Lead-acid batteries for forklifts, battery packs and forklifts

Abstract

To provide a battery separator, an electrode, a lead-acid battery, an assembled battery, and an electric vehicle that can avoid obstruction of the flow of an electrolyte through a slit.SOLUTION: A battery separator 30 includes a separator body 31 that at least covers the lower end of a negative electrode 20. A slit 37 is formed in a folded-back portion 33 that covers the lower end of the negative electrode 20 in the separator body 31. The slit 37 extends so as to pass at least a position off the center of the folded-back portion 33 in the thickness direction.SELECTED DRAWING: Figure 8

Description

[Technical field]

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

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

[0003] For example, Patent Document 1 discloses a lead-acid battery including a plate group in which a plurality of positive and negative plates are arranged so as to be alternately stacked, and a battery case for housing 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-079609 A Summary of the Invention [Problem to be solved by the invention]

[0005] 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), which may prevent the electrolyte from flowing.

[0006] Therefore, an object of one aspect of the present invention is to provide a battery separator, an electrode, a lead-acid battery, a battery pack, and an electric vehicle that are capable of preventing the flow of electrolyte through slits from being blocked. [Means for solving the problem]

[0007] A battery separator according to one aspect of the present invention comprises a separator body covering at least the ends of the electrodes, and a slit is formed in the portion of the separator body covering the ends, and the slit extends so as to pass through at least a position in the portion of the separator body covering the ends that is offset from the center of the electrodes in the thickness direction.

[0008] In this battery separator, the slits can be prevented from being completely blocked by other portions (such as a slit), and therefore it is possible to avoid impediment to the flow of the electrolyte through the slits.

[0009] In the 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 the electrolyte through the slit formed in the folded portion.

[0010] In the battery separator according to one aspect of the present invention, the slits may extend in a direction inclined with respect to a center line passing 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 overlapping the center line, a flow path for the electrolyte is easily ensured.

[0011] In the battery separator according to one aspect of the present invention, the slits may extend in a direction inclined with respect to the ridge line of the folded portion and / or may extend so as not to reach the ridge line of the folded portion. In this case, even if another portion is located at a position overlapping the ridge line, a flow path for the electrolyte is easily ensured.

[0012] In the battery separator according to one aspect of the present invention, a plurality of slits may be formed in the folded portion. In this case, even if some of the slits in the folded portion are blocked by other portions, the remaining slits tend to ensure a flow path for the electrolyte.

[0013] In the battery separator according to one aspect of the present invention, some or all of the plurality of slits may have the same length, which makes it easier to control the flow rate of the electrolyte through the slits to a constant value.

[0014] In the battery separator according to one aspect of the present invention, some or all of the plurality of slits may have different lengths, which makes it easier to determine the orientation of the battery separator during production.

[0015] In the battery separator according to one aspect of the present invention, the plurality of 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 which case the orientation of the battery separator can be easily determined during manufacturing.

[0016] 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 position of the end face of the slit, and the strength of the end face of the slit can be increased by the rib.

[0017] In the battery separator according to one aspect of the present invention, the slit may divide a plurality of ribs. In this case, since the plurality of ribs are located at the end face of the slit, the strength of the end face of the slit can be further increased by the plurality of ribs.

[0018] In a battery separator according to one aspect of the present invention, the plurality of 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 the tearing difficult, and the slit can be prevented from expanding to an undesired length.

[0019] In the battery separator according to one aspect of the present invention, the plurality of 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 the tearing difficult, and the slit can be prevented from expanding to an undesired length.

[0020] 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, which makes it easier to ensure a flow path for the electrolyte even when another portion having a certain width is positioned so as to overlap the slit.

[0021] In a battery separator according to one aspect of the present invention, an end of an 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 a 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.

[0022] In the battery separator according to one aspect of the present invention, the slits may be formed on each of one and the other sides of the leg portion in a direction perpendicular to the predetermined direction and the thickness direction, thereby making it easier to ensure a flow path for the electrolyte.

