JP7653243B2 - Lead-acid batteries for forklifts, battery packs and forklifts - Google Patents

Description

The present invention relates to battery separators, electrodes, lead-acid batteries, battery packs, and electric vehicles.

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

For example, Patent Document 1 discloses a lead-acid battery that includes a plate group in which positive and negative plates are alternately stacked, and a battery case that contains the plate group. In such a lead-acid battery, the plate group has a plurality of battery separators, and the separator body of the battery separator covers at least the end of either the positive or negative plate.

JP 2012-079609 A

In the battery separator described above, a slit is formed in the portion covering the end of the separator body, and the electrolyte in the battery container is intended to flow through this slit. However, in some cases, the slit may be blocked by other parts (such as a sack), preventing the electrolyte from flowing.

Therefore, one aspect of the present invention aims to provide a battery separator, an electrode, a lead-acid battery, a battery pack, and an electric vehicle that can avoid impeding the flow of electrolyte through the slits.

A battery separator according to one aspect of the present invention comprises a separator body that covers at least the ends of the electrode plates, and a slit is formed in the portion of the separator body that covers the ends, and the slit extends so as to pass through at least a position in the portion of the separator body that covers the ends that is offset from the center of the electrode plates in the thickness direction.

This battery separator can prevent the slits from being completely blocked by other parts (such as the slits). This makes it possible to avoid impeding the flow of electrolyte through the slits.

In a battery separator according to one aspect of the present invention, the separator body may have a folded portion that is folded back from one side to the other side in the thickness direction of the electrode plate, and the slit may be formed in the folded portion. In this case, it is possible to avoid impeding the flow of electrolyte through the slit formed in the folded portion.

In a battery separator according to one aspect of the present invention, the slits may extend in a direction that is inclined with respect to a center line that passes through the center of the thickness direction of the folded portion, and/or may extend so as not to reach the center line of the folded portion. In this case, even if another portion is located at a position that overlaps with the center line, a flow path for the electrolyte is easily ensured.

In a battery separator according to one aspect of the present invention, the slits may extend in a direction that is inclined with respect to the ridge of the folded portion, and/or may extend so as not to reach the ridge of the folded portion. In this case, even if another portion is located at a position that overlaps the ridge, a flow path for the electrolyte is easily ensured.

In a battery separator according to one aspect of the present invention, multiple slits may be formed in the folded portion. In this case, even if some slits in the folded portion are blocked by other portions, the other slits are likely to ensure a flow path for the electrolyte.

In a battery separator according to one aspect of the present invention, some or all of the multiple slits may be of equal length. In this case, it becomes easier to control the amount of electrolyte flowing through the slits at a constant level.

In a battery separator according to one aspect of the present invention, some or all of the multiple slits may have different lengths. In this case, it becomes easier to determine the orientation of the battery separator during manufacturing.

In a battery separator according to one aspect of the present invention, the slits may be formed at positions asymmetrical with respect to a center line passing through the center of the thickness direction of the folded portion. In this case, it becomes easier to determine the orientation of the battery separator during manufacturing.

In a battery separator according to one aspect of the present invention, the separator body has an inner surface on the electrode plate side and an outer surface opposite the inner surface, and at least one of the inner surface and the outer surface is provided with a plurality of ribs, and the slit may divide at least one of the ribs. In this case, the rib is located at the end face of the slit, and the strength of the end face of the slit can be increased by the rib.

In a battery separator according to one aspect of the present invention, the slit may divide multiple ribs. In this case, multiple ribs are located at the end face of the slit, and the strength of the end face of the slit can be further increased by the multiple ribs.

In a battery separator according to one aspect of the present invention, the multiple ribs may include a first rib and a second rib adjacent to each other, and one end of the slit may be located between the first rib and the second rib. In this case, even if the separator body is about to tear starting from one end of the slit, the thickness of the first rib or the second rib makes it difficult to tear, and the slit can be prevented from expanding to an undesired length.

In a battery separator according to one aspect of the present invention, the multiple ribs may include a third rib and a fourth rib adjacent to each other, and the other end of the slit may be located between the third rib and the fourth rib. In this case, even if the separator body is about to tear starting from the other end of the slit, the thickness of the third rib or the fourth rib makes it difficult to tear, and the slit can be prevented from expanding to an undesired length.

In a battery separator according to one aspect of the present invention, the width of the slit at the first position may be different from the width of the slit at the second position. This makes it easier to ensure a flow path for the electrolyte even when another part with a certain width is located at a position overlapping the slit.

