lead-acid batteries

Abstract

To provide a lead-acid battery that can suppress stratification. [Solution] A lead-acid battery 1 comprising a positive electrode plate 2, a negative electrode plate 3, and a bag-shaped separator 4, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode material, and at least the electrolyte and the positive electrode material contain phosphorus, and the value obtained by dividing the sum of the amount of phosphorus (mmol) contained in the electrolyte and the amount of phosphorus (mmol) contained in the positive electrode material by the volume of the electrolyte (L) is 8 mmol / L to 100 mmol / L, and the positive electrode plate is housed in the bag-shaped separator.

Description

[Technical Field]

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

[0002] Patent Document 1 proposes a lead-acid battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode has a positive electrode material containing a positive electrode active material, the negative electrode has a negative electrode material containing a negative electrode active material, and the electrolyte contains phosphate ions.

[0003] Patent Document 2 proposes a lead-acid battery characterized by having a positive electrode plate made of a material containing basic lead phosphate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 121510 [Patent Document 2] Japanese Patent Application Publication No. 10-012225 [Overview of the project] [Problems that the invention aims to solve]

[0005] In vehicles equipped with Idle Stop-Start (ISS) control (also known as Start-Stop control or Idle Reduction control), the engine is started many times, resulting in repeated high-current discharges of the lead-acid battery. Furthermore, in ISS-controlled or generator-controlled vehicles, the amount of power generated by the alternator is reduced, and the lead-acid battery is charged intermittently. For this reason, the lead-acid battery is used in a partially charged state called PSOC (Partial State of Charge). Under PSOC conditions, stratification, a phenomenon in which differences in the concentration of sulfuric acid in the electrolyte occur, is likely to occur. When the electrolyte stratifies, the charge acceptance capacity of the lead-acid battery decreases, shortening the battery's lifespan. [Means for solving the problem]

[0006] One aspect of the present invention relates to a lead-acid battery comprising a positive electrode plate, a negative electrode plate, and a bag-shaped separator, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode material, at least the electrolyte and the positive electrode material contain phosphorus, and the value obtained by dividing the sum of the amount of phosphorus (mmol) contained in the electrolyte and the amount of phosphorus (mmol) contained in the positive electrode material by the volume (L) of the electrolyte is 8 mmol / L to 100 mmol / L, and the positive electrode plate is housed in the bag-shaped separator. [Effects of the Invention]

[0007] The lead-acid battery according to the present invention can suppress stratification. [Brief explanation of the drawing]

[0008] [Figure 1] This is a partially cutaway perspective view showing the external appearance and internal structure of a lead-acid battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit is not greater than or equal to the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0010] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0011] A lead-acid battery comprises a positive electrode plate, a negative electrode plate, a separator interposed between the positive and negative electrode plates, and an electrolyte. The electrolyte contains sulfuric acid. Charging and discharging proceed through the movement of sulfate ions between the positive and negative electrode plates and the electrolyte. During discharge, sulfate ions move to the positive and negative electrode plates. During charging, sulfate ions move from the positive and negative electrode plates into the electrolyte.

[0012] A positive electrode plate, a negative electrode plate, and a separator constitute an electrode 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.

[0013] The positive electrode plate includes a positive electrode current collector and a positive electrode material. The positive electrode material is a positive electrode active material that exhibits capacity through oxidation-reduction reactions, and contains at least lead dioxide during charging and at least lead sulfate during discharge.

[0014] The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material is a negative electrode active material that exhibits capacity through oxidation-reduction reactions, and contains at least lead during charging and at least lead sulfate during discharging.

[0015] (1) The lead-acid battery according to an embodiment of the present disclosure includes a positive electrode plate, a negative electrode plate, and a bag-shaped separator. The positive electrode plate includes a positive electrode current collector and a positive electrode electrode material. At least the electrolyte and the positive electrode electrode material contain phosphorus. The value obtained by dividing the total amount (mmol) of phosphorus contained in the electrolyte by the volume (L) of the electrolyte is 8 mmol / L to 100 mmol / L. The positive electrode plate is housed in the bag-shaped separator. It relates to a lead-acid battery (particularly, a flooded (vented) lead-acid battery).

[0016] In the lead-acid battery described in (1) above, the electrolyte and the positive electrode electrode material contain a predetermined amount of phosphorus. Phosphorus has an effect of suppressing stratification that occurs during the DCA (Dynamic Charge Acceptance) test. Phosphorus is considered to have an effect of promoting gas generation. Due to the action of phosphorus in the electrolyte and the positive electrode electrode material, both the amount of hydrogen generated at the negative electrode plate and the amount of oxygen generated at the positive electrode plate increase. By housing the positive electrode plate in the bag-shaped separator, the effect of stirring the electrolyte by the gas generated by the action of phosphorus is enhanced, and stratification during the DCA test is significantly suppressed. Further, phosphorus has an effect of refining lead sulfate generated during discharge and improving charge acceptance.

