JP2022131790A - Clad type positive electrode plate for lead acid battery, and lead acid battery - Google Patents

Abstract

To provide a clad type positive electrode plate for a lead acid battery that can increase a chemical conversion degree of a positive electrode material, and a lead acid battery including the same.SOLUTION: A clad type positive electrode plate for a lead acid battery includes at least one porous tube 31, a positive electrode material 32 filling the porous tube 31, and a positive electrode current collector 33. The positive electrode current collector 33 includes at least one core grid 35, and a current collector part 34 connecting to an end part of the core grid 35. The core grid 35 is disposed in the tube 31, and is in contact with the positive electrode material 32. The core grid 35 includes a bar-like part 352 including a first end part 352a on the current collector part 34 side and a second end part 352b on an opposite side of the first end part. At the first end part 352a, a center of the bar-like part 352 is deviated from a center of the tube 31. At the first end part 352a, the shortest distance between the bar-like part 352 and the tube 31 is 2.0 mm or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to a clad positive plate for a lead-acid battery and a lead-acid battery.

In lead-acid batteries, a paste-type positive plate, a clad-type positive plate, and the like are used as positive plates. A clad positive electrode plate includes, for example, a plurality of porous tubes, a metal core housed in the tubes, and a positive electrode material filled in the tubes. In the clad positive plate, the battery characteristics change depending on the shape of the positive electrode current collector. Therefore, various positive electrode current collectors have been proposed.

Patent Document 1 (Japanese Patent Application Laid-Open No. 50-161640) describes a process of forming a core metal having blades by pressing a pultruded lead or lead alloy rod-shaped body at appropriate intervals, and using the core metal as a mold. a method of manufacturing a clad grid body for a lead-acid battery, which comprises the step of extracting and extracting from the grid body and injecting molten lead or lead alloy to form a frame body."

Patent Document 2 (Japanese Patent Application Laid-Open No. 56-167272) describes that ``the horizontal bar made of a lead alloy material having a comb tooth shape in which a plurality of vertical bars are suspended from the horizontal bar at predetermined intervals is folded and polymerized, A fiber-clad substrate having a vertical bar as a core metal."

JP-A-50-161640 JP-A-56-167272

In the conventional clad positive plate, there were cases where the conversion degree of the positive electrode material could not be sufficiently increased. SUMMARY OF THE INVENTION Under such circumstances, one object of the present invention is to provide a clad positive plate for a lead-acid battery and a lead-acid battery including the clad positive electrode plate, which is capable of increasing the forming degree of the positive electrode material.

One aspect of the present invention relates to clad positive plates for lead-acid batteries. The positive electrode plate includes at least one porous tube, a positive electrode material filled in the porous tube, and a positive current collector, wherein the positive current collector includes at least one metal core and and a current collecting portion connected to an end of the cored bar, the cored bar being disposed within the tube and in contact with the positive electrode material, the cored bar being connected to the collector. a rod-shaped portion having a first end facing the electrical part and a second end opposite the first end, wherein the center of the rod-shaped portion is the tube at the first end; and the shortest distance between the bar and the tube is 2.0 mm or less at the first end.

Another aspect of the invention relates to a lead-acid battery. The lead-acid battery includes the clad positive plate for lead-acid batteries of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, the clad-type positive electrode plate which can raise the conversion degree of positive electrode material, and a lead storage battery containing the same are obtained.

1 is a top view schematically showing a clad positive plate according to one embodiment of the present invention; FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1; FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2; FIG. FIG. 4 is a diagram schematically showing the arrangement of core bars shown in FIGS. 2 and 3; FIG. It is a perspective view which shows typically an example which removed the lid|cover of the lead storage battery which concerns on embodiment of this invention. 6 is a front view of the lead-acid battery of FIG. 5; FIG. FIG. 6B is a schematic cross-sectional view of the cross section taken along line VIB-VIB in FIG. 6A as viewed in the direction of the arrow; It is a graph which shows a part of the result of an Example. 1 is a schematic cross-sectional view showing the structure of an example of a conventional clad positive plate; FIG.

Hereinafter, embodiments of the present invention will be described 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 exemplified, but other numerical values and materials may be applied as long as the effects of the present invention can be obtained. In this specification, the range described as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "A or more and B or less".

(Clad positive plate)
The clad type positive plate of this embodiment is used in a lead-acid battery. The clad positive plate includes at least one porous tube, a positive electrode material filled in the porous tube, and a positive current collector. The porous tube is hereinafter sometimes referred to as "tube (T)". The positive electrode current collector includes at least one cored bar and a current collector connected to an end of the cored bar. A cored bar is placed in the tube (T) and is in contact with the positive electrode material. The cored bar includes a rod-shaped portion having a first end on the side of the current collector and a second end opposite to the first end. At the first end, the center of the bar is offset from the center of the tube (T). At the first end, the shortest distance Lmin between the rod-shaped portion and the tube (T) is 2.0 mm or less.

The direction in which the tube (T) extends is hereinafter sometimes referred to as "direction DL". From another point of view, the direction DL is the direction parallel to the central axis of the tube (T) or the longitudinal direction of the tube (T).

In the following description, the center of the rod-shaped portion at the first end means the position of the central axis of the rod-shaped portion at the first end. Similarly, the center of the tube (T) at the first end means the position of the central axis of the tube (T) at the first end. Similarly, the center of another component at the first end and the center of the component at the second end mean the position of the central axis of the component at that portion.

When the component (rod-shaped part, tube (T), etc.) is columnar or hollow cylindrical, the central axis of the component is the center of the circular cross section (the cross section perpendicular to the direction DL) of the component. is. In addition, when the component is neither cylindrical nor hollow cylindrical, the position of the center of gravity of the cross section of the component (the cross section perpendicular to the direction DL) can be the position of the central axis of the component. . That is, in this case, the line connecting the centers of gravity along the direction DL can be regarded as the central axis.