In a battery separator according to one aspect of the present invention, the end of the electrode plate may have a foot portion provided so as to protrude in a predetermined direction, and the slit may be formed at a position spaced apart from the foot portion in a direction perpendicular to the predetermined direction and the thickness direction. Since the saddle is often positioned opposite the foot portion, forming the slit at a position spaced apart from the foot portion makes it difficult for the saddle to block the slit.

In a battery separator according to one aspect of the present invention, slits may be formed on one side and the other side of the foot in a direction perpendicular to the predetermined direction and the thickness direction. This makes it easier to ensure a flow path for the electrolyte.

In a battery separator according to one aspect of the present invention, the electrode plates are stored upright in a battery case, the battery case has a plurality of protrusions that are provided integrally or separately on the bottom surface of the battery case and support the electrode plates, the separator body covers at least the lower end of the electrode plates, and the center of the slit may be located between a pair of adjacent protrusions in a horizontal direction perpendicular to the thickness direction. In this case, it is possible to prevent the slit from being completely blocked by the protrusions that support the electrode plates.

In a battery separator according to one aspect of the present invention, the length of the slit in the horizontal direction perpendicular to the thickness direction may be greater than the width of the protrusion. In this case, even if the protrusion is located at a position overlapping a portion of the slit, it is possible for the electrolyte to flow through the other portion of the slit.

In a battery separator according to one aspect of the present invention, the length of the slit in the horizontal direction perpendicular to the thickness direction may be smaller than the distance between a pair of adjacent protrusions. In this case, the slit is more likely to be located in a position that does not overlap with the protrusions, making it easier to ensure a flow path for the electrolyte through the slit.

An electrode according to one aspect of the present invention comprises an electrode plate housed in a battery case and the battery separator. This electrode also has the above-mentioned effect of being able to avoid impediment to the flow of electrolyte through the slits, because it comprises the battery separator.

A lead-acid battery according to one aspect of the present invention comprises a plate group in which a plurality of positive and negative plates are arranged so as to be alternately stacked, and a battery case in which the plate group is housed upright, and the plate group has a plurality of the battery separators, and the separator body of the battery separator covers at least the lower end portion of either the positive or negative plate. Since this lead-acid battery also comprises the battery separator, the above-mentioned effect of being able to avoid impediment to the flow of electrolyte through the slits is achieved.

The battery pack according to one aspect of the present invention includes a plurality of the lead-acid batteries and a connection member that electrically connects one of the lead-acid batteries to the other lead-acid batteries. Since this battery pack also includes the lead-acid batteries, it has the above-mentioned effect of preventing the flow of electrolyte through the slits from being impeded.

An electric vehicle according to one aspect of the present invention is equipped with the above-mentioned lead-acid battery. Since this electric vehicle also includes the above-mentioned lead-acid battery, it has the above-mentioned effect of being able to avoid impediment to the flow of electrolyte through the slits.

According to one aspect of the present invention, it is possible to provide a battery separator, an electrode, a lead-acid battery, a battery pack, and an electric vehicle that can avoid impeding the flow of electrolyte through the slits.

FIG. 1 is a diagram showing a forklift equipped with a battery pack according to an embodiment. FIG. 2 is a cross-sectional view that illustrates a lead-acid battery according to an embodiment. FIG. 3 is a cross-sectional view taken along line AA of FIG. FIG. 4 is a plan view showing the negative electrode according to the embodiment. FIG. 5 is a front view showing a negative electrode and a battery separator according to an embodiment. FIG. 6 is a cross-sectional view taken along line BB in FIG. FIG. 7 is an enlarged front view of a portion of FIG. FIG. 8 is a bottom view of the battery separator of FIG. FIG. 9 is a bottom view of a battery separator according to a modified example. Fig. 10(a) is a front view showing a negative electrode and a battery separator according to a modified example, and Fig. 10(b) is an end view taken along line CC in Fig. 10(a). FIG. 11 is a perspective view showing a separator body according to a modified example. FIG. 12 is a perspective view showing a separator body according to a modified example.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, identical or equivalent elements are given the same reference numerals, and duplicate explanations will be omitted. The sizes of the components in each drawing are conceptual, and the relative relationships of the sizes between the components are not limited to those shown in each drawing.

