lead-acid batteries

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

Technical Field

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

Background Art

[0002] Lead-acid batteries are used in various applications, including in-vehicle 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. When the charge-discharge cycle is repeated, corrosion of the positive electrode current collector occurs. When the positive electrode current collector is severely corroded, characteristics such as life cycle performance deteriorate.

[0003] Patent Document 1 (Japanese Patent Laid-Open No. 57-061262) discloses "a lead-acid battery characterized in that, in the crystal grains of the finally determined metal structure obtained by casting and subsequent processing and heat treatment of lead or a lead alloy containing no antimony or a small amount of antimony used as an anode grid material, the maximum length in the direction perpendicular to the surface of the lead grid body is 1 / 2 or less of the size of the lead grid body, and the minimum length in the direction parallel to the grid surface of the microcrystals constituting the crystal grains is 1 / 3 or more of the maximum length of the crystal grains in the same direction."

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

[0005] Patent Document 3 (Japanese Patent Laid-Open No. 52-5425) discloses "a lead-acid battery using a lead alloy grid in which a spherical solid solution phase of antimony is uniformly dispersed in a solid solution phase of lead and containing 5% or less of antimony."

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

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

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

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

[0010] [Figure 1A] This is a schematic diagram illustrating an example of a dendrite arm. [Figure 1B] This is a schematic diagram illustrating the method for calculating DAS. [Figure 2A] This is a metallurgical microscope image showing an example of the metallic structure of a positive electrode current collector. [Figure 2B] This is a metallurgical microscope image showing another example of the metallic structure of a positive electrode current collector. [Figure 2C] This graph shows an example of the relationship between the DAS (Diagnosis Analysis System) of the positive electrode current collector and the amount of corrosion. [Figure 3] This is a schematic perspective view showing an example of a lead-acid battery according to one embodiment of the present invention, with the cover removed. [Figure 4A]Figure 3 is a front view of the lead-acid battery. [Figure 4B] Figure 4A is a schematic cross-sectional view of the cross-section along the IVB-IVB line, viewed from the direction of the arrow. [Figure 5] This is a schematic top view showing an example of a clad-type positive electrode plate according to one embodiment of the present invention. [Figure 6] Figure 5 is a schematic cross-sectional view of the cross-section along the line VI-VI, as seen from the direction of the arrow. [Figure 7] This graph shows an example of the results from Experimental Example 1. [Figure 8] This graph shows another example of the results from Experiment Example 1. [Figure 9] This graph shows an example of the results from Experiment Example 2. [Figure 10] This graph shows an example of the results from Experimental Example 3. [Figure 11] This graph shows an example of the results from Experimental Example 4. [Modes for carrying out the invention]

[0011] The following describes embodiments of the present invention with examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of 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, an electrolyte, and a positive electrode plate containing a positive electrode current collector and a positive electrode material arranged around the positive electrode current collector. The positive electrode current collector includes a metallic 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. Furthermore, the metallic structure in which DAS is 20 μm or less may be referred to as "metallic structure (M)" below.

[0013] The metallic structure containing dendrite arms includes the parts that make up the dendrite arms and the parts that exist between the dendrite arms. As a result of their investigation, the inventors of the present invention have newly discovered that corrosion of the positive electrode current collector progresses more easily when the DAS is large. The present invention is based on this new finding.

[0014] DAS (Dynamic Action Set) can be altered, for example, by controlling the cooling rate of the metal material (the material for the positive electrode current collector) poured into the mold during the casting process. For instance, increasing the cooling rate can reduce DAS. Adding sulfur (S) or selenium (Se) to the metal material that forms the positive electrode current collector can also reduce DAS. Furthermore, increasing the pressure during casting can also reduce DAS.

[0015] At least a portion of the positive electrode current collector, which is surrounded by positive electrode material, is composed of a metallic structure (M). By having at least a portion composed of a metallic structure (M), corrosion of that 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 composed of a metallic structure (M), or only a part of the positive electrode current collector may be composed of a metallic structure (M). For example, at least a portion of the surface of the positive electrode current collector may be composed of a metallic structure (M). For example, in the case of a positive electrode current collector used in a clad-type positive electrode plate, the core metal may contain a metallic structure (M). At least a portion of the core metal (for example, at least a portion of the surface) may be composed of a metallic structure (M). 50% or more, 70% or more, or 90% or more of the core metal may be composed of a metallic structure (M). 50% or more, 70% or more, or 90% or more of the surface area of ​​the core metal may be composed of a metallic structure (M). Alternatively, the entire core metal may be composed of a metallic structure (M).

[0017] The proportion of metallic structure (M) in the positive electrode current collector can be measured (determined) using the following method. First, the positive electrode current collector is divided into 10 equal regions, each with approximately equal volume. Then, one location is arbitrarily selected within each region, and the DAS is measured at that cross-section using the method described later. The proportion of regions where the DAS is 20 μm or less is then determined. This proportion can be considered as the proportion of metallic structure (M) in the positive electrode current collector. Furthermore, the arithmetic mean of the DAS values ​​obtained for each of the 10 regions can be used as a single DAS value D1. This 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 value of the DAS of the entire positive electrode current collector (the value D1 described above) may be within the range exemplified here as the value of the DAS of the metal structure (M).

[0019] The metal structure (M) contains dendrites (tree-like crystals). Dendrites generally consist of primary and secondary dendrite arms. An example of such dendrite arms is schematically shown in Figure 1A. For ease of understanding, the primary dendrite arm Da1 and the secondary dendrite arm Da2 are hatched in Figure 1A.

[0020] The dendrite DR shown in Figure 1A includes a primary dendrite arm Da1 and a group of secondary dendrite arms. The group of secondary dendrite arms consists 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. Figure 1A shows the arm spacing Wda2 between two adjacent secondary dendrite arms. The DAS can be determined by performing the following measurements on multiple groups of secondary dendrite arms. In this specification, the DAS relating 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] (DAS measurement) The DAS is measured using the following method. The following explanation describes the case where the positive electrode current collector includes a core metal, but the same method can be used to measure positive electrode current collectors that do not include a core metal.

[0022] First, the mandrel is immersed in a resin such as epoxy resin to harden the resin. Next, the mandrel is cut along with the hardened resin to expose the mandrel's cross-section. Subsequently, the cross-section is polished, and the metal structure is revealed by etching. 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 are arbitrarily selected where at least three or more dendrite arms are aligned (secondary dendrite arm groups). Then, the distance L from one end to the other of the selected secondary dendrite arm groups is measured. A diagram illustrating the measurement is shown in Figure 1B.

[0023] Figure 1B shows a partial example of a group of (n-1) secondary dendrite arms Da2 aligned to form a single group of secondary dendrite arms. In the DAS measurement, a straight line S intersecting the (n-1) secondary dendrite arms is drawn on the image, as shown in Figure 1B. 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 substantially perpendicular to the direction in which each of the secondary dendrite arms extends. In Figure 1B, the intersection points of the straight line S and the boundaries of the secondary dendrite arms are numbered from 1 to n. The distance L between the two intersection points at each end of the intersection points between the boundaries of the aligned (n-1) secondary dendrite arms and the straight line S is measured.

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

[0025] The average spacing of secondary dendrite arms in the i-th secondary dendrite arm group is L i / (n i It can be calculated using (-1). Therefore, when measuring m secondary dendrite arm groups, the DAS can be calculated using the following equation (1). To calculate the DAS when measuring 5 secondary dendrite arm groups, simply replace m with 5 in equation (1).

