JP2022131788A - 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 tube 31, and a positive electrode current collector 33. The positive electrode current collector 33 includes at least one core grid 35 with first and second end parts, and a current collector part 34 connecting to the first end part 35a. 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 an eccentric part 35d including a bent part 35c in which the second end part 32b bends to get close to the tube 31. When a length of the core grid 35 in a direction where the tube 31 extends is L0 and a length in the same direction from the first end part 35a to the eccentric part 35d is L1, a ratio L1/L0 is 0.80 or more.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 Unexamined Patent Application Publication No. 8-203505) discloses that "a plurality of blades (1') are provided only on both side surfaces of a cylindrical core metal (1) parallel to the electrode plate surface, and the blades (1') A clad type anode plate characterized in that the height c of is equal to or greater than the value obtained by the formula [(tube inner diameter a - mandrel outer diameter b) / 2 x 0.74].

Patent Document 2 (Japanese Utility Model Laid-Open No. 62-064956) describes a fiber-clad anode in which a cored bar is inserted into the center of a hollow cylindrical sleeve and an active material is filled in the gap between the sleeve and the cored bar. In the plate, a fiber-clad anode plate characterized in that the diameter of the lower 1/3 of the core bar is 20 to 30% larger than the diameter of the upper 2/3.

JP-A-8-203505 Japanese Utility Model Laid-Open No. 62-064956

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 a clad positive plate for a lead-acid battery. The positive plate includes at least one porous tube, a positive electrode material filled within the tube, and a positive current collector, the positive current collector having first and second ends. and a current collector connected to the first end, the cored bar disposed within the tube and in contact with the positive electrode material , the core bar includes an eccentric portion including a bent portion that bends so that the second end approaches the tube, the length of the core bar in the direction in which the tube extends is L0, and the The ratio L1/L0 is 0.80 or more, where L1 is the length from the end of 1 to the eccentric portion.

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 plate for lead acid batteries which can raise the chemical formation degree of positive electrode material, and a lead acid 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 an example of the shape of a bent portion of the core bar shown in FIGS. 2 and 3; FIG. FIG. 4 is a diagram schematically showing an example of the shape of the metal core 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. FIG. 7 is a front view of the lead-acid battery of FIG. 6; FIG. 7B is a schematic cross-sectional view of the cross section taken along line VIIB-VIIB in FIG. 7A 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 type positive plate for lead-acid battery)
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 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 metal core having first and second ends, and a current collector connected to the first end. A cored bar is placed in the tube (T) and is in contact with the positive electrode material. The cored bar includes an eccentric portion. The eccentric portion includes a bend where the second end bends closer to the tube (T). The ratio L1/L0 is 0.80 or more, where L0 is the length of the cored bar in the direction in which the tube (T) extends, and L1 is the length from the first end to the eccentric portion in that direction. .

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).

The radius of curvature of the center axis of the cored bar at the bent portion is 2700 mm or less (for example, 1900 mm or less, 1200 mm or less, 800 mm or less, or 600 mm or less). In other words, a portion having such a radius of curvature is defined as a bent portion. The radius of curvature of the central axis of the cored bar at the bent portion may be 200 mm or less. The bent portion may be a bent portion where the metal core is sharply bent. The bent portion is a portion having a radius of curvature of 20 mm or less (for example, 10 mm or less, 5 mm or less, or 3 mm or less) of the center axis of the cored bar. As long as the core bar at the second end is not bent toward the first end side from the direction perpendicular to the inner surface of the tube (T), there is no lower limit to the radius of curvature of the central axis of the bend, The radius of curvature may be 1 mm or more (eg, 2 mm or more, or 5 mm or more). These lower and upper limits can be arbitrarily combined as long as the lower limit does not fall below the upper limit. Hereinafter, a bent portion having a radius of curvature of the central axis of the cored bar of 20 mm or less is referred to as a bent portion, and the radius of curvature of the central axis of the cored bar is greater than 20 mm and 2700 mm or less (e.g., 1900 mm or less, 1200 mm or less, 800 mm or less). , or 600 mm or less) is sometimes referred to as a curved portion.