[0023] In a battery separator according to one aspect of the present invention, the plate is housed upright in a battery case, the battery case has a plurality of protrusions that are integrally or separately provided on a bottom surface of the battery case and support the plate, the separator body covers at least the lower end of the plate, 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 plate.

[0024] In the battery separator according to one aspect of the present invention, the length of the slit in a horizontal direction perpendicular to the thickness direction may be greater than the width of the protrusion, in which case even if the protrusion is located at a position overlapping a part of the slit, it is possible for the electrolyte to flow through the other part of the slit.

[0025] In the battery separator according to one aspect of the present invention, the length of the slit in a 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 at a position that does not overlap with the protrusions, making it easier to ensure a flow path for the electrolyte through the slit.

[0026] An electrode according to one aspect of the present invention includes an electrode plate accommodated in a battery case and the battery separator. Since the electrode includes the battery separator, the electrode also has the above-mentioned effect of preventing the flow of electrolyte through the slits from being impeded.

[0027] A lead-acid battery according to one aspect of the present invention includes a plate group in which a plurality of positive and negative plates are arranged so as to be alternately stacked, and a battery case for housing the plate group upright, the plate group having a plurality of the battery separators, the separator body of the battery separator covering at least the lower end portion of either the positive or negative plate. Since the lead-acid battery includes the battery separator, the above-mentioned effect of preventing the flow of electrolyte through the slits can be achieved.

[0028] According to one aspect of the present invention, there is provided a battery pack including a plurality of the lead-acid batteries and a connection member that electrically connects one of the lead-acid batteries to the other of the lead-acid batteries. Since the battery pack also includes the lead-acid batteries, the effect of preventing the flow of the electrolyte through the slits from being impeded is achieved.

[0029] An electric vehicle according to one aspect of the present invention includes the lead-acid battery. Since the electric vehicle also includes the lead-acid battery, the above-mentioned effect of preventing the flow of electrolyte through the slits from being impeded is achieved. Effect of the Invention

[0030] 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 are capable of preventing the flow of an electrolyte through a slit from being blocked. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a diagram showing a forklift equipped with a battery pack according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view that illustrates a lead-acid battery according to an embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 4 is a plan view showing the negative electrode according to the embodiment. [Diagram 5] FIG. 5 is a front view showing a negative electrode and a battery separator according to an embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along line BB in FIG. [Figure 7] FIG. 7 is an enlarged front view of a portion of FIG. [Figure 8] FIG. 8 is a bottom view of the battery separator of FIG. [Figure 9] FIG. 9 is a bottom view of a battery separator according to a modified example. [Figure 10]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). [Figure 11] FIG. 11 is a perspective view showing a separator body according to a modified example. [Figure 12] FIG. 12 is a perspective view showing a separator body according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are given the same reference numerals, and duplicated explanations are omitted. The size of the components in each drawing is conceptual, and the relative relationship of the size between the components is not limited to that shown in each drawing.

[0033] Fig. 1 is a diagram showing a forklift 1 equipped with a battery pack 200. As shown in Fig. 1, the forklift (electric vehicle) 1 is equipped with the battery pack 200. The forklift 1 is driven by power supplied from the battery pack 200. The battery pack 200 is configured to include a plurality of lead-acid batteries 100.

[0034] FIG. 2 is a cross-sectional view showing a schematic diagram of a lead-acid battery 100. FIG. 3 is a cross-sectional view taken along line AA in FIG. 1. In FIG. 2, positive electrodes 10 and negative electrodes 20 are alternately arranged with battery separators 30 interposed therebetween from the front side to the back side of the drawing. FIG. 2 shows a cross-sectional view of a part of the positive electrode 10. FIG. 3 shows a 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 (hereinafter the same). 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.