[0017] The DCA test is a method for evaluating the charging performance of a lead-acid battery during charge-discharge cycles, and is an evaluation method according to the DCA test described in the EN standard BS EN50342-6:2015. According to the DCA test, it is possible to evaluate the charge acceptance of a lead-acid battery under PSOC conditions, particularly a flooded lead-acid battery, in a deliberately stratified state.

[0018] The bag-shaped separator that houses the positive electrode plate significantly enhances the effect of stirring the sulfuric acid accumulated at the lower part of the positive electrode plate by the oxygen gas generated at the positive electrode plate. This is because the convection of the electrolyte (sedimentation of sulfuric acid) is restricted due to the blockage of the flow path by the bag-shaped separator, and the gas tends to stay around the positive electrode plate. Since sulfuric acid is more likely to accumulate at the lower part of the positive electrode plate than at the negative electrode plate, it is important to house the positive electrode plate in the bag-shaped separator. As described above, the combined effect of promoting gas generation by phosphorus and the effect of housing the positive electrode plate in the bag-shaped separator makes it difficult for a density difference to occur between the upper and lower electrolytes in the battery, and stratification is very significantly suppressed.

[0019] In the lead-acid battery described in (1) above, the phosphorus contained in the electrolyte has the effect of increasing the amount of gas generated at the negative electrode plate and the positive electrode plate. The phosphorus contained in the electrolyte may exist as an anion derived from phosphoric acid. The anion derived from phosphoric acid is easily dissolved in the electrolyte and is chemically stable. The anion derived from phosphoric acid may be an anion with any valence from monovalent to trivalent. The anion derived from phosphoric acid may be derived from phosphoric acid (H3PO4) or may be derived from a phosphate (such as Na3PO4). The phosphate may be a hydrogen phosphate. The hydrogen phosphate may be a monohydrogen phosphate (such as Na2HPO4) or a dihydrogen phosphate (such as NaH2PO4).

[0020] (2) In the lead-acid battery described in (1) above, it is preferable that the bag-shaped separator has a base portion and a plurality of ribs that project from the base portion toward the positive electrode plate and extend along the vertical direction. The vertical direction is, for example, a direction that intersects the horizontal direction (the direction of the liquid surface of the electrolyte) at an angle greater than 45 degrees.

[0021] In the lead-acid battery described in (2) above, since a space is secured between the separator and the positive electrode plate, the stirring effect of the electrolyte by the oxygen gas generated at the positive electrode plate is enhanced. In addition, since sufficient electrolyte necessary for charge and discharge can be secured between the separator and the positive electrode plate, a decrease in the charge and discharge reaction efficiency due to stratification can be suppressed.

[0022] (3) In the lead-acid battery described in (1) or (2) above, the bag-shaped separator may further have a plurality of ribs that protrude from the base portion toward the negative electrode plate and extend along the longitudinal direction.

[0023] In the lead-acid battery described in (3) above, a space is secured between the separator and the negative electrode plate, thereby enhancing the agitation effect of the electrolyte by hydrogen gas generated at the negative electrode plate. Furthermore, the presence of ribs on the negative electrode plate side of the separator ensures that sufficient electrolyte necessary for charging and discharging is secured between the separator and the negative electrode plate, thus suppressing the decrease in charge-discharge reaction efficiency due to stratification. In addition, since the ribs and the negative electrode plate are adsorbed to some extent, it is easier to maintain the effect of suppressing electrolyte convection by packaging the positive electrode plate. On the other hand, if the gap between the separator and the negative electrode plate becomes large (for example, 0.02 mm or more), the effect of suppressing electrolyte convection by packaging the positive electrode plate with a bag-type separator may decrease.

[0024] (4) In the lead-acid battery described in any one of (1) to (3) above, the positive electrode material may contain tin (Sn). The tin content in the positive electrode material may be 5 μmol / g or more.

[0025] The lead-acid battery described in (4) above has improved high-rate discharge performance because the specific surface area of ​​the positive electrode material is increased by tin. Using more than a certain amount of phosphorus may reduce high-rate discharge performance. Tin suppresses such reduction in high-rate discharge performance.

