Lead acid storage battery

Abstract

A lead acid storage battery disclosed by the present invention comprises: a negative electrode plate which comprises a negative electrode material; an electrolyte solution; and a positive electrode plate which comprises a positive electrode collector and a positive electrode material that is arranged around the positive electrode collector. The positive electrode collector comprises a metal structure which contains a plurality of dendrite arms. The average spacing between the plurality of dendrite arms is 20 μm or less.

Description

lead acid battery

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

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. A lead-acid battery includes a negative electrode plate, a positive electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode current collector and a positive electrode active material disposed around the positive electrode current collector. Repeated charge-discharge cycles cause corrosion of the positive electrode current collector. Significant corrosion of the positive electrode current collector reduces characteristics such as cycle life.

[0003] Patent Document 1 (JP 57-061262 A) discloses "a lead-acid battery characterized in that, in the crystal grains of the metal structure finally determined by casting lead or a lead alloy containing no or a small amount of antimony used as an anode grid material and subsequent processing and heat treatment, the maximum length in the direction perpendicular to the lead grid surface is not more than 1 / 2 of the lead grid size, and the minimum length in the direction parallel to the lattice surface of the microcrystals constituting the crystal grains is not less than 1 / 3 of the maximum length of the grains in the same direction."

[0004] Patent Document 2 (Japanese Patent Laid-Open Publication No. 61-27067) discloses "a lead-acid battery having, as a conductive part, a lead alloy casting having a dendritic structure in which acid-resistant plastic is filled into gaps opening to the surface."

[0005] Patent Document 3 (JP 52-5425 A) discloses "a lead-acid battery using a lead alloy grid containing 5% or less antimony, in which a spherical solid solution phase of antimony is uniformly dispersed in a solid solution phase of lead."

[0006] JP-A-57-061262 JP-A-61-27067 JP-A-52-5425

[0007] Currently, there is a need to suppress corrosion of the positive electrode current collector. In this situation, one of the objects of the present invention is to provide a lead-acid battery in which corrosion of the positive electrode current collector is suppressed.

[0008] One aspect of the present invention relates to a lead-acid battery including: a negative electrode plate including a negative electrode material; and a positive electrode plate including an electrolyte, a positive electrode current collector, and a positive electrode material disposed around the positive electrode current collector, wherein the positive electrode current collector includes a metal structure including a plurality of dendrite arms, and the average spacing between the plurality of dendrite arms is 20 μm or less.

[0009] According to the present invention, a lead-acid battery in which corrosion of the positive electrode current collector is suppressed can be obtained.

[0010] 4A , 4B, 4C, 4D, 4E, 4F, 4G, 4G, 4H ...H, 4G, 4H, 4H, 4G, 4H, 4H, 4G, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4H, 4

[0011] The following describes embodiments of the present invention using examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the present invention are obtained. In this specification, the range described as "numerical value A to numerical value B" includes numerical value A and numerical value B.

[0012] [Lead-acid battery] A lead-acid battery according to one embodiment of the present invention includes a negative electrode plate containing a negative electrode material, and a positive electrode plate containing an electrolyte, a positive electrode collector, and a positive electrode material arranged around the positive electrode collector. The positive electrode collector includes a metal structure containing a plurality of dendrite arms. The average spacing between the plurality of dendrite arms is 20 μm or less. The average spacing between the plurality of dendrite arms may be referred to as "DAS" below. The metal structure having a DAS of 20 μm or less may be referred to as "metal structure (M)" below.

[0013] The metal structure containing dendrite arms includes a portion that constitutes the dendrite arms and a portion that exists between the dendrite arms. As a result of investigation, the present inventors have newly discovered that a large DAS facilitates the progression of corrosion of the positive electrode current collector. The present invention is based on this new finding.

[0014] For example, when producing a positive electrode current collector by casting, the DAS can be changed by changing the cooling rate of the metal material (positive electrode current collector material) poured into a mold. For example, the DAS can be reduced by increasing the cooling rate. The DAS can also be reduced by adding S (sulfur) or Se (selenium) to the metal material that becomes the positive electrode current collector. The DAS can also be reduced by increasing the pressure during casting.

[0015] At least a portion of the positive electrode current collector, around which the positive electrode material is disposed, is composed of a metal structure (M). By having at least a portion composed of a metal structure (M), corrosion of the at least portion is suppressed. As a result, corrosion of the positive electrode current collector is suppressed.

[0016] The entire positive electrode current collector may be made of the metal structure (M), or only a portion of the positive electrode current collector may be made of the metal structure (M). For example, at least a portion of the surface of the positive electrode current collector may be made of the metal structure (M). For example, in the case of a positive electrode current collector used in a clad type positive electrode plate, the core metal includes the metal structure (M). At least a portion (for example, at least a portion of the surface) of the core metal may be made of the metal structure (M). 50% by volume or more, 70% by volume or more, or 90% by volume or more of the core metal may be made of the metal structure (M). 50% by volume or more, 70% by volume or more, or 90% by volume or more of the surface area of ​​the core metal may be made of the metal structure (M). Alternatively, the entire core metal may be made of the metal structure (M).

[0017] The proportion of the positive electrode current collector that is composed of the metal structure (M) can be measured (determined) by the following method. First, the positive electrode current collector is divided equally (10 equal parts) into 10 regions with approximately equal volumes. Then, one location is arbitrarily selected from each region, and the DAS of the cross section of that location is measured using the method described below. Then, the proportion of regions with a DAS of 20 μm or less is determined. This proportion can be used as the proportion of the metal structure (M) in the positive electrode current collector. Furthermore, the arithmetic mean of the DAS determined for each of the 10 regions can be used as a single DAS value D1. The DAS value D1 can be considered to represent the DAS value for the entire positive electrode current collector.

[0018] The DAS of the metal structure (M) is 20 μm or less, and may be 13 μm or less, or 6 μm or less. The DAS may be 1 μm or more, or 3 μm or more. These lower and upper limits can be combined arbitrarily. For example, the DAS may be 1 μm or more and 20 μm or less (e.g., 13 μm or less or 6 μm or less), or 3 μm or more and 20 μm or less (e.g., 13 μm or less or 6 μm or less). The DAS value of the entire positive electrode current collector (the above-mentioned value D1) may be within the range exemplified here as the DAS value of the metal structure (M).

[0019] The metal structure (M) includes dendrites. Dendrites generally include primary and secondary dendrite arms. An example of such a dendrite arm is shown schematically in FIG. 1A. For ease of understanding, the primary dendrite arm Da1 and the secondary dendrite arm Da2 are hatched in FIG. 1A.

[0020] The dendrite DR shown in FIG. 1A includes a primary dendrite arm Da1 and a secondary dendrite arm group. The secondary dendrite arm group is composed of multiple secondary dendrite arms Da2 extending from the primary dendrite arm Da1. Each of the multiple secondary dendrite arms extends in a direction intersecting the longitudinal direction of the primary dendrite arm. FIG. 1A also shows the arm spacing Wda2 between two adjacent secondary dendrite arms. DAS can be determined by performing the following measurements on multiple secondary dendrite arm groups. In this specification, DAS, which relates to the average spacing between secondary dendrite arms, is determined by the following method, and this value is considered to be the average spacing between multiple dendrite arms in the metal structure (M).

[0021] (Measurement of DAS) DAS is measured by the following method: Although the case where the positive electrode current collector includes a core metal will be described below, the DAS can also be measured by the same method for a positive electrode current collector that does not include a core metal.

[0022] First, the core is immersed in a resin such as epoxy resin to harden the resin. Next, the core is cut along with the hardened resin to expose the cross section of the core. The cross section is then polished and etched to reveal the metal structure. The etching is performed using a mixture of lactic acid and hydrogen peroxide. Next, the metal structure is photographed using a metallurgical microscope to obtain an image of the metal structure. From the obtained image, five locations (secondary dendrite arm groups) where at least three dendrite arms are aligned are arbitrarily selected. Then, the distance L from one end to the other end of the selected secondary dendrite arm groups is measured. A diagram to explain the measurement is shown in Figure 1B.

[0023] FIG. 1B shows a portion of an example in which (n-1) secondary dendrite arms Da2 are aligned to form a single secondary dendrite arm group. In measuring the DAS, as shown in FIG. 1B, a straight line S intersecting the (n-1) secondary dendrite arms is drawn on the image. The straight line S is drawn parallel to the direction in which the secondary dendrite arms Da2 are aligned. In other words, the straight line S is drawn so as to extend in a direction substantially perpendicular to the direction in which each secondary dendrite arm extends. In FIG. 1B, the intersections of the straight line S with the boundaries of the secondary dendrite arms are numbered 1 to n. The distance L between the two intersections of the line S with the boundaries of the aligned (n-1) secondary dendrite arms is measured.

[0024] Then, the distance L is measured in the same manner for the five secondary dendrite arm groups selected as above. In this way, the number of dendrite arms (n ｉ -1) and L ｉ Here, i represents the secondary dendrite arm group number and corresponds to each of the five selected locations. That is, if five secondary dendrite arm groups are measured, i = 1 to 5.

[0025] The average value of the spacing between the secondary dendrite arms in the i-th secondary dendrite arm group is L ｉ / (n ｉ −1). Therefore, when m secondary dendrite arm groups are measured, the DAS can be calculated using the following formula (1). When calculating the DAS obtained by measuring five secondary dendrite arm groups, simply replace m in formula (1) with 5.

[0026]

[0027] An example of the relationship between the cooling rate and DAS when casting a positive electrode current collector is shown in Table 1. The cooling rate in Table 1 is determined by measuring the amount of temperature decrease per unit time when a material for the positive electrode current collector in a molten state (single liquid phase) is cooled.

[0028] Cooling rate is 11.1 K·s －１FIG. 2A shows an example of an image of the metal structure when a positive electrode current collector was produced at a cooling rate of 107.1 K s. The DAS of the metal structure shown in FIG. 2A is approximately 35 μm. －１ An example of an image of the metal structure of a positive electrode current collector manufactured by the method described above is shown in FIG. 2B. The DAS of the metal structure shown in FIG. 2B is approximately 6 μm. The material of the positive electrode current collector in these images is a Pb—Sb alloy with an Sb content of 5 mass %.

[0029] The relationship between the DAS and the amount of corrosion (g) of the positive electrode current collector is shown in Figure 2C. The data in Figure 2C represent the amount of corrosion (g) calculated from the mass change of the positive electrode current collector in the overcharge corrosion test. As shown in Figure 2C, by setting the DAS to 20 μm or less, the amount of corrosion of the positive electrode current collector can be significantly reduced.