A rod-like portion means a region whose diameter is generally constant. For example, when the diameter of the rod-shaped portion changes depending on the position in the length direction, the maximum and minimum values of the changing diameter are within ±15% (preferably ±5%) of their average value. It can be a part. The diameter of the rod-shaped portion is the diameter of the cross section perpendicular to the direction in which the rod-shaped portion extends (the direction of the central axis). If the cross-sectional shape is not circular, the diameter of the rod-shaped portion is the diameter of a circle having the same area as the cross-sectional area (equivalent circle).

The bar typically has a cylindrical shape. The diameter (eg, diameter) of the rod-shaped portion is not particularly limited, and may be in the range of 0.25 to 0.40 times (eg, 0.30 to 0.38 times) the inner diameter of the tube. The rod-shaped portion may have a shape other than a columnar shape (for example, a prismatic shape).

In a general positive electrode current collector of a clad positive plate, the position of the cored bar on the side of the current collecting portion is fixed, but the positions of other cored bars are not fixed. Therefore, when such a general positive electrode current collector is used, the position of the cored bar tends to become eccentric (that is, it tends to deviate from the central axis of the porous tube) as the distance from the current collector increases. A schematic cross-sectional view of an example of such a conventional clad positive plate is shown in FIG.

The positive plate shown in FIG. 8 includes tube 1031 , positive electrode material 1032 , and positive current collector 1033 . Positive electrode current collector 1033 includes current collector 1034 and metal core 1035 . A positive electrode material 1032 and a metal core 1035 are arranged within the tube 1031 . The tip side of the cored bar 1035 is not fixed. Therefore, when a general positive electrode current collector 1033 is used, the core metal 1035 on the current collector 1034 side is located near the center of the tube 1031, but the core metal 1035 located away from the current collector 1034 is located in the tube. It may be so eccentric that it touches the inner peripheral surface of 1031 . In FIG. 8, the portion away from the tube 1031 may be referred to as a spaced portion 1035a, and the portion of the cored bar 1035 close to the tube 1031 may be referred to as a proximal portion 1035b. In the example of FIG. 8, the metal core 1035 located near the current collecting portion 1034 is the spaced portion 1035a, and the metal core 1035 located away from the current collecting portion 1034 is the proximity portion 1035b.

The positive electrode material contains a large amount of lead monoxide, PbO, etc., which has low electrical conductivity (hereinafter sometimes referred to as "unformed active material"). Also, the ions involved in the formation reaction move through the pores of the positive electrode material. Therefore, in the positive electrode material around the proximal portion 1035b, the resistance of the unformed active material and the resistance when ions pass through the pores are relatively small. Therefore, in the vicinity of the adjacent portion 1035b, more anodization current flows in the initial stage of anodization, and as a result, the amount of PbO ₂ generated by the anodization reaction increases. PbO ₂ has a higher electrical conductivity than the unformed active material. Therefore, in the positive electrode material around the proximal portion 1035b, the conversion reaction proceeds rapidly due to the inherently low resistance and the electrical conductivity that increases as the conversion progresses.

Formation also progresses simultaneously on the negative electrode plate facing the positive electrode plate. Therefore, also in the negative electrode plate, chemical conversion progresses first from the negative electrode material in the portion facing the proximal portion 1035b of the metal core 1035 . When the formation of the active material is almost completed in the positive electrode material around the proximal portion 1035b and the negative electrode material in the portion facing the proximal portion 1035b (for example, in the latter stage of formation), most of the formation current flows in the separated portion 1035a. flow in. However, since the forming current concentrates in the spaced portion 1035a, the current density increases, and the resistance of the positive electrode material around the spaced portion 1035a is originally large. The growth rate of PbO ₂ (ie conversion efficiency) is significantly reduced compared to the adjacent portion 1035b.

Due to the mechanism described above, in the conventional clad positive plate, there is a large difference between the formation degree of the positive electrode material in the vicinity of the current collecting portion and the formation degree of the positive electrode material in the portion away from the current collecting portion. As a result, the conversion degree itself of the positive electrode material in the entire positive electrode plate tends to decrease.

It should be noted that the variation in the degree of formation of the positive electrode material is relatively small when the formation current applied during formation is small. However, when the formation current is large (for example, when high-speed formation is performed), the difference between the formation current density in the adjacent portion 1035b and the formation current density in the distant portion 1035a becomes extremely large in the initial stage of formation. Furthermore, in the latter stage of anodization when the anodization of the adjacent portion 1035b is almost completed, the anodization current concentrates on the separated portion 1035a having a large resistance, and the anodization efficiency is lowered. Therefore, when the anodization current is large, the variation in the anodization degree of the positive electrode material becomes conspicuous.

The metal core of the positive electrode current collector used in this embodiment includes a rod-shaped portion having a first end on the current collecting portion side and a second end opposite to the first end. At the first end, the center (the position of the central axis) of the rod-shaped portion is displaced from the center (the position of the central axis) of the tube (T). According to this configuration, it is possible to reduce unevenness in the degree of formation of the positive electrode as a whole, and to increase the degree of formation of the positive electrode as a whole.

A metal core is a portion of the positive electrode current collector that has a surface that is in contact with the positive electrode material. The current collector is not in contact with the positive electrode material.

The length L0 of the cored bar in the direction DL in which the tube (T) extends is not limited, and may be in the range of 150 mm to 450 mm (for example, the range of 200 mm to 400 mm). The length of the bar-shaped portion in the direction DL may be in the range of 0.95 to 1.0 times the length of the core (for example, in the range of 0.97 to 1.0 times).