It should be noted that it is possible to recognize the presence of a bent portion at a predetermined portion of the core bar without measuring the radius of curvature. For example, it is possible to select arbitrary three points from the central axis of a predetermined portion of the core bar, and to recognize the presence of a bend in that portion based on the positions of the three points.

The length L1 is the length between the first end and the bend included in the eccentric portion (more specifically, the start of the bend that is closer to the current collecting portion of the two start points of the bend). (length along direction DL). Specifically, the length (in the direction DL length along) can be L1. If there are multiple bends (bends and/or bends), the length between the bend closest to the first end and the first end is L1. The starting point of the curved portion means the two ends of the portion where the radius of curvature of the center axis of the cored bar is within the above range.

When the component (rod-shaped part, tube (T), etc.) has a cylindrical shape or a hollow cylindrical shape, the central axis of the component at a certain position P1 corresponds to the circular cross section of the component at the position P1 (position cross section perpendicular to the direction in which the component extends at P1). In addition, when the component is neither cylindrical nor hollow cylindrical, the position of the central axis of the component at a certain position P1 is the cross section of the component at the position P1 (the component extends at the position P1). direction) of the center of gravity. That is, in this case, the line connecting the centers of gravity along the direction DL can be regarded as the central axis.

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. 9 includes a porous tube 1031 , a positive electrode material 1032 and a 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. 9, the portion away from the tube 1031 may be referred to as a spaced portion 1035a, and the portion of the metal core 1035 close to the tube 1031 may be referred to as a proximal portion 1035b. In the example of FIG. 9, 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. 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 type positive plate having an eccentric metal core, the degree of formation of the positive electrode material in the entire positive electrode plate varies more than the positive electrode plate having an eccentric metal core. , the conversion degree 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 core metal of the positive electrode current collector used in this embodiment has an eccentric portion including a bent portion where the second end portion is bent to approach the tube. Also, the above ratio L1/L0 is 0.80 or more. According to this configuration, it becomes easy to reduce the overall unevenness of the cored bar. For example, it becomes easy to prevent the portion from the first end to the vicinity of the second end from contacting the tube (T). As a result, the unevenness of the formation degree of the positive electrode plate as a whole can be reduced, and the formation degree of the positive electrode as a whole can be increased. Furthermore, by arranging most of the cored bar in the vicinity of the central axis of the tube (T), the active material is evenly distributed around the cored bar. As a result, it is possible to suppress corrosion of the cored bar.

The core bar has first and second ends. 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 first end exists at the boundary between the cored bar and the current collector. The second end is the end opposite the first end.

The ratio L1/L0 is 0.80 or greater, and may be 0.81 or greater, 0.86 or greater, or 0.91 or greater. The ratio L1/L0 may be 0.99 or less, 0.98 or less, 0.97 or less, 0.95 or less, or 0.91 or less. These lower and upper limits can be arbitrarily combined as long as the lower limit is less than the upper limit. For example, the ratio L1/L0 may range from 0.80 to 0.99, 0.81 to 0.99, 0.86 to 0.99, or 0.91 to 0.99. In these ranges, the upper limit may be 0.98, 0.97, 0.95, or 0.91, so long as the lower limit is less than the upper limit.

The length L0 of the cored bar in the direction 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). When the length L0 is 360 mm or less (for example, in the range of 200 mm to 360 mm), the effects of the present invention are enhanced.

The eccentric portion may include a bend where the second end bends closer to the tube (T). A bent portion is a portion where the core bar is sharply bent. In a preferred example, the cored bar includes only one bent portion as the bent portion.

When the bent portion includes a bent portion, the core bar may be bent at an angle of 2° or more at the bent portion. For example, the angle may be 2° or greater, 5° or greater, 10° or greater, 20° or greater, 30° or greater, or 40° or greater. The angle may be 90° or less, 75° or less, 60° or less, or 45° or less. These lower and upper limits can be arbitrarily combined as long as the upper limit is not equal to or lower than the lower limit. For example, the angle ranges from 2° to 90°, from 5° to 90°, from 10° to 90°, from 20° to 90°, from 30° to 90°, or from 40° to It may be in the range of 90°. In these ranges, the upper limits may be replaced by 75°, 60°, or 45°. For example, the angle may range from 2° to 60°. The larger the angle, the longer the distance between the first end and the eccentric portion. As a result, the deviation of the degree of chemical formation in the positive electrode can be suppressed, and therefore it becomes easy to increase the degree of chemical formation of the entire positive electrode. On the other hand, by reducing the angle, it becomes easier to reduce variations in packing density of the positive electrode material. The angle may be in the range of 2° to 75° (eg, 2° to 60°, 5° to 60°, 5° to 45°).

