Current collectors, electrodes, lead-acid batteries, battery packs and electric vehicles

Abstract

To provide a current collector, electrode, lead-acid battery, battery assembly, and electric vehicle with improved reliability.SOLUTION: The current collector includes an ear 16 for current collection and a bar-shaped core 12 extending with the side on which the ear 16 is located as an upper-end side. The average cross-sectional area at the lower end of the core 12 is larger than the average cross-sectional area at the upper end of the core 12.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a current collector, an electrode, a lead-acid battery, a battery pack, and an electric vehicle. [Background technology]

[0002] Lead-acid batteries are widely used as secondary batteries for industrial or consumer use, and there is particularly high demand for lead-acid batteries (so-called batteries) for electric vehicles or for backup lead-acid batteries for UPS (Uninterruptible Power Supply), disaster prevention (emergency) radio, telephones, etc.

[0003] A lead-acid battery includes an electrode group including a plurality of electrodes, and a battery case that contains the electrode group. The electrode includes a cylindrical body, a rod-shaped core inserted into the cylindrical body, and an electrode material including an active material that is filled inside the cylindrical body (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 61-232572 Summary of the Invention [Problem to be solved by the invention]

[0005] In lead-acid batteries, when the battery is repeatedly charged and discharged, water is produced during discharge and sulfuric acid is produced during charging. In lead-acid batteries, sulfuric acid has a higher specific gravity than water and tends to settle to the bottom, resulting in a stratification phenomenon in which the electrolyte (sulfuric acid) concentration differs between the upper and lower parts of the battery. When stratification occurs, the electrolyte concentration in the lower part of the battery becomes higher, making the core metal in the lower part of the battery more susceptible to corrosion. Corrosion of the core metal can cause damage to the core metal.

[0006] An object of one aspect of the present invention is to provide a current collector, an electrode, a lead-acid battery, a battery pack, and an electric vehicle that can achieve improved reliability. [Means for solving the problem]

[0007] A current collector according to one aspect of the present invention comprises a current collecting ear portion and a rod-shaped core bar extending from one end side on which the ear portion is located, and the average cross-sectional area at the other end side in the extension direction of the core bar is larger than the average cross-sectional area at one end side of the core bar.

[0008] A current collector according to one aspect of the present invention comprises a current collecting ear, a rod-shaped core extending from one end side on which the ear is located, and one or more protrusions provided on the core and protruding outward beyond the outer surface of the core, and the average cross-sectional area at the other end side in the extension direction of the core is larger than the average cross-sectional area at one end side of the core.

[0009] In the current collector according to one aspect of the present invention, the average cross-sectional area at the other end in the extension direction of the core is larger than the average cross-sectional area at one end of the core. As a result, even if corrosion occurs at the other end of the core (the lower side of the lead-acid battery), the core is thick and has rigidity, so that damage to the core can be suppressed. Therefore, the reliability of the current collector can be improved.

[0010] In one embodiment, when the core is divided into a plurality of portions at regular intervals in the extension direction, the average cross-sectional area of ​​each portion may be larger in the portion located on the other end side than in the portion located on the one end side. In this configuration, since the portion located on the other end side is thick, it is possible to suppress breakage of the core.

[0011] In one embodiment, the cross-sectional area of ​​the core may be gradually increased from one end side to the other end side. In this configuration, the core becomes thicker in a tapered manner from one end side to the other end side. Therefore, even if corrosion occurs on the other end side of the core (the lower side of the lead-acid battery) of the current collector, the core is thick and has rigidity, so that damage to the core can be suppressed.

[0012] In one embodiment, the current collector comprises a connecting member that connects the ear portion and the core bar, and a linking portion that is provided between the connecting member and the core bar and links the connecting member to one end of the core bar, and the cross-sectional area of ​​the linking portion may be larger than the average cross-sectional area of ​​the core bar.

[0013] An electrode according to one aspect of the present invention includes a cylindrical body, an electrode material filled inside the cylindrical body, and the above-mentioned current collector, which is inserted into the cylindrical body.

[0014] An electrode according to one aspect of the present invention includes the above-mentioned current collector. Therefore, even if corrosion occurs on the other end side (the lower side of the lead-acid battery) of the core of the current collector, the core is thick and has rigidity, so that damage to the core can be suppressed. Therefore, the reliability of the electrode can be improved.

[0015] An electrode according to one aspect of the present invention comprises a cylindrical body extending in one direction, an electrode material filled inside the cylindrical body, and a current collector inserted into the cylindrical body, the current collector having an ear for collecting current and a rod-shaped core bar extending with the side on which the ear is located as one end side, the diameter of the inner surface of the cylindrical body being approximately constant along one direction of the cylindrical body, and the ratio of the outer diameter of the core bar to the diameter of the inner surface of the cylindrical body being greater at the other end side in the extension direction of the core bar than at the one end side.