[0035] As shown in Figures 2 and 3, the lead-acid battery 100 of the embodiment includes an electrode group (electrode plate group) 110, a battery case 120 that houses the electrode group 110, connecting members 130a, 130b connected to the electrode group 110, poles 140a, 140b connected to the connecting members 130a, 130b, a liquid inlet plug 150 that closes the liquid inlet of the battery case 120, and a support member 160 connected to the battery case 120.

[0036] 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 between them. An electrolyte solution 40 is filled in the space around the positive electrodes 10 between the battery separators 30.

[0037] The positive electrode 10 constitutes a plate-shaped electrode plate. The positive electrode 10 is housed upright in a 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.

[0038] 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 retaining 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.

[0039] The core metal 14 is inserted into each cylindrical body 12a. The core metal 14 has a rod shape. The core metal 14 extends along the Z direction inside the cylindrical body 12a. The core metal 14 can be obtained by, for example, casting. The constituent material of the core metal 14 may be any conductive material, for example, 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.

[0040] The lower connecting seat 18 is attached to the lower end of the plurality of cylindrical bodies 12a. The lower connecting seat 18 seals the lower end of the plurality of cylindrical bodies 12a. The lower connecting seat 18 is fitted to the lower end of the plurality of cylindrical bodies 12a. The lower connecting seat 18 may be fixed to the lower end of the plurality of cylindrical bodies 12a by a thermosetting adhesive or the like. The material of the lower connecting seat 18 may be an acid-resistant material. The material of the lower connecting seat 18 may be a resin such as polyolefin (polypropylene, polyethylene, etc.), polyethylene terephthalate (PET), polystyrene (PS), polyvinylidene fluoride (PVDF), polycarbonate (PC), etc.

[0041] 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 the multiple cylindrical bodies 12a by a thermosetting adhesive or the like.

[0042] The lower connecting seat 18 and the upper connecting seat 12c contact the cylindrical body 12a and the metal core 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 metal core 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.

[0043] FIG. 4 is a plan view showing the negative electrode 20. As shown in FIG. 4, the negative electrode 20 constitutes a plate-shaped electrode plate. The negative electrode 20 is housed upright in a battery container 120. The negative electrode 20 is, for example, a paste-type negative electrode plate. The negative electrode 20 is electrically connected to an 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 a main body portion of the negative electrode 20 and holds a negative electrode material 20c. The negative electrode material 20c may contain an active material after chemical conversion and an additive. 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 FIG. 3). The negative electrode grid 20a is provided with legs 20d and 20e. The legs 20d and 20e are protrusions 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 an electrode 3.

[0044] As shown in Fig. 2 and Fig. 3, the battery separator 30 is a battery component for preventing a short circuit between the positive electrode 10 and the negative electrode 20. The battery separator 30 is not particularly limited as long as it electronically insulates the positive electrode 10 and the negative electrode 20 while allowing ions to pass between them and has resistance 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 edge portion 20b of the negative electrode 20 is exposed from the upper part of the battery separator 30.

[0045] 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 protruding upward. The protrusions 160a are so-called saddles and are provided on the support member 160. In other words, the protrusions 160a are provided on the bottom surface of the battery case 120 (at a position above the bottom surface) separately from the battery case 120. 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 come into contact with 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.

[0046] Next, the battery separator 30 will be described in detail.

[0047] FIG. 5 is a front view showing the negative electrode 20 and the battery separator 30. FIG. 6 is a cross-sectional view taken along the line BB in FIG. 5. FIG. 7 is an enlarged front view showing a part of FIG. 5. FIG. 8 is a view of the battery separator 30 as seen from below. For convenience, the ribs 36 are omitted in FIG. 7. As shown in any one of FIGS. 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 includes a pair of sheet portions 32, a pair of seal portions 34, a joint portion 35, and a plurality (a plurality of 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 to the inner surface 31a.