The direction in which the tube (T) extends is hereinafter sometimes referred to as "direction DL". Moreover, the direction perpendicular to the direction DL may be hereinafter referred to as a “cross-sectional direction DR”. Further, the end of the eccentric portion on the first end side may be referred to as "end K". An eccentric portion is formed from the end K to the second end.

Here, the distance in the cross-sectional direction DR between the central axis of the cored bar at the end K and the central axis of the cored bar at the second end is defined as a distance E (mm). Let the inside diameter of the tube (T) be the inside diameter Dt (mm). Let Dm (mm) be the diameter of the core. Here we assume that Dt and Dm are constant. Further assume that at the end K, the central axis of the core bar intersects the central axis of the tube (T), and that the core bar is in contact with the tube at the second end. Then (E+0.5Dm) is approximately equal to 0.5Dt. The distance E, inner diameter Dt, and diameter Dm may satisfy −2.0≦(E+0.5Dm−0.5Dt)≦2.0, preferably −1.0≦(E+0.5Dm−0.5Dt ) ≤ 1.0, more preferably -0.5 ≤ (E + 0.5Dm-0.5Dt) ≤ 0.5 (for example, -0.25 ≤ (E + 0.5Dm-0.5Dt) ≤ 0.25 ). Satisfying these conditions facilitates bringing the region between the first end and the second end closer to the central axis of the tube (T). In these equations, the right side may be half the absolute value of the left side. In these equations, the right side may be 0. Any of the multiple ranges exemplified here for the value of (E+0.5Dm-0.5Dt) can be arbitrarily combined with any of the multiple ranges of L1/L0 exemplified above. The values at the end K can be used as the values of the inner diameter Dt and the diameter Dm (the same applies to the following description).

The value of the distance E (mm) is preferably in the range of 0.4 to 1.6 times (0.5Dt-0.5Dm), more preferably in the range of 0.8 to 1.2 times. Preferably, it is particularly preferably in the range of 0.9 to 1.1 times. The upper limit of these ranges may be 1.0 times. Any of the plurality of ranges illustrated for the distance E here can be arbitrarily combined with any of the plurality of ranges of L1/L0 illustrated above.

In the positive plate of this embodiment, the second end is preferably close to the tube (T), more preferably in contact with the tube (T). For example, the shortest distance between the second end and the tube (T) may be in the range 0-1 mm, preferably in the range 0-0.5 mm. The second end may be in contact with the tube (T). Satisfying these conditions facilitates bringing the region between the first end and the second end closer to the central axis of the tube (T).

A bent portion is a portion that is bent even when the core bar is not deformed by an external force. From one point of view, when the cored bar is not deformed by an external force, there is no bent portion from the first end portion to the eccentric portion. When filling the positive electrode material into the tube (T), the smaller the eccentric portion, the easier it is to fill the positive electrode material uniformly. In a typical example of this configuration, the cored bar (typically a bar-shaped portion) between the first end and the bent portion extends linearly unless a force such as gravity is applied. The state in which the core is not deformed by an external force is, for example, a state in which the cored bar, which is not arranged in the tube (T), is left standing so as not to be deformed by gravity.

The core metal may include a bar-shaped portion. Here, the rod-shaped portion means a region whose diameter is generally constant except for projections that are partially added. For example, the rod-shaped portion may be a portion in which the maximum diameter and minimum diameter of the rod-shaped portion are within ±15% (preferably ±5%) of their average value. 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). When the shape of the cross section of the rod-shaped portion is not circular, the diameter of the circle having the same area as the cross-sectional area (equivalent circle) is taken as the diameter of the rod-shaped portion.