[0016] An electrode according to one aspect of the present invention comprises a cylindrical body extending in one direction, an electrode material filled inside the cylindrical body, and a current collector inserted into the cylindrical body, the current collector having an ear for collecting current, a rod-shaped core bar extending with the side on which the ear is located as one end side, and one or more protrusions provided on the core bar and protruding outward beyond the outer surface of the core bar, the diameter of the inner surface of the cylindrical body is approximately constant along one direction of the cylindrical body, and the ratio of the outer diameter of the core bar to the diameter of the inner surface of the cylindrical body is larger at the other end side in the extension direction of the core bar than at the one end side.

[0017] In an electrode according to one aspect of the present invention, the ratio of the outer diameter of the core to the diameter of the inner surface of the cylindrical body is larger on the other end side in the extension direction of the core than on the one end side. As a result, even if corrosion occurs on the other end side (the lower side of the lead-acid battery) of the core of the current collector, the core is thick and has rigidity, so that damage to the core can be suppressed. Therefore, the reliability of the electrode can be improved.

[0018] An electrode according to one aspect of the present invention comprises a cylindrical body extending in one direction, an electrode material filled inside the cylindrical body, and a current collector inserted into the cylindrical body, the current collector having an ear for collecting current and a rod-shaped core bar extending with the side on which the ear is located as one end side, the diameter of the inner surface of the cylindrical body being approximately constant along one direction of the cylindrical body, and the distance between the inner surface of the cylindrical body and the outer surface of the core bar being smaller at the other end side in the extension direction of the core bar than at the one end side.

[0019] An electrode according to one aspect of the present invention comprises a cylindrical body extending in one direction, an electrode material filled inside the cylindrical body, and a current collector inserted into the cylindrical body, the current collector having an ear for collecting current, a rod-shaped core bar extending with the side on which the ear is located as one end side, and one or more protrusions provided on the core bar and protruding outward beyond the outer surface of the core bar, the diameter of the inner surface of the cylindrical body being approximately constant along one direction of the cylindrical body, and the distance between the inner surface of the cylindrical body and the outer surface of the core bar being smaller at the other end side in the extension direction of the core bar than at the one end side.

[0020] In an electrode according to one aspect of the present invention, the distance between the inner surface of the cylindrical body and the outer surface of the core is smaller on the other end side in the extension direction of the core than on the one end side. As a result, even if corrosion occurs on the other end side (the lower side of the lead-acid battery) of the core of the current collector, the core is thick and has rigidity, so that damage to the core can be suppressed. Therefore, the reliability of the electrode can be improved.

[0021] In one embodiment, the packing density of the electrode material filled between the cylindrical body and the metal core may be lower at the other end side of the metal core than at one end side of the metal core. In this configuration, even if the other end side of the metal core expands due to corrosion, the packing density of the electrode material is low, so that the cylindrical body can be prevented from being damaged by the expansion of the metal core.

[0022] A lead-acid battery according to one aspect of the present invention includes the above-described electrode.

[0023] A battery pack according to one aspect of the present invention includes a plurality of the above-described lead-acid batteries.

[0024] An electric vehicle according to one aspect of the present invention includes the lead-acid battery described above. Effect of the Invention

[0025] According to one aspect of the present invention, reliability can be improved. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing a forklift equipped with a battery pack according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view that illustrates a lead-acid battery. [Diagram 3] FIG. 3 is a partial cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view showing the positive electrode of FIG. [Diagram 5] FIG. 5 is a front view showing the core, the connecting portion, and the lug portion of the positive electrode in FIG. [Figure 6] 6(a) is a partial cross-sectional view taken along line VIa-VIa in FIG. 5, FIG. 6(b) is a partial cross-sectional view taken along line VIb-VIb in FIG. 5, FIG. 6(c) is a partial cross-sectional view taken along line VIc-VIc in FIG. 5, and FIG. 6(d) is a partial cross-sectional view taken along line VId-VId in FIG. 5. [Figure 7]7(a) is a partial cross-sectional view taken along line VIIa-VIIa in FIG. 4, FIG. 7(b) is a partial cross-sectional view taken along line VIIb-VIIb in FIG. 4, and FIG. 7(c) is a partial cross-sectional view taken along line VIIc-VIIc in FIG. [Figure 8] FIG. 8 is a front view showing a core metal, a connecting portion, and an ear portion in a positive electrode according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are given the same reference numerals, and duplicated explanations are omitted. The size of the components in each drawing is conceptual, and the relative relationship of the size between the components is not limited to that shown in each drawing.

[0028] Fig. 1 is a diagram showing a forklift equipped with a battery pack. As shown in Fig. 1, a forklift (electric vehicle) 100 is equipped with a battery pack 200. The forklift 100 is driven by power supplied from the battery pack 200. The battery pack 200 is configured to include a plurality of lead-acid batteries 1.