[0026]

number

[0027] Table 1 shows an example of the relationship between the cooling rate and DAS during casting of a positive electrode current collector. The cooling rate in Table 1 is determined by measuring the temperature drop per unit time when the material of the positive electrode current collector, which is in a molten state (liquid phase single phase), is cooled. [Table 1]

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

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

[0030] In a lead-acid battery according to one embodiment of the present invention, the negative electrode plate, electrolyte, and positive electrode plate are arranged inside the 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 liquid-type (vented) lead-acid battery. The lead-acid battery according to one embodiment of the present invention can be used for any application, for example, as a battery for electric vehicles (such as forklifts) or as a battery for other vehicles (such as automobiles and motorcycles).

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

[0032] A fully charged lead-acid battery refers to a lead-acid battery that has been fully charged after chemical formation. Full charging of a lead-acid battery can be done immediately after chemical formation or some time after formation (for example, a lead-acid battery that has been chemically formed and is in use (preferably in the early stages of use) may be fully charged). An early-stage battery refers to a battery that has not been in use for very long and has hardly deteriorated.

[0033] The following describes a lead-acid battery according to one embodiment of the present invention, broken down by its main constituent elements.

[0034] (Positive plate) The positive electrode plates of lead-acid batteries can be classified into paste type, clad type, and others. A paste-type positive electrode plate comprises a positive electrode current collector and a positive electrode material. The positive electrode material is held by the positive electrode current collector. 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, or it may be formed by casting a 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 core inserted into each tube, a current collector connecting the multiple cores, a positive electrode material (including positive electrode active material) filled into each tube and positioned around the cores, and a connecting seat connecting the multiple tubes. In a clad positive electrode plate, the positive electrode material is the material excluding the tubes, cores, current collector, and connecting seat. In descriptions of clad positive electrode plates, the cores and current collectors are sometimes collectively referred to as the positive electrode current collector. The cores function as the positive electrode current collector.

[0036] Positive electrodes may have components such as mats or pasting paper attached to them. Since such components (attached components) are used integrally with the positive electrode plate, they are considered to be included in the positive electrode plate. Furthermore, if the positive electrode plate includes such components, 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 attached components.

[0037] (Positive electrode current collector) The positive electrode current collector is formed using a lead alloy. A Pb-Sb alloy is preferred as the lead alloy used for the positive electrode current collector due to its corrosion resistance and mechanical strength. The positive electrode current collector may have a surface layer. The surface layer and the inner layers of the positive electrode current collector may have different compositions. The surface layer may be formed on a portion of the positive electrode current collector. At least a portion of the surface layer may be composed of a metallic 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 a redox reaction. The positive electrode material may also contain other additives as needed.

[0039] Unformed paste-type positive electrode plates are obtained by placing positive electrode paste around a positive electrode current collector, followed by curing and drying. The positive electrode paste is prepared by kneading lead powder, additives, water, and sulfuric acid. Unformed clad-type positive electrode plates are formed by filling porous tubes, into which core metals connected at the current collector, with lead powder or slurry-like lead powder, and then joining multiple tubes together. Subsequently, positive electrode plates are obtained by forming these unformed positive electrode plates. Formation can be carried out by charging the electrode group, including the unformed positive electrode plates, while immersed in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery. However, formation may also be carried out before the assembly of the lead-acid battery or the electrode group.

[0040] The positive electrode current collector may be made of an alloy containing Pb and Sb. In that case, the Sb content in the positive electrode current collector may be 3.5% by mass or more, 5% by mass or more, 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 also contain trace components other than Pb and Sb. The content of such trace components may be more than 0% by mass and 1% by mass or less (for example, more than 0% by mass and 0.5% by mass or less). Examples of such trace components include As, S, Se, Sn, and Ag.

[0042] As mentioned above, the positive electrode plate may be a clad-type positive electrode plate. In that case, the positive electrode current collector may include a core metal. The core metal is a long, slender rod (for example, a round rod). The diameter of the core metal (the diameter of a round rod-shaped core metal) may be 2.4 mm or more, 2.7 mm or more, and 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] There are no particular limitations on the length of the core wire; it is selected according to the size of the positive electrode plate. The length of the core wire may be, for example, 100 mm or more and 400 mm or less.

[0044] (Method for analyzing the composition of the positive electrode current collector) The quantitative analysis of elements other than lead contained in the positive electrode current collector can be performed according to the lead-separated inductively coupled plasma emission spectroscopy method described in JIS H2105. When analyzing the elemental content of the positive electrode current collector of a positive electrode plate removed from a lead-acid battery, first, the positive electrode plate is vibrated to detach the positive electrode material from the positive electrode current collector, and then the remaining positive electrode material around the positive electrode current collector is removed using a ceramic knife. After that, a portion of the positive electrode current collector with metallic luster is taken 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, and the solution is filtered and the filtrate is collected. The elements in the filtrate are analyzed using a calibration curve method with an inductively coupled plasma (ICP) emission spectrometer (e.g., Shimadzu Corporation, ICPS-8000). From the above analysis results, the elemental content (mass %) 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 contain an organic condensate as an organic shrinkage inhibitor.

[0046] Note that materials such as mats and pasting paper may be attached to the negative electrode plate. Since such materials (attached materials) are used integrally with the negative electrode plate, they are considered to be included in the negative electrode plate. Furthermore, if the negative electrode plate includes attached materials, the negative electrode material is the negative electrode current collector and the attached materials excluding the attached materials. However, if attached materials such as mats are attached to the separator, the thickness of the attached materials is included in the thickness of the separator.

[0047] The negative electrode plate can be formed by applying or filling a negative electrode paste onto a negative electrode current collector, then curing and drying it to produce an uncured negative electrode plate, and subsequently curing the uncured negative electrode plate. The negative electrode paste is prepared by kneading lead powder, an organic shrinkage inhibitor, and various additives as needed, with water and sulfuric acid. During curing, it is preferable to cure the uncured negative electrode plate at a temperature higher than room temperature and at high humidity.

[0048] The chemical conversion can be carried out by immersing the electrode plate group, including the unconverted negative electrode plate, in the sulfuric acid-containing electrolyte in the lead-acid battery case and then charging the electrode plate group. However, the chemical conversion may also be performed before the assembly of the lead-acid battery or the electrode plate group. Spongy lead is produced by the chemical conversion.

[0049] (Negative electrode current collector) The negative electrode current collector may have a frame portion with tabs and a grid portion continuous with the frame portion. The grid portion may have multiple square grids.

[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, which are generally called grids, current collectors with circles or ellipses punched out, and current collectors with grids radiating from the lugs 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 makes it easier to support 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, or a Pb-Ca-Sn alloy. These leads or lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as additive elements. 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 the ear part of the negative electrode current collector. The surface layer of the ear part may contain Sn or an Sn alloy.

[0052] (Negative electrode material) The negative electrode material contains a negative electrode active material (lead or lead sulfate) that exhibits capacitance through an oxidation-reduction reaction. The negative electrode material may contain an anti-shrinkage agent, a carbonaceous material, and / or other additives. Examples of the additives include, but are not limited to, barium sulfate, fibers (such as resin fibers). Note that the negative electrode active material in the charged state is spongy lead, but an unformed negative electrode plate is usually produced using lead powder.