Figure 1 is a diagram showing a forklift 1 equipped with a battery pack 200. As shown in Figure 1, the forklift (electric vehicle) 1 is equipped with a battery pack 200. The forklift 1 is driven by power supplied from the battery pack 200. The battery pack 200 is composed of a plurality of lead-acid batteries 100.

Figure 2 is a cross-sectional view showing a schematic diagram of the lead-acid battery 100. Figure 3 is a cross-sectional view taken along line A-A in Figure 1. In Figure 2, positive electrodes 10 and negative electrodes 20 are alternately arranged with battery separators 30 interposed therebetween from the front to the back of the drawing. Figure 2 shows a cross-sectional view of a portion of the positive electrode 10. Figure 3 shows the laminated structure of the positive electrodes, negative electrodes 20, and battery separators 30 when the lead-acid battery 100 is viewed from above. The terms "upper" and "lower" correspond to the upper and lower sides in the height direction of the battery case 120 (the same applies below). The Z direction corresponds to the height direction of the battery case 120, the X direction corresponds to the direction perpendicular to the Z direction, and the Y direction corresponds to the direction perpendicular to the Z direction and perpendicular to the X direction.

As shown in Figures 2 and 3, the lead-acid battery 100 according to the embodiment includes an electrode group (electrode plate group) 110, a battery case 120 that houses the electrode group 110, connecting members 130a and 130b connected to the electrode group 110, poles 140a and 140b connected to the connecting members 130a and 130b, a liquid port plug 150 that closes the liquid inlet of the battery case 120, and a support member 160 connected to the battery case 120.

The electrode group 110 includes a plurality of positive electrodes 10, a plurality of negative electrodes 20, and a plurality of battery separators 30. The positive electrodes 10 and the negative electrodes 20 are arranged alternately in the X direction with the battery separators 30 interposed therebetween. The space around the positive electrodes 10 between the battery separators 30 is filled with an electrolyte 40.

The positive electrode 10 constitutes a plate-shaped electrode plate. The positive electrode 10 is stored upright in the battery case 120. The positive electrode 10 has a plurality of cylindrical bodies 12a, a plurality of core metals (current collectors) 14, a positive electrode material (electrode material) 16, a lower connecting seat (sealing member) 18, an upper connecting seat 12c, and an ear portion 12d.

The multiple cylindrical bodies 12a are arranged adjacent to each other in a row along the Y direction. The multiple cylindrical bodies 12a constitute a group of tubes (clad tubes) for holding active material. The cylindrical bodies 12a extend in the Z direction. The cylindrical bodies 12a are formed of a porous body. The cylindrical bodies 12a may be formed of a base material such as a woven fabric or a nonwoven fabric. An acid-resistant material can be used as the material of the base material.

The core metal 14 is inserted into each cylindrical body 12a. The core metal 14 is rod-shaped. The core metal 14 extends along the Z direction inside the cylindrical body 12a. The core metal 14 can be obtained, for example, by casting. The constituent material of the core metal 14 may be any conductive material, such as a lead alloy such as a lead-calcium-tin alloy or a lead-antimony-arsenic alloy. The positive electrode material 16 is filled inside the cylindrical body 12a. The positive electrode material 16 includes an active material. The active material includes both the active material after chemical formation and the raw material of the active material before chemical formation. The positive electrode material 16 here includes the active material after chemical formation. The cylindrical electrode of the positive electrode 10 is electrically connected to the pole 140a via the upper connecting seat 12c, the ear portion 12d, and the connecting member 130a.

The lower linking seat 18 is attached to the lower ends of the multiple cylindrical bodies 12a. The lower linking seat 18 seals the lower ends of the multiple cylindrical bodies 12a. The lower linking seat 18 is fitted to the lower ends of the multiple cylindrical bodies 12a. The lower linking seat 18 may be fixed to the lower ends of the multiple cylindrical bodies 12a with a thermosetting adhesive or the like. The material of the lower linking seat 18 may be an acid-resistant material. Examples of the material of the lower linking seat 18 include resins such as polyolefin (polypropylene, polyethylene, etc.), polyethylene terephthalate (PET), polystyrene (PS), polyvinylidene fluoride (PVDF), and polycarbonate (PC).

The upper linking seat 12c is attached to the upper end of the cylindrical body 12a. The upper linking seat 12c seals the upper end of the cylindrical body 12a. The upper linking seat 12c is fixed to the upper end of the cylindrical body 12a by welding. The welding can be achieved by heating, ultrasonic irradiation, laser irradiation, etc. The upper linking seat 12c may be fixed to the upper ends of multiple cylindrical bodies 12a by a thermosetting adhesive, etc.