[0029] FIG. 2 is a cross-sectional view showing a schematic diagram of a lead-acid battery. FIG. 3 is a partial cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a perspective view showing a positive electrode. In FIG. 2, positive electrodes and negative electrodes are alternately arranged with separators interposed between them from the front side to the back side of the drawing. FIG. 2 shows a cross-sectional view of a part of a positive electrode. FIG. 3 shows a laminated structure of a positive electrode, a negative electrode, and a separator when the lead-acid battery is viewed from above. The terms "upper" and "lower" correspond to the upper and lower sides in the height direction of the battery case (hereinafter the same). The Z direction corresponds to the height direction of the battery case, the X direction corresponds to the direction perpendicular to the Z direction, and the Y direction corresponds to the direction perpendicular to the Z direction and perpendicular to the X direction.

[0030] As shown in Figures 2 and 3, the lead-acid battery 1 includes an electrode group 2, a battery case 3 that houses the electrode group 2, straps 4a, 4b connected to the electrode group 2, poles 5a, 5b connected to the straps 4a, 4b, a liquid inlet plug 6 that closes the liquid inlet of the battery case 3, and a support member 7 connected to the battery case 3.

[0031] The electrode group 2 includes a plurality of positive electrodes 10, a plurality of negative electrodes 20, and a plurality of separators 30. The positive electrodes 10 and the negative electrodes 20 are alternately arranged in the X direction with the separators 30 interposed therebetween. The space around the positive electrodes 10 between the separators 30 is filled with an electrolyte 40. The material of the separator 30 is not particularly limited as long as it prevents electrical connection between the positive electrodes 10 and the negative electrodes 20 and allows the electrolyte 40 to pass through. Examples of the material of the separator 30 include a mixture of microporous polyethylene, glass fiber, and synthetic resin.

[0032] 1, 2, and 3, the positive electrode 10 is, for example, a plate-shaped electrode. The positive electrode 10 has a plurality of cylindrical bodies 11, a plurality of core metals (current collectors) 12, a positive electrode material (electrode material) 13, a lower linking seat 14, an upper linking seat 15, an ear portion (current collector) 16, a connection member (current collector) 17, and a coupling portion (current collector) 18.

[0033] The multiple cylindrical bodies 11 are arranged in a row adjacent to each other along the Y direction. The multiple cylindrical bodies 11 constitute a group of tubes (clad tubes) for retaining active material. A group of clad tubes (material unit) having a continuous tube structure is also called a "gauntlet." The cylindrical bodies 11 extend in the Z direction (one direction). A structure in which multiple cylindrical bodies 11 are arranged in a row may be obtained by using cylindrical bodies 11 that are separate from each other, or may be obtained by forming multiple through holes between substrates facing each other. A connection part such as a seam (seamed part) may be arranged between adjacent cylindrical bodies 11.

[0034] The cylindrical body 11 has a cylindrical shape. The cylindrical body 11 may have an elliptical cylindrical shape, a square cylindrical shape (for example, a square cylindrical shape with rounded corners), or the like. The length of the cylindrical body 11 is, for example, 160 to 580 mm. The inner diameter (diameter of the inner surface 11s) of the cylindrical body 11 may be, for example, 4 mm or more. The inner diameter of the cylindrical body 11 may be, for example, 10 mm or less. The diameter (outer diameter) of the cylindrical body 11 may be, for example, 5 mm or more. The diameter of the cylindrical body 11 may be, for example, 12 mm or less. The thickness of the cylindrical body 11 may be, for example, 100 μm or more. The thickness of the cylindrical body 11 may be, for example, 2000 μm or less.

[0035] The cylindrical body 11 is formed of a porous body. The cylindrical body 11 may be formed of a base material such as a woven fabric or a nonwoven fabric. An acid-resistant material can be used as the base material. Examples of the base material include resins such as polyolefin (polypropylene, polyethylene, etc.), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), and polycarbonate (PC), and inorganic materials such as glass fiber, silicon carbide, and alumina. From the viewpoint of easily improving cycle characteristics, the cylindrical body 11 preferably contains a thermoplastic resin, and more preferably contains a polyester.

[0036] In the cylindrical body 11, a resin may be held on the substrate. Examples of the resin include acrylic resin, epoxy resin, phenol resin, melamine resin, and styrene resin. The resin may be held on the inner or outer surface of the substrate, or on the surface inside the pores in the substrate, or may be attached to the substrate. The resin may be held on a part of the substrate, or on the entire substrate.

[0037] The core metal 12 is inserted into each cylindrical body 11. The core metal 12 is rod-shaped. The core metal 12 extends in the Z direction inside the cylindrical body 11 with the side where the ear portion 16 is located as the upper end side. The cross section of the core metal 12 is, for example, circular. The cross section of the core metal 12 may be elliptical, polygonal, or the like. The core metal 12 can be obtained, for example, by casting (pressure casting). The constituent material of the core metal 12 may be any conductive material, and examples of the material include lead alloys such as lead-calcium-tin alloy and lead-antimony-arsenic alloy. The lead alloy may contain selenium, silver, bismuth, or the like. The length of the core metal 12 is, for example, 150 to 600 mm.