[0030] In a lead-acid battery according to one embodiment of the present invention, a negative electrode plate, an electrolyte, and a positive electrode plate are disposed in a battery case. The lead-acid battery according to one embodiment of the present invention may be either a valve-regulated (sealed) lead-acid battery (VRLA type lead-acid battery) or a flooded (vented) lead-acid battery. The lead-acid battery according to one embodiment of the present invention may be used for any purpose, such as a storage battery for electric vehicles (forklifts, etc.) or other vehicles (automobiles, motorcycles, etc.).

[0031] In this specification, the fully charged state of a flooded lead-acid battery is defined by JIS D 5301:2006. More specifically, the fully charged state is defined as a state in which a lead-acid battery is charged in a water tank at 25°C ± 2°C with a current (A) that is 0.2 times the value in Ah listed as the rated capacity, until the terminal voltage during charging or the electrolyte density converted to a temperature of 20°C, measured every 15 minutes, shows a constant value to three significant digits three times in a row. The value listed as the rated capacity is expressed in Ah. The unit of current set based on the value listed as the rated capacity is A.

[0032] A fully charged lead-acid battery refers to a fully charged lead-acid battery that has already been formed. A lead-acid battery can be fully charged immediately after formation, or after some time has passed since formation (for example, a lead-acid battery that has been in use (preferably in the early stages of use) after formation can be fully charged). A battery in the early stages of use refers to a battery that has not been in use for very long and has hardly deteriorated.

[0033] Hereinafter, a lead-acid battery according to one embodiment of the present invention will be described in terms of each of its main components.

[0034] (Positive Electrode Plate) Positive electrode plates for lead-acid batteries can be classified into paste type, clad type, etc. A paste type positive electrode plate includes a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. In a paste type positive electrode plate, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode current collector. The positive electrode current collector can be formed using a lead alloy, and may be formed by casting the lead alloy. The positive electrode current collector of a paste type positive electrode plate may be a grid-shaped current collector.

[0035] An example of a clad positive electrode plate includes multiple porous tubes, a metal core inserted into each tube, a current collector connecting the multiple metal cores, a positive electrode material (including a positive electrode active material) filled into each tube and arranged around the metal cores, and a connecting seat connecting the multiple tubes. In a clad positive electrode plate, the positive electrode material excludes the tubes, the metal cores, the current collector, and the connecting seat. In describing a clad positive electrode plate, the metal cores and the current collector are sometimes collectively referred to as a positive electrode current collector member. The metal core functions as a positive electrode current collector.

[0036] A positive electrode plate may have a mat, pasting paper, or other material attached to it. Such a material (attaching material) is used integrally with the positive electrode plate, and is therefore considered to be included in the positive electrode plate. In addition, when the positive electrode plate includes such a material, the positive electrode material, in the case of a paste-type positive electrode plate, is the positive electrode plate excluding the positive electrode current collector and the adhesive material.

[0037] (Positive electrode current collector) The positive electrode current collector is formed using a lead alloy. As the lead alloy used for the positive electrode current collector, a Pb—Sb alloy is preferred in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have a surface layer. The surface layer and the inner layer of the positive electrode current collector may have different compositions. The surface layer may be formed on a part of the positive electrode current collector. At least a part of the surface layer may be composed of a metal structure (M).

[0038] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacity through an oxidation-reduction reaction. The positive electrode material may also contain other additives as needed.

[0039] Unformed paste-type positive plates are obtained by placing a positive electrode paste around a positive electrode current collector, aging it, and drying it. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. Unformed clad-type positive plates are formed by filling porous tubes with lead powder or lead powder slurry, into which core metals connected by current collectors are inserted, and then connecting multiple tubes with a connecting rod. These unformed positive plates are then chemically formed to obtain positive plates. Chemical formation can be performed by charging a plate group including unformed positive plates while immersing them in an electrolyte containing sulfuric acid in a lead-acid battery container. However, chemical formation may also be performed before assembling the lead-acid battery or plate group.

[0040] The positive electrode current collector may be made of an alloy containing Pb and Sb. In this case, the Sb content in the positive electrode current collector may be 3.5% by mass or more, or 5% by mass or more, and may be 10% by mass or less, or 8% by mass or less. For example, the content may be 3.5% by mass or more and 10% by mass or less, or 5% by mass or more and 8% by mass or less.

[0041] When the positive electrode current collector is made of an alloy containing Pb and Sb, the alloy may contain trace elements other than Pb and Sb. The content of such trace elements may be greater than 0% by mass and less than or equal to 1% by mass (e.g., greater than 0% by mass and less than or equal to 0.5% by mass). Examples of such trace elements include As, S, Se, Sn, and Ag.

[0042] As described above, the positive electrode plate may be a clad type positive electrode plate. In this case, the positive electrode current collector may include a core metal. The core metal is an elongated rod-like shape (e.g., a round bar-like shape). The diameter of the core metal (the diameter of the round bar-like core metal) may be 2.4 mm or more, or 2.7 mm or more, and may be less than 3.6 mm or 3.3 mm or less. For example, the diameter may be 2.4 mm or more and less than 3.6 mm, or 2.7 mm or more and 3.3 mm or less.

[0043] The length of the core is not particularly limited and is selected depending on the size of the positive electrode plate. The length of the core may be, for example, 100 mm or more and 400 mm or less.

[0044] (Method for Analyzing the Composition of Positive Electrode Current Collector) The amount of elements other than lead contained in the positive electrode current collector can be determined by lead separation inductively coupled plasma optical emission spectroscopy as described in JIS H2105. When analyzing the content of elements contained in the positive electrode current collector of a positive electrode plate removed from a lead-acid battery, first vibrate the positive electrode plate to remove the positive electrode material from the positive electrode current collector, and then use a ceramic knife to remove the positive electrode material remaining around the positive electrode current collector. A portion of the positive electrode current collector having a metallic luster is then collected as a sample and its mass is measured. The collected sample is dissolved in tartaric acid and dilute nitric acid to obtain an aqueous solution. Hydrochloric acid is added to the obtained aqueous solution to precipitate lead chloride, followed by filtration and collection of the filtrate. The elements in the filtrate are analyzed by the calibration curve method using an inductively coupled plasma (ICP) optical emission spectrometer (e.g., ICPS-8000, manufactured by Shimadzu Corporation). From the above analysis results, the content (mass %) of the elements in the positive electrode current collector is determined.

[0045] (Negative electrode plate) The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. The negative electrode material may include an organic condensation product as an organic shrinkage preventer.

[0046] Note that a mat, pasting paper, or other member may be attached to the negative electrode plate. Such a member (attaching member) is used integrally with the negative electrode plate and is therefore considered to be included in the negative electrode plate. Furthermore, when the negative electrode plate includes an attaching member, the negative electrode material does not include the negative electrode current collector and the attaching member. However, when an attaching member such as a mat is attached to the separator, the thickness of the attaching member is included in the thickness of the separator.

[0047] The negative electrode plate can be formed by applying or filling a negative electrode paste to a negative electrode current collector, aging and drying the paste to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is produced by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed, and kneading the mixture. During aging, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature and at a high humidity.

[0048] 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.

[0049] (Negative Electrode Current Collector) The negative electrode current collector may have a frame portion having lugs and a lattice portion continuous with the frame portion. The lattice portion may have a plurality of square squares.

[0050] 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. Examples of current collectors include grid-shaped current collectors, generally called grids, current collectors punched into circles or ellipses, and current collectors with grids radially extending from the ears of the current collector. Even current collectors that are not grid-shaped may be called grids. Using a negative electrode grid as the negative electrode current collector is preferable because it facilitates supporting the negative electrode material.

[0051] 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. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, and the like. The negative electrode current collector may have a surface layer. The surface layer and the inner layer of the negative electrode current collector may have different compositions. The surface layer may be formed on a part of the negative electrode current collector. The surface layer may be formed on an edge portion of the negative electrode current collector. The surface layer of the edge portion may contain Sn or an Sn alloy.

[0052] (Negative Electrode Material) The negative electrode material includes a negative electrode active material (lead or lead sulfate) that generates capacity through an oxidation-reduction reaction. The negative electrode material may also include a shrinkage inhibitor, a carbonaceous material, and / or other additives. Examples of additives include, but are not limited to, barium sulfate and fibers (e.g., resin fibers). Note that the negative electrode active material in a charged state is sponge lead, but unformed negative plates are typically made using lead powder.

[0053] The negative electrode material may include a polymer compound, which may be hereinafter referred to as a "polymer compound (P)."

[0054] The first example of the polymer compound (P) is measured using deuterated chloroform as a solvent. １ It is a polymer compound having a peak in the range of 3.2 ppm to 3.8 ppm in the chemical shift of the H-NMR spectrum. １ Unless otherwise specified, the H-NMR spectrum was measured using deuterated chloroform as a solvent. ２－４ It is a polymer compound containing a repeating structure of alkylene units. The polymer compound included in the first example of polymer compound (P) and the polymer compound included in the second example of polymer compound (P) at least partially overlap. A commercially available polymer compound (P) may be used as the polymer compound (P). Alternatively, the polymer compound (P) may be synthesized by a known method.

[0055] In lead-acid batteries, water in the electrolyte is electrolyzed at the negative electrode plate during charging, generating hydrogen gas. If the overcharge charge is large, the amount of electrolyte lost due to water electrolysis increases. Furthermore, if the overcharge charge is large, the deterioration of the positive electrode current collector accelerates. As a result, the life of the lead-acid battery is shortened. Therefore, reducing the overcharge charge is particularly important for lead-acid batteries. Adding a polymer compound (P) to the negative electrode material can suppress the overcharge charge.

[0056] The reason why the polymer compound (P) can reduce the amount of electricity in overcharge is considered to be as follows. ２－４ Because it contains a repeating structure of alkylene units, it is prone to adopt a linear structure. Therefore, the polymer compound (P) added to the negative electrode material thinly and widely covers the surface of the lead in the negative electrode material. Covering the surface of the lead with the polymer compound (P) increases the hydrogen overvoltage, thereby making it less likely for a side reaction that generates hydrogen during overcharge to occur. On the other hand, adding a large amount of polymer compound (P) may result in a decrease in charge acceptance. In the present invention, the polymer compound (P) content is high in the center of the negative electrode plate, where a large amount of hydrogen gas is generated during overcharge. Therefore, it is possible to effectively reduce the amount of overcharge electricity while suppressing the amount of polymer compound (P) throughout the negative electrode plate. In other words, the present invention can achieve high charge acceptance and a low overcharge electricity.