[0026] (5) A lead-acid battery described in any one of (1) to (4) above is useful as a power source for applications where charging and discharging are controlled in an undercharged state called a partially charged state (PSOC). Specific examples of power sources for applications where charging and discharging are controlled by PSOC include ISS-controlled vehicles (ISS-controlled vehicles) and power sources for auxiliary equipment. In other words, the effect of suppressing stratification by the configuration of the present invention is more likely to become apparent in lead-acid batteries where charging and discharging are controlled by PSOC.

[0027] In this specification, the fully charged state of a liquid lead-acid battery is defined according to the definition in JIS D5301:2019. More specifically, in a water bath at 25°C ± 2°C, the 20-hour rate current I is charged until the terminal voltage (in volts) or the electrolyte density converted to 20°C shows a constant value with three significant figures for three consecutive 15-minute intervals. 20 Twice the current 2 × I 20 (Unit: A) The fully charged state of a lead-acid battery is defined as the state in which it has been charged. Note that n-hour rate current I n This refers to a current (A) that is 1 / n of the Ah value listed for the n-hour rate rated capacity. The value listed for the rated capacity is a value in Ah (ampere-hour). The unit of the current set based on the value listed for the rated capacity is A (ampere).

[0028] A fully charged lead-acid battery is a lead-acid battery that has been charged to its full capacity after chemical formation. The timing for charging a lead-acid battery to its full capacity can be immediately after chemical formation, or after a certain amount of time has passed since formation (e.g., 720 hours or less). For example, a lead-acid battery that has been chemically formed and is in use (preferably in the early stages of use) may be charged.

[0029] In this specification, a battery in its initial use refers to a battery that has not been used for very long and has not deteriorated much (for example, a battery that has been in use for less than 720 hours, including the time elapsed since chemical preparation).

[0030] Furthermore, the stratification suppression effect can be evaluated from (i) the charge acceptance of the lead-acid battery, (ii) the average current value during charging in the DCA test, and (iii) the density difference between the upper and lower electrolytes in the battery case.

[0031] 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.

[0032] The following describes examples of components of a lead-acid battery.

[0033] (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.

[0034] The positive electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a sheet of lead or a lead alloy. 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.

[0035] 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.

[0036] The positive electrode material contains a positive electrode active material that exhibits capacity through a redox reaction. The positive electrode active material includes lead dioxide, lead sulfate, etc. The positive electrode material further contains phosphorus (P).

[0037] Phosphorus may be incorporated into the positive electrode material by adding phosphorus compounds such as phosphoric acid and phosphates to the positive electrode paste used when manufacturing the unformed positive electrode plate. Alternatively, phosphorus may be introduced into the positive electrode material by dissolving at least one selected from the group consisting of phosphoric acid and phosphates in an electrolyte and allowing the electrolyte to react with the positive electrode material. In this case, anions derived from phosphoric acid are also present in the electrolyte. However, up to approximately 90% is adsorbed onto the positive electrode material.

[0038] The amount of phosphorus contained in the positive electrode material is controlled so that the value obtained by dividing the sum of the amount of phosphorus contained in the electrolyte (mmol) and the amount of phosphorus contained in the positive electrode material (mmol) by the volume of the electrolyte (L) (hereinafter also referred to as "P content (EP)") is between 8 mmol / L and 100 mmol / L. The P content (EP) may be controlled to be 25 mmol / L or more, or 50 mmol / L or less. The P content (EP) may be controlled to be between 25 mmol / L and 100 mmol / L, or between 25 mmol / L and 50 mmol / L.

[0039] The positive electrode material may further contain tin (Sn). Tin has the effect of increasing the specific surface area of ​​the positive electrode material. The larger the specific surface area of ​​the positive electrode material, the better the high-rate discharge performance. Tin can compensate for the shortcomings of phosphorus from the standpoint of high-rate discharge performance.

[0040] Tin can be incorporated in the form of a tin compound into the raw material paste (positive electrode paste) of the positive electrode material during the manufacturing process of the positive electrode plate. Examples of tin compounds that can be used include tin oxide (SnO) and tin sulfate (SnSO4).

[0041] The tin content in the positive electrode material is, for example, 5 μmol / g or more, and may be between 5 μmol / g and 15 μmol / g.

[0042] The phosphorus and tin content in the positive electrode material can be measured by taking samples of the positive electrode material from the positive electrode plate removed from a fully charged lead-acid battery and measuring them using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). The samples of the positive electrode material are taken from the positive electrode plate removed from a fully charged lead-acid battery.