[0038] The core metals 12 are connected to the connection member 17 via the connecting portions 18. The connecting member 17 connects the current collecting lugs 16 to the multiple core metals 12. The connecting portions 18 are provided between the connection member 17 and each of the multiple core metals 12. The connecting portions 18 connect the connection member 17 to an upper end portion (one end portion) of each of the multiple core metals 12.

[0039] The positive electrode material 13 is filled inside the cylindrical body 11. The positive electrode material 13 includes an active material. The active material includes both the active material after chemical conversion and the raw material of the active material before chemical conversion. The positive electrode material 13 here includes the active material after chemical conversion. The positive electrode material 13 after chemical conversion can be obtained, for example, by chemical conversion of an unchemical positive electrode material 13 containing the raw material of the positive electrode active material. The positive electrode material 13 after chemical conversion can be obtained, for example, by aging and drying a positive electrode material paste containing the raw material of the positive electrode active material to obtain the unchemical positive electrode material 13, and then chemical conversion of the unchemical positive electrode material 13. Examples of the raw material of the positive electrode active material include lead powder and red lead. Examples of the positive electrode active material in the positive electrode material 13 after chemical conversion include lead dioxide. The positive electrode material 13 may further contain an additive as necessary. Examples of the additive of the positive electrode material 13 include short fibers for reinforcement. Examples of reinforcing short fibers include acrylic fibers, polyethylene fibers, polypropylene fibers, and polyethylene terephthalate fibers (PET fibers).

[0040] The cylindrical body 11, the metal core 12 and the positive electrode material 13 constitute a cylindrical electrode (rod-shaped electrode). The cylindrical electrode of the positive electrode 10 is electrically connected to the electrode post 5a via the connecting portion 18, the connecting member 17, the lug portion 16 and the strap 4a.

[0041] The lower connecting seat 14 is attached to the lower ends of the multiple cylindrical bodies 11. The lower ends of the cylindrical bodies 11 are the terminal portion on one end side of the cylindrical bodies 11, in other words, the end of the cylindrical bodies 11 on the bottom side of the battery case 3. The lower connecting seat 14 seals the lower ends of the multiple cylindrical bodies 11. The lower connecting seat 14 is fitted into the lower ends of the multiple cylindrical bodies 11. The lower connecting seat 14 may be fixed to the lower ends of the multiple cylindrical bodies 11 by a thermosetting adhesive or the like.

[0042] The upper linking seat 15 is attached to the upper end of the cylindrical body 11. The upper end of the cylindrical body 11 is the terminal portion on the other end side of the cylindrical body 11, in other words, the end of the cylindrical body 11 on the top side of the battery case 3. The upper linking seat 15 is fixed to the upper end of the cylindrical body 11 by welding. In welding, the boundary portion between the upper linking seat 15 and the cylindrical body 11 and the upper linking seat 15 may be integrated. The welding can be achieved by heating, ultrasonic irradiation, laser irradiation, etc. The upper linking seat 15 may be fixed to the upper ends of multiple cylindrical bodies 11 by a thermosetting adhesive or the like.

[0043] As shown in FIG. 2 and FIG. 3, the negative electrode 20 is, for example, a plate-shaped electrode. The negative electrode 20 is, for example, a paste-type negative electrode plate. The negative electrode 20 is electrically connected to the electrode pole 5b via a strap 4b. The negative electrode 20 has a negative electrode current collector and a negative electrode material that is an electrode material held by the negative electrode current collector. A plate-shaped current collector can be used as the negative electrode current collector. The compositions of the negative electrode current collector and the core metal 12 of the positive electrode 10 may be the same or different from each other. The negative electrode material contains an active material. The negative electrode material here contains the active material after chemical formation.

[0044] The negative electrode material after chemical formation can be obtained, for example, by chemically forming an unformed negative electrode material containing a raw material of the negative electrode active material. The negative electrode material after chemical formation can be obtained, for example, by aging and drying a negative electrode material paste containing a raw material of the negative electrode active material to obtain an unformed negative electrode material, and then chemically forming the unformed negative electrode material. Examples of raw materials for the negative electrode active material include lead powder. Examples of negative electrode active materials in the negative electrode material after chemical formation include porous spongy lead. The negative electrode material can further contain additives as necessary. Examples of additives for the negative electrode material include barium sulfate, reinforcing short fibers, carbon materials (carbonaceous conductive materials), and resins having at least one selected from the group consisting of sulfonic groups and sulfonic acid groups (resins having sulfonic groups and / or sulfonic acid groups). The reinforcing short fibers can be the same reinforcing short fibers as those used in the positive electrode material.

[0045] Examples of carbon materials include carbon black and graphite. Examples of carbon black include furnace black (Ketjen Black (registered trademark), etc.), channel black, acetylene black, and thermal black. Examples of resins having a sulfonic group and / or a sulfonate group include lignin sulfonic acid, lignin sulfonate salts, and condensates of phenols, aminoarylsulfonic acid, and formaldehyde. Examples of lignin sulfonate salts include alkali metal salts of lignin sulfonic acid. Examples of phenols include bisphenol-based compounds such as bisphenol. Examples of aminoarylsulfonic acids include aminobenzenesulfonic acid and aminonaphthalenesulfonic acid.