[0057] (Polymer Compound (P)) The polymer compound (P) is １ In the chemical shift of the H-NMR spectrum, the polymer compound (P) has a peak in the range of 3.2 ppm to 3.8 ppm. ２－４ Contains an alkylene unit. ２－４ Examples of the alkylene unit include an oxyethylene unit, an oxypropylene unit, an oxytrimethylene unit, an oxy2-methyl-1,3-propylene unit, an oxy1,4-butylene unit, and an oxy1,3-butylene unit. ２－４The alkylene unit may have one type or two or more types.

[0058] The polymer compound (P) is an oxy-C ２－４ It is preferable that the repeating unit contains a repeating structure of an alkylene unit. ２－４ It may contain an alkylene unit, and two or more kinds of oxy C ２－４ The polymer compound (P) may contain one of the above repeating structures, or may contain two or more of the above repeating structures.

[0059] Oxy C ２－４ The polymer compound (P) having a repeating structure of alkylene units also includes those classified as surfactants (more specifically, nonionic surfactants).

[0060] Examples of the polymer compound (P) include oxy C ２－４ Hydroxy compounds having a repeating structure of alkylene units (polyC ２－４ Alkylene glycol, oxy C ２－４ Copolymer containing repeating alkylene units, polyol polyC ２－４ alkylene oxide adducts), ethers or esters of these hydroxy compounds, and the like.

[0061] As copolymers, different oxy C ２－４ The copolymer may be a block copolymer.

[0062] The polyol may be any of aliphatic polyols, alicyclic polyols, aromatic polyols, and heterocyclic polyols. From the viewpoint of facilitating thin spreading of the polymer compound (P) on the lead surface, aliphatic polyols and alicyclic polyols (e.g., polyhydroxycyclohexane, polyhydroxynorbornane, etc.) are preferred, and aliphatic polyols are particularly preferred. Examples of aliphatic polyols include aliphatic diols and polyols with a triol or higher (e.g., glycerin, trimethylolpropane, pentaerythritol, sugar alcohols, etc.). Examples of aliphatic diols include alkylene glycols with 5 or more carbon atoms. Examples of alkylene glycols include C ５～１４ Alkylene glycol or C ５－１０ The sugar alcohol may be, for example, erythritol, xylitol, mannitol, sorbitol, etc. In the polyol polyalkylene oxide adduct, the alkylene oxide is an oxy C of the polymer compound (P). ２－４ Corresponding to an alkylene unit, at least C ２－４ The polyol contains an alkylene oxide. From the viewpoint that the polymer compound (P) easily has a linear structure, the polyol is preferably a diol.

[0063] The etherified product is the above-mentioned oxy C ２－４ At least some of the terminal —OH groups (—OH groups consisting of a hydrogen atom of the terminal group and an oxygen atom bonded to this hydrogen atom) of the hydroxy compound having a repeating structure of alkylene units are etherified to —OR ２ group, wherein R ２ is an organic group.) Some or all of the terminals of the polymer compound (P) may be etherified. For example, one terminal of the main chain of the linear polymer compound (P) is an —OH group and the other terminal is an —OR group. ２ It may also be a group.

[0064] The esterified product is the above-mentioned oxy C ２－４At least some of the terminal —OH groups (—OH groups consisting of a hydrogen atom of the terminal group and an oxygen atom bonded to this hydrogen atom) of a hydroxy compound having a repeating structure of alkylene units are esterified to form —O—C(═O)—R ３ group, wherein R ３ is an organic group.) Some or all of the terminals of the polymer compound (P) may be esterified. For example, one terminal of the main chain of the linear polymer compound (P) is an —OH group and the other terminal is —O—C(═O)—R ３ It may also be a group.

[0065] organic group R ２ and R ３ Each of the above may include a hydrocarbon group. The hydrocarbon group may have a substituent (for example, a hydroxy group, an alkoxy group, and / or a carboxy group). The hydrocarbon group may be any of aliphatic, alicyclic, and aromatic. The aromatic hydrocarbon group and the alicyclic hydrocarbon group may have an aliphatic hydrocarbon group (for example, an alkyl group, an alkenyl group, an alkynyl group) as a substituent. The number of carbon atoms in the aliphatic hydrocarbon group as a substituent may be, for example, 1 to 30, 1 to 20, 1 to 10, 1 to 6, or 1 to 4.

[0066] Examples of aromatic hydrocarbon groups include aromatic hydrocarbon groups having 24 or less carbon atoms (e.g., 6 to 24). The number of carbon atoms in the aromatic hydrocarbon group may be 20 or less (e.g., 6 to 20), 14 or less (e.g., 6 to 14), or 12 or less (e.g., 6 to 12). Examples of aromatic hydrocarbon groups include aryl groups and bisaryl groups. Examples of aryl groups include phenyl groups and naphthyl groups. Examples of bisaryl groups include monovalent groups corresponding to bisarenes. Examples of bisarenes include biphenyl, bisarylalkanes (e.g., bisC ６－１０ Aryl C １－４ Alkanes (such as 2,2-bisphenylpropane) are also included.

[0067] Examples of alicyclic hydrocarbon groups include alicyclic hydrocarbon groups having 16 or less carbon atoms. The alicyclic hydrocarbon group may be a bridged cyclic hydrocarbon group. The number of carbon atoms in the alicyclic hydrocarbon group may be 10 or less or 8 or less. The number of carbon atoms in the alicyclic hydrocarbon group may be, for example, 5 or more, or 6 or more.

[0068] The alicyclic hydrocarbon group may have 5 (or 6) or more and 16 (or less), 5 (or 6) or more and 10 (or less), or 5 (or 6) or more and 8 (or less) carbon atoms.

[0069] Examples of alicyclic hydrocarbon groups include cycloalkyl groups (cyclopentyl, cyclohexyl, cyclooctyl, etc.), cycloalkenyl groups (cyclohexenyl, cyclooctenyl, etc.), etc. Alicyclic hydrocarbon groups also include hydrogenated products of the above aromatic hydrocarbon groups.

[0070] From the viewpoint of facilitating a thin adhesion of the polymer compound (P) to the lead surface, among the hydrocarbon groups, an aliphatic hydrocarbon group is preferred. The aliphatic hydrocarbon group may be saturated or unsaturated. Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a dienyl group having two carbon-carbon double bonds, and a trienyl group having three carbon-carbon double bonds. The aliphatic hydrocarbon group may be either linear or branched.

[0071] The number of carbon atoms in the aliphatic hydrocarbon group is, for example, 30 or less, and may be 26 or 22 or less, 20 or 16 or less, 14 or 10 or less, or 8 or 6 or less. The lower limit of the number of carbon atoms depends on the type of aliphatic hydrocarbon group: 1 or more for alkyl groups, 2 or more for alkenyl groups and alkynyl groups, 3 or more for dienyl groups, and 4 or more for trienyl groups. Among these, alkyl groups and alkenyl groups are preferred from the viewpoint of facilitating thin adhesion of the polymer compound (P) to the lead surface.

[0072] Specific examples of alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, i-pentyl, s-pentyl, 3-pentyl, t-pentyl, n-hexyl, 2-ethylhexyl, n-octyl, n-nonyl, n-decyl, i-decyl, undecyl, lauryl (dodecyl), tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, icosyl, heneicosyl, and behenyl.

[0073] Specific examples of the alkenyl group include vinyl, 1-propenyl, allyl, cis-9-heptadecen-1-yl, palmitoleyl, and oleyl. ２－３０ Alkenyl group or C ２－２６ may be an alkenyl group, C ２－２２ Alkenyl group or C ２－２０ may be an alkenyl group, C １０－２０ It may also be an alkenyl group.

[0074] Among the polymer compounds (P), oxy C ２－４ Ethers of hydroxy compounds having repeating alkylene units and oxy C ２－４ The use of at least one selected from the group consisting of esters of hydroxy compounds having a repeating alkylene unit structure is preferred because it can further enhance the effect of suppressing the decrease in charge acceptance. Furthermore, the use of these polymer compounds (P) can also reduce the amount of electricity during overcharge. Among these polymer compounds (P), those having a repeating oxypropylene unit structure or a repeating oxyethylene unit structure are preferred.

[0075] The polymer compound (P) may have one or more hydrophobic groups. Examples of the hydrophobic group include the above-mentioned hydrocarbon groups, such as aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and long-chain aliphatic hydrocarbon groups. Examples of the long-chain aliphatic hydrocarbon group include the above-mentioned aliphatic hydrocarbon groups (e.g., alkyl groups, alkenyl groups, etc.) having 8 or more carbon atoms, preferably 12 or more, and more preferably 16 or more. Among these, polymer compounds (P) having long-chain aliphatic hydrocarbon groups are preferred because they are less likely to cause excessive adsorption to lead and further enhance the effect of suppressing a decrease in charge acceptance. The polymer compound (P) may have at least one hydrophobic group that is a long-chain aliphatic hydrocarbon group. The long-chain aliphatic hydrocarbon group may have 30 or less, 26 or less, or 22 or less carbon atoms.

[0076] The long-chain aliphatic hydrocarbon group may have 8 or more (or 12 or more) and 30 or less, 8 or more (or 12 or more) and 26 or less, 8 or more (or 12 or more) and 22 or less, 10 or more and 30 or less (or 26 or less), or 10 or more and 22 or less carbon atoms.

[0077] Among the polymer compounds (P), those having both hydrophilic and hydrophobic groups correspond to nonionic surfactants. The repeating structure of oxyethylene units exhibits high hydrophilicity and can serve as the hydrophilic group in nonionic surfactants. Therefore, it is preferable that the polymer compound (P) having the hydrophobic group contains a repeating structure of oxyethylene units. Such polymer compounds (P) selectively adsorb lead while suppressing excessive coverage of the lead surface due to the balance between hydrophobicity and high hydrophilicity due to the repeating structure of oxyethylene units, thereby further enhancing the effect of suppressing a decrease in charge acceptance while reducing the amount of overcharge electricity. Such polymer compounds (P) can ensure high adsorption to lead even when they have a relatively low molecular weight (e.g., Mn of 1000 or less).