The lower connecting seat 18 and the upper connecting seat 12c contact the cylindrical body 12a and the core metal 14 and the positive electrode material 16 arranged inside the cylindrical body 12a. The lower connecting seat 18 and the upper connecting seat 12c hold the cylindrical body 12a, the core metal 14, and the positive electrode material 16. One end of the ear portion 12d is connected to the upper connecting seat 12c. The other end of the ear portion 12d is connected to the connecting member 130a.

Figure 4 is a plan view showing the negative electrode 20. As shown in Figure 4, the negative electrode 20 constitutes a plate-shaped electrode plate. The negative electrode 20 is housed upright in the battery case 120. The negative electrode 20 is, for example, a paste-type negative electrode plate. The negative electrode 20 is electrically connected to the electrode column 140b via a connecting member 130b. The negative electrode 20 has a negative electrode grid 20a and an ear portion 20b. The negative electrode grid 20a is the main body of the negative electrode 20 and holds the negative electrode material 20c. The negative electrode material 20c may contain an active material and an additive after chemical formation. The active material is, for example, sponge-like lead. Examples of the additive include barium sulfate, a carbon material, or short reinforcing fibers. The ear portion 20b is a terminal portion protruding upward from the negative electrode grid 20a. The negative electrode grid 20a is covered by a battery separator 30 (see Figure 3). The negative electrode grid 20a is provided with legs 20d and 20e. The legs 20d and 20e are protruding parts that protrude downward (in a predetermined direction) from the negative electrode grid 20a. The legs 20d and 20e are arranged at a predetermined interval. The negative electrode 20 and the battery separator 30 constitute the electrode 3.

2 and 3, the battery separator 30 is a battery component for preventing short circuit between the positive electrode 10 and the negative electrode 20. There are no particular limitations on the battery separator 30, so long as it electronically insulates the positive electrode 10 and the negative electrode 20 while allowing ions to pass between them and is resistant to oxidation on the positive electrode 10 side and reduction on the negative electrode 20 side. Examples of materials for the battery separator 30 include glass fiber, resin, and inorganic substances. The battery separator 30 covers the negative electrode 20. The ear portion 20b of the negative electrode 20 is exposed from the top of the battery separator 30.

The support member 160 is disposed on the bottom surface of the battery case 120 and supports the positive electrode 10 and the negative electrode 20. The support member 160 has a plurality of protrusions 160a that protrude upward. The protrusions 160a are so-called saddles and are provided on the support member 160. In other words, the protrusions 160a are provided separately from the battery case 120 on the bottom surface of the battery case 120 (at a position above the bottom surface). The protrusions 160a extend in the X direction. The protrusions 160a are aligned in the Y direction. The protrusions 160a support the positive electrode 10 and the negative electrode 20. The protrusions 160a abut against the battery separator 30 that covers the negative electrode 20. Specifically, when the negative electrode 20 covered with the battery separator 30 is housed in the battery case 120, the protrusion 160a faces the legs 20d, 20e of the negative electrode 20, and the battery separator 30 abuts and is sandwiched between the protrusion 160a and the legs 20d, 20e.

Next, we will explain the battery separator 30 in detail.

Figure 5 is a front view showing the negative electrode 20 and the battery separator 30. Figure 6 is a cross-sectional view taken along line B-B in Figure 5. Figure 7 is a front view showing an enlarged portion of Figure 5. Figure 8 is a view of the battery separator 30 as seen from below. For convenience, the ribs 36 are omitted in Figure 7. As shown in any of Figures 5 to 8, the battery separator 30 includes a pouch-shaped separator body 31 that covers at least the lower end of the negative electrode 20. The separator body 31 has a pair of sheet portions 32, a pair of seal portions 34, a joint portion 35, and a plurality (multiple rows) of ribs 36. The separator body 31 includes an inner surface 31a on the negative electrode 20 side and an outer surface 31b opposite the inner surface 31a.

The sheet portion 32 is a sheet-like portion and exhibits flexibility. The sheet portion 32 is arranged on one side and the other side of the thickness direction (hereinafter also simply referred to as the "thickness direction") of the negative electrode 20. The sheet portion 32 arranged on one side of the thickness direction and the sheet portion 32 arranged on the other side of the thickness direction have their lower ends integrally connected via a folded portion 33. The folded portion 33 is a sheet-like portion that is connected to the lower end of each of the pair of sheet portions 32 and is bent in a U-shape so as to fold back from one side to the other side in the thickness direction, exhibiting flexibility.