[0043] Specifically, a suitable amount of dry positive electrode material is taken as a sample, and its mass is measured. The positive electrode material sample is recovered from the positive electrode plate using the following procedure: First, a fully charged lead-acid battery is disassembled, and the obtained positive electrode plate is washed with water for 3 to 4 hours to remove the electrolyte from the positive electrode plate. The washed positive electrode plate is dried in a constant temperature bath at 60°C ± 5°C for 5 hours or more. After drying, if the positive electrode plate contains adhesive material, the adhesive material is removed from the positive electrode plate by peeling it off. A sample of positive electrode material for analysis is obtained by taking a sample of the positive electrode material from near the center of the top, bottom, left, and right sides when viewed from the front of the positive electrode plate.

[0044] Next, the entire sample is dissolved in a mixed aqueous solution containing tartaric acid, nitric acid, and hydrogen peroxide. The solution obtained by total dissolution is diluted to a fixed volume with deionized water as needed, and then the emission intensity of phosphorus or tin in the solution is measured by ICP-AES using an ICP emission spectrometer. Then, the mass of phosphorus or tin contained in the solution is determined using a pre-prepared calibration curve. The ratio of the obtained mass of phosphorus or tin to the mass of the sample of positive electrode material subjected to analysis is determined as the phosphorus or tin content. For example, the ICPS-8000 manufactured by Shimadzu Corporation is used as an ICP emission spectrometer.

[0045] The amount of phosphorus (mmol) contained in the positive electrode material can be calculated from the sample mass, the measured value, and the total mass of the positive electrode material.

[0046] Positive electrodes are obtained by chemically converting unconverted positive electrodes. Unconverted positive electrodes are obtained by filling a positive electrode current collector with positive electrode paste, allowing it to mature, and drying. Positive electrode paste is prepared, for example, by kneading a mixture containing lead powder, water, and sulfuric acid (and optionally phosphorus (or phosphorus compounds) and / or tin compounds). Such positive electrodes are also called paste-type positive electrodes.

[0047] Chemical treatment may be carried out by immersing the electrode plate group, including the untreated positive electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and charging the electrode plate group. Chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group.

[0048] (Negative electrode plate) The negative electrode plate comprises a negative electrode current collector and a negative electrode material. The negative electrode material is held by the negative electrode current collector. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. Note that adhesive members such as conductive layers, mats, and pasting paper may be attached to the negative electrode plate. The adhesive members are included as components of the negative electrode plate. When the negative electrode plate includes adhesive members, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive members.

[0049] The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. The processing method may be expansion or punching. Using a grid-like current collector as the negative electrode current collector makes it easier to support the negative electrode material.

[0050] The lead alloy used for the negative electrode current collector may be any of the following: a Pb-Sb alloy, a Pb-Ca alloy, or a Pb-Ca-Sn alloy. The lead alloy used for the negative electrode current collector may also contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. The negative electrode current collector may have metal layers of different compositions, and the metal layers may be one layer or multiple layers.

[0051] The negative electrode material contains a negative electrode active material that exhibits capacity through an oxidation-reduction reaction. The negative electrode active material includes lead, lead sulfate, etc. The negative electrode material may contain other additives as needed. The additives may include organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc.

[0052] 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.

[0053] 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.

[0054] The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more and 3% by mass or less.

[0055] The negative electrode plate is obtained by chemically converting an unconverted negative electrode plate. The unconverted negative electrode plate is obtained by filling a negative electrode current collector with negative electrode paste, allowing it to mature, and drying. The negative electrode paste is prepared by kneading a mixture containing lead powder, water, and sulfuric acid. The negative electrode paste may optionally contain organic shrinkage inhibitors, carbonaceous materials, barium sulfate, etc.

[0056] The chemical treatment may be carried out by immersing the electrode plate group, including the untreated negative electrode plate, in an electrolyte containing sulfuric acid in the lead-acid battery case, thereby charging the electrode plate group. The chemical treatment may also be carried out before the assembly of the lead-acid battery or the electrode plate group. The negative electrode active material in the charged state contains spongy lead.

[0057] (Bag-shaped separator) The bag-shaped separator is made of a microporous membrane. The bag-shaped separator houses the positive electrode plate. To dramatically improve DCA performance, it is important to house the positive electrode plate in a bag-shaped separator. The bag-shaped separator plays a role in blocking the electrolyte flow path near the lower end of the positive electrode plate, suppressing the sedimentation of sulfuric acid below the positive electrode plate.

[0058] The microporous membrane is formed from a polymer material (but different from fibers). The microporous membrane may contain a filler (for example, a particulate filler such as silica) dispersed in a matrix formed from the polymer material. The polymer material is preferably acid-resistant. Polyolefins such as polyethylene and polypropylene are preferred as the polymer material.

[0059] The bag-shaped separator may have a base portion and a plurality of ribs (hereinafter also referred to as "first ribs") that protrude toward the positive electrode plate from one main surface of the base portion and extend along the longitudinal direction. The first ribs protrude from one main surface of the base portion.