[0078] Among the above polymer compounds (P), polyoxypropylene-polyoxyethylene block copolymers, etherified products of hydroxy compounds having a repeating structure of oxyethylene units, and esterified products of hydroxy compounds having a repeating structure of oxyethylene units correspond to nonionic surfactants.

[0079] Examples of the polymer compound (P) having a hydrophobic group and a repeating structure of oxyethylene units include etherified polyethylene glycol (e.g., alkyl ethers), esterified polyethylene glycol (e.g., carboxylic acid esters), etherified polyethylene oxide adducts of the above polyols (e.g., alkyl ethers), and esterified polyethylene oxide adducts of the above polyols (e.g., triols or higher polyols) (e.g., carboxylic acid esters). Specific examples of such polymer compounds (P) include, but are not limited to, polyethylene glycol oleate, polyethylene glycol dioleate, polyethylene glycol dilaurate, polyethylene glycol distearate, polyoxyethylene coconut oil fatty acid sorbitan, polyoxyethylene sorbitan oleate, polyoxyethylene sorbitan stearate, polyoxyethylene lauryl ether, polyoxyethylene tetradecyl ether, and polyoxyethylene cetyl ether. Among these, the use of esterified polyethylene glycol and esterified polyethylene oxide adducts of the above polyols is preferred because they can ensure higher charge acceptance and significantly reduce the amount of electricity in overcharge.

[0080] Among the polymer compounds (P), those classified as surfactants preferably have an HLB of 4 or more, more preferably 4.3 or more, from the viewpoint of further reducing the amount of electrolyte loss. From the viewpoint of easily ensuring higher charge acceptance, the HLB of the polymer compound (P) is preferably 18 or less, more preferably 10 or less or 9 or less, and even more preferably 8.5 or less.

[0081] The HLB of the polymer compound (P) may be 4 or more (or 4.3 or more) and 18 or less, or 4 or more (or 4.3 or more) and 10 or less. From the viewpoint of achieving an excellent balance between reducing the amount of electricity in overcharge and improving charge acceptance, the HLB of the polymer compound (P) is preferably 4 or more (or 4.3 or more) and 9 or less, or 4 or more (or 4.3 or more) and 8.5 or less. HLB is an abbreviation for Hydrophile Lipophile Balance and is a value that represents the balance between the hydrophobicity and hydrophilicity of a surfactant (mainly a nonionic surfactant). The HLB value of the polymer compound (P) is determined by the Griffin method.

[0082] Oxy C is more effective in reducing the amount of overcharge electricity and is easier to secure higher charge acceptance. ２－４ It is also preferable that the repeating structure of alkylene contains at least a repeating structure of an oxypropylene unit. In this case, the charge acceptance tends to be lower than that of a repeating structure of an oxyethylene unit, but even in this case, it is possible to ensure high charge acceptance while suppressing the amount of overcharge electricity to a low level. The polymer compound (P) containing an oxypropylene unit is １ In the chemical shift of the H-NMR spectrum, -CH< and -CH of the oxypropylene unit are present in the range of 3.2 ppm to 3.8 ppm. ２ The peaks are split because the electron densities around the nuclei of the hydrogen atoms in these groups are different. １ In the chemical shift of the H-NMR spectrum, for example, there are peaks in the range of 3.2 ppm to 3.42 ppm and in the range of more than 3.42 ppm to 3.8 ppm. The peak in the range of 3.2 ppm to 3.42 ppm is due to -CH ２ The peaks in the range of more than 3.42 ppm and less than 3.8 ppm are derived from -CH< and -CH ２ -Derived from.

[0083] Examples of the polymer compound (P) containing at least a repeating structure of an oxypropylene unit include polypropylene glycol, a copolymer containing a repeating structure of an oxypropylene unit, a polypropylene oxide adduct of the above polyol, or an etherified or esterified product thereof. Examples of the copolymer include an oxypropylene-oxyalkylene copolymer (wherein the oxyalkylene is a C alkylene other than oxypropylene). ２－４ Examples of the oxypropylene-oxyalkylene copolymer include an oxypropylene-oxyethylene copolymer and an oxypropylene-oxytrimethylene copolymer. The oxypropylene-oxyalkylene copolymer is sometimes referred to as a polyoxypropylene-polyoxyalkylene copolymer (for example, a polyoxypropylene-polyoxyethylene copolymer). The oxypropylene-oxyalkylene copolymer may be a block copolymer (for example, a polyoxypropylene-polyoxyethylene block copolymer). Examples of the etherified products include polypropylene glycol alkyl ethers and alkyl ethers of oxypropylene-oxyalkylene copolymers (such as alkyl ethers of polyoxypropylene-polyoxyethylene copolymers). Examples of the esterified products include polypropylene glycol esters of carboxylic acids and carboxylic acid esters of oxypropylene-oxyalkylene copolymers (such as carboxylic acid esters of polyoxypropylene-polyoxyethylene copolymers).

[0084] Examples of the polymer compound (P) containing at least a repeating structure of oxypropylene units include polypropylene glycol, polyoxypropylene-polyoxyethylene copolymers (such as polyoxypropylene-polyoxyethylene block copolymers), polyoxyethylene-polyoxypropylene alkyl ethers (such as alkyl ethers (butyl ethers) in which the above R2 is an alkyl having 10 or less carbon atoms (or 8 or less or 6 or less) carbon atoms), polypropylene glycol carboxylate (such as the above R ３and polypropylene glycol carboxylates (such as polypropylene glycol acetate) in which the alkyl group has 10 or less carbon atoms (or 8 or less, or 6 or less) and polypropylene oxide adducts of triol or higher polyols (such as polypropylene oxide adducts of glycerin), but are not limited to these.

[0085] In the polymer compound (P) containing a repeating structure of oxypropylene units, the proportion of oxypropylene units is, for example, 5 mol% or more, and may be 10 mol% or more, or 20 mol% or more. The proportion of oxypropylene units is, for example, 100 mol% or less. In the copolymer, the proportion of oxypropylene units may be 90 mol% or less, 75 mol% or less, or 60 mol% or less.

[0086] In the polymer compound (P) containing a repeating structure of oxypropylene units, the proportion of oxypropylene units may be 5 mol% or more and 100 mol% or less (or 90 mol% or less), 10 mol% or more and 100 mol% or less (or 90 mol% or less), 20 mol% or more and 100 mol% or less (or 90 mol% or less), 5 mol% or more and 75 mol% or less (or 60 mol% or less), 10 mol% or more and 75 mol% or less (or 60 mol% or less), or 20 mol% or more and 75 mol% or less (or 60 mol% or less).

[0087] From the viewpoint of increasing the adsorption ability to lead and facilitating the formation of a linear structure, the polymer compound (P) is preferably an oxy-C ２－４ It is preferable that the polymer compound (P) contains a large number of alkylene units. For example, the polymer compound (P) contains an oxygen atom bonded to a terminal group and a —CH ２ The polymer compound (P) contains a - group and / or a -CH< group. １ In the H-NMR spectrum, the integral value of the peak between 3.2 ppm and 3.8 ppm is ２The proportion of the integral of the peak of the hydrogen atom of the - group and the integral of the peak of the hydrogen atom of the -CH< group in the total of the integral of the peak of the hydrogen atom of the -CH< group becomes large. This proportion is, for example, 50% or more, and may be 80% or more. From the viewpoint of further enhancing the effect of reducing the overcharge quantity of electricity and easily ensuring higher charge acceptance, the above proportion is preferably 85% or more, and more preferably 90% or more. For example, when the polymer compound (P) has an -OH group at its terminal and a -CH bonded to the oxygen atom of this -OH group, ２ When it has a - group or a -CH< group, １ In the H-NMR spectrum, -CH ２ The peaks of the hydrogen atoms of the - group and -CH< group have chemical shifts in the range of more than 3.8 ppm to 4.0 ppm.

[0088] The negative electrode material may contain one type of polymer compound (P) or two or more types of polymer compounds (P).

[0089] The polymer compound (P) may include, for example, a compound having an Mn of 5 million or less, a compound having an Mn of 3 million or less, or a compound having an Mn of 2 million or less, a compound having an Mn of 500,000 or less, or a compound having an Mn of 10,000 or less. From the viewpoint of ensuring higher charge acceptance, the polymer compound (P) preferably includes a compound having an Mn of 10,000 or less, a compound having an Mn of 5,000 or less, or a compound having an Mn of 4,000 or less, or a compound having an Mn of 3,000 or less, or a compound having an Mn of 2,500 or less. The Mn of such a compound may be 300 or more, 400 or more, or even 500 or more. From the viewpoint of further enhancing the effect of reducing the amount of electricity during overcharge, the Mn of such a compound is preferably 1,000 or more, more preferably 1,500 or more, or 1,800 or more. Two or more compounds having different Mn may be used as the polymer compound (P). In other words, the polymer compound (P) may have multiple Mn peaks in the molecular weight distribution.

[0090] The Mn of the above compounds is 300 or more (or 400 or more) and 5 million or less, 300 or more (or 400 or more) and 3 million or less, 300 or more (or 400 or more) and 2 million or less, 300 or more (or 400 or more) and 500,000 or less, 300 or more (or 400 or more) and 100,000 or less, 300 or more (or 400 or more) and 50,000 or less, 300 or more (or 400 or more) and 20,000 or less, 300 or more (or 400 or more) and 10,000 or less, 300 or more (or 400 or more) and 5,000 or less, 300 or more (or 400 or more) and up to 4,000, 300 or more (or 400 or more) and up to 3,000, 300 or more (or 400 or more) and up to 2,500, 500 or more (or 1,000 or more) and up to 5 million, 500 or more (or 1,000 or more) and up to 3 million, 500 or more (or 1,000 or more) and up to 2 million, 500 or more (or 1,000 or more) and up to 500,000, 500 or more (or 1,000 or more) and up to 100,000, 500 or more (or 1,000 or more) and up to 50,000, 500 or more (or 1,000 or more) 20,000 or less, 500 or more (or 1,000 or more) 10,000 or less, 500 or more (or 1,000 or more) 5,000 or less, 500 or more (or 1,000 or more) 4,000 or less, 500 or more (or 1,000 or more) 3,000 or less, 500 or more (or 1,000 or more) 2,500 or less, 1,500 or more (or 1,800 or more) 5 million or less, 1,500 or more (or 1,800 or more) 3 million or less, 1,500 or more (or 1,800 or more) 2 million or less, 1,500 or more (or 1,800 or more) or more) but not more than 500,000, 1,500 or more (or 1,800 or more) but not more than 100,000, 1,500 or more (or 1,800 or more) but not more than 50,000, 1,500 or more (or 1,800 or more) but not more than 20,000, 1,500 or more (or 1,800 or more) but not more than 10,000, 1,500 or more (or 1,800 or more) but not more than 5,000, 1,500 or more (or 1,800 or more) but not more than 4,000, 1,500 or more (or 1,800 or more) but not more than 3,000, or 1,500 or more (or 1,800 or more) but not more than 2,500.