At the first end, the shortest distance Lmin between the rod-shaped portion and the tube (T) (inner peripheral surface of the tube (T)) is 2.0 mm or less, 1.5 mm or less, 1.0 mm or less, or 0.5 mm or less. It may be 5 mm or less. For example, the shortest distance Lmin may be 0 mm, that is, the rod-shaped portion and the tube (T) may be in contact at the first end. From the viewpoint of increasing the chemical formation degree of the positive electrode material, the shortest distance Lmin is preferably small.

In the positive electrode plate of the present embodiment, the center of the second end of the rod-shaped portion (the position of the central axis of the rod-shaped portion at the second end) is the first end across the central axis of the tube (T). (the position of the central axis of the bar at the first end). According to this configuration, it is possible to particularly reduce unevenness in the degree of formation of the entire positive electrode material, and particularly to increase the degree of formation of the entire positive electrode material. In addition, the entire portion of the rod-shaped portion may be in contact with the inner peripheral surface of the tube (T). Also in this case, it is possible to reduce unevenness in the formation degree of the entire positive electrode material, and to increase the formation degree of the entire positive electrode material.

At the first end, the distance G1 (mm) between the center of the rod-shaped portion and the center of the tube (T), the inner diameter Dt1 (mm) of the tube (T), and the diameter Db1 (mm) of the rod-shaped portion are (0.5Dt1-0.5Db1-2.0) ≤ G1 may be satisfied, and (0.5Dt1-0.5Db1-2.0) ≤ G1 ≤ (0.5Dt1-0.5Db1) good. When the rod-shaped portion is cylindrical, the diameter Db1 is the diameter Db1 of the rod-shaped portion. When the rod-shaped portion is cylindrical, the maximum distance G1 (mm) at the first end is (0.5Dt1-0.5Db1) mm. The distance G1 may range from 0.3 to 1 times the maximum value. The distance G1 may be 1.0 mm or more, or 2.0 mm or more.

In the positive electrode plate of this embodiment, the second end may be in contact with the inner peripheral surface of the tube (T). For example, both the first end and the second end may contact the inner peripheral surface of the tube. According to these configurations, it is possible to particularly reduce the unevenness of the conversion degree in the entire positive electrode material.

Generally, the positive electrode plate of this embodiment includes a plurality of tubes (T) arranged in a row, and the positive electrode current collector includes a plurality of metal cores each having its end connected by a current collector. The number of tubes (T) and the number of core bars are the same. The number of tubes (T) and core bars is not limited, and may be in the range of 1 to 30 (for example, in the range of 13 to 20).

(lead-acid battery)
The lead-acid battery of this embodiment includes the clad positive plate for lead-acid batteries of this embodiment. This makes it possible to suppress initial self-discharge of the battery and improve initial discharge capacity. The configuration other than the positive electrode plate is not particularly limited, and a known configuration used for a clad lead-acid battery may be applied.

Examples of main components of the clad positive plate of the present embodiment and a lead-acid battery including the clad positive plate will be described below. However, the components of the present invention are not limited to the following examples. An example in which the positive electrode plate includes a plurality of porous tubes (T) will be described below.

(Clad positive plate)
The clad positive plate includes a plurality of porous tubes (T), a positive electrode material filled in the tubes (T), and a positive current collector. The positive electrode current collector has the characteristics described above. A clad positive plate usually includes a link connecting multiple tubes (T).

(Positive electrode current collector)
The positive electrode current collector is made of, for example, a lead alloy. As the lead alloy, it is preferable to use a Pb--Sb alloy. The Pb--Sb-based alloy may contain at least one element selected from the group consisting of arsenic, selenium, bismuth, and tin, if necessary.

The core metal of the positive electrode current collector may include a tapered portion on the side of the current collector and a bar-shaped portion extending from the tapered portion. The tapered portion has a diameter that decreases from the current collector side toward the rod-like portion side, and may have a truncated cone shape (including a shape similar to a truncated cone shape). The cored bar may include a columnar portion arranged between the tapered portion and the current collecting portion. The columnar portion usually has a columnar shape (including a columnar-like shape). In the vicinity of the current collecting portion, a tapered portion or a tapered portion and a columnar portion are arranged so as to close the opening of the tube (T) on the side of the current collecting portion. Resin (e.g., polyolefin (polyethylene, polypropylene, etc.)) is present in the gap between a portion of the tapered portion and the inner peripheral surface of the tube, or the gap between a portion of the tapered portion and the columnar portion and the inner peripheral surface of the tube. It may be filled.

When the core bar includes a tapered portion (a tapered portion that is not a rod-shaped portion) on the side of the current collector and a rod-shaped portion connected thereto, the first end of the rod-shaped portion serves as a boundary between the tapered portion and the rod-shaped portion. . Therefore, the shortest distance Lmin between the rod-shaped portion and the tube (T) at the first end is the shortest distance between the surface of the rod-shaped portion and the tube (T) at the boundary between the tapered portion and the rod-shaped portion.

The manufacturing method of the positive electrode current collector is not particularly limited, and it may be manufactured by a known method. For example, the positive electrode current collector may be manufactured by a casting method (including a die casting method).

(porous tube)
A porous tube (tube (T)) accommodates a metal core and a positive electrode material therein. The tube (T) has a hollow cylindrical shape as a whole. The tube (T) is porous and permeable to the electrolyte. A tube (T) is usually a tubular fiber assembly. The tubular fiber aggregate may be an aggregate formed by knitting fibers into a tubular shape. The tubular fiber assembly may be a tubular non-woven fabric or woven fabric. Examples of fibers include inorganic fibers (such as glass fibers) and resin fibers. The tube (T) may be heat-treated as necessary. The tube (T) may be formed by impregnating a tubular fiber assembly with a resin.