[0060] The bag-shaped separator may further have a plurality of ribs (hereinafter also referred to as "second ribs") that protrude from the other main surface of the base toward the negative electrode plate and extend along the longitudinal direction.

[0061] The average thickness of the base portion is preferably between 100 μm and 300 μm, and more preferably between 150 μm and 250 μm. In this case, it becomes easier to ensure the height of the first rib (and, if necessary, the second rib) while ensuring high charge and discharge characteristics.

[0062] The first rib is formed on the side of the separator facing the positive electrode plate. The height of the first rib is, for example, 0.25 mm or more. In this case, sufficient space is easily secured between the separator and the positive electrode plate, and the stirring effect of the electrolyte by oxygen gas generated at the positive electrode plate is enhanced. In addition, oxidative degradation of the separator is significantly suppressed. The height of the first rib may be 0.30 mm or more. From the viewpoint of ensuring high charge-discharge characteristics, the height of the first rib is, for example, 1.0 mm or less, and preferably 0.7 mm or less.

[0063] The second rib is formed on the side of the separator facing the negative electrode plate. The height of the second rib is preferably, for example, 0.05 mm or more. In this case, sufficient space is easily secured between the separator and the negative electrode plate, and the stirring effect of the electrolyte by hydrogen gas generated at the negative electrode plate is enhanced. The height of the second rib is, for example, 0.50 mm or less, preferably 0.40 mm or less, and may be 0.20 mm or less.

[0064] The pattern of the first or second ribs (hereinafter simply referred to as "ribs") in the base portion is not particularly limited. The ribs may be formed randomly, or they may be formed in a striped, curved, or grid pattern. From the viewpoint of improving the agitation of the electrolyte, it is preferable that multiple ribs are arranged in a striped pattern. The orientation of the striped ribs is preferably, for example, in the vertical direction. That is, it is preferable that multiple ribs extend in a striped pattern along the vertical direction. The vertical direction may be a direction that intersects the horizontal direction (the direction of the electrolyte surface) at an angle greater than 45 degrees, and it is preferable that it intersects the horizontal direction (the direction of the electrolyte surface) at an angle of 80 degrees or more.

[0065] The average pitch of the striped first ribs is, for example, 1 mm to 15 mm, and preferably 5 mm to 10 mm. In this case, the effect of stirring the electrolyte and the effect of suppressing oxidative degradation of the separator are enhanced. For example, it is preferable that first ribs with such an average pitch are formed on 70% or more of the area of ​​the region of the separator (base portion) facing the positive electrode plate. First ribs do not need to be formed in regions that do not face the positive electrode plate, such as the ends of the separator, or in regions that face regions where there is no positive electrode material on the positive electrode plate.

[0066] The average pitch of the striped second ribs is preferably, for example, 0.3 mm to 10 mm, and more preferably 0.5 mm to 5 mm. In this case, the stirring effect of the electrolyte is enhanced. For example, it is preferable that second ribs with such an average pitch are formed on 70% or more of the area of ​​the region of the separator (base portion) facing the negative electrode plate. Second ribs do not need to be formed in regions that do not face the negative electrode plate, such as the ends of the separator, or in regions that face regions where there is no negative electrode material on the negative electrode plate.

[0067] The rib pitch is the distance between the tops of adjacent ribs (more specifically, the distance between the centers of adjacent ribs in the direction across the rib). The average rib pitch is obtained by averaging the rib pitch measured at 10 arbitrarily selected locations.

[0068] The separator is obtained, for example, by extruding a resin composition containing a pore-forming agent and a polymer material into a sheet, and then removing the pore-forming agent to form pores in the matrix of the polymer material. The ribs may be formed, for example, during extrusion molding, or they may be formed after the sheet is formed by pressing with a roller having grooves corresponding to the ribs. If a filler is used, it is preferable to add it to the resin composition.

[0069] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid. Preferably, the electrolyte contains phosphorus as an anion derived from phosphoric acid. The electrolyte may optionally contain cations (e.g., metal cations) and / or anions not derived from sulfuric acid. As the metal cation, at least one ion selected from the group consisting of Na, Li, and Al is preferred.

[0070] Qualitative and quantitative analysis of phosphorus in electrolytes can be performed by liquid chromatography-mass spectrometry (LC-MS).

[0071] The density of the electrolyte in a fully charged lead-acid battery at 20°C is, for example, 1.20 g / cm³. 3or more, 1.25 g / cm 3 or more. The density of the electrolytic solution at 20 °C is 1.35 g / cm 3 or less, and preferably 1.32 g / cm 3 or less. The density of the electrolytic solution at 20 °C in a fully charged lead storage battery is, for example, 1.20 g / cm 3 ~1.35 g / cm 3 and may be 1.25 g / cm 3 ~1.32 g / cm 3 as well.