[0091] The content of the polymer compound (P) in the negative electrode material is, for example, 8 ppm or more, and may be 10 ppm or more, by mass. From the viewpoint of further enhancing the effect of reducing the overcharge electricity quantity, the content of the polymer compound (P) in the negative electrode material is, by mass, preferably 20 ppm or more, and more preferably 30 ppm or more. The content of the polymer compound (P) in the negative electrode material is, for example, 1000 ppm or less, or may be less than 1000 ppm, 700 ppm or less, 600 ppm or less, or 500 ppm or less. From the viewpoint of easily ensuring higher charge acceptance, the content of the polymer compound (P) in the negative electrode material is, by mass, preferably 400 ppm or less, more preferably 300 ppm or less, and may be 200 ppm or less or 160 ppm or less, 150 ppm or less or 120 ppm or less, or may be 100 ppm or less.

[0092] The content (by mass) of the polymer compound (P) in the negative electrode material is 8 ppm or more (or 10 ppm or more) and 1000 ppm or less, 8 ppm or more (or 10 ppm or more) and less than 1000 ppm, 8 ppm or more (or 10 ppm or more) and 700 ppm or less, 8 ppm or more (or 10 ppm or more) and 600 ppm or less, 8 ppm or more (or 10 ppm or more) and 500 ppm or less, 8 ppm or more (or 8 ppm or more (or 10 ppm or more) 400 ppm or less, 8 ppm or more (or 10 ppm or more) 300 ppm or less, 8 ppm or more (or 10 ppm or more) 200 ppm or less, 8 ppm or more (or 10 ppm or more) 160 ppm or less, 8 ppm or more (or 10 ppm or more) 150 ppm or less, 8 ppm or more (or 10 ppm or more) 120 ppm or less, 8 ppm or more (or 10 ppm or more) 100 ppm m or less, 20 ppm or more (or 30 ppm or more) and 1000 ppm or less, 20 ppm or more (or 30 ppm or more) and less than 1000 ppm, 20 ppm or more (or 30 ppm or more) and 700 ppm or less, 20 ppm or more (or 30 ppm or more) and 600 ppm or less, 20 ppm or more (or 30 ppm or more) and 500 ppm or less, 20 ppm or more (or 30 ppm or more) and 400 ppm or less, 20 The concentration may be 20 ppm or more (or 30 ppm or more) to 300 ppm or less, 20 ppm or more (or 30 ppm or more) to 200 ppm or less, 20 ppm or more (or 30 ppm or more) to 160 ppm or less, 20 ppm or more (or 30 ppm or more) to 150 ppm or less, 20 ppm or more (or 30 ppm or more) to 120 ppm or less, or 20 ppm or more (or 30 ppm or more) to 100 ppm or less.

[0093] (Organic shrinkage preventer) As already mentioned, the negative electrode material may contain an organic condensate as an organic shrinkage preventer. The organic condensate may be, for example, one synthesized by a known method, or a commercially available product. The negative electrode material may contain one type of organic shrinkage preventer, or may contain two or more types. The negative electrode material may contain a lignin compound as an organic shrinkage preventer, or may contain an organic shrinkage preventer other than a lignin compound.

[0094] (Barium Sulfate) The negative electrode material may contain barium sulfate. The content of barium sulfate in the negative electrode material is, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The content of barium sulfate in the negative electrode material is 3% by mass or less, and may be 2% by mass or less. These lower and upper limits may be combined in any desired manner.

[0095] The content of barium sulfate in the negative electrode material may be 0.05% by mass or more and 3% by mass or less, 0.05% by mass or more and 2% by mass or less, 0.10% by mass or more and 3% by mass or less, or 0.10% by mass or more and 2% by mass or less.

[0096] (Carbonous Material) The negative electrode material may contain a carbonaceous material. Examples of the carbonaceous material include carbon black, graphite, hard carbon, and soft carbon. Examples of carbon black include acetylene black, furnace black, and lamp black. Furnace black also includes Ketjen Black (trade name). The graphite may be any carbonaceous material containing a graphite-type crystalline structure, and may be either artificial graphite or natural graphite. One type of carbonaceous material may be used alone, or two or more types may be used in combination.

[0097] The content of the carbonaceous material in the negative electrode material is, for example, preferably 0.05% by mass or more, and may be 0.10% by mass or more. The content of the carbonaceous material is, for example, 5% by mass or less, and may be 3% by mass or less. These lower and upper limits can be combined in any manner.

[0098] The content of the carbonaceous material in the negative electrode material may be, for example, 0.05% by mass or more and 5% by mass or less, 0.05% by mass or more and 3% by mass or less, 0.10% by mass or more and 5% by mass or less, or 0.10% by mass or more and 3% by mass or less.

[0099] (Analysis of Negative Electrode Material or Constituent Components) The following describes a method for analyzing the negative electrode material or its constituent components. Prior to measurement or analysis, a fully charged lead-acid battery is disassembled to obtain a negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. The washing is continued until a pH test paper is pressed against the washed surface of the negative electrode plate and no color change is confirmed. However, the washing time is limited to within two hours. The washed negative electrode plate is dried in a reduced pressure environment at 60±5°C for approximately six hours. If the negative electrode plate contains an adhesive material, the adhesive material is removed as necessary. Next, a sample (hereinafter referred to as sample A) is obtained by separating the negative electrode material from the negative electrode plate. Sample A is crushed as necessary and subjected to analysis.

[0100] (1) Analysis of Polymer Compound (P) (1-1) Qualitative Analysis of Polymer Compound (P) A pulverized sample A is used. 150.0±0.1 mL of chloroform is added to 100.0±0.1 g of sample A, and the mixture is stirred at 20±5°C for 16 hours to extract the polymer compound (P). The solid content is then removed by filtration. The polymer compound (P) obtained by extraction is dissolved in a chloroform solution, or the polymer compound (P) is obtained by drying the chloroform solution. The polymer compound (P) is identified by obtaining information from at least one of infrared spectroscopy, ultraviolet-visible absorption spectroscopy, NMR spectroscopy, LC-MS, and pyrolysis GC-MS.

[0101] The chloroform-soluble matter is recovered by distilling off the chloroform under reduced pressure from the chloroform solution in which the polymer compound (P) obtained by extraction is dissolved. The chloroform-soluble matter is dissolved in deuterated chloroform and subjected to the following conditions: １ The H-NMR spectrum is measured. １ From the H-NMR spectrum, a peak in the chemical shift range of 3.2 ppm to 3.8 ppm is confirmed. ２－４ Identify the type of alkylene unit.

[0102] Apparatus: AL400 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd. Observation frequency: 395.88 MHz Pulse width: 6.30 μs Pulse repetition time: 74.1411 seconds Number of accumulations: 32 Measurement temperature: room temperature (20 to 35°C) Reference: 7.24 ppm Sample tube diameter: 5 mm

[0103] １ From the H-NMR spectrum, the integral value (V １ ) is determined. In addition, the —CH bonded to the oxygen atom bonded to the terminal group of the polymer compound (P) is determined. ２ For each hydrogen atom of the - group and the -CH< group, １ The sum of the integral values ​​of the peaks in the H-NMR spectrum (V ２ ) is found. Then, V １ and V ２ From V １ V １ and V ２ Percentage of the total (= V １ / (V １ +V ２ ) × 100(%).

[0104] In addition, in qualitative analysis, １ When calculating the integral value of a peak in a H-NMR spectrum, １ In the H-NMR spectrum, two points without significant signals are determined on either side of the relevant peak, and each integral value is calculated using the line connecting these two points as the baseline. For example, for a peak present in the chemical shift range of 3.2 ppm to 3.8 ppm, the line connecting the two points at 3.2 ppm and 3.8 ppm in the spectrum is used as the baseline. For example, for a peak present in the chemical shift range of more than 3.8 ppm but not more than 4.0 ppm, the line connecting the two points at 3.8 ppm and 4.0 ppm in the spectrum is used as the baseline.

[0105] (1-2) Quantitative Analysis of Polymer Compound (P) The appropriate amount of the chloroform-soluble matter was measured with an accuracy of ±0.0001 g. ｒ (g) Dissolve in deuterated chloroform together with tetrachloroethane (TCE),​１ The H-NMR spectrum is measured. The integral value (S ａ ) and the integral value of the peak due to TCE (S ｒ ) and the mass-based content C of the polymer compound (P) in the negative electrode material was calculated from the following formula: ｎ (ppm) is calculated.

[0106] C ｎ = S ａ / S ｒ ×N ｒ / N ａ ×M ａ / M ｒ ×m ｒ / m×1000000 (in the formula, M ａ indicates the molecular weight of a structure whose chemical shift shows a peak in the range of 3.2 to 3.8 ppm (more specifically, oxy C ２－４ (molecular weight of repeating alkylene units), and N ａ is the number of hydrogen atoms bonded to the carbon atoms in the main chain of the repeating structure. ｒ、 M ｒ are the number of hydrogen atoms contained in the molecule of the reference material, the molecular weight of the reference material, and m (g) is the mass of the negative electrode material used for extraction. Note that since the reference material in this analysis is TCE, N ｒ = 2, M ｒ = 168. Also, m = 100.

[0107] For example, when the polymer compound (P) is polypropylene glycol, M ａ is 58, and N ａ is 3. When the polymer compound (P) is polyethylene glycol, M ａ is 44, and N ａ is 4. N ａ and M ａ is the N of each monomer unit ａ value and M ａ The value is an average value obtained by using the molar ratio (mol %) of each monomer unit contained in the repeating structure.

[0108] In quantitative analysis, １The integral value of the peak in the H-NMR spectrum is determined using data processing software "ALICE" manufactured by JEOL Ltd.