[0046] The support member 7 is disposed on the bottom surface of the battery case 3 and supports the lower connecting seat 14. The support member 7 has a plurality of ridges 7a that protrude in the Z direction. The ridges 7a are provided on the bottom surface of the battery case 3. The ridges 7a extend in the X direction. The ridges 7a are aligned in the Y direction. The ridges 7a abut against the lower connecting seat 14 (see FIG. 2). That is, the support member 7 supports the portion of the lower connecting seat 14 on the bottom side of the battery case 3 with the ridges 7a. It is sufficient that the ridges 7a are in contact with the positive electrode 10, and they do not need to be in contact with the negative electrode 20.

[0047] Next, the main parts of the positive electrode 10 according to this embodiment will be described.

[0048] In the positive electrode 10, the average cross-sectional area at the lower end (other end) side of the core 12 in the Z direction is larger than the average cross-sectional area at the upper end (one end) side of the core 12. The average cross-sectional area at the lower end side in the Z direction (extending direction) of the core 12 is the cross-sectional area of ​​the cross-section cut in a direction perpendicular to the Z direction of the core 12 at the lower end side of the Z direction of the core 12, averaged over the Z direction on the lower end side of the core 12. The average cross-sectional area at the upper end side of the core 12 is the cross-sectional area of ​​the cross-section cut in a direction perpendicular to the Z direction of the core 12 at the upper end side of the core 12, averaged over the Z direction on the upper end side of the core 12.

[0049] As shown in Fig. 5, when the core bar 12 is divided into a plurality of parts at regular intervals in the Z direction, the average cross-sectional area of ​​the part located at the lower end side is larger than that of the part located at the upper end side. In this embodiment, the core bar 12 is divided into three parts, a first part 12a, a second part 12b, and a third part 12c. In this embodiment, the first part 12a, the second part 12b, and the third part 12c have the same length. That is, when the length of the first part 12a is L1, the length of the second part 12b is L2, and the length of the third part 12c is L3, the following relationship is satisfied. L1 ≒ L2 ≒ L3

[0050] The average cross-sectional area of ​​the first portion 12a is the cross-sectional area of ​​the cross section of the first portion 12a cut in a direction perpendicular to the Z direction of the core metal 12, averaging the cross-sectional area of ​​the first portion 12a in the Z direction. The average cross-sectional area of ​​the second portion 12b is the cross-sectional area of ​​the cross section of the second portion 12b cut in a direction perpendicular to the Z direction of the core metal 12, averaging the cross-sectional area of ​​the second portion 12b in the Z direction. The average cross-sectional area of ​​the third portion 12c is the cross-sectional area of ​​the cross section of the third portion 12c cut in a direction perpendicular to the Z direction of the core metal 12, averaging the cross-sectional area of ​​the third portion 12c in the Z direction.

[0051] The third average cross-sectional area is larger than the first average cross-sectional area and the second average cross-sectional area. The second average cross-sectional area is larger than the first average cross-sectional area. That is, the first average cross-sectional area, the second average cross-sectional area, and the third average cross-sectional area satisfy the following relationship. 1st average cross-sectional area < 2nd average cross-sectional area < 3rd average cross-sectional area

[0052] In this embodiment, the cross-sectional area of ​​the core metal 12 gradually increases from the upper end side to the lower end side. That is, the core metal 12 has a tapered shape that becomes wider from the upper end side to the lower end side. As shown in Figures 6(a), 6(b), and 6(c), the cross-sectional area A1 of the first portion 12a, the cross-sectional area A2 of the second portion 12b, and the cross-sectional area A3 of the third portion 12c satisfy the following relationship. A1 <A2<A3 6(d), the cross-sectional area A4 of the connecting portion 18 is larger than the cross-sectional area A1 of the first portion 12a, the cross-sectional area A2 of the second portion 12b, and the cross-sectional area A3 of the third portion 12c. That is, the cross-sectional area A1 of the first portion 12a, the cross-sectional area A2 of the second portion 12b, the cross-sectional area A3 of the third portion 12c, and the cross-sectional area A4 of the connecting portion 18 satisfy the following relationship. A1 <A2<A3<A4

[0053] The cross-sectional area of ​​the core metal 12 can be measured as follows. First, the core metal 12 is cut into a first portion 12a, a second portion 12b, and a third portion 12c. For example, a shear can be used to cut the core metal 12. Next, the cut first portion 12a, the second portion 12b, and the third portion 12c are filled with a cured resin (coated with the resin). For example, epicoat:tetraethylenepentamine=4:1 can be used as the cured resin. Next, each of the resin-filled first portion 12a, the second portion 12b, and the third portion 12c is cut in a direction perpendicular to the Z direction, for example, at the center. For example, a diamond cutter can be used to cut the first portion 12a, the second portion 12b, and the third portion 12c.