The length of the tube (T) may be selected according to the length of the cored bar. For example, the length of the tube (T) may be longer to some extent than the length L0 of the cored bar in the direction DL. The inner diameter and thickness of the tube (T) are selected according to the shape of the cored bar and/or the use of the lead-acid battery.

The inner diameter of the tube (T) is not particularly limited, and may be in the range of 9.0 mm to 10.5 mm (for example, the range of 9.3 mm to 10.3 mm). The inner diameter of the tube (T) is the diameter in a cross section perpendicular to the longitudinal direction of the tube (T) and is usually constant. The cross section of the tube (T) has a perfect circle or a shape close to a perfect circle. Therefore, the cross-sectional shape of the tube (T) can be regarded as a perfect circle.

The thickness of the tube (T) is not particularly limited as long as it functions as the tube of the clad positive electrode plate. The thickness of the tube (T) may be in the range 0.1mm to 0.8mm (eg in the range 0.3mm to 0.6mm).

The positive electrode material includes a positive electrode active material (specifically, at least one of lead dioxide and lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed.

The method for manufacturing the clad positive electrode plate is not limited, and for example, it may be manufactured by the following method. First, each of a plurality of cored bars is housed in a plurality of tubes (T). Next, an unformed positive electrode plate is formed by filling the tube (T) with an unformed positive electrode material (material to be a positive electrode material). A positive electrode plate is obtained by chemically forming the unformed positive electrode plate.

When the unformed positive electrode material is filled into the tube (T), the position of the second end can be controlled by tilting the tube (T). For example, filling may be performed by tilting the tube (T) so that the second end is located in the direction opposite to the direction in which the first end exists with respect to the central axis of the tube (T). . Such filling allows the center of the second end to lie in the opposite direction to the center of the first end across the central axis of the tube (T).

An unformed positive electrode plate may be produced by the following procedure. First, each of the plurality of cored bars is accommodated in the tube (T). Next, one end of each of the plurality of tubes (T) and the current collecting portion are fixed by upper connecting members. Next, the unformed positive electrode material is filled into the tubes (T) through the openings at the other ends of the plurality of tubes (T). Next, the openings at the other ends of the plurality of tubes (T) are sealed with the lower joints. Thus, an unformed positive electrode plate is obtained.

As the unformed positive electrode material, known materials used in lead-acid batteries may be used. The unformed positive electrode material includes lead-containing powder. The powder contains at least lead monoxide. The powder may further contain at least one selected from the group consisting of metallic lead, red lead, and lead sulfate. The unformed positive electrode material may contain additives as necessary.

The filling of the unformed positive electrode material may be either dry filling or wet filling. For example, in the case of dry filling, the dry material is directly filled into the tube (T). In the case of wet filling, the material in slurry form is filled into the tube (T). The slurry-like material may be prepared by mixing lead-containing powder, water, sulfuric acid, and, if necessary, additives.

In conventional clad positive plates, it is more difficult to fix the metal core on the central axis of the tube in the manufacturing process than in dry filling, and the metal core tends to become eccentric. Therefore, when wet filling is performed, the degree of formation tends to vary. According to the positive electrode plate of the present embodiment, even in the case of wet filling, it is possible to suppress variations in the conversion degree.

The unformed positive electrode plate is formed. Formation produces lead dioxide. The formation may be performed by charging the electrode plate group including the unformed electrode plate while immersing the electrode plate group in the electrolytic solution in the battery case of the lead-acid battery. Alternatively, chemical conversion of the positive electrode plate may be performed before assembly of the electrode plate group.

(lead-acid battery)
The lead-acid battery of this embodiment typically includes a positive plate, a negative plate, a separator, an electrolyte, a battery case, and a lid. The positive plate is the clad positive plate of this embodiment. Components other than the clad positive plate are not particularly limited, and known components used in lead-acid batteries may be used.

The battery case accommodates a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution. A separator is disposed between the positive plate and the negative plate. A positive electrode plate, a separator, and a negative electrode plate are laminated to form an electrode group. The plate group may include a plurality of positive plates and a plurality of negative plates. The lid seals the opening of the container.

(negative plate)
The negative plate includes a negative current collector and a negative electrode material. The negative electrode material is a portion of the negative electrode plate excluding the negative electrode current collector. A member such as a mat or pasting paper may be attached to the negative electrode plate. Since such a member (attaching member) is used integrally with the negative electrode plate, it is included in the negative electrode plate. Moreover, when the negative electrode plate includes such a member, the negative electrode material is the portion excluding the negative electrode current collector and the sticking member.

The negative electrode current collector may be formed by casting lead or a lead alloy, or may be formed by working a lead or lead alloy sheet. Processing methods include, for example, expanding processing and punching processing. A grid-like current collector (negative grid) is preferably used as the negative electrode current collector because it facilitates carrying the negative electrode material.

The lead alloy constituting the negative electrode current collector may be any of Pb--Sb-based alloys, Pb--Ca-based alloys, and Pb--Ca--Sn-based alloys. The lead or lead alloy forming the negative electrode current collector may contain at least one element selected from the group consisting of Ba, Ag, Al, Bi, As, and Se as an additive element.

The negative electrode material contains, as an essential component, a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction. The negative electrode material may contain additives such as organic shrinkage agents, carbonaceous materials, barium sulfate, and the like. The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually made using a lead-containing powder. The lead-containing powder preferably contains lead monoxide and may further contain metallic lead.

At least one of lignins and synthetic organic shrink-proofing agents may be used as the organic shrink-proofing agent. Examples of lignins include lignin, lignin derivatives such as ligninsulfonic acid or salts thereof (alkali metal salts such as sodium salts, etc.). Synthetic organic expanders are organic polymers containing elemental sulfur. Synthetic organic shrink-proofing agents include, but are not limited to, condensates of compounds having sulfur-containing groups and aromatic rings with aldehyde compounds (aldehydes or condensates thereof).

