JP7697225B2 - Clad type positive electrode plate for lead-acid battery and lead-acid battery - Google Patents

Description

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

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

Patent document 1 (JP Patent Publication 50-161640) discloses a method for manufacturing a clad grid for a lead-acid battery, comprising the steps of: pressing a drawn lead or lead alloy rod at appropriate intervals to form a core with blades; and removing the core from a mold and injecting molten lead or lead alloy into the mold to form a frame.

Patent document 2 (JP Patent Publication 56-167272) discloses a fiber clad substrate made of "a comb-like lead alloy horizontal bar with multiple vertical bars hanging down at predetermined intervals, the horizontal bar being folded and overlapped, with the vertical bars serving as a core metal."

Japanese Unexamined Patent Publication No. 50-161640 Japanese Unexamined Patent Publication No. 56-167272

In conventional clad positive plates, it was sometimes impossible to sufficiently increase the chemical conversion of the positive electrode material. In this situation, one of the objects of the present invention is to provide a clad positive plate for a lead-acid battery that can increase the chemical conversion of the positive electrode material, and a lead-acid battery that includes the same.

One aspect of the present invention relates to a clad type positive plate for a lead acid battery. The positive plate includes at least one porous tube, a positive electrode material filled in the porous tube, and a positive current collector. The positive current collector includes at least one core and a current collector connected to an end of the core. The core is disposed in the tube and is in contact with the positive electrode material. The core includes a rod-shaped portion having a first end on the current collector side and a second end opposite the first end. At the first end, the center of the rod-shaped portion is offset from the center of the tube. At the first end, the shortest distance between the rod-shaped portion and the tube is 2.0 mm or less.

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

According to the present invention, a clad type positive electrode plate capable of increasing the degree of chemical conversion of the positive electrode material, and a lead-acid battery including the same can be obtained.

FIG. 2 is a top view showing a schematic diagram of a clad type positive electrode plate according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a diagram showing a schematic arrangement of the core metals shown in FIGS. 2 and 3 . FIG. 1 is a perspective view showing a schematic example of a lead-acid battery according to an embodiment of the present invention with the lid removed. FIG. 6 is a front view of the lead-acid battery of FIG. 5 . 6B is a schematic cross-sectional view taken along line VIB-VIB in FIG. 6A, as viewed from the direction of the arrows. 1 is a graph showing some of the results of the examples. FIG. 1 is a schematic cross-sectional view showing a structure of an example of a conventional clad type positive electrode plate.

The following describes an embodiment of the present invention using examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present invention are obtained. In this specification, the range described as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to A and less than or equal to B."

(Clad positive electrode plate)
The clad type positive plate of this embodiment is used in a lead-acid battery. The clad type positive plate includes at least one porous tube, a positive electrode material filled in the porous tube, and a positive electrode current collector. The porous tube may be referred to as a "tube (T)" below. The positive electrode current collector includes at least one core metal and a current collector connected to an end of the core metal. The core metal is disposed in the tube (T) and is in contact with the positive electrode material. The core metal includes a rod-shaped portion having a first end on the current collector side and a second end opposite to the first end. At the first end, the center of the rod-shaped portion 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 may be referred to below as the "direction DL." From another perspective, the direction DL is a 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 part at the first end means the position of the central axis of the rod-shaped part 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 centers of other components at the first end and the centers of components at the second end mean the positions of the central axes of the components in the relevant parts.

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

The rod-shaped portion refers to a region whose diameter is generally constant. For example, if the diameter of the rod-shaped portion varies with the position in the longitudinal direction, the maximum and minimum values of the varying diameters may be within a range of ±15% (preferably ±5%) of their average value. The diameter of the rod-shaped portion is the diameter of a cross section perpendicular to the direction in which the rod-shaped portion extends (the direction of the central axis). If the cross section is not circular, the diameter of the rod-shaped portion is the diameter of a circle (equivalent circle) having the same area as the area of the cross section.

The rod-shaped portion typically has a cylindrical shape. There is no particular limitation on the diameter (e.g., diameter) of the rod-shaped portion, and it may be in the range of 0.25 to 0.40 times (e.g., 0.30 to 0.38 times) the inner diameter of the tube. The rod-shaped portion may have a shape other than a cylindrical shape (e.g., a prismatic shape).