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 0.45 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 the positive electrode plate of this embodiment, the cored bar may include a rod-shaped portion extending from the first end to the eccentric portion, and the rod-shaped portion preferably does not contact the tube (T). According to this configuration, it is possible to particularly increase the chemical formation degree of the positive electrode material, and it is possible to particularly suppress corrosion of the positive electrode core metal. In addition, in the area from the first end to the eccentric portion, a portion of the rod-shaped portion bent by gravity or the like during filling of the electrode material may come into contact with the tube (T). Even in such a case, according to the positive electrode plate of the present embodiment, the length of the portion of the metal core near the central axis of the tube (T) can be made longer than that of the conventional positive electrode current collector. It is possible. Therefore, even if a portion of the rod-shaped portion is in contact with the tube (T) in the region from the first end to the eccentric portion, it is possible to obtain the effects of the present invention.

A typical bar is columnar (e.g., cylindrical) and extends from a first end to a second end (or near the first and second ends) and a second end It has a bend on the side. The diameter (eg, diameter) of the rod-shaped portion is not particularly limited, and may be in the range of 2.0 mm to 4.0 mm (eg, 2.5 mm to 3.5 mm). In addition, the core bar may be tapered in the vicinity of the second end (for example, in a range where the distance from the second end is about 5 mm), but that portion can be substantially regarded as a rod-shaped portion. . When the shape of the cross section of the rod-shaped portion is not circular, the diameter of the circle having the same area as the cross-sectional area (equivalent circle) is taken as the diameter of the rod-shaped portion.

The core bar may be composed of only the rod-shaped portion, or may be composed of the rod-shaped portion and a tapered portion described later. The length of the rod-shaped portion (rod-shaped portion of the cored bar) in the direction DL is in the range of 0.93 to 1.0 times (for example, the range of 0.96 to 1.0 times) the length of the cored bar in the direction DL. There may be.

Generally, the positive electrode plate of the present 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 a first 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 3 to 20).

In the positive electrode plate of the present embodiment, the plurality of metal cores may be eccentric in the same direction at their respective eccentric portions. From another point of view, the plurality of cored bars may be bent in the same direction at their respective bending portions. According to these configurations, when filling the tube (T) with the positive electrode material, it becomes easier to bring the second end closer to the tube (T). The eccentric direction (bending direction) of the cored bar is not limited, and may be parallel or perpendicular to the direction in which the plurality of tubes (T) are arranged. Making the eccentric direction of the core metal parallel to the direction in which the plurality of tubes (T) are arranged facilitates the manufacture of the core metal by casting.

A plurality of different configurations described above can be arbitrarily combined as long as there is no contradiction. The positive electrode plate of this embodiment may satisfy at least one of the plurality of configurations described above.

(lead-acid battery)
The lead-acid battery of this embodiment includes the clad positive plate of this embodiment. According to this configuration, the chemical conversion degree of the positive electrode plate can be increased, and as a result, it is possible to suppress the initial self-discharge of the battery and improve the 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). The positive electrode current collector has the characteristics described above.

(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 (for example, polyolefin (polyethylene, polypropylene, etc.) ) may be filled.

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). In that case, casting may be performed so that the eccentric portion of the cored bar is formed during casting. Alternatively, the bent portion of the eccentric portion of the cored bar may be formed by bending a portion of the cored bar of the cast positive electrode current collector.

(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 8.5 mm to 11 mm (for example, the range of 9.0 mm to 10.5 mm or 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). 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 filling the unformed positive electrode material into the tube (T), it is preferable to fill the tube (T) with the second end of the metal core in contact with the tube (T). For example, in a cross section including the second end (a cross section perpendicular to the central axis of the tube (T)), the positive electrode current collector and the tube (T) are tilted so that the second end is positioned at the lowest position. Filling may be performed in the state. This makes it possible to reduce the distance between the second end and the tube (T). For example, filling can be completed with the second end in contact with 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 of the cross-section taken along line II--II of FIG. 1 as viewed in the direction of the arrow. FIG. 3 is a schematic cross-sectional view of the cross-section taken along line III--III in FIG. 2 as viewed in the direction of the arrow. In addition, in FIG. 3, illustration of the upper joint is omitted.