(Fully charged state)
In this specification, the fully charged state of a lead-acid battery is 2.8 V / After constant-current charging until reaching the cell, further constant-current charging was performed for 2 hours at a current of 0.2 times the numerical value described as the rated capacity.

A fully charged lead-acid battery refers to a lead-acid battery obtained by fully charging an existing chemical lead-acid battery. The lead-acid battery may be fully charged immediately after the formation as long as it is after the formation, or after some time has passed since the formation. may be used). A battery in the early stage of use means a battery in which not much time has passed since the start of use and which has hardly deteriorated.

Examples of carbonaceous materials contained in the negative electrode material include carbon black, graphite and the like. Examples of carbon black include acetylene black, furnace black, lamp black, and the like. Graphite may be a carbon material containing a graphite-type crystal structure, and may be either artificial graphite or natural graphite.

The manufacturing method of the negative electrode plate is not limited, and it may be manufactured by the following method. First, a negative electrode paste is prepared by kneading powder containing lead and various additives with water and sulfuric acid. Next, the negative electrode current collector is coated or filled with the negative electrode paste, and the obtained electrode plate is aged and dried to obtain an unformed negative electrode plate. Thereafter, a negative electrode plate is obtained by chemically forming the unformed negative electrode plate.

The formation of the unformed negative electrode plate may be performed by charging the electrode plate group including the unformed negative electrode plate while the electrode plate group including the unformed negative electrode plate is immersed in the electrolytic solution in the battery case of the lead-acid battery. . Alternatively, formation may be performed prior to assembly of the lead-acid battery or plate assembly.

(separator)
A nonwoven fabric, a microporous film, or the like is used for the separator placed between the negative electrode plate and the positive electrode plate. The thickness and the number of separators interposed between the negative electrode plate and the positive electrode plate may be selected according to the distance between the electrodes. As fibers constituting the separator (for example, non-woven fabric), glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers such as polyethylene terephthalate fibers, etc.), pulp fibers, and the like can be used. The nonwoven fabric may contain components other than fibers (inorganic powder, polymer as a binder, etc.).

The separator may be sheet-like, or may be in another shape (for example, bag-like). Alternatively, the separator may be a separator obtained by folding a sheet-like separator into a bellows shape.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid. The specific gravity of the electrolyte at 20° C. in a fully charged lead-acid battery is, for example, 1.20 or more, and may be 1.23 or more. The specific gravity of the electrolytic solution at 20° C. is, for example, 1.32 or less, and may be 1.30 or less. The specific gravity of the electrolyte at 20°C in a fully charged lead-acid battery is 1.20 or more (or 1.23 or more) and 1.32 or less, or 1.20 or more (or 1.23 or more) and 1.30 or less. may

Examples of embodiments of the invention are described below with reference to the drawings. The components described above can be applied to the components of the example described below. Also, the examples described below can be modified based on the above description. Also, the matters described below may be applied to the above embodiments. In addition, in the embodiments described below, components that are not essential to the positive electrode plate and lead-acid battery of the present invention may be omitted.

FIG. 1 is a top view schematically showing a clad positive electrode plate 30 according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line II--II of FIG. FIG. 3 is a schematic cross-sectional view along line III--III of FIG. In addition, in FIG. 3, illustration of the upper joint is omitted. FIG. 4 is a cross-sectional view (a cross-sectional view perpendicular to the direction DL) at the first end 352a. Note that hatching is omitted in FIG. Also shown in FIG. 4 is the position of the second end 352b projected onto the cross-section of FIG. A direction DR shown in some drawings is a direction in which the plurality of tubes 31 are arranged, and is a direction perpendicular to the direction DL.

The clad positive plate 30 includes a plurality of porous tubes 31 (tubes (T)) arranged in a line, a positive electrode material 32 and a positive current collector 33 . The positive electrode current collector 33 includes a plurality of core metals 35 and current collectors 34 connected to respective ends of the plurality of core metals 35 . The plurality of cored bars 35 are arranged in a row. One core bar 35 is accommodated in each tube 31 . The tube 31 is filled with a positive electrode material 32 . The tube 31 and cored bar 35, which are not shown in FIGS. 2 and 3, also have the same structures as those shown in FIGS.

As shown in FIGS. 2 and 3, the metal core 35 is a portion of the positive electrode current collector 33 that is housed in the tube 31 and has a surface that is in contact with the positive electrode material 32. . One end of each of the plurality of cored bars 35 is connected by a current collector 34 .

One end and the other end of a plurality of tubes 31 arranged in a row are fixed by upper connecting seat 38 and lower connecting seat 39, respectively. The opening of the tube 31 on the side of the current collector 34 is sealed with a metal core 35 and an upper connecting member 38 . The other opening of each tube 31 is sealed by a lower connecting seat 39 . An ear portion 34 a for collecting current from the clad positive electrode plate 30 is formed at one end in the longitudinal direction of the current collecting portion 34 . Ears 34a protrude outwardly from upper linking seat 38. As shown in FIG. The upper connecting seat 38 and the lower connecting seat 39 are made of resin or the like.

The cored bar 35 includes a tapered portion 351 on the current collector 34 side and a rod-shaped portion 352 extending from the tapered portion 351 . The bar-shaped portion 352 has a first end 352a on the current collector 34 side and a second end 352b opposite to the first end 352a. As shown in FIG. 2, the length of the core bar 35 in the direction DL in which the tube 31 extends is L0, and the length of the bar-shaped portion 352 in the direction DL is L1.