In a typical positive electrode collector of a clad type positive electrode plate, the position of the core metal on the current collecting side is fixed, but the positions of the other core metals are not fixed. Therefore, when such a typical positive electrode collector is used, the position of the core metal tends to become eccentric the further away from the current collecting side (i.e., the more likely it is to be misaligned from the central axis of the porous tube). A schematic cross-sectional view of an example of such a conventional clad type positive electrode plate is shown in Figure 8.

The positive electrode plate shown in FIG. 8 includes a tube 1031, a positive electrode material 1032, and a positive current collector 1033. The positive current collector 1033 includes a current collector 1034 and a core 1035. The positive electrode material 1032 and the core 1035 are disposed in the tube 1031. The tip side of the core 1035 is not fixed. Therefore, when a general positive current collector 1033 is used, the core 1035 on the current collector 1034 side is located near the center of the tube 1031, but the core 1035 located away from the current collector 1034 may be eccentric enough to come into contact with the inner surface of the tube 1031. In FIG. 8, the part away from the tube 1031 may be referred to as the separated part 1035a, and the part of the core 1035 close to the tube 1031 may be referred to as the close part 1035b. In the example shown in FIG. 8, the core metal 1035 located close to the current collecting portion 1034 is the separated portion 1035a, and the core metal 1035 located away from the current collecting portion 1034 is the adjacent portion 1035b.

The positive electrode material contains a large amount of lead monoxide PbO (hereinafter sometimes referred to as "unformed active material") with low electrical conductivity. In addition, ions involved in the chemical reaction move through the pores of the positive electrode material. Therefore, in the positive electrode material around the adjacent portion 1035b, the resistance of the unformed active material and the resistance when the ions pass through the pores are relatively small. Therefore, in the vicinity of the adjacent portion 1035b, a larger chemical current flows in the early stage of chemical formation, and as a result, the amount of PbO ₂ generated by the chemical reaction is large. PbO ₂ has a higher electrical conductivity than the unformed active material. Therefore, in the positive electrode material around the adjacent portion 1035b, the chemical reaction proceeds rapidly due to the originally small resistance and the electrical conductivity that improves as chemical formation progresses.

The chemical formation also proceeds simultaneously in the negative plate facing the positive plate. Therefore, in the negative plate, the chemical formation proceeds first from the negative electrode material in the portion facing the adjacent portion 1035b of the core metal 1035. When the chemical formation of the active material is almost completed in the positive electrode material around the adjacent portion 1035b and in the negative electrode material in the portion facing the adjacent portion 1035b (for example, in the later stage of chemical formation), most of the chemical formation current flows into the separated portion 1035a. However, since the chemical formation current is concentrated in the separated portion 1035a, the current density is increased, and the resistance of the positive electrode material around the separated portion 1035a is originally large, in the separated portion 1035a, the increase rate of _PbO2 relative to the applied amount of electricity (i.e., chemical formation efficiency) is significantly lower than in the adjacent portion 1035b.

Due to the above mechanism, in conventional clad-type positive plates, there was a large difference in the degree of formation of the positive electrode material near the current collector and that of the positive electrode material in the area away from the current collector. As a result, there was a tendency for the degree of formation of the positive electrode material itself in the entire positive plate to decrease.

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), in the early stages of formation, the difference between the formation current density in the adjacent portion 1035b and the formation current density in the separated portion 1035a becomes extremely large. Furthermore, in the later stages of formation when the formation of the adjacent portion 1035b is almost complete, the formation current concentrates in the separated portion 1035a, which has a high resistance, and the formation efficiency decreases. Therefore, when the formation current is large, the variation in the degree of formation of the positive electrode material becomes significant.

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

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

The length L0 of the core 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 (e.g., in the range of 200 mm to 400 mm). The length of the rod-shaped portion in the direction DL may be in the range of 0.95 to 1.0 times the length of the core (e.g., 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) (the inner surface of the tube (T)) is 2.0 mm or less, and may be 1.5 mm or less, 1.0 mm or less, or 0.5 mm or less. For example, the shortest distance Lmin may be 0 mm, i.e., the rod-shaped portion and the tube (T) may be in contact at the first end. From the viewpoint of increasing the degree of chemical conversion of the positive electrode material, it is preferable that the shortest distance Lmin is small.