[0072] The P content rate (EP) is the value obtained by dividing the total amount of phosphorus (mmol) contained in the positive electrode material determined by the method described above and the amount of phosphorus (mmol) contained in the electrolytic solution by the volume (L) of the electrolytic solution (P content rate (EP) = ((amount of phosphorus (mmol) contained in the positive electrode material) + amount of phosphorus (mmol) in the electrolytic solution)) / volume (L) of the electrolytic solution).

[0073] The mass of the electrolytic solution can be calculated from the mass of the cell containing the electrolytic solution and the mass of the cell from which the electrolytic solution has been removed by washing and drying. The volume (L) of the electrolytic solution can be calculated from the mass of the electrolytic solution and the density of the electrolytic solution.

[0074] (Example of a lead storage battery) FIG. 1 shows a part of the appearance and internal structure of a lead storage battery according to an embodiment. The lead storage battery 1 includes a battery case 12 that houses a plate group 11 and an electrolytic solution (not shown). Inside the battery case 12, a plurality of cell chambers 14 are partitioned by a partition wall 13. One plate group 11 is housed in each cell chamber 14. The opening of the battery case 12 is closed by a lid 15 having a positive electrode terminal 16 and a negative electrode terminal 17. The lid 15 is provided with a liquid port plug 18 for each cell chamber. When replenishing water, the liquid port plug 18 is removed and replenishing liquid is supplied. The liquid port plug 18 may have a function of discharging the gas generated in the cell chamber 14 to the outside of the battery.

[0075] Each electrode plate group 11 is constructed by stacking multiple positive electrode plates 2 and negative electrode plates 3 via separators 4. Here, a bag-shaped separator 4 that houses the positive 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 positive electrode strap 6 that connects multiple positive electrode plates 2 in parallel is connected to a through connector 8, and a negative electrode strap 5 that connects multiple negative electrode plates 3 in parallel is connected to a negative electrode column 7. The negative electrode column 7 is connected to a negative 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 positive electrode column 9 is connected to the positive electrode strap 6, and a through connector 8 is connected to the negative electrode strap 5. The positive electrode column 9 is connected to a positive 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.

[0076] Note that Figure 1 is merely one example of a liquid-type lead-acid battery, and the structure of the lead-acid battery relating to this disclosure is not limited to the example shown.

[0077] The following describes the evaluation method for lead-acid batteries. For the evaluation, a lead-acid battery (nominal voltage 12V) with 6 cells (connected in series), each consisting of 7 positive electrodes and 7 negative electrodes, will be used. However, the battery used for evaluation is not limited to a battery with a nominal voltage of 12V; a battery other than 12V (6 cells) may also be used. In that case, the test voltage may be the product of 12 / 6 = 2 (V) and the number of cells under the following conditions.

[0078] (Charge acceptance) For a fully charged lead-acid battery with a nominal voltage of 12V, the following tests were conducted, and the amount of charge collected over 10 minutes in (c) was defined as the charge acceptance. (a) 2 × I 20 Discharge for 5.0 hours at (unit: A) (temperature in the water bath: 25±1 ℃) (b) Rest for 12 hours (temperature in the air chamber: 0±1℃) (c) Charge at 14.4V (2.4V / cell) for 10 minutes with a maximum current of 50A (temperature in the chamber should be 0±1℃).

[0079] (DCA performance) Measurements are taken in accordance with the DCA test described in the EN standard (BS EN50342-6:2015). The higher the average current value during charging, normalized by the conversion formula, the better the DCA performance.

[0080] (The difference in density between the upper and lower electrolytes in the battery case) In a water tank at 25±2℃, a fully charged test battery was placed in I 20 After discharging for 1 hour at a constant current of 0.2 times the value, I 20 Charge with a constant current of 1.0 times the normal voltage, and once the voltage reaches 15V (2.5V / cell), charge at a constant voltage for 2 hours. The upper limit current during charging is I 20 The current value is set to 1.0 times the original value. Then, electrolyte is sampled from the upper part of the battery case (within 10 mm below the liquid surface) and the lower part (within 10 mm above the lower edge of the electrode plate), the density is measured, and the density difference is calculated.

[0081] (High-rate discharge performance) For a fully charged lead-acid battery with a nominal voltage of 12V, the discharge current is 60 × I 20 At point A, discharge the battery at 30±1℃ until the terminal voltage reaches 8.4V (1.4V / cell), and determine the discharge time. A longer discharge duration indicates superior high-rate discharge performance.