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 current collecting portion 34 and a plurality of metal cores 35 . A plurality of core bars 35 are also arranged in a line in the same direction as the tube 31 . 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. . The core bar 35 has a first end 35a and a second end 35b. One ends (first ends 35 a ) of the plurality of cored bars 35 are 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 cored bar 35 has a bent portion 35 c that bends so that the second end 35 b approaches the tube 31 . The bent portion 35c is formed in the bar-shaped portion 352. As shown in FIG. The core bar 35 from the starting point of the bent portion 35c (the starting point on the first end 35a side of the two starting points) to the second end 35b is the eccentric portion 35d. The end K is the end on the first end 35a side of the two ends of the eccentric portion 35d. In addition, when the curvature radius of the bent portion 35c is sufficiently small, the length of the bent portion 35c (the length along the direction DL) is so short that it can be ignored. Therefore, in FIGS. 2 and 3, the length of the bent portion 35c is ignored and the position of the bent portion 35c is regarded as the end portion K. As shown in FIG. The diameter of the tapered portion 351 decreases from the current collecting portion 34 side toward the bar portion 352 side.

Let L0 be the length of the core bar 35 in the direction DL in which the tube 31 extends, and L1 be the length from the first end 35a to the bent portion 35c in the direction DL. The ratio L1/L0 is in the range described above. According to this configuration, the chemical formation degree of the positive electrode plate can be increased.

In the illustrated example, the second end 35b is in contact with the tube 31, and the rod-shaped portion 352 is not in contact with the tube 31 in the region from the first end 35a to the bent portion 35c. Further, the cored bar 35 is bent only at the bent portion 35c.

FIG. 4 schematically shows an enlarged view of the cross section of the bent portion 35c. As shown in FIG. 4, the cored bar 35 is bent at an angle α. The angle α is an angle (an angle of 90° or less) formed by the central axes 35t of two portions (for example, portions having a length of about 20 to 30 mm) adjacent to each other across the bent portion 35c of the core bar 35. As described above, in a preferred example, all the core bars 35 are bent in the same direction at the bent portions 35c.

FIG. 5 is a diagram schematically showing the arrangement of the cored bar 35 shown in FIGS. 2 and 3. As shown in FIG. FIG. 5 shows the arrangement of the core bar 35 (more specifically, the bar-shaped portion 352) from the second end portion 35b side to the bent portion 35c. The cross-sectional direction DR of the central axis 35t of the cored bar 35 at the bent portion 35c and the central axis 35t of the cored bar at the second end portion 35b (the direction perpendicular to the longitudinal direction DL of the tube 31. That is, parallel to the paper surface of FIG. 5) direction) is defined as distance E (mm). Let the inner diameter of the tube 31 be Dt (mm). Let Dm (mm) be the diameter of the cored bar 35 . Now assume that Dt and Dm are substantially constant. Furthermore, at the bent portion 35c, the position of the central axis 35t of the core metal 35 and the position of the central axis 31t of the tube (T) are the same, and the core metal 35 is in contact with the tube at the second end 35b. Assume that Then (E+0.5Dm) is approximately equal to 0.5Dt.

FIG. 6 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. 7A is a front view of the lead-acid battery of FIG. 6, and FIG. 7B is a schematic cross-sectional view of the cross-section taken along line VIIB-VIIB of FIG. 7A 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. The liquid in the beaker is then 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 portion 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 tube, and a positive current collector, wherein the positive current collector is , at least one metal core having first and second ends, and a current collector connected to the first end, the metal core disposed within the tube, and The core bar is in contact with the positive electrode material, and the core bar includes an eccentric portion including a bent portion that bends so that the second end portion approaches the tube, and the length of the core bar in the direction in which the tube extends. is L0, and the length from the first end portion to the eccentric portion in the direction is L1, the ratio L1/L0 is 0.80 or more.

(2) In the clad positive plate for a lead-acid battery according to (1) above, a radius of curvature of the center axis of the metal core may be 2700 mm or less at the bent portion.

(3) In the clad positive electrode plate for a lead-acid battery according to (1) or (2) above, the cross-sectional direction DR is a direction perpendicular to the direction in which the tube extends, and the first The distance E in the cross-sectional direction DR between the center axis of the core metal at the end K and the center axis of the core metal at the second end when the end on the end side is defined as the end K (mm), the inner diameter Dt (mm) of the tube, and the diameter Dm (mm) of the core metal may satisfy −2.0≦(E+0.5Dm−0.5Dt)≦2.0. .