In the positive electrode plate of this 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) may be located in the opposite direction to the center of the first end (the position of the central axis of the rod-shaped portion at the first end) across the central axis of the tube (T). With this configuration, the bias in the degree of chemical conversion of the entire positive electrode material can be particularly reduced, and the degree of chemical conversion of the entire positive electrode material can be particularly increased. Note that all parts of the rod-shaped portion may be in contact with the inner surface of the tube (T). In this case, too, the bias in the degree of chemical conversion of the entire positive electrode material can be reduced, and the degree of chemical conversion of the entire positive electrode material can be increased.

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 may satisfy (0.5Dt1-0.5Db1-2.0) ≦ G1, or may satisfy (0.5Dt1-0.5Db1-2.0) ≦ G1 ≦ (0.5Dt1-0.5Db1). 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 distance G1 (mm) at the first end is at most (0.5Dt1-0.5Db1) mm. The distance G1 may be in the range of 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 circumferential surface of the tube (T). For example, both the first end and the second end may be in contact with the inner circumferential surface of the tube. These configurations can particularly reduce the bias in the degree of chemical conversion throughout the positive electrode material.

Typically, the positive electrode plate of this embodiment includes multiple tubes (T) arranged in a row, and the positive electrode current collector includes multiple cores whose ends are connected by current collecting parts. The number of tubes (T) is the same as the number of cores. There is no limit to the number of tubes (T) and cores, and each 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 type positive electrode plate for the lead-acid battery of this embodiment. This makes it possible to suppress the initial self-discharge of the battery and to improve the initial discharge capacity. There is no particular limitation on the configuration other than the positive electrode plate, and a known configuration used in a clad type lead-acid battery may be applied.

Below, examples of the main components of the clad positive plate of this embodiment and the lead-acid battery including the same are described. However, the components of the present invention are not limited to the following examples. Below, an example is described in which the positive plate includes multiple porous tubes (T).

(Clad positive electrode plate)
The clad type 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 current collector has the above-mentioned characteristics. The clad type positive plate usually includes a linking member that connects the plurality of 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 based alloy. The Pb-Sb based alloy may contain at least one element selected from the group consisting of arsenic, selenium, bismuth, and tin, as necessary.

The core metal of the positive electrode current collector may include a tapered portion on the current collector side and a rod-shaped portion extending from the tapered portion. The tapered portion may have a diameter that decreases from the current collector side toward the rod-shaped portion side and may have a truncated cone shape (including a shape similar to a truncated cone shape). The core metal may include a columnar portion disposed between the tapered portion and the current collector. The columnar portion usually has a cylindrical shape (including a shape similar to a cylindrical shape). In the vicinity of the current collector, the tapered portion, or the tapered portion and the columnar portion are disposed so as to block the opening on the current collector side of the tube (T). A resin (e.g., polyolefin (polyethylene, polypropylene, etc.)) may be filled in the gap between a part of the tapered portion and the inner surface of the tube, or the gap between a part of the tapered portion and the columnar portion and the inner surface of the tube.

When the core includes a tapered portion (a tapered portion that is not a rod-shaped portion) on the current collecting portion side and a rod-shaped portion connected thereto, the first end of the rod-shaped portion is the 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.

There are no particular limitations on the manufacturing method of the positive electrode collector, and it may be manufactured by a known method. For example, the positive electrode collector may be manufactured by a casting method (including a die casting method).

(Porous tube)
The porous tube (tube (T)) accommodates a core metal and a positive electrode material therein. The tube (T) has a hollow cylindrical shape as a whole. The tube (T) is porous and allows an electrolyte to pass through. The tube (T) is usually a tubular fiber assembly. The tubular fiber assembly may be an assembly formed by weaving fibers into a tube shape. The tubular fiber assembly may be a tubular nonwoven fabric or woven fabric. Examples of fibers include inorganic fibers (such as glass fibers), resin fibers, and the like. 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 core. For example, the length of the tube (T) may be somewhat longer than the length L0 of the core in the direction DL. The inner diameter and thickness of the tube (T) may be selected according to the shape of the core and/or the use of the lead-acid battery.

