive electrode plates were stacked with the separator interposed between them. In this way, an electrode plate assembly was formed with seven unformed negative electrode plates and six unformed positive electrode plates.

[0106] The positive and negative plate lugs were welded to the positive and negative shelf sections, respectively, using the cast-on-strap method. The plate assembly was inserted into a polypropylene battery case, electrolyte was poured in, and chemical formation was performed inside the battery case to assemble a flooded lead-acid battery with a rated voltage of 12V and a 5-hour rate capacity of 30Ah. The 5-hour rate capacity refers to the capacity when discharged at a current (A) equal to 1 / 5 of the Ah value listed in the rated capacity. Six plate groups were connected in series inside the battery case.

[0107] An aqueous sulfuric acid solution was used as the electrolyte. The specific gravity of the electrolyte after formation at 20°C was 1.285. The COD of the electrolyte removed from a fully charged lead-acid battery was adjusted to the value (170 mg / L) shown in Table 1 by mass. The COD was controlled by changing the amount of the penetrant used in producing the microporous membrane.

[0108] As described above, the lead acid battery R1 of Comparative Example 1 was produced.

[0109] 《Lead acid battery R2~R7》 The preparation conditions for the dispersion and negative electrode paste were controlled so that the number of barium sulfate particles per gram of the negative electrode material would be the values ​​shown in Table 1. The amount of penetrant used in producing the microporous membrane was also controlled so that the COD, by mass, of the electrolyte removed from a fully charged lead-acid battery would be the value shown in Table 1. Lead-acid batteries R2 to R7 of Comparative Examples 2 to 7 were produced in the same manner as in Comparative Example 1, except as described above.

[0110] 《Lead acid batteries E1~E20》 The preparation conditions for the dispersion and negative electrode paste were controlled so that the number of barium sulfate particles per gram of the negative electrode material would be the values ​​shown in Table 1. The amount of penetrant used in producing the microporous membrane was also controlled so that the COD, by mass, of the electrolyte removed from a fully charged lead-acid battery would be the value shown in Table 1. Lead-acid batteries E1 to E20 of Examples 1 to 20 were produced in the same manner as in Comparative Example 1, except as described above.

[0111] 《Lead acid battery R8》 The number of barium sulfate particles per gram of negative electrode material is the number in Table 1 (7.3 × 10 8 The preparation conditions for the dispersion and negative electrode paste were controlled so that the COD (mass basis) of the electrolyte removed from the fully charged lead-acid battery was the value shown in Table 1 (120 mg / L). The amount of penetrant used in producing the microporous membrane was controlled so that the COD (mass basis) of the electrolyte removed from the fully charged lead-acid battery was the value shown in Table 1 (120 mg / L). The content of barium sulfate particles in the negative electrode material of the negative plate in the fully charged lead-acid battery after formation was 0.1 mass%. A lead-acid battery R8 of Comparative Example 8 was produced in the same manner as in Comparative Example 1, except as described above.

[0112] 《Lead acid batteries E21~E24》 The preparation conditions for the dispersion and negative electrode paste were controlled so that the number of barium sulfate particles per gram of the negative electrode material would be the values ​​shown in Table 1. The amount of penetrant used in producing the microporous membrane was controlled so that the COD (mass basis) of the electrolyte removed from a fully charged lead-acid battery would be the value shown in Table 1 (120 mg / L). The barium sulfate particle content in the negative electrode material of the negative electrode plate in the fully charged lead-acid battery after chemical formation was the content shown in Table 1. Lead-acid batteries E21 to E24 of Examples 22 to 25 were produced in the same manner as in Examples 6 to 8, except as described above.

[0113] The light load life performance (life times) described above was evaluated for each battery. The relative values, with the life times of Comparative Example 7 taken as 100%, are shown in Table 1. The larger the value, the better the light load life performance.

[0114] [Table 1]

[0115] In battery R1, the number of barium sulfate particles per gram of the negative electrode material is small and the COD is large, so the light load life performance is very poor.

[0116] In batteries R2 to R5, the number of barium sulfate particles per gram of the negative electrode material is sufficiently large, but the COD is large, so no significant improvement in light load life performance is observed.

[0117] In batteries R6, 7, and 8, the COD was small, but the number of barium sulfate particles per gram of the negative electrode material was small, so no significant improvement was observed in the light load life performance.

[0118] On the other hand, in batteries E1 to E20, the COD was less than 170 mg / L and the number of barium sulfate particles per gram of the negative electrode material was sufficiently large, resulting in a significant improvement in light-load life performance. In particular, the improvement in light-load life performance was significant when the COD was 120 mg / L or less.

[0119] Comparing batteries R8 and E21 to E24, it can be seen that the light load life performance changes depending not on the content of barium sulfate particles in the negative electrode material but on the number of barium sulfate particles per gram of the negative electrode material. [Industrial Applicability]

[0120] The lead-acid battery according to the present disclosure is suitable as a starting power source for various vehicles (commercial vehicles such as trucks and taxis, motorcycles, etc.), for example, a lead-acid battery employing start-stop control. The lead-acid battery can also be suitably used as a power source for industrial power storage devices such as electric vehicles (forklifts, etc.). These uses are merely examples. The uses of the lead-acid battery according to the present disclosure are not limited to these. [Explanation of symbols]

[0121] 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: lid, 16: negative electrode terminal, 17: positive electrode terminal, 18: liquid vent plug

Claims

1. The battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator interposed between the positive electrode plate and the negative electrode plate, The negative electrode plate includes a negative electrode current collector and a negative electrode material, the negative electrode material includes lead and barium sulfate particles; The number of the barium sulfate particles contained per 1 g of the negative electrode material is 1.0 × 10 ９ or more, A lead-acid battery, wherein the chemical oxygen demand in the electrolyte is less than 170 mg / L.

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

3. The number of the barium sulfate particles contained per gram of the negative electrode material is 1.2 × 10 9 The lead-acid battery according to claim 1 , wherein the number of the lead-acid battery cells is equal to or greater than 100.

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