[0109] (1-3) Measurement of Mn of polymer compound (P) Using the above chloroform-soluble fraction, GPC measurement of the polymer compound (P) is carried out using the following apparatus under the following conditions. Separately, a calibration curve (calibration curve) is created from a plot of Mn of a standard substance versus elution time. Based on this calibration curve and the GPC measurement results of the polymer compound (P), the Mn of the polymer compound (P) is calculated. However, esterified products or etherified products may be in a decomposed state in the chloroform-soluble fraction.

[0110] Analysis system: 20A system (manufactured by Shimadzu Corporation) Column: Two GPC KF-805L (manufactured by Shodex) connected in series Column temperature: 30°C ± 1°C Mobile phase: tetrahydrofuran Flow rate: 1 mL / min Concentration: 0.20 mass% Injection volume: 10 μL Standard substance: polyethylene glycol (Mn = 2,000,000, 200,000, 20,000, 2,000, 200) Detector: differential refractive index detector (manufactured by Shodex, Shodex RI-201H)

[0111] (Separator) A separator can be disposed between the negative electrode plate and the positive electrode plate. The separator can be at least one selected from a nonwoven fabric and a microporous membrane. The thickness of the separator disposed between the negative electrode plate and the positive electrode plate can be selected according to the distance between the electrodes. The number of separators can be selected according to the number of gaps between the electrodes.

[0112] A nonwoven fabric is a mat of intertwined fibers, primarily composed of fibers. For example, 60% or more by mass of the nonwoven fabric is made of fibers. Examples of fibers that can be used include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (e.g., polyethylene terephthalate fibers), pulp fibers, and the like. Among these, glass fibers are preferred. The nonwoven fabric may also contain components other than fibers, such as acid-resistant inorganic powders and polymers as binders.

[0113] On the other hand, a microporous membrane is a porous sheet mainly composed of components other than fiber components, and can be obtained, for example, by extruding a composition containing a pore-forming agent (such as a polymer powder and / or oil) into a sheet, and then removing the pore-forming agent to form pores. Microporous membranes are preferably made of acid-resistant materials, and are preferably composed mainly of polymer components. The polymer component is preferably polyolefin (such as polyethylene or polypropylene).

[0114] The separator may be made of, for example, only a nonwoven fabric or only a microporous membrane. Furthermore, the separator may be a laminate of a nonwoven fabric and a microporous membrane, a laminate of different or the same materials, or a laminate of different or the same materials with recesses and protrusions interlocked, as needed.

[0115] The separator may be sheet-shaped or bag-shaped. A single sheet-shaped separator may be sandwiched between the positive electrode plate and the negative electrode plate. Alternatively, the electrode plates may be sandwiched between a single folded sheet-shaped separator. In this case, a positive electrode plate sandwiched between folded sheet-shaped separators may be stacked on top of a negative electrode plate sandwiched between folded sheet-shaped separators, or one of the positive electrode plate and the negative electrode plate may be sandwiched between folded sheet-shaped separators and stacked on top of the other electrode plate. Alternatively, a sheet-shaped separator may be folded into an accordion shape, and the positive electrode plate and the negative electrode plate may be sandwiched between the accordion-shaped separators so that the separator is interposed between them. When the separator is arranged so that the folded portion is aligned with the vertical direction of the lead-acid battery, the positive electrode plate can be accommodated in the recess on one main surface side, and the negative electrode plate can be accommodated in the recess on the other main surface side (that is, a single separator can be interposed between adjacent positive and negative electrode plates). When a pouch-shaped separator is used, the pouch-shaped separator may accommodate either the positive electrode plate or the negative electrode plate.

[0116] In this specification, the up-down direction of the electrode plate means the up-down direction (vertical direction) when the electrode plate is placed in a lead-acid battery installed in a normal state of use.

[0117] (Electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, which may be gelled as necessary. The electrolyte may contain at least one selected from the group consisting of cations (e.g., metal cations) and anions (e.g., anions other than sulfate anions (e.g., phosphate ions)). Examples of metal cations include at least one selected from the group consisting of sodium ions, lithium ions, magnesium ions, and aluminum ions.

[0118] The specific gravity of the electrolyte at 20°C may be, for example, 1.20 or more, 1.25 or more, 1.28 or more, or 1.29 or more. The specific gravity of the electrolyte at 20°C may be 1.35 or less, 1.32 or less, or 1.31 or less. These lower and upper limits can be combined arbitrarily. For example, the specific gravity may be 1.28 or more and 1.32 or less, or 1.29 or more and 1.31 or less. These specific gravities of the electrolyte are those of the electrolyte at 20°C in a fully charged battery.

[0119] Increasing the specific gravity of the electrolyte can increase the discharge capacity of a lead-acid battery. In this respect, the specific gravity of the electrolyte is preferably 1.28 or more, and may be 1.29 or more. On the other hand, if the specific gravity of the electrolyte is too high, the positive electrode current collector tends to be easily corroded. In this respect, the specific gravity of the electrolyte is preferably 1.32 or less, and may be 1.31 or less.

[0120] By increasing the specific gravity of the electrolyte, it is possible to increase the capacity of a lead-acid battery. However, increasing the specific gravity of the electrolyte makes the positive electrode current collector more susceptible to corrosion. Therefore, it has been difficult to achieve both high capacity and high cycle life performance by increasing the specific gravity of the electrolyte. However, the lead-acid battery of this embodiment makes it possible to achieve both.

[0121] A lead-acid battery can be obtained by a manufacturing method including a step of assembling a lead-acid battery by placing a positive electrode plate, a negative electrode plate, and an electrolyte in a battery case. In the step of assembling a lead-acid battery, a separator is usually disposed between the positive electrode plate and the negative electrode plate. The step of assembling a lead-acid battery may include a step of chemically converting at least one of the positive electrode plate and the negative electrode plate, if necessary, after the step of placing the positive electrode plate, the negative electrode plate, and the electrolyte in the battery case. The positive electrode plate, the negative electrode plate, the electrolyte, and the separator are each prepared before being placed in the battery case.

[0122] As an example of a lead-acid battery according to one embodiment of the present invention, a lead-acid battery 1 is shown in Fig. 3. Fig. 3 is a perspective view schematically showing an example of the lead-acid battery 1 with the cover removed. The lead-acid battery 1 in Fig. 3 is a clad type lead-acid battery. Fig. 4A is a front view of the lead-acid battery in Fig. 3. Fig. 4B is a schematic cross-sectional view of the cross section taken along line IVB-IVB in Fig. 4A as viewed from the direction of the arrows.

[0123] The lead-acid battery 1 includes a battery case 10 that contains an electrode plate pack 11 and an electrolyte 12. The electrode plate pack 11 is formed by stacking a plurality of negative electrode plates 2 and clad positive electrode plates 3 with separators 4 interposed therebetween. Here, the state in which the sheet-like separator 4 is sandwiched between the negative electrode plates 2 and the positive electrode plates 3 is shown, but the shape of the separator is not particularly limited.

[0124] An upwardly protruding current collecting lug (not shown) is provided on the top of each of the multiple negative electrode plates 2. An upwardly protruding current collecting lug (not shown) is also provided on the top of each of the multiple positive electrode plates 3. The lugs of the negative electrode plates 2 are connected and integrated by a negative electrode strap 5a. Similarly, the lugs of the positive electrode plates 3 are connected and integrated by a positive electrode strap 5b. The lower end of a negative electrode pole 6a is fixed to the upper part of the negative electrode strap 5a, and the lower end of a positive electrode pole 6b is fixed to the upper part of the positive electrode strap 5b.

[0125] FIG. 5 is a schematic top view of a clad-type positive electrode plate 3. FIG. 6 is a schematic cross-sectional view of the cross section taken along line VI-VI in FIG. 5, viewed from the direction of the arrows. The positive electrode plate 3 includes multiple porous tubes 31, metal cores (positive electrode current collectors) 32 housed within the tubes 31, a positive electrode material 33 housed within the tubes 31, and a current collector 34 connecting the multiple metal cores 32. Each tube 31 houses one metal core 32, and the multiple metal cores 32 are aligned in a row, with one longitudinal end connected by the current collector 34. The multiple tubes 31, with the metal cores 32 housed within them, are aligned in a row perpendicular to the longitudinal direction of the tubes 31 (or, from another perspective, along the longitudinal direction of the current collector 34). The current collector 34 and one end of each of the multiple tubes 31 facing the current collector 34 are covered by an upper connecting seat 35. The opening of the tube 31 on the collector 34 side is sealed by one end of the core 32 on the collector 34 side and an upper connecting seat 35. A lug 34a for collecting current from the positive electrode plate 3 is formed at one longitudinal end of the collector 34. The lug 34a protrudes outward from the upper connecting seat 35. The other longitudinal ends of the multiple tubes 31 are connected by a lower connecting seat 36. The opening on the other end side of each tube 31 is sealed by the lower connecting seat 36.

[0126] A lead-acid battery according to one aspect of the present invention will be summarized below.

[0127] (1) A lead-acid battery comprising: a negative electrode plate including a negative electrode material, an electrolyte, a positive electrode plate including a positive electrode collector and a positive electrode material arranged around the positive electrode collector, wherein the positive electrode collector has a metal structure including a plurality of dendrite arms, and the average spacing between the plurality of dendrite arms is 20 μm or less. The average spacing between the plurality of dendrite arms may be 13 μm or less or 6 μm or less, or may be 1 μm or more or 3 μm or more.

[0128] (2) In the lead-acid battery of (1), the positive electrode current collector may be made of an alloy containing Pb and Sb, and the Sb content in the alloy may be 3.5% by mass or more and 10% by mass or less. The Sb content in the positive electrode current collector may be 5% by mass or more and 8% by mass or less.

[0129] (3) In the lead-acid battery of (1) or (2), the specific gravity of the electrolyte at 20° C. may be 1.29 or more and 1.32 or less.

[0130] (4) In the lead-acid battery of any one of (1) to (3), the positive electrode plate may be a clad type positive electrode plate. In this case, the positive electrode current collector may include a metal core, and the diameter of the metal core may be 2.4 mm or more and less than 3.6 mm. The diameter of the metal core may be 2.7 mm or more and 3.3 mm or less.

[0131] (5) In the lead-acid battery according to any one of (1) to (4), the negative electrode material may contain a polymer compound, and the polymer compound may have a specific surface area measured using deuterated chloroform as a solvent. １ The chemical shift of the H-NMR spectrum may have a peak in the range of 3.2 ppm to 3.8 ppm.