There is no particular limit to the inner diameter of the tube (T), and it may be in the range of 9.0 mm to 10.5 mm (for example, in 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 shape that is a perfect circle or close to a perfect circle. Therefore, the cross-sectional shape of the tube (T) can be considered to be a perfect circle.

There is no particular limitation on the thickness of the tube (T), as long as it functions as a tube for a clad-type positive electrode plate. The thickness of the tube (T) may be in the range of 0.1 mm to 0.8 mm (for example, in the range of 0.3 mm to 0.6 mm).

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

There is no limitation on the manufacturing method of the clad type positive electrode plate, and for example, it may be manufactured by the following method. First, each of the multiple core metals is housed in multiple tubes (T). Next, an unformed positive electrode plate is formed by filling the tube (T) with unformed positive electrode material (material that will become the positive electrode material). The unformed positive electrode plate is formed to obtain a positive electrode plate.

When filling the tube (T) with unformed positive electrode material, the position of the second end can be controlled by tilting the tube (T). For example, the tube (T) may be tilted so that the second end is located in the opposite direction to the direction in which the first end is located relative to the central axis of the tube (T). By filling in this way, the center of the second end can be positioned in the opposite direction to the center of the first end across the central axis of the tube (T).

The unformed positive electrode plate may be manufactured by the following procedure. First, each of the multiple core metals is housed in a tube (T). Next, one end of each of the multiple tubes (T) is fixed to the current collector with an upper connecting member. Next, the unformed positive electrode material is filled into the tube (T) through the opening at the other end of each of the multiple tubes (T). Next, the opening at the other end of each of the multiple tubes (T) is sealed with a lower connecting member. In this manner, an unformed positive electrode plate is obtained.

The unformed positive electrode material may be a known material used in lead-acid batteries. The unformed positive electrode material includes a powder containing lead. The powder includes at least lead monoxide. The powder may further include at least one selected from the group consisting of metallic lead, red lead, and lead sulfate. The unformed positive electrode material may include an additive 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 filled directly into the tube (T). In the case of wet filling, a slurry material is filled into the tube (T). The slurry material may be prepared by mixing a lead-containing powder, water, sulfuric acid, and, if necessary, additives.

In conventional clad positive electrode plates, it is difficult to fix the core metal on the central axis of the tube when wet filling is used compared to dry filling, and the core metal is prone to becoming eccentric. Therefore, when wet filling is used, variations in the degree of formation are likely to occur. With the positive electrode plate of this embodiment, it is possible to suppress variations in the degree of formation even when wet filling is used.

The unformed positive plates are formed. The formation produces lead dioxide. Formation may be performed by charging the plate group, which includes the unformed plates, while immersing the plate group in the electrolyte in the lead-acid battery container. Alternatively, the formation of the positive plates may be performed before the assembly of the plate group.

(lead acid battery)
The lead-acid battery of this embodiment usually includes a positive plate, a negative plate, a separator, an electrolyte, a battery case, and a lid. The positive plate is a clad type positive plate of this embodiment. There is no particular limitation on the components other than the clad type positive plate, and known components used in lead-acid batteries may be used.

The battery case contains positive and negative electrode plates, a separator, and an electrolyte. The separator is disposed between the positive and negative electrode plates. The positive and negative electrode plates are stacked to form a plate assembly. The plate assembly may include multiple positive and negative electrode plates. The lid seals the opening of the battery case.

(Negative electrode plate)
The negative electrode plate includes a negative current collector and a negative electrode material. The negative electrode material is the portion of the negative electrode plate excluding the negative current collector. Note that a member such as a mat or pasting paper may be attached to the negative electrode plate. Such a member (attaching member) is used integrally with the negative electrode plate, and is therefore included in the negative electrode plate. In addition, when the negative electrode plate includes such a member, the negative electrode material is the portion excluding the negative electrode collector and the attaching member.

The negative electrode current collector may be formed by casting lead or a lead alloy, or by processing a lead or lead alloy sheet. Examples of processing methods include expanding and punching. It is preferable to use a lattice-shaped current collector (negative electrode lattice) as the negative electrode current collector, as this makes it easier to support the negative electrode material.