[0054] Subsequently, the cut surface is resin-embedded with the above-mentioned cured resin, and the cut surface is polished with abrasive paper up to 2000 grit. After polishing the cut surface, the cut surface is observed with a microscope (manufactured by Keyence: VHX-1000), and the cross-sectional area is measured. For measuring the cross-sectional area, the area measurement software attached to the above-mentioned microscope can be used. The cross-sectional area may be measured using the area of an arbitrary figure (for example, a circle) similar (approximate) to the cross-sectional shapes of the first portion 12a, the second portion 12b, and the third portion 12c.

[0055] When measuring the cross-sectional area of the core metal 12 from the state of the lead storage battery 1 (the state after assembly), the lead storage battery 1 is disassembled, the positive electrode 10 is taken out, washed with running water for 24 hours, and the sulfuric acid in the positive electrode 10 is washed away. Subsequently, the positive electrode 10 is taken out of the water and dried in a dryer at 60°C for 72 hours. Then, the cross-sectional area of the core metal 12 is measured from the dried positive electrode 10 by the same procedure as above. In this embodiment, when corrosion has occurred on the core metal 12, the corroded portion is also measured as part of the cross-sectional area. That is, including the corroded portion, it is measured as the cross-sectional area of the core metal 12.

[0056] Table 1 shows the measurement results of the cross-sectional areas of the first portion 12a, the second portion 12b, and the third portion 12c of the core metal 12 of this embodiment.

Table 1

[0057] The diameter of the core metal 12 gradually increases from the upper end side to the lower end side. As shown in FIGS. 6(a), 6(b), and 6(c), the diameters D1 of the first portion 12a, D2 of the second portion 12b, and D3 of the third portion 12c satisfy the following relationship. D1 <D2<D3 6(d), the diameter D4 of the connecting portion 18 is larger than the diameter D1 of the first portion 12a, the diameter D2 of the second portion 12b, and the diameter D3 of the third portion 12c. That is, the diameter D1 of the first portion 12a, the diameter D2 of the second portion 12b, the diameter D3 of the third portion 12c, and the diameter D4 of the connecting portion 18 satisfy the following relationship. D1 <D2<D3<D4

[0058] 7(a), 7(b), and 7(c), the inner diameter D5 of the cylindrical body 11 (diameter of the inner surface 11s) is substantially constant over the Z direction (extension direction) of the cylindrical body 11. The ratio of the outer diameter of the core 12 to the inner diameter D5 of the cylindrical body 11 is larger at the lower end side of the core 12 in the Z direction than at the upper end side. When the ratio of the outer diameter of the first portion 12a to the inner diameter D5 of the cylindrical body 11 is R1, the ratio of the outer diameter of the second portion 12b to the inner diameter D5 of the cylindrical body 11 is R2, and the ratio of the outer diameter of the third portion 12c to the inner diameter D5 of the cylindrical body 11 is R3, the following relationship is satisfied. R1 <R2<R3

[0059] From another point of view, the distance between the inner surface 11s of the cylindrical body 11 and the outer surface 12s of the core 12 is smaller on the lower end side in the Z direction of the core 12 than on the upper end side. A distance L11 between the inner surface 11s of the cylindrical body 11 and the outer surface 12s of the first portion 12a, a distance L12 between the inner surface 11s of the cylindrical body 11 and the outer surface 12s of the second portion 12b, and a distance L13 between the inner surface 11s of the cylindrical body 11 and the outer surface 12s of the third portion 12c satisfy the following relationship. L11>L12>L13

[0060] In the positive electrode 10, the filling density (bulk density) of the positive electrode material 13 filled between the cylindrical body 11 and the metal core 12 is lower at the lower end side of the metal core 12 than at the upper end side. In other words, the filling density is higher at the upper end side of the metal core 12 than at the lower end side. In this embodiment, the filling density of the positive electrode material 13 in the first portion 12a is lower than the filling density of the positive electrode material 13 in the second portion 12b. The filling density of the positive electrode material 13 in the third portion 12c is lower than the filling density of the positive electrode material 13 in the second portion 12b. In other words, when the filling density of the positive electrode material 13 in the first portion 12a is PD1, the filling density of the positive electrode material 13 in the second portion 12b is PD2, and the filling density of the positive electrode material 13 in the third portion 12c is PD3, the following relationship is satisfied. PD1>PD2>PD3

[0061] The packing density can be measured as follows. First, in a state where the cylindrical body 11 is filled with the core metal 12 and the positive electrode material 13, the cylindrical body 11 and the core metal 12 are cut. For example, a shear can be used to cut the cylindrical body 11 and the core metal 12. For example, the core metal 12 is cut so as to have a first portion 12a, a second portion 12b, and a third portion 12c. Next, the positive electrode material 13 is taken out, for example, from the central portion (predetermined range) of each of the first portion 12a, the second portion 12b, and the third portion 12c. Next, the pore distribution of the taken-out positive electrode material 13 is measured as it is without being crushed. As a result, the packing density (bulk density) of the positive electrode material 13 in each portion is obtained as a measurement result.