(4) In any one of (1) to (3) above, the second end may be in contact with the tube.

(5) In the clad positive electrode plate for a lead-acid battery according to any one of (1) to (4) above, the core metal may include a rod-shaped portion extending from the first end to the eccentric portion, The bar may not be in contact with the tube.

(6) The clad positive electrode plate for a lead-acid battery according to any one of (1) to (5) above may include a plurality of the tubes arranged in a line, and the positive electrode current collectors each include the first may include a plurality of the cored bar, the ends of which are connected by the current collector.

(7) In the clad positive plate for a lead-acid battery according to (6) above, the plurality of metal cores may be eccentric in the same direction at the respective eccentric portions.

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

(Example 1)
In Example 1, lead-acid batteries A1 to A4 and CA1 to CA4 are produced and evaluated.

<<Lead-acid batteries A1 to A4, CA1 to CA4>>
(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 positive electrode plate to be produced 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, the above ratio L1/L0 is changed as shown in Table 1 to manufacture a plurality of positive electrode current collectors. As the core metal of the positive electrode current collector, a core metal having a bent portion at a position where the length from the first end is L1 is used. No bending portion is formed in the portion of the core bar other than the bending portion. Assuming that the position of the central axis of the core bar and the position of the central axis of the tube (T) are the same at the bent part, the bent part of the core bar is in contact with the tube at the second end change the angle of In other words, the angle of the bent portion of the cored bar is changed so that (E+0.5Dm-0.5Dt) is 0 mm. The diameter of the bar-shaped portion of the core bar is 3.0 mm.

In addition, in manufacturing the battery CA4, a positive electrode current collector having no bent portion is used. 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. The length L0 of each cored bar is 295 mm. 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. 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 metallic 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 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 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. 7B 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 a lid is adhered to the opening of the battery case. Next, dilute sulfuric acid (concentration: 14% by mass) is poured into 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 A4 and CA1 to CA4 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 ratio L1/L0 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.

The cored bar of the positive electrode current collector of battery CA4 is a conventional cored bar that does not have a bent portion, and as shown in FIG. For example, the metal core of the positive electrode current collector of battery CA4 is in contact with the tube within a range of 0.60L0 to L0 from the first end. The metal core of battery CA4 does not include a portion with a radius of curvature of 2700 mm or less.

For the batteries A1 to A4 and CA1 to CA3 shown in Table 1, FIG. 8 shows the relationship between the ratio L1/L0 and the formation degree of the entire positive electrode material. As shown in Table 1 and FIG. 8, by setting the ratio L1/L0 to 0.80 or more, the conversion degree of the entire positive electrode material was reduced to that of batteries CA1 to CA3 (comparative examples) and battery CA4 (conventional example). can be higher than In batteries CA1 to CA3 and battery CA4, the degree of chemical conversion is high in the lower portion, but the degree of chemical conversion in the upper portion is low, and the degree of chemical conversion is highly uneven. As a result, the degree of formation of the whole is low. On the other hand, in the batteries A1 to A4, the unevenness of the degree of formation is small, and the degree of formation as a whole is high.

(Evaluation of cycle life)
Cycle life is evaluated for batteries A1, A4, CA1, CA2, and CA4 described above. Specifically, first, each battery is subjected to a cycle test by the following method. A cycle test is performed by repeating a charging/discharging process in which one cycle is a discharging process and a charging process. The discharging process is carried out by discharging at a constant current (50A) for 3 hours so that 75% (150Ah) of the nominal capacity (200Ah) of each battery is discharged in 3 hours. The charging process is performed by charging at 45A for 3 hours and then at 20A for 2 hours. In the first charge, 90% of the discharge amount (150 Ah) is charged, and in the entire charging process, 117% of the discharge amount (150 Ah) is charged. These conditions are close to the conditions of use of batteries for forklifts.

The discharge capacity of the battery is measured every 100 cycles of the cycle test. First, the battery is charged at 40 A for 5 hours and the electrolyte is thoroughly stirred. Then, the specific gravity of the electrolyte is adjusted to 1.280 (converted at 20° C.) at the end of charging. Next, after storing the battery in a water tank at 30° C. for 12 hours, the discharge capacity is measured in the water tank under conditions of a discharge current of 40 A and a final voltage of 1.70 V.