The sealing portion 34 is a portion that connects the pair of sheet portions 32 and seals the space between the pair of sheet portions 32. The sealing portion 34 is provided at both ends of the pair of sheet portions 32 in the width direction (left and right direction in FIG. 5, hereinafter also simply referred to as the "width direction") perpendicular to both the thickness direction and the vertical direction. The sealing portion 34 extends in the vertical direction from the upper end to the lower end of the pair of sheet portions 32. The sealing portion 34 is, for example, an ultrasonic welding portion, a heat seal portion, a cold seal portion, a gear seal portion, etc. The gear seal portion is a portion that is mechanically bonded by pressure using a gear. The sealing portion 34 does not have to be completely sealed. From the viewpoint of the fluidity of the electrolyte 40 in the battery separator 30, at least one of the sealing portions 34 may be provided with an area through which the electrolyte 40 can pass.

The joint 35 is a portion that joins the pair of sheet portions 32. The joint 35 is provided at the upper end of the pair of sheet portions 32. Specifically, the joint 35 is provided in a region on the opposite side of the ear portion 20b from the center in the width direction at the upper end of the pair of sheet portions 32. The joint 35 extends along the width direction. The joint 35 is, for example, a portion where the sheet portion 32 itself is welded. From the viewpoint of preventing welding defects, the joint 35 may be formed by ultrasonic welding or the like.

The ribs 36 are provided, for example, to improve the durability of the separator body 31 and the fluidity of the electrolyte 40 in the battery case 120. A plurality of ribs 36 are provided on the outer surface 31b of the separator body 31. Each of the plurality of ribs 36 includes a rib 36 that extends continuously from the upper end to the lower end along the vertical direction on the outer surface of one sheet portion 32, a rib 36 that extends continuously from the upper end to the lower end along the vertical direction on the outer surface of the other sheet portion 32, and a rib 36 that extends continuously on the outer surface of the folded portion 33 so as to connect the lower ends of these ribs. The plurality of ribs 36 protrude from the outer surface of the sheet portion 32 and the outer surface of the folded portion 33. The plurality of ribs 36 are spaced apart from each other in the width direction. The plurality of ribs 36 extend parallel to each other. The cross section of the rib 36 perpendicular to the extension direction of the rib 36 is rectangular, but is not limited thereto. The cross section of the rib 36 may be, for example, trapezoidal or inverted trapezoidal.

In this embodiment, a slit 37 is formed in the folded portion 33 (the portion covering the end of the separator body 31). The slit 37 is an opening that penetrates the inside and outside of the separator body 31. The slit 37 constitutes a non-jointed portion at the lower ends of the pair of sheet portions 32. The slit 37 is a long opening that extends at least through a position that is off-center in the thickness direction of the folded portion 33. There are no particular limitations on the method of forming the slit 37, but for example, the slit 37 may be formed by cutting with a cutter.

When viewed from below, the slits 37 extend so as not to reach the ridgeline R1 of the folded portion 33. For example, the ridgeline R1 is a line formed by a connection of the lowermost parts of the folded portion 33. The ridgeline R1 here is the centerline. The centerline is a line that passes through the center in the thickness direction of the folded portion 33. For example, the centerline is a line that passes through the center in the width direction and thickness direction and runs along the width direction when the folded portion 33 is viewed from below. The slits 37 here extend along the width direction when viewed from below. Multiple slits 37 are formed in the folded portion 33, and the multiple slits 37 are equal in length. The length of the slits 37 is the dimension in the extension direction of the slits 37.

The slit 37 divides the multiple ribs 36. The end face of the rib 36 exposed through the slit 37 and the end face of the sheet portion 32 are connected so as to be located on the same plane as the end face of the slit 37. The multiple ribs 36 include a first rib 361 and a second rib 362 adjacent to each other, and a third rib 363 and a fourth rib 364 adjacent to each other. One end of the slit 37 is located between the first rib 361 and the second rib 362. The other end of the slit is located between the third rib 363 and the fourth rib 364. For example, the width of the slit 37 at a first position (e.g., a central position) is different from the width of the slit 37 at a second position (e.g., a position between one end and the center). The width of the slit 37 is a dimension in a direction perpendicular to the extension direction of the slit 37.