[0053] The negative electrode material may contain a polymer compound. In the following, the polymer compound may be referred to as "polymer compound (P)".

[0054] The first example of the polymer compound (P) is a polymer compound having a peak in the range of 3.2 ppm or more and 3.8 ppm or less in the chemical shift of the 1H-NMR spectrum measured using deuterated chloroform as a solvent. In this specification, 1 the 1H-NMR spectrum is a spectrum measured using deuterated chloroform as a solvent unless otherwise specified. The second example of the polymer compound (P) is oxy-C 1 The 1H-NMR spectrum is a spectrum measured using deuterated chloroform as a solvent unless otherwise specified. The second example of the polymer compound (P) is oxy-C 2-4This is a polymer compound containing a repeating alkylene unit structure. 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) overlap in at least part. A commercially available polymer compound (P) may be used. Alternatively, polymer compound (P) may be synthesized by known methods.

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

[0056] The polymer compound (P) can reduce the amount of overcharged electricity for the following reasons: The polymer compound (P) contains oxy C 2-4 Because it contains repeating structures of alkylene units, it is easy to form a linear structure. Therefore, the polymer compound (P) added to the negative electrode material thinly and broadly covers the surface of the lead in the negative electrode material. When the surface of the lead is covered with the polymer compound (P), the hydrogen overpotential increases, and as a result, the side reaction that generates hydrogen during overcharging becomes less likely to occur. On the other hand, if the amount of polymer compound (P) added is large, a decrease in charge acceptance may occur. In this invention, the polymer compound (P) content is high in the central part of the negative electrode plate where the amount of hydrogen gas generated during overcharging is large. Therefore, it is possible to suppress the amount of polymer compound (P) in the entire negative electrode plate while effectively reducing the amount of overcharged electricity. In other words, according to this invention, high charge acceptance performance and a low amount of overcharged electricity can be achieved.

[0057] (Polymer compounds (P)) Polymer compound (P) is, 1In the chemical shift of the H-NMR spectrum, there is a peak in the range of 3.2 ppm to 3.8 ppm. Such polymer compounds (P) are oxy C 2-4 It has an alkylene unit. Oxy C 2-4 Examples of alkylene units include oxyethylene units, oxypropylene units, oxytrimethylene units, oxy2-methyl-1,3-propylene units, oxy1,4-butylene units, and oxy1,3-butylene units. Polymer compound (P) is such an oxyC 2-4 It may have one type of alkylene unit, or it may have two or more types.

[0058] Polymer compound (P) is oxy C 2-4 Preferably, the repeating structure includes a type of oxy C. 2-4 It may also contain alkylene units, and two or more oxyC 2-4 It may also contain alkylene units. The polymer compound (P) may contain one of the above repeating structures, or it may contain two or more of the above repeating structures.

[0059] Oxy C 2-4 Polymer compounds (P) having a repeating alkylene unit structure include those classified as surfactants (more specifically, nonionic surfactants).

[0060] Examples of polymer compounds (P) include oxy C 2-4 Hydroxyl compounds having a repeating alkylene unit structure (poly C 2-4 Alkylene glycol, oxyC 2-4 Copolymers containing repeating alkylene structures, polyols, polyC 2-4 Examples include alkylene oxide adducts, etherified or esterified versions of these hydroxy compounds, and so on.

[0061] As copolymers, different oxyC 2-4Examples include copolymers containing alkylene units. The copolymer may also be a block copolymer.

[0062] The polyol may be any of the following: aliphatic polyol, alicyclic polyol, aromatic polyol, or heterocyclic polyol. From the viewpoint of the polymer compound (P) spreading thinly on the lead surface, aliphatic polyols and alicyclic polyols (e.g., polyhydroxycyclohexane, polyhydroxynorbornane, etc.) are preferred, and aliphatic polyols are preferred among them. Examples of aliphatic polyols include aliphatic diols and polyols with more than one triol (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 Alkylene glycol may also be used. Examples of sugar alcohols include erythritol, xylitol, mannitol, and sorbitol. In polyalkylene oxide adducts of polyols, the alkylene oxide is the oxy C of the polymer compound (P). 2-4 It corresponds to an alkylene unit, and at least C 2-4 It contains alkylene oxide. From the viewpoint of the polymer compound (P) readily adopting a linear structure, the polyol is preferably a diol.

[0063] The etherified product is the above oxy C 2-4 At least some of the terminal -OH groups (-OH groups composed of a hydrogen atom at the terminal and an oxygen atom bonded to this hydrogen atom) of a hydroxy compound having a repeating alkylene unit structure are etherified into -OR 2 Having a base (wherein R 2 ( is an organic group.) Some of the ends of the polymer compound (P) may be etherified, or all of the ends may be etherified. For example, one end of the main chain of a linear polymer compound (P) may be an -OH group and the other end may be an -OR group. 2 It may be based on.

[0064] The esterified product is the above oxy C 2-4 -OC(=O)-R hydroxy compounds having a repeating alkylene unit structure in which at least some of the terminal -OH groups (-OH groups composed of a terminal hydrogen atom and an oxygen atom bonded to this hydrogen atom) are esterified. 3 Having a base (wherein R 3 ( is an organic group.) Some of the ends of the polymer compound (P) may be esterified, or all of the ends may be esterified. For example, one end of the main chain of a linear polymer compound (P) may be an -OH group and the other end may be -OC(=O)-R 3 It may be based on.

[0065] organic group R 2 and R 3 Examples of each include hydrocarbon groups. Hydrocarbon groups may have substituents (e.g., hydroxyl groups, alkoxy groups, and / or carboxyl groups). Hydrocarbon groups may be aliphatic, alicyclic, or aromatic. Aromatic hydrocarbon groups and alicyclic hydrocarbon groups may have aliphatic hydrocarbon groups (e.g., alkyl groups, alkenyl groups, alkynyl groups, etc.) as substituents. 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 with 24 or fewer carbon atoms (e.g., 6 to 24). The number of carbon atoms in an aromatic hydrocarbon group may be 20 or fewer (e.g., 6 to 20), 14 or fewer (e.g., 6 to 14), or 12 or fewer (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 biphenyls and bisarylalkanes (e.g., bis-C). 6-10Aryl C 1-4 Examples include alkanes (such as 2,2-bisphenylpropane).

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

[0068] The number of carbon atoms in the alicyclic hydrocarbon group may be 5 (or 6) to 16, 5 (or 6) to 10, or 5 (or 6) to 8.

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

[0070] From the viewpoint of easily allowing a thin layer of polymer compound (P) to adhere to the lead surface, aliphatic hydrocarbon groups are preferred among hydrocarbon groups. Aliphatic hydrocarbon groups may be saturated or unsaturated. Examples of aliphatic hydrocarbon groups include alkyl groups, alkenyl groups, alkynyl groups, dienyl groups having two carbon-carbon double bonds, and trienyl groups having three carbon-carbon double bonds. Aliphatic hydrocarbon groups may be linear or branched.

[0071] The number of carbon atoms in the aliphatic hydrocarbon group is, for example, 30 or less, but 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 and alkynyl groups, 3 or more for dienyl groups, and 4 or more for trienyl groups. From the viewpoint of easily allowing a thin layer of polymer compound (P) to adhere to the lead surface, alkyl and alkenyl groups are preferred.

[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, eicosyl, henicosyl, and behenyl.