As shown in FIG. 4, the center 352c1 of the bar-shaped portion 352 is offset from the center 35c1 of the tube 31 at the first end 352a. That is, the distance G1 (mm) between the center 352c1 and the center 35c1 at the first end 352a is greater than zero. At the first end portion 352a, the shortest distance Lmin between the rod-shaped portion 352 and the tube 31 is 2.0 mm or less. Although Lmin is greater than 0 mm in FIGS. 3 and 4 for easy understanding, Lmin is 0 mm in a preferred example. In that case, the bar-shaped portion 352 contacts the inner peripheral surface of the tube 31 . In that case, the distance G1=0.5Dt1-0.5Db1. Dt1 (mm) is the inner diameter of the tube 31 at the first end 352a, and Db1 (mm) is the diameter of the rod-shaped portion 352 at the first end 352a.

In the cross section at the first end portion 352a shown in FIG. 4, there are a distance Lmin and a distance Lmax as the distance between the rod-shaped portion 352 and the tube 31 on a straight line A passing through the centers 352c1 and 35c1. The distance Lmax is the longer distance. The distance Lmin may be in the range of 0 to 0.5 times (for example, 0 to 0.2 times) the distance Lmax.

In the example shown in FIG. 4 , the center 352c2 of the second end 352b is positioned opposite the center 352c1 of the first end 352a across the central axis of the tube 31 . Here, being located in the direction opposite to the center 352c1 of the first end portion 352a across the central axis of the tube 31 means, for example, that the center 352c1 and the central axis of the tube 31 in the cross-sectional view of FIG. It means that the center 35c1 is located in a region sandwiched between two lines B that form a predetermined angle (for example, 30°) with a straight line A passing through (the center 35c1). As shown in FIG. 4, the line B is a line starting from the center 352c1.

2 to 4 show an example in which the first end portion 352a of the rod-shaped portion 352 is eccentric with respect to the central axis of the tube 31 in a direction parallel to the in-plane direction of the positive electrode plate 30. . However, the first end 352a of the rod-shaped portion 352 may be eccentric in directions other than the direction shown. For example, the first end 352 a of the bar-shaped portion 352 may be eccentric in a direction perpendicular to the in-plane direction of the positive electrode plate 30 .

FIG. 5 is a perspective view schematically showing an example of the lead-acid battery 1 according to one embodiment of the present invention with the lid removed. 6A is a front view of the lead-acid battery of FIG. 5, and FIG. 6B is a schematic cross-sectional view of the cross section taken along line VIB-VIB of FIG. 6A as viewed in the direction of the arrow.

A lead-acid battery 1 includes a battery case 10 containing an electrode plate group 11 and an electrolytic solution 12 . The electrode plate group 11 is configured by stacking a plurality of negative electrode plates 2 and a plurality of positive electrode plates 30 with separators 4 interposed therebetween. The positive electrode plate 30 is the above-described clad positive electrode plate. In this embodiment, the sheet-like separator 4 is sandwiched between the negative electrode plate 2 and the clad positive electrode plate 30, but the shape of the separator is not particularly limited.

An upper portion of each of the plurality of negative electrode plates 2 is provided with a current-collecting ear (not shown) projecting upward. Each upper portion of the clad positive plate 30 is also provided with a current collecting ear (not shown) protruding upward. The ear portions of the negative electrode plate 2 are connected and integrated by a negative electrode strap 5a. Similarly, the tabs of the clad type positive electrode plate 30 are also connected and integrated by the positive electrode strap 5b. The lower end of the negative electrode column 6a is fixed to the upper portion of the negative electrode strap 5a. The lower end of the positive electrode column 6b is fixed to the upper portion of the positive electrode strap 5b.

(Evaluation of formation degree)
The formation degree of the positive electrode material is evaluated by the following procedure using the clad type positive plate taken out from the dismantled lead-acid battery after formation has been completed.
First, in the positive electrode plate taken out, the portion where the metal core is present is divided into three equal parts, ie, an upper part, a middle part, and a lower part from the current collector side along the direction DL in which the tube (T) extends. . Then, the upper, middle and lower positive electrode materials are separately taken out. The analysis of the upper positive electrode material is described below, but the middle and lower positive electrode materials are similarly analyzed. About 1.5 g of the positive electrode material is taken out from the upper part, and its mass W (g) is measured.

Next, about 1.5 g of the collected positive electrode material is placed in a beaker, and 50 cm ³ of acetic acid aqueous solution (concentration: 5% by mass) is added. Next, the acetic acid aqueous solution in the beaker is heated to boil for 10 minutes. This step dissolves the lead monoxide in the positive electrode material. Next, after cooling the heated solution, it is filtered through a filter paper (JIS 3801-1995 Class 6), and the residue on the filter paper is washed with distilled water. Thus, the melt (including dissolved lead monoxide) is removed. Next, the above residue (including lead dioxide) is poured into another beaker with distilled water. Further, the residue left on the filter paper is dissolved in a mixture of 10 cm ³ of 30% nitric acid solution and 1 cm ³ of hydrogen peroxide solution and distilled water, and placed in a beaker. The liquid in the beaker is then heated to 80° C. for 10 minutes and then cooled. Next, the liquid in the beaker is filtered and the filtrate (containing dissolved lead dioxide) is placed in a volumetric flask. Further, the filter paper is washed with distilled water and the washing liquid is put into a volumetric flask so that the liquid in the volumetric flask is 250 cm ³ . A 50 cm ³ aliquot of this filtrate is taken and 1 g of tartaric acid and 20 cm ³ of 28% by weight aqueous ammonia are added. A few drops of BT indicator are added to the resulting solution, and then titrated with a 0.1 mol/L EDTA (ethylenediaminetetraacetic acid) aqueous solution. The point at which the color of the solution changes from reddish purple to blue is defined as the end point of the titration, and the amount of EDTA solution at that time is recorded. The content of lead dioxide (% by mass) is calculated by the following formula. FA is the titer of 0.1 mol/L EDTA aqueous solution.
PbO ₂ content (% by mass) = 100 x (dropped amount of EDTA solution (cm ³ )) x 23.92 x 5 x FA/(mass of sample W (g))

Since the _PbO2 content (% by mass) determined by the above method reflects the degree of formation, the value of the content (% by mass) is a relative evaluation value of the degree of formation. It is used as a value of conversion degree (%).