[0062] When measuring the packing density from the state of the lead-acid battery 1 (after assembly), the lead-acid battery 1 is disassembled, the positive electrode 10 is removed, and the positive electrode 10 is washed in running water for 24 hours to wash away the sulfuric acid in the positive electrode 10. The positive electrode 10 is then removed from the water and dried in a dryer at 60° C. for 72 hours. The packing density of the dried positive electrode 10 is then measured in the same manner as above.

[0063] The method for manufacturing the lead-acid battery 1 described above includes at least an electrode manufacturing step for manufacturing electrodes, and an assembly step for obtaining the lead-acid battery 1 by assembling each component member.

[0064] In the electrode manufacturing process, a positive electrode 10 is obtained. The electrode manufacturing process includes a step of forming a cylindrical body 11, a step of attaching an upper connecting seat 15 to the upper end of the cylindrical body 11, a step of inserting a core metal 12 into the cylindrical body 11, a step of filling the cylindrical body 11 with a positive electrode material 13, and a step of sealing the lower end of the cylindrical body 11 with a lower connecting seat 14. In the step of inserting the core metal 12 into the cylindrical body 11, with the upper connecting seat 15 attached to the upper end of the cylindrical body 11, the core metal 12 is inserted into the cylindrical body 11 from its lower end via the upper connecting seat 15.

[0065] In the assembly process, for example, unformed positive electrodes 10 and unformed negative electrodes 20 are stacked via separators 30, and the current collectors of the electrodes of the same polarity are welded with a connecting member to obtain an electrode group 2. The electrode group 2 is inserted and arranged in a battery container 3 to prepare an unformed battery. Dilute sulfuric acid is poured into the unformed battery and a direct current is passed through it to perform battery container formation. The specific gravity of the sulfuric acid after formation is adjusted to an appropriate specific gravity to obtain a lead-acid battery 1. The formation process is not limited to being performed after the assembly method, and may be performed during the electrode manufacturing method (tank formation).

[0066] As described above, in the lead-acid battery 1 according to this embodiment, the average cross-sectional area of ​​the metal core 12 at the lower end side in the Z direction is larger than the average cross-sectional area of ​​the metal core 12 at the upper end side. In this embodiment, when the metal core 12 is divided into the first portion 12a, the second portion 12b, and the third portion 12c at regular intervals in the Z direction, the average cross-sectional areas of the first portion 12a, the second portion 12b, and the third portion 12c are larger at the lower end side than at the upper end side. As a result, even if corrosion occurs at the lower end side of the metal core 12 in the lead-acid battery 1, the metal core 12 is thick and has rigidity, so that the occurrence of damage to the metal core 12 can be suppressed. Therefore, the reliability of the lead-acid battery 1 can be improved.

[0067] In the lead-acid battery 1 according to this embodiment, the cross-sectional area of ​​the metal core 12 gradually increases from the upper end side toward the lower end side. In this configuration, the metal core 12 becomes thicker in a tapered manner from the upper end side toward the lower end side. Therefore, in the lead-acid battery 1, even if corrosion occurs on the lower end side of the metal core 12, the metal core 12 is thick and has rigidity, so that damage to the metal core 12 can be effectively suppressed.

[0068] From another point of view, in the lead-acid battery 1 according to this embodiment, the ratio of the outer diameter of the core metal 12 to the inner diameter of the inner side surface 11s of the cylindrical body 11 is larger at the lower end side in the Z direction of the core metal 12 than at the upper end side. From yet another point of view, in the lead-acid battery 1 according to this embodiment, the distance between the inner side surface 11s of the cylindrical body 11 and the outer side surface 12s of the core metal 12 is smaller at the lower end side in the Z direction of the core metal 12 than at the upper end side. With these configurations, even if corrosion occurs at the lower end side of the core metal 12 in the lead-acid battery 1, the core metal 12 is thick and has rigidity, so that the core metal 12 can be prevented from being damaged. Therefore, the reliability of the lead-acid battery 1 can be improved.

[0069] In the lead-acid battery 1 according to this embodiment, the average cross-sectional area of ​​the lower end portion of the metal core 12 in the Z direction is made larger than the average cross-sectional area of ​​the upper end portion of the metal core 12, thereby making it possible to reduce the electrical resistance value of the lower end portion of the metal core 12. This makes it possible to facilitate charging of the lead-acid battery 1.

[0070] In the lead-acid battery 1 according to this embodiment, the packing density of the positive electrode material 13 packed between the cylindrical body 11 and the metal core 12 is lower at the lower end side of the metal core 12 than at the upper end side. In this configuration, even if the lower end side of the metal core 12 expands due to corrosion, the packing density of the positive electrode material 13 is low, so that damage to the cylindrical body 11 caused by the expansion of the metal core 12 can be suppressed.