The lead alloy constituting the negative electrode current collector may be any of Pb-Sb alloys, Pb-Ca alloys, and Pb-Ca-Sn alloys. The lead or lead alloy constituting 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 inhibitors, carbonaceous materials, and barium sulfate. The negative electrode active material in a charged state is spongy lead, but unformed negative plates are usually made using a powder containing lead. The lead-containing powder preferably contains lead monoxide and may further contain metallic lead.

As the organic shrink-proofing agent, at least one of lignins and synthetic organic shrink-proofing agents may be used. Examples of lignins include lignin, lignin derivatives such as lignin sulfonic acid or its salts (such as alkali metal salts such as sodium salts). Synthetic organic shrink-proofing agents are organic polymers containing elemental sulfur. Examples of synthetic organic shrink-proofing agents include, but are not limited to, condensation products of a compound having a sulfur-containing group and an aromatic ring with an aldehyde compound (aldehyde or its condensation product).

(fully charged)
In this specification, the fully charged state of a lead-acid battery refers to a state in which the battery is charged in a water bath at 25° C. at a constant current (A) of 0.2 times the value given as the rated capacity (unit: Ah) until the battery reaches 2.8 V/cell, and then further charged at a constant current of 0.2 times the value given as the rated capacity for 2 hours.

A fully charged lead-acid battery refers to a lead-acid battery that has already been chemically prepared and is fully charged. A lead-acid battery can be fully charged immediately after chemical preparation, or after some time has passed since chemical preparation (for example, a lead-acid battery that is in use (preferably in the early stages of use) after chemical preparation can be fully charged). A battery in the early stages of use refers to a battery that has not been in use for very long and has hardly deteriorated at all.

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

There is no limitation on the manufacturing method of the negative electrode plate, and it may be manufactured by the following method. First, a negative electrode paste is prepared by adding water and sulfuric acid to a powder containing lead and various additives and kneading them. Next, the negative electrode paste is applied or filled onto a negative electrode collector, and the obtained electrode plate is aged and dried to obtain an unformed negative electrode plate. After that, the unformed negative electrode plate is formed to obtain a negative electrode plate.

The formation of unformed negative plates may be performed by charging the plate group, which includes the unformed negative plates, while the plate group is immersed in the electrolyte in the lead-acid battery container. Alternatively, the formation may be performed before assembly of the lead-acid battery or the plate group.

(Separator)
The separator disposed between the negative and positive electrodes may be made of a nonwoven fabric or a microporous membrane. The thickness and number of the separators to be disposed between the negative and positive electrodes may be selected according to the distance between the electrodes. The fibers constituting the separator (e.g., nonwoven fabric) may be glass fibers, polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers such as polyethylene terephthalate fibers), pulp fibers, etc. The nonwoven fabric may contain components other than fibers (inorganic powder, polymers as binders, etc.).

The separator may be in a sheet shape or in another shape (e.g., a bag shape). Alternatively, the separator may be a separator obtained by folding a sheet-shaped separator into an accordion shape.

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

Examples of embodiments of the present invention will be described below with reference to the drawings. The components described above can be applied to the components of the examples described below. The examples described below can be modified based on the above description. The matters described below may also be applied to the above embodiments. 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.

Figure 1 is a top view showing a clad type positive electrode plate 30 according to one embodiment of the present invention. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic cross-sectional view taken along line III-III in Figure 2. Note that the illustration of the upper link is omitted in Figure 3. Figure 4 is a cross-sectional view (cross-sectional view perpendicular to direction DL) at the first end 352a. Note that hatching is omitted in Figure 4. Figure 4 also shows the position of the second end 352b projected onto the cross section of Figure 4. The direction DR shown in some of the figures is the direction in which the multiple tubes 31 are lined up, and is perpendicular to direction DL.

The clad type positive electrode plate 30 includes a number of porous tubes 31 (tubes (T)) arranged in a row, a positive electrode material 32, and a positive electrode current collector 33. The positive electrode current collector 33 includes a number of cores 35 and a current collector 34 connected to each end of the number of cores 35. The number of cores 35 are arranged in a row. Each tube 31 contains one core 35. The tube 31 is filled with a positive electrode material 32. The tubes 31 and cores 35 not shown in Figures 2 and 3 also have the same structure as those shown in Figures 2 and 3.

As shown in Figures 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 multiple metal cores 35 is connected by the current collector 34.