A clad positive electrode plate and a lead-acid battery according to one aspect of the present invention are collectively described below.

(1) A clad positive plate for a lead-acid battery, comprising at least one porous tube;
A positive electrode material filled in the porous tube, and a positive current collector, wherein the positive current collector includes at least one metal core and a current collector connected to an end of the metal core. wherein the core metal is disposed in the tube and is in contact with the positive electrode material, the core metal having a first end on the current collector side and the first a bar having an end and an opposite second end, at the first end the center of the bar is offset from the center of the tube, and at the first end A clad type positive electrode plate for a lead-acid battery, wherein the shortest distance between the rod-shaped portion and the tube is 2.0 mm or less.

(2) In the clad positive plate for a lead-acid battery according to (1) above, the center of the second end is located in the direction opposite to the center of the first end across the central axis of the tube. You may

(3) In the clad positive plate for a lead-acid battery according to (1) or (2) above, at the first end, a distance G1 (mm) between the center of the rod-shaped portion and the center of the tube, The inner diameter Dt1 (mm) of the tube and the diameter Db1 (mm) of the rod-shaped portion satisfy (0.5Dt1-0.5Db1-2.0)≤G1≤(0.5Dt1-0.5Db1). good too.

(4) In the clad positive electrode plate for a lead-acid battery according to any one of (1) to (3) above, the second end may be in contact with the inner peripheral surface of the tube.

(5) The clad positive electrode plate for a lead-acid battery according to any one of (1) to (4) above may include a plurality of the tubes arranged in a line, and the positive electrode current collectors each include the end portion may include a plurality of the metal cores connected by the current collector.

(6) In the clad positive electrode plate for a lead-acid battery of (5) above, the plurality of metal cores may be inclined in the same direction.

(7) A lead-acid battery comprising the clad positive plate for a lead-acid battery according to any one of (1) to (6) above.

[Example]
EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples. All lead-acid batteries in the following examples are single cell batteries with a rated voltage of 2V.

<<Lead-acid batteries A1 to A7, CA1 to CA2>>
(1) Fabrication of Clad Type Positive Electrode Plate A clad type positive plate having a metal core as shown in FIGS. 2 and 3 is fabricated by the following procedure. The fabricated positive electrode plate has substantially the same configuration as the positive electrode plate shown in FIG. 1, except for the number of tubes and metal cores.

First, a positive electrode current collector is manufactured by casting. At this time, a plurality of positive electrode current collectors are manufactured by changing the distance between the center of the rod-shaped portion at the first end and the center of the tube (T). Specifically, at the first end, the shortest distance Lmin between the bar-shaped portion of the cored bar and the tube (T) is changed to the value shown in Table 1 to produce a plurality of positive electrode current collectors. The rod-shaped portion of the cored bar is columnar (diameter: 3.0 mm). The length L0 of each cored bar is 295 mm.

The number of metal cores contained in one positive electrode current collector is 15. Fifteen core metals of the manufactured positive electrode current collector are accommodated in fifteen tubes. Next, by covering the current collecting portion and one end of the tube with resin, a resin-made upper linking seat is formed. The material of the positive electrode current collector is a Pb—Sb alloy. A porous tube made of glass fiber is used for the tube. The tube has a length of 310 mm, an outer diameter of 9.5 mm and an inner diameter of 9.0 mm.

Next, the positive electrode slurry is filled through the opening of the tube (opening on the side opposite to the current collector). At this time, the positive electrode current collector and the tube integrated together are tilted, and the positive electrode slurry is filled in a state in which the second end of the metal core is in contact with the tube. Specifically, when the rod-shaped portion is eccentric at the first end, the tube is tilted so as to be arranged as shown in FIG. 4 and filled with positive electrode slurry.

The 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. The mass ratio of lead powder and red lead is set to 9:1. The opening of the tube is then sealed with the lower engagement. Thus, an unformed clad positive electrode plate is produced. The filling amount of the positive electrode slurry is adjusted so that each positive electrode plate after chemical conversion contains 841±8 g of the positive electrode active material after chemical conversion in terms of PbO ₂ .

(2) Preparation of negative electrode Lead powder (containing 80% by mass of lead oxide and 20% by mass of metal lead), 0.15% by mass of an organic shrinkage inhibitor (sodium lignin sulfonate), and 1.2% by mass of barium sulfate, Mix with water and dilute sulfuric acid to prepare a negative electrode paste. A cast grid made of an Sb-based alloy as a negative electrode current collector is filled with a negative electrode paste and dried to prepare an unformed negative electrode plate. At this time, a grid-like current collector with a thickness of 2.6 mm was used to prepare a negative electrode plate (negative electrode plate A) with a thickness of 2.7 mm, and a grid-like current collector with a thickness of 4.4 mm was used. A negative electrode plate (negative electrode plate B) having a thickness of 4.5 mm is produced by using The negative plate A and the negative plate B are produced in the same number. The amount of the negative electrode paste was adjusted so that the amount of the negative electrode active material contained in one negative electrode plate A was 420±6 g in terms of Pb, and the amount of the negative electrode active material contained in one negative electrode plate B was 750±6 g in terms of Pb. Adjust filling volume. The length of the negative plate is the same as the tube length of the positive plate, and the width of the negative plate is the same as the width of the positive plate.