The slit 37 is formed at a position spaced apart from the legs 20d and 20e in the width direction. The slit 37 is formed on each of one side and the other side of the leg 20e in the width direction. In the width direction, the center of the slit 37 is located between a pair of adjacent protrusions 160a. In the width direction, the length of the slit 37 is greater than the width of the protrusions 160a. In the width direction, the length of the slit 37 is less than the distance between a pair of adjacent protrusions 160a.

Next, an example of a method for manufacturing the lead-acid battery 100 will be described. The method for manufacturing the lead-acid battery 100 includes at least an assembly process for assembling each component to obtain the lead-acid battery 100. In the assembly process, for example, an unformed positive electrode 10 and an unformed negative electrode 20 covered with a battery separator 30 are stacked, and the current collectors of the electrodes of the same polarity are welded with a strap to obtain an electrode group 110. The electrode group 110 is inserted and placed in a battery case 120 to produce an unformed battery. Dilute sulfuric acid is poured into the unformed battery and a direct current is passed through it to perform battery case formation. The lead-acid battery 100 is obtained by adjusting the specific gravity of the sulfuric acid after formation to an appropriate specific gravity. Note that the formation process is not limited to being performed after the assembly process, and may be performed before the assembly process (tank formation).

As described above, in the battery separator 30, the electrode 3, the lead-acid battery 100, the battery pack 200, and the forklift 1, the slit 37 extends so as to pass through at least a position that is off-center in the thickness direction in the folded portion 33 of the separator body 31. This makes it possible to prevent the slit 37 from being completely blocked by the protruding portion 160a. This makes it possible to avoid impeding the flow of the electrolyte 40 through the slit 37.

In the battery separator 30, the slits 37 are formed in the folded portion 33. In this case, it is possible to avoid impeding the flow of the electrolyte 40 through the slits 37 formed in the folded portion 33.

In the battery separator 30, the slits 37 extend so as not to reach the center line passing through the center of the thickness direction of the folded portion 33. In this case, even if the protrusion 160a is located at a position overlapping the center line, it is easy to ensure a flow path for the electrolyte 40.

In the battery separator 30, the slits 37 extend so as not to reach the ridgeline R1 of the folded portion 33. In this case, even if the protrusion 160a is located at a position overlapping the ridgeline R1, it is easier to ensure a flow path for the electrolyte 40.

In the battery separator 30, multiple slits 37 are formed in the folded portion 33. In this case, even if some of the slits 37 in the folded portion 33 are blocked by the protruding portion 160a, the other slits 37 tend to ensure a flow path for the electrolyte 40.

In the battery separator 30, the multiple slits 37 are equal in length. In this case, it is easier to control the flow rate of the electrolyte 40 through the slits 37 to a constant amount. Since the slits 37 only need to be formed to the same length, manufacturing efficiency can be improved.

In the battery separator 30, the slits 37 divide the ribs 36. In this case, the ribs 36 are located at the end faces of the slits 37, so the strength of the end faces of the slits 37 can be increased by the ribs 36. The end faces of the slits 37 are less likely to be damaged.

In the battery separator 30, the slits 37 divide the multiple ribs 36. In this case, since the multiple ribs 36 are located at the end face of the slits 37, the strength of the end face of the slits 37 can be further increased by the multiple ribs 36. The end face of the slits 37 becomes even less susceptible to damage.

In the battery separator 30, the multiple ribs 36 include a first rib 361 and a second rib 362 adjacent to each other. One end of the slit 37 is located between the first rib 361 and the second rib 362. In this case, even if the separator body 31 is about to tear starting from one end of the slit 37, the thickness of the first rib 361 or the second rib 362 makes it difficult to tear, and the slit 37 can be prevented from expanding to an undesired length. In addition, when the slit 37 is formed by cutting with a cutter, the rib 36 is not located at the cutting start position (the position where the cutter blade enters), so defects such as the cutter blade getting caught on the rib 36 are less likely to occur.

In the battery separator 30, the multiple ribs 36 include a third rib 363 and a fourth rib 364 that are adjacent to each other. The other end of the slit 37 is located between the third rib 363 and the fourth rib 364. In this case, even if the separator body 31 is about to tear starting from the other end of the slit 37, the thickness of the third rib 363 or the fourth rib 364 makes it difficult to tear, and the slit 37 can be prevented from expanding to an undesired length. In addition, when the slit 37 is formed by cutting with a cutter, the rib 36 is not located at the end of the cut (the position where the cutter blade leaves), so defects such as the cutter blade getting caught on the rib 36 are less likely to occur.