[0073] Specific examples of alkenyl groups include vinyl, 1-propenyl, allyl, cis-9-heptadecene-1-yl, palmitrail, and oleyl. For example, an alkenyl group is C 2-30 Alkenyl group or C 2-26 It may also be an alkenyl group, C 2-22 Alkenyl group or C 2-20 It may also be an alkenyl group, C 10-20 It may also be an alkenyl group.

[0074] Among polymer compounds (P), oxy C 2-4 Ethereums and oxyC of hydroxy compounds having a repeating alkylene unit structure 2-4Using at least one selected from the group consisting of esterified hydroxy compounds having a repeating alkylene unit structure is preferable because it can further enhance the effect of suppressing the decrease in charge acceptance. Furthermore, the amount of overcharged electricity can also be reduced when these polymer compounds (P) are used. Among such 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 hydrophobic groups include aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and long-chain aliphatic hydrocarbon groups from among the hydrocarbon groups mentioned above. Examples of long-chain aliphatic hydrocarbon groups include those with 8 or more carbon atoms from among the aliphatic hydrocarbon groups (alkyl groups, alkenyl groups, etc.) mentioned above, 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 the decrease in charge acceptance. At least one of the hydrophobic groups in the polymer compound (P) may be a long-chain aliphatic hydrocarbon group. The number of carbon atoms in the long-chain aliphatic hydrocarbon group may be 30 or less, 26 or less, or 22 or less.

[0076] The number of carbon atoms in the long-chain aliphatic hydrocarbon group may be 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.

[0077] Among 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 a 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 a polymer compound (P), through a balance between hydrophobicity and high hydrophilicity due to the repeating structure of oxyethylene units, can selectively adsorb to lead while suppressing excessive coating of the lead surface. Thus, it can reduce the amount of overcharged electricity and further enhance the effect of suppressing the decrease in charge acceptance. Such a polymer compound (P) can ensure high adsorption to lead even with a relatively low molecular weight (for example, Mn is 1000 or less).

[0078] Among the polymer compounds (P) mentioned above, polyoxypropylene-polyoxyethylene block copolymers, etherified hydroxy compounds having a repeating oxyethylene unit structure, and esterified hydroxy compounds having a repeating oxyethylene unit structure are considered nonionic surfactants.

[0079] Polymer compounds (P) having hydrophobic groups and containing a repeating structure of oxyethylene units include polyethylene glycol ethers (such as alkyl ethers), polyethylene glycol esters (such as carboxylic acid esters), ethers of polyethylene oxide adducts of the above polyols (such as alkyl ethers), and esters of polyethylene oxide adducts of the above polyols (such as triols or more) (such as 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 polyethylene glycol esters and polyethylene oxide adducts of the above polyols is preferred because it ensures higher charge acceptance and significantly reduces the amount of overcharged electricity.

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

[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 overcharged electricity 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 stands for Hydrophobic Lipophile Balance and is a numerical value that represents the balance between hydrophobicity and hydrophilicity of a surfactant (mainly nonionic surfactants). The HLB value of a polymer compound (P) is determined by the Griffin method.

[0082] From the perspective of further enhancing the effect of reducing the amount of overcharged electricity and making it easier to ensure higher charge acceptance, oxyC 2-4 It is also preferable that the repeating structure of the alkylene includes at least a repeating structure of oxypropylene units. In this case, the charge acceptance tends to be lower compared to the case of a repeating structure of oxyethylene units, but even in this case, high charge acceptance can be ensured while keeping the amount of overcharged electricity low. The polymer compound (P) containing oxypropylene units is 1 In the chemical shift of the H-NMR spectrum, peaks originating from the -CH< and -CH2- groups of the oxypropylene unit are present in the range of 3.2 ppm to 3.8 ppm. The peaks appear split due to the differing electron densities around the hydrogen nuclei in these groups. Such polymer compounds (P) are, 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 3.42 ppm to 3.8 ppm. The peak in the range of 3.2 ppm to 3.42 ppm originates from -CH2-, while the peak in the range of 3.42 ppm to 3.8 ppm originates from -CH< and -CH2-.

[0083] Examples of polymer compounds (P) containing at least a repeating oxypropylene unit structure include polypropylene glycol, copolymers containing a repeating oxypropylene unit structure, polypropylene oxide adducts of the above polyols, or etherified or esterified products thereof. Examples of copolymers include oxypropylene-oxyalkylene copolymers (wherein oxyalkylene is C other than oxypropylene). 2-4Examples include alkylenes. Examples of oxypropylene-oxyalkylene copolymers include oxypropylene-oxyethylene copolymers and oxypropylene-oxytrimethylene copolymers. Oxypropylene-oxyalkylene copolymers are sometimes referred to as polyoxypropylene-polyoxyalkylene copolymers (for example, polyoxypropylene-polyoxyethylene copolymers). Oxypropylene-oxyalkylene copolymers may also be block copolymers (for example, polyoxypropylene-polyoxyethylene block copolymers). Examples of etherified products include polypropylene glycol alkyl ethers and alkyl ethers of oxypropylene-oxyalkylene copolymers (such as alkyl ethers of polyoxypropylene-polyoxyethylene copolymers). Examples of 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 polymer compounds (P) containing at least a repeating structure of oxypropylene units include polypropylene glycol, polyoxypropylene-polyoxyethylene copolymer (such as polyoxypropylene-polyoxyethylene block copolymer), polyoxyethylene-polyoxypropylene alkyl ether (such as alkyl ether (butyl ether) in which the above R2 has 10 or fewer carbon atoms (or 8 or fewer or 6 or fewer)), and polypropylene glycol carboxylic acid (the above R 3 Examples include, but are not limited to, polypropylene glycol carboxylic acids (such as polypropylene glycol acetate) in which the alkyl group has 10 or fewer carbon atoms (or 8 or fewer or 6 or fewer carbon atoms), and polypropylene oxide adducts of triols or more polyols (such as polypropylene oxide adducts of glycerin).

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

[0086] In a 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 adsorption to lead and making it easier to form a linear structure, the polymer compound (P) is oxy C 2-4 It is preferable that the polymer compound (P) contains a large number of alkylene units. Such a polymer compound (P) contains, for example, an oxygen atom bonded to a terminal group and a -CH2- group and / or -CH< group bonded to the oxygen atom. 1 In the 1H-NMR spectrum, the integral value of the peak in the 3.2 ppm to 3.8 ppm range accounts for a large proportion of the sum of the integral values ​​of this peak, the integral value of the hydrogen atom peak of the -CH2- group, and the integral value of the hydrogen atom peak of the -CH< group. 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 amount of overcharged electricity and making it easier to ensure 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 also has an -CH2- group or an -CH< group bonded to the oxygen atom of this -OH group, 1In the 1H-NMR spectrum, the peaks for hydrogen atoms in the -CH2- and -CH< groups have chemical shifts in the range of 3.8 ppm to 4.0 ppm.

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

[0089] The polymer compound (P) may, for example, contain compounds with Mn of 5 million or less, 3 million or less, or 2 million or less, 500,000 or less, or 100,000 or less, or 50,000 or less, or 20,000 or less. From the viewpoint of ensuring higher charge acceptance, the polymer compound (P) preferably contains compounds with Mn of 10,000 or less, may contain compounds with Mn of 5,000 or less, or 4,000 or less, or 3,000 or less, or 2,500 or less. The Mn of such compounds may be 300 or more, or 400 or more, or 500 or more. From the viewpoint of further enhancing the effect of reducing the amount of overcharged electricity, the Mn of such compounds is preferably 1,000 or more, and more preferably 1,500 or more, or 1,800 or more. Two or more compounds with different Mn values ​​may be used as the polymer compound (P). In other words, the polymer compound (P) may have multiple Mn peaks in its molecular weight distribution.