[0071] Although the embodiment of the present invention has been described above, the present invention is not necessarily limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0072] 8, the positive electrode 10 may further include a protrusion (current collector) 19. The protrusion 19 is provided on the core metal 12 and protrudes outward beyond the outer surface of the core metal 12. One or more protrusions 19 may be provided. The protrusion 19 has, for example, a circular or elliptical shape.

[0073] In the above embodiment, the forklift 100 has been described as an example of the electric vehicle. However, the electric vehicle may be, for example, a golf cart. Also, although the forklift 100 is described as an example in which the battery pack 200 is mounted, the lead storage battery 1 may be mounted. [Explanation of symbols]

[0074] 1...lead-acid battery, 11...cylindrical body, 11s...inner surface, 12...core metal (current collector), 12s...outer surface, 13...positive electrode material (electrode material), 16...ear portion (current collector), 17...connecting member (current collector), 18...connecting portion (current collector), 19...protruding portion, 100...forklift (electric vehicle), 200...battery pack.

Claims

1. A current collecting lug; a rod-shaped core bar extending from one end side where the ear portion is located; A current collector in which, when the core is divided into multiple parts at regular intervals in the extension direction of the core, the average cross-sectional area of ​​each of the parts is larger for the part located on the other end side of the extension direction of the core than for the part located on the one end side.

2. A current collecting lug; a rod-shaped core bar extending from one end side where the ear portion is located; one or more protrusions provided on the core bar and protruding outward beyond an outer surface of the core bar; A current collector in which, when the core is divided into multiple parts at regular intervals in the extension direction of the core, the average cross-sectional area of ​​each of the parts is larger for the part located on the other end side of the extension direction of the core than for the part located on the one end side.

3. The current collector according to claim 1 , wherein the cross-sectional area of ​​the core metal gradually increases from the one end side toward the other end side.

4. a connecting member that connects the ear portion and the core metal; a connecting portion provided between the connecting member and the core metal and connecting the connecting member and the one end of the core metal, The current collector according to claim 1 , wherein a cross-sectional area of ​​the connecting portion is larger than the average cross-sectional area of ​​the core metal.

5. A cylindrical body; An electrode material filled inside the cylindrical body; An electrode comprising: the current collector according to any one of claims 1 to 4, the current collector being inserted into the cylindrical body.

6. A cylindrical body extending in one direction; An electrode material filled inside the cylindrical body; A current collector is inserted into the cylindrical body, The current collector has a current collecting lug and a rod-shaped core metal extending from a side where the lug is located as one end side, a diameter of an inner surface of the cylindrical body is substantially constant along the one direction of the cylindrical body, An electrode, in which when the core is divided into multiple parts at regular intervals in the extension direction of the core, the ratio of the outer diameter of the core to the diameter of the inner surface of the cylindrical body in each part is larger for the part located on the other end side of the extension direction of the core than for the part located on the one end side.

7. A cylindrical body extending in one direction; An electrode material filled inside the cylindrical body; A current collector is inserted into the cylindrical body, the current collector has a current collecting lug, a rod-shaped core extending from one end side where the lug is located, and one or more protrusions provided on the core and protruding outward beyond an outer surface of the core, a diameter of an inner surface of the cylindrical body is substantially constant along the one direction of the cylindrical body, An electrode, in which when the core is divided into multiple parts at regular intervals in the extension direction of the core, the ratio of the outer diameter of the core to the diameter of the inner surface of the cylindrical body in each part is larger for the part located on the other end side of the extension direction of the core than for the part located on the one end side.

8. A cylindrical body extending in one direction; An electrode material filled inside the cylindrical body; A current collector is inserted into the cylindrical body, The current collector has a current collecting lug and a rod-shaped core metal extending from a side where the lug is located as one end side, a diameter of an inner surface of the cylindrical body is substantially constant along the one direction of the cylindrical body, An electrode, in which when the core is divided into multiple parts at regular intervals in the extension direction of the core, the distance between the inner surface of the cylindrical body and the outer surface of the core in each part is smaller in the part located on the other end side of the extension direction of the core than in the part located on the one end side.

9. A cylindrical body extending in one direction; An electrode material filled inside the cylindrical body; A current collector is inserted into the cylindrical body, the current collector has a current collecting lug, a rod-shaped core extending from one end side where the lug is located, and one or more protrusions provided on the core and protruding outward beyond an outer surface of the core, a diameter of an inner surface of the cylindrical body is substantially constant along the one direction of the cylindrical body, An electrode, in which when the core is divided into multiple parts at regular intervals in the extension direction of the core, the distance between the inner surface of the cylindrical body and the outer surface of the core in each part is smaller in the part located on the other end side of the extension direction of the core than in the part located on the one end side.

10. The electrode according to any one of claims 6 to 9, wherein the filling density of the electrode material filled between the cylindrical body and the core metal is lower on the other end side of the core metal than on the one end side.

11. A lead-acid battery comprising the electrode according to any one of claims 5 to 10.

12. A battery pack comprising a plurality of the lead-acid batteries according to claim 11.

13. An electric vehicle comprising the lead-acid battery according to claim 12.

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