In the battery separator 30, the width of the slit 37 at the first position is different from the width of the slit 37 at the second position. This makes it easier to ensure a flow path for the electrolyte 40 when a convex portion 160a with a certain width is located at a position overlapping the slit 37.

In the battery separator 30, the slits 37 are formed at a position spaced apart from the legs 20d, 20e in the width direction. Since the protrusions 160a are located at a position facing the legs 20d, 20e, forming the slits 37 at a position spaced apart from the legs 20d, 20e makes it difficult for the protrusions 160a to block the slits 37. This makes it easier to prevent the legs 20d, 20e from shorting out through the slits 37 due to fallen active material.

In the battery separator 30, the slits 37 are formed on one side and the other side of the foot 20e in the width direction. In this case, it becomes easier to ensure a flow path for the electrolyte 40, and it becomes possible to suppress short circuits.

In the battery separator 30, the center of the slit 37 in the width direction is located between a pair of adjacent protrusions 160a. In this case, it is possible to prevent the slit 37 from being completely blocked by the protrusions 160a.

In the battery separator 30, the length of the slit 37 in the width direction is greater than the width of the protruding portion 160a. In this case, even if the protruding portion 160a is located at a position overlapping a portion of the slit 37, it is possible for the electrolyte 40 to flow through the other portion of the slit 37.

In the battery separator 30, the length of the slit 37 in the width direction is smaller than the distance between a pair of adjacent protrusions 160a. In this case, the slit 37 is more likely to be located in a position that does not overlap with the protrusions 160a, making it easier to ensure a flow path for the electrolyte 40 through the slit 37.

Although the embodiments have been described above, one aspect of the present invention is not limited to the above embodiments.

In the above embodiment, the ribs 36 extend linearly, but this is not limited thereto. For example, the ribs 36 may extend in a wavy line or a zigzag pattern. The ribs 36 may be formed intermittently, may be dot-shaped, may be circular, may be elliptical, or may be polygonal. The ribs 36 may be polygonal pyramid-shaped, may be truncated polygonal pyramid-shaped, may be conical, or may be truncated conical. The cross section of the ribs 36 may be semicircular or polygonal. The ribs 36 may extend along the vertical direction, or alternatively or additionally may extend along the width direction.

In the above embodiment, the slit 37 divides multiple ribs 36, but it is sufficient if it divides at least one rib 36. In the above embodiment, the width of the slit 37 at the first position is different from the width of the slit 37 at the second position, but they may be the same. The first position and the second position are not particularly limited as long as they are different positions on the slit 37. In the above embodiment, the ridge line R1 is also the center line of the folded portion 33, but the ridge line R1 does not have to be a center line.

In the above embodiment, two slits 37 are formed, but three or more slits 37 may be formed. In the above embodiment, all of the slits 37 have the same length, but when three or more slits 37 are formed, some of the slits may have the same length. Alternatively, in the above embodiment, some or all of the multiple slits 37 may have different lengths. In this case, it is easier to determine the orientation of the battery separator 30 during manufacturing.

Figure 9 is a view of a battery separator 530 according to a modified example, viewed from below. As shown in Figure 9, instead of or in addition to the slit 37 (see Figure 8), the folded portion 33 may have a slit 337 formed therein that extends in a direction inclined relative to the center line and/or edge line R1 passing through the center of the thickness direction of the folded portion 33. In this case, even if the protrusion 160a is located at a position overlapping the center line and/or edge line R1, the slit 337 is unlikely to be completely blocked, making it easier to ensure a flow path for the electrolyte 40.

When slits 337 are formed in addition to slits 37, they are formed in asymmetric positions with respect to the center line of the folded portion 33. In this case, it becomes easier to determine the orientation of the battery separator 30 during manufacturing. Slits 37 may also extend in a direction inclined with respect to the center line and/or ridge line R1 that passes through the center of the thickness direction of the folded portion 33.

In the above embodiment, the separator body 31 includes the folded portion 33, but is not limited thereto, and may have a configuration that at least covers the end of the negative electrode 20. For example, as shown in FIG. 10(a) and FIG. 10(b), the separator body 31 may have a welded portion 431 that welds the lower end of each of the pair of sheet portions 32 (the lower end of each of the sheet portions 32 arranged on one side and the other side in the thickness direction of the negative electrode 20). In this case, a slit 437 similar to the slit 37 (see FIG. 8) may be formed by a portion other than the welded portion 431 at the lower end of the sheet portion 32. Note that, for convenience, the rib 36 is omitted in FIG. 10(a).