[0132] (6) In the lead-acid battery according to any one of (1) to (5), the negative electrode material may contain a polymer compound, and the polymer compound may be oxy-C ２－４ It may contain alkylene units as a repeating structure.

[0133] (7) In the lead-acid battery described in (6) above, the polymer compound is the oxy C ２－４(8) In the lead-acid battery according to any one of (1) to (7), the polymer compound may include at least one selected from the group consisting of a hydroxy compound containing the repeating structure of alkylene units, an etherified product of the hydroxy compound, and an esterified product of the hydroxy compound. (9) In the lead-acid battery according to any one of (1) to (7), the polymer compound may include at least one selected from the group consisting of polypropylene glycol, polyoxyethylene oleate, polyethylene glycol dilaurate, polyethylene glycol distearate, and polyethylene glycol dioleate.

[0134] EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0135] (Experimental Example 1) In Experimental Example 1, six types of lead-acid batteries (lead-acid batteries A1 to A4, CA1, and CA2) were fabricated using positive electrode current collectors with different DAS, and their characteristics were measured. The six types of lead-acid batteries were fabricated using the following method. {Lead-acid battery A1} (a) Fabrication of negative electrode plate: Lead powder, barium sulfate, carbon black, and an organic shrinkage preventer (sodium lignin sulfonate) were mixed with an appropriate amount of aqueous sulfuric acid solution to obtain a negative electrode paste. The components were mixed so that the barium sulfate content, carbon black content, and organic shrinkage preventer content in the negative electrode material were 1.5% by mass, 0.3% by mass, and 0.1% by mass, respectively. The negative electrode paste was filled into the mesh portion of a cast grid made of a Pb—Sb alloy, which served as a negative electrode current collector, and then aged and dried to obtain an unformed negative electrode plate.

[0136] (b) Fabrication of Positive Electrode Plate First, a positive electrode current collector, which is an integrated assembly of multiple cores and current collectors connecting the cores, is fabricated by casting. The positive electrode current collector includes 15 cores. One end of each core is integrated with the current collector. The current collector includes a lug. The material of the positive electrode current collector is a Pb—Sb alloy with an Sb content of 5% by mass. The cores have a round rod shape with a diameter of 3 mm. The positive electrode current collector is fabricated by melting the material under atmospheric pressure, pouring it into a mold, and cooling it. The DAS of the positive electrode current collector is controlled by adjusting the cooling rate (this also applies to the following experimental examples). Furthermore, a positive electrode current collector for DAS measurement is fabricated under the same conditions as the positive electrode current collector used in the fabrication of lead-acid batteries. The DAS of the cores (positive electrode current collector) of this measurement positive electrode current collector is measured using the method described above (this also applies to the following experimental examples). Specifically, in measuring the DAS, the core metal is divided into multiple equal regions (specifically, 10 equal regions) so that the regions have approximately equal volumes, and the DAS is measured for each region. The arithmetic mean of the DAS values ​​obtained for each of the 10 regions is taken as the DAS for the entire positive electrode current collector (the value D1 described above). The DAS shown below is the DAS value for the entire positive electrode current collector.

[0137] Next, the multiple cores of the positive electrode current collector are housed in multiple tubes. The current collectors and the longitudinal ends of the tubes on the current collector side are covered with resin so that the tabs are exposed, forming upper resin connecting seats. The tubes are porous tubes made of glass fiber.

[0138] A positive electrode slurry is prepared by kneading lead powder (containing 80% by mass of lead oxide and 20% by mass of metallic lead), red lead, water, and dilute sulfuric acid. This positive electrode slurry is filled into the opening at the other end of the tube in the longitudinal direction. The mass ratio of lead powder to red lead is 8:2. Next, the opening at the other end of the tube is sealed with a lower connecting member and dried. In this manner, an unformed clad positive electrode plate is produced.

[0139] (c) Preparation of Test Battery A liquid-type battery with a rated voltage of 2 V and a rated 5-hour rate capacity of 165 Ah was prepared. The electrode plate assembly of the test battery consisted of three positive electrodes sandwiched between four negative electrodes. The positive and negative electrodes were stacked with a polyethylene separator between them to form an electrode plate assembly. The electrode plate assembly was placed in a synthetic resin battery case together with an electrolyte (aqueous sulfuric acid solution). The battery case was then covered with a lid and subjected to chemical formation within the battery case to prepare a liquid-type lead-acid battery A1. The specific gravity of the electrolyte after chemical formation at 20°C was 1.32. The battery height was 426 mm (height from the bottom of the battery case to the liquid level: 338 mm), and the volume of the electrolyte was 1,700 mL.

[0140] {Lead-acid batteries A2 to A4, CA1, CA2} Five types of positive current collecting members having the same shape as the positive current collecting member of lead-acid battery A1 were fabricated by changing the manufacturing conditions of the positive current collecting member. Specifically, the positive current collecting members were fabricated by changing the cooling rate during casting of the positive current collecting members. Furthermore, positive current collecting members for DAS measurement were fabricated under the same conditions as the positive current collecting members used in the fabrication of lead-acid batteries. The DAS of the core metals (positive current collectors) of these measurement positive current collecting members was measured using the method described above.

[0141] Next, lead-acid batteries A2 to A4, CA1, and CA2 are fabricated in the same manner as the lead-acid battery A1, except that the above-mentioned positive electrode current collecting member is used.

[0142] [Evaluation of Battery Characteristics] The batteries prepared in Experimental Examples 1 to 4 were evaluated by the following method.

[0143] (i) Charge-Discharge Cycle Test First, a fully charged battery is prepared, and a charge-discharge cycle test is performed on the battery in a water tank at 15°C ± 2°C, in which the battery is repeatedly discharged and charged. Discharge and charge are performed under the following conditions. Discharge: Discharge for 3 hours at a current of 0.25 C (A). Here, C is the value of the rated capacity when the rated capacity is expressed in units of ampere-hours (Ah) (this also applies to the following tests). Charging: Charge an amount of electricity that is 120% of the discharged amount of electricity at a current of 0.18 C (A).

[0144] Before the start of the charge-discharge cycle test and after every 100 charge-discharge cycles, the following (ii) capacity test and (iii) high-rate discharge performance test were conducted. After each test, the battery was fully charged. The life cycle performance was also determined by the following method (iv).

[0145] (ii) Capacity Test The capacity test is performed by placing the battery in a water tank at 30±2°C. The battery is discharged at a current of 0.2 C (A) until the final voltage reaches 1.7 V, and the discharged quantity of electricity (discharge capacity) is measured.

[0146] (iii) High-rate discharge performance test The high-rate discharge performance test is performed by placing the battery in a water tank at 30±2°C. Discharge is performed under conditions of a discharge current of 1.0 C (A) and an end voltage of 1.4 (V), and the discharge duration is measured.

[0147] (iv) Determination of life cycle performance The number of cycles when the battery to be evaluated satisfies at least one of the following conditions (a) and (b) is determined to be the life cycle number of the battery. The larger the number of life cycles, the better the characteristics of the lead-acid battery. (a) In the charge / discharge cycle test in (i) above, the end-of-discharge voltage is below 1.5 V. (b) In the capacity test in (ii) above, the measured capacity is below 80% of the capacity before the start of the charge / discharge cycles (initial capacity).

[0148] (v) Capacity Retention Ratio The capacity retention ratio was calculated using the following formula: Capacity Retention Ratio (%) = 100 × X(600) / X(0), where X(600) is the discharge capacity after 600 cycles in the charge-discharge cycle test in (i) above, and X(0) is the discharge capacity before the start of the charge-discharge cycle test. The discharge capacity is the value of the discharge capacity measured in the capacity test in (ii) above.

[0149] The DAS and evaluation results of the positive electrode current collector of the above battery are shown in Table 2. The life cycle numbers (relative values) shown in Table 2 are relative values ​​when the life cycle number of lead acid battery A4 is set to 100.

[0150]

[0151] The results of Table 2 are shown in the graph of Figure 7. As shown in Figure 7, when the DAS is 20 μm or less, the life cycle performance is significantly improved. The smaller the DAS, the better the life cycle performance.

[0152] Furthermore, the high-rate discharge performance of the lead-acid batteries A1, A4, and CA1 was evaluated initially and after charge-discharge cycles using the method described above. The evaluation results are shown in Figure 8. The data shown in Figure 8 are values ​​when the initial high-rate discharge capacity is taken as 100%. As shown in Figure 8, by setting the DAS to 20 μm or less, good high-rate discharge performance can be achieved even after 600 cycles.

[0153] (Experimental Example 2) In Experimental Example 2, 12 types of lead-acid batteries were fabricated in the same manner as lead-acid battery A1, except that the material of the positive current collecting member and the casting conditions during manufacturing were changed. The Sb content of the material of the positive current collecting member was set to the amount shown in Figure 9. Furthermore, a positive current collecting member for DAS measurement was fabricated under the same conditions as the positive current collecting member used in the fabrication of the lead-acid battery. The DAS of the core metal (positive current collector) of this measurement positive current collecting member was measured using the method described above.

[0154] The capacity retention rates of 12 types of lead-acid batteries were measured using the method described above. The capacity retention rates and DAS of these lead-acid batteries are shown in Figure 9. The higher the capacity retention rate, the better the characteristics of the lead-acid battery. As shown in Figure 9, when the DAS is 20 μm or less, a high capacity retention rate can be achieved even when the Sb content is changed.

[0155] (Experimental Example 3) In Experimental Example 3, 15 types of lead-acid batteries were fabricated using the same method as lead-acid battery A1, except that the specific gravity of the electrolyte and the casting conditions during the production of the positive current collector were changed. The specific gravity of the electrolyte (sulfuric acid aqueous solution) was changed by changing the concentration of the sulfuric acid aqueous solution. The positive current collector was fabricated using a 5% by mass Pb—Sb alloy, similar to the positive current collector of lead-acid battery A1. The casting conditions for the positive current collector were changed similarly to Experimental Example 1. The DAS of the core metal of the positive current collector fabricated in Experimental Example 3 was 3 μm, 20 μm, and 35 μm.

[0156] The life cycle performance of 15 types of lead-acid batteries was evaluated using the method described above. The relationship between the specific gravity and DAS of the electrolyte and the life cycle performance of these batteries is shown in Figure 10 . As described above, the specific gravity of the electrolyte is the specific gravity of the electrolyte at 20°C in a fully charged lead-acid battery. The life cycle performance on the vertical axis of the graph in Figure 10 indicates the relative value of the number of life cycles of each battery, with the number of life cycles of a battery with an electrolyte specific gravity of 1.28 and a DAS of 20 μm set to 100.