One end and the other end of the multiple tubes 31 arranged in a row are fixed by an upper link 38 and a lower link 39, respectively. The opening of the tube 31 on the current collector 34 side is sealed by a core metal 35 and an upper link 38. The other opening of each tube 31 is sealed by a lower link 39. An ear 34a for collecting current from the clad positive electrode plate 30 is formed at one longitudinal end of the current collector 34. The ear 34a protrudes outward from the upper link 38. The upper link 38 and the lower link 39 are formed of resin or the like.

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

As shown in FIG. 4, at the first end 352a, the center 352c1 of the rod-shaped portion 352 is offset from the center 35c1 of the tube 31. That is, the distance G1 (mm) between the centers 352c1 and 35c1 at the first end 352a is greater than 0. At the first end 352a, the shortest distance Lmin between the rod-shaped portion 352 and the tube 31 is 2.0 mm or less. Note that, for ease of understanding, Lmin is greater than 0 mm in FIG. 3 and FIG. 4, but in a preferred example, Lmin is 0 mm. In that case, the rod-shaped portion 352 contacts the inner surface of the tube 31. In that case, the distance G1 = 0.5Dt1 - 0.5Db1. Note that 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 of the first end 352a shown in FIG. 4, on a straight line A passing through the centers 352c1 and 35c1, there are a distance Lmin and a distance Lmax between the rod-shaped portion 352 and the tube 31. The distance Lmax is the longer distance. The distance Lmin may be in the range of 0 to 0.5 times (for example, in the range of 0 to 0.2 times) the distance Lmax.

In the example shown in FIG. 4, the center 352c2 of the second end 352b is located in the opposite direction to the center 352c1 of the first end 352a across the central axis of the tube 31. Here, being located in the opposite direction to the center 352c1 of the first end 352a across the central axis of the tube 31 means, for example, that in the projection of the cross section of FIG. 4, the angle between the center 352c1 and a straight line A passing through the central axis (center 35c1) of the tube 31 is a predetermined angle (for example, 30°) and that the line B is located in the area between the center 352c1 and the straight line A passing through the central axis (center 35c1) of the tube 31. As shown in FIG. 4, the line B is a line that starts from the center 352c1.

2 to 4 show an example in which the first end 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 a direction other than the direction shown. For example, the first end 352a of the rod-shaped portion 352 may be eccentric in a direction perpendicular to the in-plane direction of the positive electrode plate 30.

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

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

The upper part of each of the multiple negative electrode plates 2 is provided with an upwardly protruding current collecting lug (not shown). The upper part of each of the multiple clad type positive electrode plates 30 is also provided with an upwardly protruding current collecting lug (not shown). The lugs of the negative electrode plates 2 are connected and integrated by a negative electrode strap 5a. Similarly, the lugs of the clad type positive electrode plates 30 are connected and integrated by a positive electrode strap 5b. The lower end of the negative electrode pole 6a is fixed to the upper part of the negative electrode strap 5a. The lower end of the positive electrode pole 6b is fixed to the upper part of the positive electrode strap 5b.

(Evaluation of chemical conversion degree)
The degree of formation of the positive electrode material is evaluated by dismantling a lead-acid battery after formation and using the clad positive electrode plate taken out according to the following procedure.
First, the portion of the removed positive electrode plate where the core metal exists is divided into three equal parts, 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 positive electrode material of each of the upper, middle, and lower parts is taken out separately. Below, the analysis of the upper positive electrode material will be described, but the positive electrode material of the middle and lower parts is also analyzed in the same manner. Approximately 1.5 g is taken from the removed upper positive electrode material, 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 an aqueous acetic acid solution (concentration: 5% by mass) is added. Next, the aqueous acetic acid solution in the beaker is heated and boiled for 10 minutes. This process dissolves the lead monoxide in the positive electrode material. Next, the heated solution is cooled, and then filtered with filter paper (6 types of JIS 3801-1995), and the residue on the filter paper is washed with distilled water. In this way, the dissolved material (including dissolved lead monoxide) is removed. Next, the above residue (including lead dioxide) is poured into another beaker with distilled water. Furthermore, the residue remaining on the filter paper is dissolved using 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 the beaker. Next, the liquid in the beaker is heated to 80°C for 10 minutes, and then cooled. Next, the liquid in the beaker is filtered, and the filtrate (including dissolved lead dioxide) is placed in a measuring flask. Furthermore, the filter paper is washed with distilled water and the washing liquid is put into a measuring flask to make the liquid in the measuring flask 250 ^cm3 . 50 ^cm3 of this filtrate is taken, to which 1 g of tartaric acid and 20 ^cm3 of 28% by mass ammonia water are added. A few drops of BT indicator are added to the resulting liquid and 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 set as the end point of the titration, and the amount of EDTA solution at that time is recorded. The content of lead dioxide (mass%) is calculated using the following formula. FA is the titer of the 0.1 mol/L EDTA aqueous solution.
_PbO2 content (mass%)=100×(amount of EDTA solution dropped ( ^cm3 ))×23.92×5×FA/(mass of sample W (g))