As shown in FIG. 11, the separator body 31 may be configured such that both ends of the pair of sheet parts 32 in the width direction are integrally connected via the folded-back portion 533 (i.e., a cylindrical configuration with the vertical direction as the axial direction). As shown in FIG. 12, the separator body 31 may be configured such that one or the other end of the pair of sheet parts 32 in the width direction is integrally connected via the folded-back portion 633. As shown in particular, in the stacked sheet parts 32, the one and the other ends in the width direction that are continuous at the folded-back portion 633 may be alternately switched in the stacking direction, thereby realizing a configuration in which the separator body 31 is folded in an accordion-like manner. In these cases, slits similar to the slits 37 may be formed in the folded-back portions 533 and 633. Note that, for convenience, the ribs 36 are omitted in FIG. 11 and FIG. 12.

In the above embodiment, the protrusion 160a is provided on the bottom surface of the battery case 120 separately from the battery case 120, but the protrusion 160a may be provided integrally with the battery case 120. In the above embodiment, the forklift 1 is described as an example of an electric vehicle (electric car), but the electric vehicle may be, for example, a golf cart. In addition, the forklift 1 is described as an example of a configuration in which the battery pack 200 is mounted, but the forklift 1 may be equipped with a lead-acid battery 100.

The components in the above embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. The components in the above embodiments or modifications can be applied to the components in other embodiments or modifications as desired. Parts of the components in the above embodiments or modifications can be omitted as appropriate without departing from the gist of one aspect of the present invention.

1...forklift (electric vehicle), 3...electrode, 20...negative electrode (plate), 20d, 20e...foot, 30, 530...battery separator, 31...separator body, 31a...inner surface, 31b...outer surface, 33, 533, 633...folded portion, 36...rib, 37, 337, 437...slit, 100...lead-acid battery, 110...electrode group (plate group), 120...battery case, 160a...projection, 200...battery assembly, 361...first rib, 362...second rib, 363...third rib, 364...fourth rib, R1...ridge line.

Claims (9)

an electrode plate group in which a plurality of positive electrode plates and negative electrode plates are arranged so as to be alternately stacked;
A battery case that houses the electrode plate group upright,
The electrode plate group includes a plurality of battery separators,
a separator body of the battery separator covering at least a lower end portion of either the positive electrode plate or the negative electrode plate;
A slit is formed in a portion of the separator body that covers the end portion,
The slit extends so as to pass through at least a position offset from the center in the thickness direction of either the positive electrode plate or the negative electrode plate in the portion covering the end of the separator body ,
the separator body has a folded portion that is folded back from one side to the other side in a thickness direction of either the positive electrode plate or the negative electrode plate,
The lead-acid battery for a forklift , wherein the slit is formed in the folded portion . The lead-acid battery for a forklift according to claim 1 , wherein the slit is formed in a plurality of the folded portion. The lead-acid battery for a forklift according to claim 2 , wherein some or all of the plurality of slits have an equal length. The lead-acid battery for a forklift according to claim 2 , wherein some or all of the plurality of slits have different lengths. The separator body has an inner surface on either side of the positive electrode plate and the negative electrode plate , and an outer surface opposite to the inner surface,
At least one of the inner surface and the outer surface is provided with a plurality of ribs,
The lead-acid battery for a forklift according to any one of claims 1 to 4 , wherein the slit divides at least one of the ribs. Either one of the positive electrode plate and the negative electrode plate has a foot portion provided so as to protrude in a predetermined direction at an end thereof,
The lead-acid battery for a forklift according to any one of claims 1 to 5 , wherein the slits are formed at positions spaced apart from the foot portions in a direction perpendicular to the predetermined direction and the thickness direction. Either the positive electrode plate or the negative electrode plate is housed upright in a battery case;
The battery case has a plurality of protrusions that are provided integrally or separately on a bottom surface of the battery case and support either the positive electrode plate or the negative electrode plate ,
The separator body covers at least a lower end portion of either the positive electrode plate or the negative electrode plate ,
The lead-acid battery for a forklift according to any one of claims 1 to 6 , wherein a center of the slit is located between a pair of adjacent protrusions in a horizontal direction perpendicular to the thickness direction. A battery pack comprising a plurality of the forklift lead-acid batteries according to any one of claims 1 to 7 . A forklift comprising the battery pack according to claim 8 .

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