[0157] As shown in Figure 10, when the DAS is 20 μm or less, high life cycle performance can be achieved. In particular, when the DAS is 35 μm, the life cycle performance is significantly reduced when the specific gravity of the electrolyte is 1.29 or more. However, when the DAS is 20 μm or less, the reduction in life cycle performance is small even when the specific gravity of the electrolyte is 1.29 or more (specifically, 1.29 or more and 1.32 or less).

[0158] (Experimental Example 4) In Experimental Example 4, ten types of lead-acid batteries were fabricated in the same manner as the lead-acid battery A1 in Experimental Example 1, except that the size of the core metal of the positive current collector and the casting conditions for the positive current collector were changed. In Experimental Example 4, the diameter of the core metal was set to the diameter shown in FIG. 11 . Furthermore, the cooling conditions during casting of the positive current collector were changed to set the DAS to 3 μm or 20 μm. Furthermore, the specific gravity of the electrolyte was set to 1.32.

[0159] The capacity retention rates of the ten types of lead-acid batteries thus fabricated were measured by the method described above. The relationship between the diameter of the core bar, the DAS, and the capacity retention rates of the lead-acid batteries is shown in FIG.

[0160] As shown in Fig. 11, when the DAS is 20 µm or less, a high capacity retention rate is achieved. Furthermore, when the DAS is 20 µm or less and the diameter of the core is 2.4 mm or more and less than 3.6 mm (e.g., 2.4 mm or more and 3.3 mm or less), an even higher capacity retention rate is achieved. Furthermore, when the DAS is 20 µm or less and the diameter of the core is 2.7 mm or more and 3.3 mm or less, an especially high capacity retention rate is achieved.

[0161] [Evaluation of Battery Characteristics] The batteries fabricated in Experimental Examples 5 to 7 were evaluated by the following method.

[0162] (I) Charge-discharge cycle test A charge-discharge cycle test is carried out under the same conditions as the charge-discharge cycle test in (i) above, except that the temperature of the water tank in which the battery is placed is set to 75°C ± 2°C and that the amount of electricity charged during charging is 130% of the amount of electricity discharged.

[0163] Before the start of the charge-discharge cycle test and after every 100 charge-discharge cycles, the following (II) capacity test and (III) low-temperature high-rate discharge performance test were conducted. After each test, the battery was fully charged. The life cycle performance was also evaluated by the following method (IV).

[0164] (II) Capacity Test The capacity test is carried out under the same conditions as the capacity test in (ii) above.

[0165] (III) Low-temperature high-rate discharge performance test The low-temperature high-rate discharge performance test is performed by placing the battery in a water tank at -15±2°C. Discharge is performed under the conditions of a discharge current of 1.0 C (A) and an end voltage of 1.0 (V), and the discharge duration is measured.

[0166] (IV) Judgment of life cycle performance The life cycle performance (number of life cycles) is evaluated using the same criteria as for the judgment of life cycle performance in (iv) above.

[0167] (Experimental Example 5) In Experimental Example 5, a lead-acid battery was fabricated by adding a polymer compound (P) to the negative electrode material. Specifically, 10 types of lead-acid batteries (batteries E1 to E10) were fabricated under the same conditions and methods as for lead-acid battery A2 in Experimental Example 1, except that the amount of polymer compound (P) added to the negative electrode material was varied. Specifically, the DAS of the positive electrode current collector of these batteries was 6 μm. Polypropylene glycol (PPG) was used as the polymer compound (P). The life cycle performance of the fabricated lead-acid batteries and battery A2 was evaluated using the method described above in (IV). The evaluation results are shown in Table 3. In Table 3, the PPG content is the proportion (by mass) of polypropylene glycol in the negative electrode material. The life cycle performance in Table 3 is the relative value of the number of life cycles of each battery, with the number of life cycles of battery A2 being 100. A higher value indicates better life cycle performance.

[0168]

[0169] As shown in Table 3, the content of PPG (polymer compound (P)) is preferably in the range of 30 ppm to 500 ppm, and more preferably in the range of 50 to 400 ppm.

[0170] (Experimental Example 6) In Experimental Example 6, lead-acid batteries were fabricated by adding a polymer compound (P) to the negative electrode material. Specifically, 10 types of lead-acid batteries (batteries F1 to F5) were fabricated in the same manner as lead-acid battery A2 in Experimental Example 1, except that the type of polymer compound (P) added to the negative electrode material was varied. The content of the polymer compound (P) in the negative electrode material was 300 ppm (by mass). The polymer compounds (P) used are listed in Table 4. The results of the evaluation of the life cycle performance of the fabricated batteries (see above, section (IV)) are shown in Table 4. The relative values ​​in Table 4 are the relative values ​​of the life cycle number of each battery when the life cycle number of battery A2 is set to 100.

[0171]

[0172] The larger the relative value in Table 4, the more excellent the cycle performance. As shown in Table 4, even when the type of polymer compound (P) is changed, the cycle performance can be significantly improved compared to when no polymer compound (P) is used.

[0173] Furthermore, the amount of electrolyte lost by each charge / discharge cycle was measured for the above batteries. Table 5 shows the amount of electrolyte lost by 100 cycles of the charge / discharge cycle test (I) above. The relative values ​​in Table 5 are the relative values ​​of the amount of electrolyte lost (by mass) for each battery, when the amount of electrolyte lost (by mass) for Battery A2 is set to 100.

[0174]

[0175] The lower the reduction amount (relative value) of the electrolyte in Table 5, the better. As shown in Table 5, the reduction of the electrolyte can be suppressed by adding a polymer compound (P) to the negative electrode material. ２－４ In the batteries F2 to F5 using an esterified alkylene glycol, the decrease in the electrolyte can be particularly suppressed.

[0176] Experimental Example 7 In Experimental Example 7, lead-acid batteries were fabricated by adding a polymer compound (P) to the negative electrode material. Specifically, batteries G1 and CG1 were fabricated under the same conditions and by the same method as the lead-acid batteries A2 and CA1 of Experimental Example 1, except that the polymer compound (P) was added to the negative electrode material. That is, the DAS of the positive electrode current collector of battery G1 was 6 μm, and the DAS of the positive electrode current collector of battery CG1 was 35 μm. Polypropylene glycol was used as the polymer compound (P). The content of the polymer compound (P) in the negative electrode material was 300 ppm (by mass). The fabricated batteries G1 and CG1, and batteries A2 and CA1 were subjected to the above-described (I) charge-discharge cycle test and (II) capacity test. The results of the capacity test are shown in Table 6.

[0177]

[0178] The discharge capacity (%) in Table 6 is a relative value when the discharge capacity before the start of the charge-discharge cycle test for each battery is set to 100%. Note that when the discharge capacity reaches about 80% of the initial capacity, it is determined that the battery has reached the end of its life, and no further charge-discharge cycles are performed. As shown in Table 6, when the DAS is 20 μm or less, the effect of adding the polymer compound (P) is significant.

[0179] The above-mentioned batteries G1 and CG1, and batteries A2 and CA1 were subjected to 300 charge-discharge cycles, and then the above-mentioned (III) low-temperature high-rate discharge performance test was conducted. The test results are shown in Table 7. The low-temperature high-rate discharge capacities in Table 7 are relative values ​​when the low-temperature high-rate discharge capacity of battery CA1 is set to 100%.

[0180]

[0181] As shown in Table 7, by adding the polymer compound (P) to the negative electrode material, the low-temperature high-rate discharge performance after charge-discharge cycles can be improved.

[0182] The present invention can be used in lead-acid batteries.

[0183] 1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 10: Battery case 11: Plate group 12: Electrolyte 31: Tube 32: Core (positive electrode current collector) 33: Positive electrode material

Claims

1. a negative plate including a negative electrode material; An electrolyte; a positive electrode plate including a positive electrode current collector and a positive electrode material disposed around the positive electrode current collector; the positive electrode current collector includes a metal structure including a plurality of dendrite arms; A lead-acid battery, wherein the average spacing between the plurality of dendrite arms is 20 μm or less.

2. 2. The lead-acid battery according to claim 1, wherein an average spacing between the plurality of dendrite arms is 1 μm or more.

3. The lead-acid battery according to any one of claims 1 to 2, wherein an average spacing between the plurality of dendrite arms is 3 µm or more and 13 µm or less.

4. The lead acid battery according to any one of claims 1 to 3, wherein an average spacing between the plurality of dendrite arms is 6 µm or less.

5. the positive electrode current collector is made of an alloy containing Pb and Sb, The lead acid battery according to any one of claims 1 to 4, wherein the Sb content in the alloy is 3.5% by mass or more and 10% by mass or less.

6. 6. The lead acid battery according to claim 5, wherein the content of Sb in the alloy is 5% by mass or more and 8% by mass or less.

7. The lead acid battery according to any one of claims 1 to 6, wherein the specific gravity of the electrolyte at 20 ° C. is 1.29 or more and 1.32 or less.

8. The positive electrode plate is a clad type positive electrode plate, The positive electrode current collector includes a core metal, The lead-acid battery according to any one of claims 1 to 7, wherein the diameter of the core metal is 2.4 mm or more and less than 3.6 mm.

9. 9. The lead-acid battery according to claim 8, wherein the diameter of the core is 2.7 mm or more and 3.3 mm or less.

10. The negative electrode material includes a polymer compound, The polymer compound is measured using deuterated chloroform as a solvent. １ The lead acid battery according to any one of claims 1 to 9, having a peak in the range of 3.2 ppm to 3.8 ppm in terms of chemical shift in H-NMR spectrum.

11. The negative electrode material includes a polymer compound, The polymer compound is oxyC ２－４ The lead acid battery according to any one of claims 1 to 10, comprising an alkylene unit as a repeating structure.

12. The polymer compound is ２－４ The lead acid battery according to claim 11, comprising at least one selected from the group consisting of a hydroxy compound containing the repeating structure of an alkylene unit, an etherified product of the hydroxy compound, and an esterified product of the hydroxy compound.

13. The lead-acid battery according to any one of claims 10 to 12, wherein the polymer compound is one or more selected from polypropylene glycol, polyoxyethylene oleate, polyethylene glycol dilaurate, polyethylene glycol distearate, and polyethylene glycol dioleate.