[0090] The Mn content of the above compounds is as follows: 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 Above (or 400 or more) 4000 or less, 300 or (or 400 or more) 3000 or less, 300 or (or 400 or more) 2500 or less, 500 or (or 1000 or more) 5 million or less, 500 or (or 1000 or more) 3 million or less, 500 or (or 1000 or more) 2 million or less, 500 or (or 1000 or more) 500,000 or less, 500 or (or 1000 or more) 100,000 or less, 500 or (or 1000 or more) 50,000 or less, 500 or (or 1000 or more) (Above) 20000 or less, 500 or more (or 1000 or more) 10000 or less, 500 or more (or 1000 or more) 5000 or less, 500 or more (or 1000 or more) 4000 or less, 500 or more (or 1000 or more) 3000 or less, 500 or more (or 1000 or more) 2500 or less, 1500 or more (or 1800 or more) 5 million or less, 1500 or more (or 1800 or more) 3 million or less, 1500 or more (or 1800 or more) 2 million or less, 1500 or more (or 1800 It may also be 500,000 or less (or 1,800 or more) and 100,000 or less, 1,500 or more (or 1,800 or more) and 50,000 or less, 1,500 or more (or 1,800 or more) and 20,000 or less, 1,500 or more (or 1,800 or more) and 10,000 or less, 1,500 or more (or 1,800 or more) and 5,000 or less, 1,500 or more (or 1,800 or more) and 4,000 or less, 1,500 or more (or 1,800 or more) and 3,000 or less, or 1,500 or more (or 1,800 or more) and 2,500 or less.

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

[0092] The content (by mass) of polymer compounds (P) in the negative electrode material is as follows: 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 (and (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 It may also be 20 ppm or more (or 30 ppm or more) and 300 ppm or less, 20 ppm or more (or 30 ppm or more) and 200 ppm or less, 20 ppm or more (or 30 ppm or more) and 160 ppm or less, 20 ppm or more (or 30 ppm or more) and 150 ppm or less, 20 ppm or more (or 30 ppm or more) and 120 ppm or less, or 20 ppm or more (or 30 ppm or more) and 100 ppm or less.

[0093] (Organic shrinkage inhibitor) As previously mentioned, the negative electrode material may contain an organic condensate as an organic shrinkage inhibitor. The organic condensate may be synthesized by known methods, for example, or a commercially available product may be used. The negative electrode material may contain one organic shrinkage inhibitor or two or more. The negative electrode material may contain a lignin compound as an organic shrinkage inhibitor, or it may contain an organic shrinkage inhibitor other than a lignin compound.

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

[0095] The barium sulfate content 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] (carbonaceous material) The negative electrode material may include carbonaceous materials. Examples of carbonaceous materials 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 Ketjenblack (trade name). Graphite may be any carbonaceous material containing a graphite-type crystal 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 carbonaceous material content in the negative electrode material is preferably, for example, 0.05% by mass or more, and may be 0.10% by mass or more. The carbonaceous material content is, for example, 5% by mass or less, and may be 3% by mass or less. These lower and upper limits can be combined arbitrarily.

[0098] The carbonaceous material content 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 the method for analyzing the negative electrode material or its components. Prior to measurement or analysis, a fully charged lead-acid battery is disassembled to obtain the negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid. Washing is continued until a pH test paper is pressed against the surface of the washed negative electrode plate and the color of the test paper does not change. However, the washing time should be no more than 2 hours. The washed negative electrode plate is dried under reduced pressure at 60±5℃ for about 6 hours. If the negative electrode plate contains adhesive material, remove the adhesive material 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 compounds (P) (1-1) Qualitative analysis of polymer compounds (P) The 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 solids are then removed by filtration. The polymer compound (P) obtained by extraction is identified from the chloroform solution containing the extracted polymer compound (P) or from the polymer compound (P) obtained by drying the chloroform solution, by obtaining information from at least one of the following: infrared spectroscopy, ultraviolet-visible absorption spectroscopy, NMR spectroscopy, LC-MS, and pyrolysis GC-MS.

[0101] The polymer compound (P) obtained by extraction is dissolved in a chloroform solution, and the chloroform-soluble components are recovered by distilling off the chloroform under reduced pressure. The chloroform-soluble components are dissolved in deuterated chloroform and then under the following conditions. 1 Measure the H-NMR spectrum. 1 From the 1H-NMR spectrum, identify peaks with a chemical shift in the range of 3.2 ppm to 3.8 ppm. Also, from the peaks in this range, identify oxy C 2-4 Identify the type of alkylene unit.

[0102] Equipment: AL400 type nuclear magnetic resonance spectrometer manufactured by JEOL Ltd. Observation frequency: 395.88MHz Pulse width: 6.30 μs Pulse repetition time: 74.1411 seconds Total number of times: 32 Measurement temperature: room temperature (20~35℃) Reference: 7.24 ppm Sample tube diameter: 5mm

[0103] 1 From the 1H-NMR spectrum, determine the integral value (V1) of the peaks whose chemical shift is in the range of 3.2 ppm to 3.8 ppm. Also, for each of the hydrogen atoms of the -CH2- group and -CH< group bonded to the oxygen atom bonded to the terminal group of the polymer compound (P), 1 First, calculate the sum of the integral values ​​of the peaks in the H-NMR spectrum (V2). Then, from V1 and V2, calculate the proportion of V1 to the sum of V1 and V2 (=V1 / (V1+V2)×100(%)).

[0104] Furthermore, in qualitative analysis, 1 When determining the integral value of the peaks in the H-NMR spectrum, 1 In the 1H-NMR spectrum, two points without significant signals are determined on either side of the peak in question, and the integral value is calculated using the straight line connecting these two points as the baseline. For example, for a peak with a chemical shift in the range of 3.2 ppm to 3.8 ppm, the baseline is the straight line connecting the two points at 3.2 ppm and 3.8 ppm in the spectrum. For example, for a peak with a chemical shift greater than 3.8 ppm and less than or equal to 4.0 ppm, the baseline is the straight line connecting the two points at 3.8 ppm and 4.0 ppm in the spectrum.

[0105] (1-2) Quantitative analysis of polymer compounds (P) The appropriate amount of the above chloroform-soluble component was measured with an accuracy of ±0.0001g. r (g) Dissolve in deuterated chloroform together with tetrachloroethane (TCE), 1Measure the 1H-NMR spectrum. Calculate the integral value (S) of the peaks where the chemical shift is in the range of 3.2–3.8 ppm. a ) and the integral value of the peak originating from TCE (S r ) is determined, and the mass-based content C of the polymer compound (P) in the negative electrode material is calculated from the following formula. n Calculate (ppm).