[0082] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0083] Lead-acid batteries R1-1 to R1-7 (1) Fabrication of the negative electrode plate A negative electrode paste is prepared by mixing lead oxide, carbon black, barium sulfate, lignin, water, and sulfuric acid. The negative electrode paste is filled into the mesh of an expanded grid made of antimony-free Pb-Ca-Sn alloy, which serves as the negative electrode current collector, and then aged and dried to obtain an unformed negative electrode plate. The amounts of carbon black, barium sulfate, and lignin are adjusted so that they are 0.3 mass%, 2.1 mass%, and 0.1 mass%, respectively, when measured in the fully charged, already formed state.

[0084] (2) Fabrication of the positive electrode plate A positive electrode paste is prepared by mixing lead oxide, water, and sulfuric acid. The positive electrode paste is filled into the mesh of an expanded grid made of antimony-free Pb-Ca-Sn alloy, which serves as the positive electrode current collector, and then aged and dried to obtain an unformed positive electrode plate.

[0085] (3) First separator A bag-shaped first separator is prepared by folding a polyethylene microporous membrane in half. The average thickness of the base of the first separator is 0.25 mm. The first separator has ribs A on the outside of the bag, but no ribs on the inside. Ribs A are striped and extend along the longitudinal direction. The height of ribs A is 0.45 mm, and the average pitch is 9.8 mm. Note that the ribs described here are those located 30 mm inward from both ends in the width direction of the separator. There are secondary ribs with a height of 0.1 to 0.2 mm and a pitch of 1 mm within a 25 mm range from both ends of the separator, but these secondary ribs are excluded.

[0086] (4) Preparation of electrolyte The electrolyte is prepared by dissolving phosphoric acid (H3PO4) in an aqueous sulfuric acid solution so that the sum of the amount of phosphorus (mmol) in the electrolyte and the amount of phosphorus (mmol) in the positive electrode material, divided by the volume (L) of the electrolyte (P content (EP)), is as shown in Table 1. The density of the electrolyte after chemical conversion is 1.28 ± 0.01 g / cm³. 3 It is within the range of [the specified range].

[0087] (5) Manufacturing of lead-acid batteries Unformed negative electrode plates are housed in a bag-shaped first separator, and seven unformed negative electrode plates and seven unformed positive electrode plates are stacked alternately to form an electrode plate group. Therefore, rib A is a first rib that protrudes toward the positive electrode plates on the outside of the bag and extends along the longitudinal direction.

[0088] The tabs of the positive electrode plates and the tabs of the negative electrode plates are welded to the positive and negative electrode straps, respectively, using the cast-on-strap (COS) method. The electrode plates are inserted into a polypropylene battery case, electrolyte is poured in, and chemical conversion is performed inside the case to assemble a liquid lead-acid battery with a nominal voltage of 12V and a rated 20-hour rate capacity of 40Ah. Six electrode plate groups are connected in series inside the battery case.

[0089] (6) Evaluation The fabricated lead-acid battery was fully charged using the procedure described above, and its charge acceptance, DCA performance, and density difference between the upper and lower electrolytes in the battery case were evaluated using the method described above. The results are shown in Table 1. Each evaluation is expressed as a relative value (%) with the result of lead-acid battery R1 set to 100%.

[0090] 《Lead acid battery E1-1~E1-7》 A second separator is prepared, similar to the first separator, except that it does not have ribs on the outside of the bag, but has ribs A on the inside of the bag. A lead-acid battery is assembled and evaluated in the same manner as above, except that the unformed positive electrode plate is housed in the bag-shaped second separator. The results are shown in Table 1.

[0091] [Table 1]

[0092] Table 1 shows that when the phosphorus content (EP) is between 8 and 100 mmol / L, charge acceptance improves and DCA performance improves. Furthermore, it can be seen that housing the positive electrode plate in a bag-shaped separator dramatically improves DCA performance compared to housing the negative electrode plate in such a separator. This is because the promotion of gas generation by phosphorus and the suppression of convection in the electrolyte around the positive electrode plate promote the stirring of sulfate ions, thereby greatly mitigating stratification.

[0093] 《Lead acid battery R2-1~R2-6》 A third separator is prepared, similar to the first separator, except that it has rib A on the outside of the bag and rib B on the inside of the bag. The average thickness of the base of the third separator is 0.2 mm. Rib A is striped and extends along the longitudinal direction. The height of rib A is 0.4 mm and the average pitch is 9.8 mm. Rib B is striped and extends along the longitudinal direction. The height of rib B is 0.10 mm and the average pitch is 0.98 mm. Then, an unformed negative electrode plate is placed in the bag-shaped third separator, and a lead-acid battery similar to the one described above is assembled and evaluated. Thus, rib A is the first rib that protrudes toward the positive electrode plate on the outside of the bag and extends along the longitudinal direction, and rib B is the second rib that protrudes toward the negative electrode plate on the inside of the bag and extends along the longitudinal direction. The results are shown in Table 2.