(3) Preparation of lead-acid battery Four unformed negative electrode plates and three unformed clad positive plates are alternately stacked with a separator (polypropylene microporous film) interposed between them. . Thereby, an electrode group as shown in FIG. 6B is formed. Negative plate A is used as the outer two negative plates of the electrode plate group, and negative electrode plate B is used as the inner two negative plates.

Next, the electrode plate group is housed in a polypropylene battery case, and dilute sulfuric acid (concentration: 14% by mass) is injected into the battery case. Next, the lid is glued to the opening of the container. Next, chemical conversion is performed while the container is held in a water bath at 30°C. Formation is performed by high-speed formation. The high-speed formation is carried out by applying a constant formation current of 31.5 A for 40 hours. Lead-acid batteries A1 to A7 and CA1 to CA2 are thus obtained.

(4) Evaluation of Formation Degree The degree of formation of the positive electrode material of the lead-acid battery is evaluated according to the described procedure.

Table 1 shows the value of the shortest distance Lmin and the conversion degree of the positive electrode material in the battery. Table 1 shows the formation degree of the positive electrode material of each part and the formation degree of the entire positive electrode material. The formation degree of the entire positive electrode material is the average value of the formation degrees of the positive electrode material in each part. It should be noted that the formation degree shown in Table 1 is the average value of the evaluation results of three batteries produced for each battery.

In the core metal of the positive electrode current collector of battery CA1, the center of the tube and the center of the rod-shaped core metal match at the end on the current collector side. That is, the positive electrode current collector of battery CA1 is a conventionally used general positive electrode current collector. For the batteries shown in Table 1, FIG. 7 shows the relationship between the shortest distance Lmin and the formation degree of the entire positive electrode material. As shown in Table 1 and FIG. 7, by setting the shortest distance Lmin to 2.0 mm or less, the formation degree of the entire positive electrode material can be improved. Batteries CA1 and CA2 whose shortest distance is longer than 2.0 mm have a large difference between the degree of formation in the upper portion and the degree of formation in the lower portion. On the other hand, in the batteries A1 to A7 in which the shortest distance is 2.0 mm or less, the variation in the degree of formation is small, and as a result, the degree of formation of the entire positive electrode material is high. From the viewpoint of increasing the conversion degree of the entire positive electrode material, the shortest distance Lmin is preferably as small as possible, preferably 1.5 mm or less, more preferably 1.0 mm or less, and particularly preferably 0.5 mm or less.

(Example 2)
In Example 2, batteries CB1 and B1 are produced under the same conditions as batteries CA1 and A6 described above, except that the chemical formation conditions for the positive electrode plate are changed. The positive electrode plate is chemically formed by normal chemical formation instead of high-speed chemical formation. Usually, formation is carried out by applying a constant formation current of 18.5 A for a formation time of 68 hours. Table 2 shows the value of the shortest distance Lmin and the conversion degree of the positive electrode material in the produced battery.

As shown in Table 2, the formation degree of the entire positive electrode material of Battery B1, in which the shortest distance Lmin is 2.0 mm or less, is higher than that of Battery CB1. As described above, it is effective to set the shortest distance Lmin to 2.0 mm or less even when performing normal formation.

INDUSTRIAL APPLICABILITY The present invention is used in clad positive plates and lead-acid batteries containing the same. There is no limitation on the use of the lead-acid battery, and it can be used for various purposes. INDUSTRIAL APPLICABILITY The lead-acid battery of the present invention is suitably used for industrial long-life storage batteries, storage batteries for electric vehicles (eg, forklifts), and the like. Moreover, the lead-acid battery of the present invention may be used as a storage battery for vehicles such as automobiles and motorcycles.

Reference Signs List 1: lead-acid battery 30: clad positive plate 30: positive plate 31: tube 32: positive electrode material 33: positive current collector 34: current collector 35: metal cores 35c1, 352c1, 352c2: center 352: rod-shaped portion 352a: First end 352b: second end

Claims (7)

at least one porous tube;
a positive electrode material filled in the porous tube;
a positive electrode current collector;
The positive electrode current collector includes at least one metal core and a current collector connected to an end of the metal core,
the cored bar is disposed within the tube and is in contact with the positive electrode material;
the core metal includes a bar-shaped portion having a first end on the current collecting portion side and a second end opposite to the first end;
at the first end, the center of the bar is offset from the center of the tube;
A clad positive electrode plate for a lead-acid battery, wherein the shortest distance between the rod-shaped portion and the tube at the first end is 2.0 mm or less. 2. The clad positive electrode plate for a lead-acid battery according to claim 1, wherein the center of said second end is located in a direction opposite to the center of said first end with respect to the central axis of said tube. At the first end, the distance G1 (mm) between the center of the rod-shaped portion and the center of the tube, the inner diameter Dt1 (mm) of the tube, and the diameter Db1 (mm) of the rod-shaped portion , (0.5Dt1-0.5Db1-2.0)≤G1≤(0.5Dt1-0.5Db1). 4. The clad positive electrode plate for a lead-acid battery according to claim 1, wherein said second end is in contact with the inner peripheral surface of said tube. comprising a plurality of said tubes arranged in a row;
5. The clad positive electrode plate for a lead-acid battery according to claim 1, wherein said positive electrode current collector includes a plurality of said metal cores each of said ends being connected by said current collecting portion. 6. The clad positive electrode plate for a lead-acid battery according to claim 5, wherein said plurality of cored bars are inclined in the same direction. A lead-acid battery comprising the clad positive plate for a lead-acid battery according to any one of claims 1 to 6.

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