[0106] C n =S a / S r ×N r / N a ×M a / M r xm r / m × 1,000,000 (In the formula, M a This refers to the molecular weight of a structure that shows a peak in the chemical shift range of 3.2 to 3.8 ppm (more specifically, oxy C 2-4 The molecular weight of the repeating alkylene unit structure is N a N is the number of hydrogen atoms bonded to the carbon atoms in the repeating main chain. r、 M r (where m(g) is the mass of the negative electrode material used for extraction, and the numbers represent the number of hydrogen atoms in the molecule of the reference substance and the molecular weight of the reference substance, respectively.) Note that the reference substance in this analysis is TCE, therefore N r =2, M r = 168. Also, m = 100.

[0107] For example, if the polymer compound (P) is polypropylene glycol, then M a It is 58, N a It is 3. When the polymer compound (P) is polyethylene glycol, M a It is 44, N a It is 4. a and M a This is the N of each monomer unit. a Value and M a This 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, 1 The integrated value of the peaks in the 1H-NMR spectrum is determined using the data processing software "ALICE" manufactured by JEOL Ltd.

[0109] (1-3) Measurement of Mn of Polymer Compound (P) Using the above chloroform-soluble component, GPC measurement of the polymer compound (P) is carried out using the following apparatus under the following conditions. Separately, a calibration curve (calibration line) is created from the plot of Mn of the standard substance and the 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, etc., may be in a decomposed state in the chloroform-soluble component.

[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 arranged between the negative electrode plate and the positive electrode plate. As the separator, at least one selected from non-woven fabrics and microporous membranes is used. The thickness of the separator interposed between the negative electrode plate and the positive electrode plate may be selected according to the inter-electrode distance. The number of separators may be selected according to the number of inter-electrodes.

[0112] Nonwoven fabrics are mats made by intertwining fibers without weaving, and are primarily composed of fibers. For example, nonwoven fabrics are formed of fibers by 60% or more by mass. Suitable fibers include glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers (such as polyethylene terephthalate fibers), etc.), and pulp fibers. Glass fibers are preferred among these. Nonwoven fabrics 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 materials other than fiber components. For example, it can be obtained by extruding a composition containing a pore-forming agent (such as 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 those mainly composed of polymer components are preferred. Polyolefins (such as polyethylene and polypropylene) are preferred as polymer components.

[0114] The separator may be composed of, for example, only a nonwoven fabric, or only a microporous membrane. Furthermore, the separator may, as needed, be a laminate of a nonwoven fabric and a microporous membrane, a combination of different or the same type of material, or a combination of different or the same type of material with interlocking protrusions and indentations.

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

[0116] In this specification, the vertical direction in relation to the electrode plate refers to the vertical direction when the electrode plate is arranged in a lead-acid battery installed under normal operating conditions.

[0117] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, which may be gelled if necessary. The electrolyte may optionally 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 is, for example, 1.20 or higher, and may be 1.25 or higher, 1.28 or higher, or 1.29 or higher. The specific gravity of the electrolyte at 20°C is 1.35 or lower, and may be 1.32 or lower, or 1.31 or lower. These lower and upper limits can be combined arbitrarily. For example, the specific gravity may be 1.28 or higher and 1.32 or lower, or 1.29 or higher and 1.31 or lower. These specific gravities of the electrolyte are those of the electrolyte in a fully charged battery at 20°C.

[0119] The discharge capacity of a lead-acid battery can be increased by increasing the specific gravity of the electrolyte. In this respect, the specific gravity of the electrolyte is preferably 1.28 or higher, and may be 1.29 or higher. On the other hand, if the specific gravity of the electrolyte is too high, the positive electrode current collector tends to corrode easily. In this respect, the specific gravity of the electrolyte is preferably 1.32 or lower, and may be 1.31 or lower.

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

[0121] A lead-acid battery can be obtained by a manufacturing method that includes the step of assembling the battery by housing a positive electrode plate, a negative electrode plate, and an electrolyte in a battery case. In the lead-acid battery assembly process, a separator is usually positioned between the positive electrode plate and the negative electrode plate. After housing the positive electrode plate, negative electrode plate, and electrolyte in the battery case, the lead-acid battery assembly process may optionally include a step of chemically forming at least one of the positive electrode plate and the negative electrode plate. The positive electrode plate, negative electrode plate, electrolyte, and separator are each prepared before being housed in the battery case.

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

[0123] The lead-acid battery 1 comprises a battery case 10 that houses an electrode plate group 11 and an electrolyte 12. The electrode plate group 11 is composed of multiple negative electrode plates 2 and clad-type positive electrode plates 3, stacked with separators 4 in between. Here, a sheet-like separator 4 is shown sandwiched between the negative electrode plate 2 and the positive electrode plate 3, but the form of the separator is not particularly limited.

[0124] Each of the multiple negative electrode plates 2 has an upward-projecting current-collecting tab (not shown) on its upper part. Each of the multiple positive electrode plates 3 also has an upward-projecting current-collecting tab (not shown) on its upper part. The tabs of the negative electrode plates 2 are connected and integrated by a negative electrode strap 5a. Similarly, the tabs of the positive electrode plates 3 are connected and integrated by a positive electrode strap 5b. The lower end of the negative electrode column 6a is fixed to the upper part of the negative electrode strap 5a, and the lower end of the positive electrode column 6b is fixed to the upper part of the positive electrode strap 5b.

[0125] Figure 5 schematically shows a top view of a clad-type positive electrode plate 3. Figure 6 is a schematic cross-sectional view of the cross section along line VI-VI in Figure 5, viewed from the direction of the arrow. The positive electrode plate 3 comprises a plurality of porous tubes 31, core metals (positive electrode current collectors) 32 housed within the tubes 31, positive electrode material 33 housed within the tubes 31, and a current collector 34 connecting the plurality of core metals 32. Each tube 31 houses one core metal 32, and the plurality of core metals 32 are arranged in a line, with one end in the longitudinal direction connected by the current collector 34. The plurality of tubes 31, with the core metals 32 housed within them, are arranged in a line perpendicular to the longitudinal direction of the tubes 31 (or, from another viewpoint, along the longitudinal direction of the current collector 34). The current collector 34 and one end of the plurality of tubes 31 on the current collector 34 side are covered by an upper connecting seat 35. The opening of the tube 31 on the current collector 34 side is sealed by one end of the core metal 32 on the current collector 34 side and the upper connecting seat 35. A lug portion 34a for collecting current from the positive electrode plate 3 is formed at one end of the current collector 34 in the longitudinal direction. The lug portion 34a protrudes outward from the upper connecting seat 35. The other ends of the multiple tubes 31 in the longitudinal direction 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 relating to one aspect of the present invention is described below.

[0127] (1) A lead-acid battery, A negative electrode plate containing a negative electrode material, Electrolyte and A positive electrode plate comprising a positive electrode current collector and a positive electrode material disposed around the positive electrode current collector, The positive electrode current collector includes a metallic structure containing a plurality of dendrite arms, A lead-acid battery in which the average distance between the multiple 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 it may be 1 μm or more or 3 μm or more.

[0128] (2) In the lead-acid battery described in (1) above, 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, or 8% by mass or less.

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

[0130] (4) In any one of the lead-acid batteries described in (1) to (3) 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, and the diameter of the core metal may be 2.4 mm or more and less than 3.6 mm. The diameter of the core metal may be 2.7 mm or more, or 3.3 mm or less.

[0131] (5) In any one of the lead-acid batteries described in (1) to (4) above, the negative electrode material may contain a polymer compound, and the polymer compound is 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 any one of the lead-acid batteries described in (1) to (5) above, the negative electrode material may include a polymer compound, wherein the polymer compound is oxy C 2-4 Alkylene units may be repeatedly incorporated into the structure.