The _PbO2 content (mass%) obtained by the above method reflects the degree of conversion, and therefore the content (mass%) is used as the conversion degree (%), which is a relative evaluation value of the conversion degree.

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

(1) A clad type 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, the positive electrode material including at least one metal core and a current collector connected to an end of the metal core, the metal core being disposed in the tube and in contact with the positive electrode material, the metal core including a rod-shaped portion having a first end on the current collector side and a second end opposite to the first end, the center of the rod-shaped portion being offset from the center of the tube at the first end, and the shortest distance between the rod-shaped portion and the tube at the first end being 2.0 mm or less.

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

(3) In the clad type positive electrode plate for a lead-acid battery described above in (1) or (2), 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 may satisfy (0.5Dt1-0.5Db1-2.0)≦G1≦(0.5Dt1-0.5Db1).

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

(5) The clad type 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 row, and the positive electrode current collector may include a plurality of the core metals, each of whose ends is connected by the current collecting portion.

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

(7) A lead-acid battery including any one of the clad positive electrode plates for lead-acid batteries described above in (1) to (6).

[Example]
The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. Note that all of the 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 electrode plate having a metal core as shown in Figures 2 and 3 is fabricated by the following procedure. The fabricated positive electrode plate has a configuration generally similar to that of the positive electrode plate shown in Figure 1, except for the number of tubes and metal cores.

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

The number of cores contained in one positive electrode collector is 15. The 15 cores of the manufactured positive electrode collector are housed in 15 tubes. Next, the collector and one end of the tube are covered with resin to form a resin upper link. The material of the positive electrode collector is a Pb-Sb alloy. A porous tube made of glass fiber is used for the tube. The length of the tube is 310 mm, the outer diameter is 9.5 mm, and the inner diameter is 9.0 mm.

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

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 to red lead is 9:1. Next, the opening of the tube is sealed with a lower connecting member. In this way, an unformed clad type positive electrode plate is produced. The amount of the positive electrode slurry is adjusted so that the positive electrode plate after the formation is completed contains 841±8 g of the formed positive electrode active material per plate in terms of _PbO2 .

(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 organic shrinkage inhibitor (sodium lignin sulfonate), and 1.2% by mass of barium sulfate are mixed with water and dilute sulfuric acid to prepare a negative electrode paste. The negative electrode paste is filled into a cast grid made of an Sb-based alloy as a negative electrode collector, and dried to prepare an unformed negative electrode plate. At this time, a negative electrode plate (negative electrode plate A) having a thickness of 2.7 mm is prepared using a grid-shaped collector having a thickness of 2.6 mm, and a negative electrode plate (negative electrode plate B) having a thickness of 4.5 mm is prepared using a grid-shaped collector having a thickness of 4.4 mm. The same number of negative electrode plates A and B are prepared. The amount of negative electrode paste filled is adjusted so that the amount of negative electrode active material contained in one negative electrode plate A is 420±6 g, calculated as Pb, and the amount of negative electrode active material contained in one negative electrode plate B is 750±6 g, calculated as Pb. The length of the negative electrode plate is the same as the length of the positive electrode tube, and the width of the negative electrode plate is the same as the width of the positive electrode plate.