Let X2 be the number of cycles when the measured discharge capacity falls below 135 A, and let C2 be the discharge capacity at that time. Furthermore, let C1 be the discharge capacity at the time of discharge capacity measurement one before that. The life cycle number X is calculated by the following formula.
X=X2-100+100×(C1-135)/(C1-C2)
Table 2 shows the battery ratio L1/L0 and the evaluation results of the life cycle number.

As shown in Table 2, the life cycle numbers of batteries A1 and A4 with L1/L0 of 0.80 or more are significantly higher than those of the other batteries. The reason for this is not clear at present, but one possible reason is that deterioration of the positive electrode current collectors of batteries A1 and A4 is small.

(Example 2)
In Example 2, the conditions were the same as those of Battery A2 in Example 1, except that the angle of the bent portion was changed so that the value of (E+0.5Dm−0.5Dt) was the value shown in Table 2. A plurality of batteries (Batteries B2-B4, and Batteries CB1 and CB2) are produced. Then, the positive electrode material of the produced battery is evaluated in the same manner as in Example 1. Table 3 shows the value of (E+0.5Dm-0.5Dt) and the evaluation results. Since Battery B1 is the same as Battery A2, Table 3 shows the results of Battery A2 for Battery B1.

As shown in Table 3, by setting the value of (E+0.5Dm−0.5Dt) to −2.0 mm or more, it is possible to reduce unevenness in the degree of formation and increase the degree of formation of the positive electrode material as a whole. A particularly high effect can be obtained when the value is in the range of -1.0 to 0 mm (for example, in the range of -0.5 to 0 mm). Considering the structure of the cored bar, if the absolute value of (E+0.5Dm-0.5Dt) is within a predetermined range (for example, the amplitude from 0 mm is the same range), a certain degree of effect can be expected.

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 (forklifts, etc.), 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 31: tube 32: positive electrode material 33: positive current collector 34: current collector 35: metal core 35a: first end 35b: second end 35c: bending part (curved part)
35d: Eccentric portion 352: Rod-shaped portion DL: Direction K: End α: Angle

Claims (8)

at least one porous tube;
a positive electrode material filled in the tube;
a positive electrode current collector;
The positive electrode current collector includes at least one metal core having first and second ends, and a current collector connected to the first end,
the cored bar is disposed within the tube and is in contact with the positive electrode material;
the core bar includes an eccentric portion including a bent portion that bends so that the second end approaches the tube;
When the length of the core bar in the direction in which the tube extends is L0, and the length from the first end portion to the eccentric portion in the direction is L1, the ratio L1/L0 is 0.80 or more. A clad positive plate for lead-acid batteries. 2. The clad positive electrode plate for a lead-acid battery according to claim 1, wherein the radius of curvature of the central axis of said metal core at said bent portion is 2700 mm or less. When the direction perpendicular to the direction in which the tube extends is defined as a cross-sectional direction DR, and the end of the eccentric portion on the first end side is defined as an end K,
distance E (mm) in the cross-sectional direction DR between the central axis of the cored bar at the end K and the central axis of the cored bar at the second end; an inner diameter Dt (mm) of the tube; 3. The clad positive electrode plate for a lead-acid battery according to claim 1, wherein the diameter Dm (mm) of said metal core satisfies −2.0≦(E+0.5Dm−0.5Dt)≦2.0. 4. The clad positive plate for a lead-acid battery according to claim 1, wherein said second end is in contact with said tube. the core bar includes a bar-shaped portion that continues from the first end to the eccentric portion;
The clad positive plate for a lead-acid battery according to any one of claims 1 to 4, wherein said rod-shaped portion is not in contact with said tube. comprising a plurality of said tubes arranged in a row;
The clad type for a lead-acid battery according to any one of claims 1 to 5, wherein said positive electrode current collector includes a plurality of said metal cores each having said first end connected by said current collector. positive plate. 7. The clad positive electrode plate for a lead-acid battery according to claim 6, wherein said plurality of cored bars are eccentric in the same direction at said eccentric portions. A lead-acid battery comprising the clad positive plate for a lead-acid battery according to any one of claims 1 to 7.

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