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

[0134] [Examples] The present invention will be described in detail 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-A4, CA1, CA2) are fabricated using positive electrode current collectors with different DAS values, and their characteristics are measured. The six types of lead-acid batteries are fabricated using the following method. 《Lead acid battery A1》 (a) Fabrication of the negative electrode plate A negative electrode paste is obtained by mixing lead powder, barium sulfate, carbon black, and sodium ligninsulfonate, an organic shrinkage inhibitor, with an appropriate amount of sulfuric acid aqueous solution. At this time, the components are mixed so that the barium sulfate content in the negative electrode material is 1.5% by mass, the carbon black content is 0.3% by mass, and the organic shrinkage inhibitor content is 0.1% by mass. The negative electrode paste is filled into the mesh of a cast grid made of Pb-Sb alloy, which is the negative electrode current collector, and is aged and dried to obtain an unformed negative electrode plate.

[0136] (b) Fabrication of the positive electrode plate First, a positive electrode current collector is manufactured by casting, in which multiple cores and a current collector connecting the multiple cores are integrated. The positive electrode current collector contains 15 cores. One end of each core is integrated with the current collector. The current collector includes lugs. A Pb-Sb alloy with a Sb content of 5 mass% is used as the material for the positive electrode current collector. The cores have a round bar shape with a diameter of 3 mm. The positive electrode current collector is manufactured by melting the material under atmospheric pressure, pouring it into a mold, and cooling it. At this time, the DAS of the positive electrode current collector is controlled by adjusting the cooling rate (the same applies to the experimental examples below). Furthermore, a positive electrode current collector for DAS measurement is manufactured under the same conditions as the positive electrode current collector used in the manufacture 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 (the same applies to the experimental examples below). Specifically, in DAS measurement, the core metal is divided into multiple equal regions (specifically, 10 equal regions) so that they have roughly equal volumes, and the DAS is measured for each region. The arithmetic mean of the DAS obtained for each of the 10 regions is then taken as the DAS for the entire positive electrode current collector (the value D1 mentioned above). The DAS shown below is the value of the DAS for the entire positive electrode current collector.

[0137] Next, multiple core metals of the positive electrode current collector are housed within multiple tubes. A resin upper connecting seat is formed by covering the current collector portion and one end of the tube on the current collector side with resin, so that the lugs are exposed. A porous tube made of glass fiber is used as the tube.

[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 tube through the opening at the other end in the longitudinal direction. The mass ratio of lead powder to red lead is 8:2. Then, the opening at the other end of the tube is sealed with a lower joint and dried. In this way, an unformed clad positive electrode plate is produced.

[0139] (c) Preparation of test batteries A liquid-type battery with a rated voltage of 2V and a rated 5-hour rate capacity of 165Ah will be manufactured. The electrode plate group of the test battery will consist of three positive electrodes and four negative electrodes sandwiching them. The positive and negative electrodes will be stacked with a polyethylene separator interposed between them to form the electrode plate group. The electrode plate group will be placed in a synthetic resin battery case together with an electrolyte (sulfuric acid aqueous solution). Next, the battery case will be covered and chemical conversion will be carried out inside the battery case to manufacture a liquid-type lead-acid battery A1. The specific gravity of the electrolyte after conversion at 20°C will be 1.32. The height of the battery will be 426 mm (height from the bottom of the battery case to the liquid level will be 338 mm), and the volume of electrolyte will be 1700 mL.

[0140] 《Lead acid battery A2~A4, CA1, CA2》 Five types of positive electrode current collectors with the same shape as the positive electrode current collector of lead-acid battery A1 will be manufactured by changing the manufacturing conditions of the positive electrode current collector. Specifically, the positive electrode current collector will be manufactured by changing the cooling rate during casting. Furthermore, a positive electrode current collector for DAS measurement will be manufactured under the same conditions as the positive electrode current collector used in the manufacture of lead-acid batteries. The DAS will be measured for the core metal (positive electrode current collector) of this measurement positive electrode current collector using the method described above.

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

[0142] [Evaluation of battery characteristics] The batteries produced in Experimental Examples 1-4 will be evaluated using the following method.

[0143] (i) Charge-discharge cycle test First, prepare a fully charged battery and perform a charge-discharge cycle test on it in a water bath at 15°C ± 2°C, repeatedly discharging and charging it. Discharging and charging will be performed under the following conditions. Discharge: Discharge at a current of 0.25 C (A) for 3 hours. Here, C is the rated capacity value expressed in ampere-hours (Ah) (the same applies to the following tests). Charging: Charge the battery with a current of 0.18C(A) to 120% of the discharged amount.

[0144] Before starting the charge-discharge cycle test, and after every 100 charge-discharge cycles, the following (ii) capacity test and (iii) high-rate discharge performance test will be performed. After each test, the battery will be fully charged. Furthermore, the life cycle performance will be determined by the following method (iv).

[0145] (ii) Capacity test The capacity test is performed with the battery placed in a water bath at 30±2℃. The discharge amount (discharge capacity) is measured by discharging at a current of 0.2C(A) until the cutoff voltage reaches 1.7(V).

[0146] (iii) High-rate discharge performance test The high-rate discharge performance test is performed with the battery placed in a water bath at 30±2℃. Discharge is performed under conditions of a discharge current of 1.0C(A) and a cutoff voltage of 1.4(V), and the discharge duration is measured.

[0147] (iv) Determination of life cycle performance The number of cycles at which the battery under evaluation satisfies at least one of the following conditions (a) and (b) is determined as the battery's life cycle count. A higher life cycle count indicates better performance for the lead-acid battery. (a) In the charge-discharge cycle test described in (i) above, the discharge end voltage is below 1.5V. (b) In the capacity test described in (ii) above, the measured capacity is less than 80% of the capacity before the start of the charge-discharge cycle (initial capacity).

[0148] (v) Capacity retention rate The capacity retention rate is calculated using the following formula. Capacity maintenance rate (%)=100×X(600) / X(0) Here, X(600) is the discharge capacity after 600 cycles in the charge-discharge cycle test described 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 described in (ii) above.

[0149] Table 2 shows the DAS and evaluation results for the positive electrode current collector of the above battery. The life cycle count (relative value) shown in Table 2 is the relative value when the life cycle count of lead-acid battery A4 is set to 100.

[0150] [Table 2]

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

[0152] Furthermore, the high-rate discharge performance of lead-acid batteries A1, A4, and CA1 was evaluated using the method described above, both initially and after charge-discharge cycles. The evaluation results are shown in Figure 8. The data shown in Figure 8 are values ​​when the initial high-rate discharge capacity is set to 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, twelve types of lead-acid batteries are manufactured using the same method as lead-acid battery A1, except that the material of the positive electrode current collector and the casting conditions during manufacturing are changed. The Sb content of the positive electrode current collector material is set to the amount shown in Figure 9. Furthermore, a positive electrode current collector for DAS measurement is manufactured under the same conditions as the positive electrode current collector used in the manufacture of the lead-acid batteries. The DAS is measured for the core metal (positive electrode current collector) of this measurement positive electrode current collector using the method described above.