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

The plate group is then placed in a polypropylene container, and dilute sulfuric acid (concentration: 14% by mass) is poured into the container. A lid is then attached to the opening of the container. The container is then placed in a water tank at 30°C for chemical formation. Chemical formation is carried out using high-speed chemical formation. High-speed chemical formation is carried out by passing a constant chemical current of 31.5 A for a chemical formation time of 40 hours. In this way, lead-acid batteries A1 to A7 and CA1 to CA2 are obtained.

(4) Evaluation of the degree of formation The degree of formation of the positive electrode material of the above-mentioned lead-acid battery is evaluated by the procedure described below.

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

The core metal of the positive electrode collector of battery CA1 has the center of the tube and the center of the core metal rod-shaped part aligned at the end on the collector side. That is, the positive electrode collector of battery CA1 is a typical positive electrode collector that has been used in the past. For the batteries shown in Table 1, the relationship between the shortest distance Lmin and the degree of formation of the entire positive electrode material is shown in Figure 7. As shown in Table 1 and Figure 7, by setting the shortest distance Lmin to 2.0 mm or less, the degree of formation of the entire positive electrode material can be improved. In batteries CA1 and CA2, which have a shortest distance greater than 2.0 mm, the difference between the degree of formation in the upper part and the degree of formation in the lower part is large. On the other hand, in batteries A1 to A7, which have a shortest distance of 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 degree of formation of the entire positive electrode material, it is preferable that the shortest distance Lmin is small, 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 fabricated under the same conditions as the batteries CA1 and A6 described above, except that the formation conditions of the positive plate are changed. The positive plate is formed by normal formation, not high-speed formation. The normal formation is performed by passing a constant formation current of 18.5 A for a formation time of 68 hours. The values of the above-mentioned shortest distance Lmin in the fabricated batteries and the formation degree of the positive electrode material are shown in Table 2.

As shown in Table 2, the degree of chemical formation 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. Thus, even when performing normal chemical formation, it is effective to set the shortest distance Lmin to 2.0 mm or less.

The present invention is used in a clad-type positive electrode plate and a lead-acid battery including the same. The use of the lead-acid battery is not limited, and it can be used for various purposes. The lead-acid battery of the present invention is suitable for use as a long-life industrial storage battery and a storage battery for electric vehicles (forklifts, etc.). The lead-acid battery of the present invention may also be used as a storage battery for vehicles such as automobiles and motorcycles.

1: Lead-acid battery 30: Clad type positive electrode plate 30: Positive electrode plate 31: Tube 32: Positive electrode material 33: Positive electrode current collector 34: Current collector 35: Core metal 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 collecting portion connected to an end of the metal core,
the mandrel is disposed within the tube and in contact with the positive electrode material;
the core metal includes a rod-shaped portion having a first end portion on the current collecting portion side and a second end portion opposite to the first end portion,
At the first end, the center of the rod is offset from the center of the tube;
At the first end, the shortest distance between the rod-shaped portion and the tube is 2.0 mm or less;
A clad type positive electrode plate for a lead-acid battery, wherein a center of the second end is located in a direction opposite to a center of the first end across a central axis of the tube . 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 collecting portion connected to an end of the metal core,
the mandrel is disposed within the tube and in contact with the positive electrode material;
the core metal includes a rod-shaped portion having a first end portion on the current collecting portion side and a second end portion opposite to the first end portion,
At the first end, the center of the rod is offset from the center of the tube;
At the first end, the shortest distance between the rod-shaped portion and the tube is 2.0 mm or less;
the tube is cylindrical;
A clad type positive electrode plate for a lead-acid battery , wherein one core metal is disposed in one tube . The clad positive electrode plate for a lead-acid battery according to claim 1 or 2, wherein 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 satisfy (0.5Dt1-0.5Db1-2.0) ≦ G1 ≦ (0.5Dt1-0.5Db1). The clad positive electrode plate for a lead-acid battery according to any one of claims 1 to 3, wherein the second end is in contact with the inner peripheral surface of the tube. A plurality of the tubes arranged in a row,
The positive electrode collector includes a plurality of the core metals, each of the ends of which is connected by the current collecting portion. The clad type positive electrode plate for a lead acid battery according to any one of claims 1 to 4. The clad positive electrode plate for a lead-acid battery according to claim 5, wherein the plurality of metal cores are inclined in the same direction. A lead-acid battery comprising the clad positive electrode plate for lead-acid batteries according to any one of claims 1 to 6.

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