[0094] 《Lead acid battery R3-1~R3-6》 A fourth separator is prepared, similar to the third separator, except that it has rib B on the outside of the bag and rib A on the inside of the bag. Then, an unformed negative electrode plate is placed in the bag-shaped fourth separator, and a lead-acid battery similar to the one described above is assembled and evaluated. Thus, rib B is the first rib that protrudes toward the positive electrode plate on the outside of the bag and extends along the longitudinal direction, and rib A is the second rib that protrudes toward the negative electrode plate on the inside of the bag and extends along the longitudinal direction. The results are shown in Table 2.

[0095] 《Lead acid batteries E2-1~E2-7》 An unformed positive electrode plate is placed in a bag-shaped fourth separator, and a lead-acid battery similar to the one described above is assembled and evaluated. Therefore, rib A is the first rib that protrudes toward the positive electrode plate on the inside of the bag and extends along the longitudinal direction, and rib B is the second rib that protrudes toward the negative electrode plate on the outside of the bag and extends along the longitudinal direction. The results are shown in Table 2.

[0096] 《Lead acid battery E3-1~E3-7》 An unformed positive electrode plate is placed in a bag-shaped third separator, and a lead-acid battery similar to the one described above is assembled and evaluated. Therefore, rib B is the first rib that protrudes toward the positive electrode plate on the inside of the bag and extends along the longitudinal direction, and rib A is the second rib that protrudes toward the negative electrode plate on the outside of the bag and extends along the longitudinal direction. The results are shown in Table 2.

[0097] [Table 2]

[0098] Table 2 shows that providing ribs on both sides of the separator base further suppresses electrolyte convection and sulfate ion sedimentation. However, it is clear that housing the positive electrode plate in a bag-shaped separator is crucial for dramatically improving DCA performance.

[0099] Lead-acid batteries E4-1 to E4-4 When preparing the positive electrode paste, the positive electrode plate and the lead-acid battery equipped therewith were fabricated in the same manner as battery R1-6, except that tin sulfate (SnSO4) was added so that the tin content of the positive electrode material measured by the procedure described above was as shown in Table 3. The DCA performance and the density difference between the upper and lower electrolytes in the battery case were evaluated in the same manner. The results are shown in Table 3. In addition, the high-rate discharge performance was evaluated using the method described above. Each evaluation is shown as a relative value (%) with the result of lead-acid battery R1-1 set to 100%.

[0100] [Table 3]

[0101] Table 3 shows that including Sn in the positive electrode material significantly improves high-rate discharge performance. [Industrial applicability]

[0102] The lead-acid battery according to the present invention is suitable as a lead-acid battery whose charging and discharging are controlled by a PSOC, for example, as a starting power source or auxiliary lead-acid battery for vehicles controlled by an ISS, but its applications are not particularly limited. [Explanation of Symbols]

[0103] 1: Lead-acid battery, 2: Positive electrode plate, 3: Negative electrode plate, 4: Separator, 5: Negative electrode strap, 6: Positive electrode strap, 7: Negative electrode post, 8: Through connector, 9: Positive electrode post, 11: Electrode plate group, 12: Battery case, 13: Partition wall, 14: Cell chamber, 15: Cover, 16: Positive electrode terminal, 17: Negative electrode terminal, 18: Electrode cap

Claims

1. A positive electrode plate, a negative electrode plate, a bag-shaped separator, Equipped with, The positive electrode plate includes a positive electrode current collector and a positive electrode material. At least the electrolyte and the positive electrode material contain phosphorus, The value obtained by dividing the sum of the amount of phosphorus (mol) contained in the electrolyte and the amount of phosphorus (mol) contained in the positive electrode material by the volume (L) of the electrolyte is between 8 mmol / L and 100 mmol / L. A lead-acid battery in which the positive electrode plate is housed in the bag-shaped separator.

2. The lead-acid battery according to claim 1, wherein the bag-shaped separator comprises a base portion, a plurality of ribs protruding from the base portion toward the positive electrode plate, and a plurality of ribs protruding from the base portion toward the negative electrode plate.

3. The positive electrode material contains tin, The liquid lead-acid battery according to claim 1, wherein the tin content in the positive electrode material is 5 μmol / g or more.

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