[0154] The capacity retention rate of 12 types of lead-acid batteries was measured using the method described above. The capacity retention rates and DAS values ​​of these lead-acid batteries are shown in Figure 9. A higher capacity retention rate indicates better lead-acid battery characteristics. 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 are manufactured using the same method as lead-acid battery A1, except that the specific gravity of the electrolyte and the casting conditions during the manufacture of the positive electrode current collector are changed. The specific gravity of the electrolyte (sulfuric acid aqueous solution) is changed by changing the concentration of the sulfuric acid aqueous solution. The positive electrode current collector is manufactured using a 5 mass% Pb-Sb alloy, similar to the positive electrode current collector of lead-acid battery A1. The casting conditions for the positive electrode current collector are changed in the same way as in Experimental Example 1. The DAS of the core metal of the positive electrode current collector manufactured in Experimental Example 3 are 3 μm, 20 μm, and 35 μm.

[0156] The life cycle performance of 15 types of lead-acid batteries is evaluated using the method described above. Figure 10 shows the relationship between the specific gravity of the electrolyte, DAS, and life cycle performance for these batteries. As mentioned 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 shows the relative value of the life cycle performance of each battery, with the life cycle performance 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, high lifetime cycle performance can be achieved when the DAS is 20 μm or less. In particular, when the DAS is 35 μm, lifetime cycle performance deteriorates significantly when the specific gravity of the electrolyte exceeds 1.29. However, when the DAS is 20 μm or less, the deterioration in lifetime cycle performance is small even when the specific gravity of the electrolyte exceeds 1.29 (specifically, between 1.29 and 1.32).

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

[0159] The capacity retention rate of the 10 types of lead-acid batteries produced was measured using the method described above. Figure 11 shows the relationship between the core diameter, DAS, and capacity retention rate for these lead-acid batteries.

[0160] As shown in Figure 11, a high capacity retention rate is achieved when the DAS is 20 μm or less. Furthermore, an even higher capacity retention rate is achieved when the DAS is 20 μm or less and the core metal diameter is 2.4 mm or more and less than 3.6 mm (for example, 2.4 mm or more and 3.3 mm or less). In addition, a particularly high capacity retention rate is achieved when the DAS is 20 μm or less and the core metal diameter is 2.7 mm or more and 3.3 mm or less.

[0161] [Evaluation of battery characteristics] The batteries prepared in Experimental Examples 5-7 will be evaluated using the following method.

[0162] (I) Charge-discharge cycle test The charge-discharge cycle test is performed 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 130% of the discharge amount is charged during charging.

[0163] Before starting 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 will be performed. After each test, the battery will be fully charged. Furthermore, the life cycle performance is determined by the following method (IV).

[0164] (II) Capacity test The capacity test shall be conducted under the same conditions as the capacity test described in (ii) above.

[0165] (III) Low-temperature high-rate discharge performance test The low-temperature high-rate discharge performance test is conducted with the battery placed in a water bath at -15±2℃. Discharge is performed under conditions of a discharge current of 1.0C(A) and a cutoff voltage of 1.0(V), and the discharge duration is measured.

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

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

[0168] [Table 3]

[0169] As shown in Table 3, the PPG (polymer compound (P)) content 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, a lead-acid battery is fabricated by adding a polymer compound (P) to the negative electrode material. Specifically, ten types of lead-acid batteries (batteries F1 to F5) are fabricated using the same method as lead-acid battery A2 in Experimental Example 1, except that the type of polymer compound (P) added to the negative electrode material is changed. The polymer compound (P) content in the negative electrode material is set to 300 ppm (by mass). The polymer compounds (P) used are listed in Table 4. The evaluation results of the life cycle performance described in (IV) above for the fabricated batteries are shown in Table 4. The relative values ​​in Table 4 are the relative life cycle numbers of each battery, with the life cycle number of battery A2 set to 100.

[0171] [Table 4]

[0172] Table 4 indicates that a larger relative value indicates better cycle performance. As shown in Table 4, changing the type of polymer compound (P) can significantly improve cycle performance compared to not using polymer compound (P).

[0173] Furthermore, the amount of electrolyte loss due to charge-discharge cycles is measured for the above batteries. Table 5 shows the amount of electrolyte loss after 100 charge-discharge cycles as described in (I) above. The relative values ​​in Table 5 are the relative values ​​of the amount of electrolyte loss (by mass) for each battery, with the amount of electrolyte loss (by mass) for battery A2 set to 100.

[0174] [Table 5]

[0175] A lower electrolyte reduction (relative value) in Table 5 is preferable. As shown in Table 5, the reduction of electrolyte can be suppressed by adding a polymer compound (P) to the negative electrode material. 2-4 In batteries F2 to F5 that use alkylene glycol esters, the reduction in electrolyte can be particularly suppressed.

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

[0177] [Table 6]

[0178] The discharge capacity (%) in Table 6 is a relative value for each battery, with the discharge capacity before the start of the charge-discharge cycle test set to 100%. Note that when the discharge capacity reaches approximately 80% of the initial capacity, it is considered that the battery has reached the end of its lifespan, 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 polymer compounds (P) is significant.

[0179] For batteries G1 and CG1, and batteries A2 and CA1, the above charge-discharge cycles were performed 300 times, and then the (III) low-temperature high-rate discharge performance test described above was carried out. The test results are shown in Table 7. The low-temperature high-rate discharge capacity in Table 7 is a relative value when the low-temperature high-rate discharge capacity of battery CA1 is set to 100%.

[0180] [Table 7]

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

[0182] This invention can be used in lead-acid batteries. [Explanation of symbols]

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

Claims

1. A negative electrode plate containing a negative electrode material, Electrolyte and A positive electrode plate comprising a positive electrode current collector and a positive electrode material disposed around the positive electrode current collector, The positive electrode current collector is composed of a Pb-Sb alloy and includes a metallic structure containing multiple dendrite arms. The average distance between the plurality of dendrite arms is 6 μm or less. A lead-acid battery in which the specific gravity of the electrolyte at 20°C is 1.29 or higher and 1.32 or lower.

2. The negative electrode material comprises a polymer compound, The polymer compound is measured using deuterated chloroform as a solvent. １ The lead-acid battery according to claim 1, wherein the chemical shift of the H-NMR spectrum has a peak in the range of 3.2 ppm to 3.8 ppm.

3. The negative electrode material comprises a polymer compound, The aforementioned polymer compound is oxyC ２－４ A lead-acid battery according to claim 1 or 2, comprising an alkylene unit as a repeating structure.

4. The polymer compound is the oxy C ２－４ The lead-acid battery according to claim 3, comprising at least one selected from the group consisting of a hydroxy compound having the repeating structure of the alkylene unit, an ether of the hydroxy compound, and an ester of the hydroxy compound.

5. The lead-acid battery according to any one of claims 2 to 4, wherein the polymer compound is one or more selected from polypropylene glycol, polyoxyethylene oleate ester, polyethylene glycol dilaurate, polyethylene glycol distearate, and polyethylene glycol dioleate.

6. The lead-acid battery according to any one of claims 1 to 5, wherein the average distance between the plurality of dendrite arms is 1 μm or more.

7. The lead-acid battery according to any one of claims 1 to 6, wherein the average distance between the plurality of dendrite arms is 3 μm or more.

8. The lead-acid battery according to any one of claims 1 to 7, wherein the Sb content in the Pb-Sb alloy is 3.5% by mass or more and 10% by mass or less.

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

10. The aforementioned 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 9, wherein the diameter of the core metal is 2.4 mm or more and less than 3.6 mm.

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