[0048] The sheet portion 32 is a sheet-like portion and exhibits flexibility. The sheet portion 32 is disposed on one side and the other side in the thickness direction (hereinafter also simply referred to as the "thickness direction") of the negative electrode 20. The sheet portion 32 disposed on one side in the thickness direction and the sheet portion 32 disposed on the other side in the thickness direction have their lower ends integrally continuous with each other via a folded portion 33. The folded portion 33 is a sheet-like portion that is connected to the lower end portions of each of the pair of sheet portions 32, bent in a U-shape so as to be folded back from one side to the other side in the thickness direction, and exhibits flexibility.

[0049] The seal 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 seal 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 up-down direction. The seal portion 34 extends in the up-down direction from the upper end to the lower end of the pair of sheet portions 32. The seal portion 34 is, for example, an ultrasonic welding portion, a heat seal portion, a cold seal portion, a gear seal portion, or the like. The gear seal portion is a portion that is mechanically bonded by pressure using a gear. The seal portion 34 does not need to be completely sealed. From the viewpoint of the fluidity of the electrolyte 40 in the battery separator 30, at least one of the seal portions 34 may be provided with an area through which the electrolyte 40 can pass.

[0050] The joint 35 is a portion that joins the pair of sheet portions 32. The joint 35 is provided at the upper end portions 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 side from the center in the width direction at the upper end portions 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 portions 32 themselves are welded. From the viewpoint of preventing welding defects, the joint 35 may be formed by ultrasonic welding or the like.

[0051] 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 container 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.

[0052] In this embodiment, a slit 37 is formed in the folded portion 33 (a portion covering an end of the separator body 31). The slit 37 is an opening portion that penetrates the inside and outside of the separator body 31. The slit 37 constitutes a non-joint portion that is not joined at the lower ends of the pair of sheet portions 32. The slit 37 is a long opening portion that extends so as to pass through at least a position off the center of the folded portion 33 in the thickness direction. There is no particular limitation on the method of forming the slit 37, and for example, the slit 37 may be formed by cutting with a cutter.

[0053] When viewed from below, the slits 37 extend so as not to reach the ridge line R1 of the folded portion 33. For example, the ridge line R1 is a line formed by a connection of the lowermost parts of the folded portion 33. The ridge line R1 here is a center line. The center line is a line passing through the center in the thickness direction of the folded portion 33. For example, the center line is a line passing through the center in the width direction and thickness direction and along the width direction when viewed from below of the folded portion 33. The slits 37 here extend along the width direction when viewed from below. A plurality of slits 37 are formed in the folded portion 33, and the plurality of slits 37 have the same length. The length of the slits 37 is the dimension in the extension direction of the slits 37.

[0054] The slit 37 divides the plurality of 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 to be located on the same plane as the end face of the slit 37. The plurality of 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 central position). The width of the slit 37 is a dimension in a direction perpendicular to the extension direction of the slit 37.

[0055] The slit 37 is formed at a position spaced apart from the foot portions 20d, 20e in the width direction. The slit 37 is formed on each of one side and the other side of the foot portion 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.

[0056] 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 member to obtain the lead-acid battery 100. In the assembly process, for example, the unformed positive electrode 10 and the negative electrode 20 covered with the unformed 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 arranged in a battery container 120 to prepare an unformed battery. Dilute sulfuric acid is poured into the unformed battery and a direct current is passed through it to perform battery container formation. The specific gravity of the sulfuric acid after formation is adjusted to an appropriate specific gravity to obtain the lead-acid battery 100. The formation process is not limited to being performed after the assembly process, and may be performed before the assembly process (tank formation).

[0057] 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-back 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 the flow of the electrolyte 40 through the slit 37 being hindered.

[0058] 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.

[0059] In the battery separator 30, the slits 37 extend so as not to reach the center line passing through the center in the thickness direction of the folded-back portion 33. In this case, even if the protrusions 160a are located at positions overlapping the center line, a flow path for the electrolyte 40 is easily ensured.

[0060] In the battery separator 30, the slits 37 extend so as not to reach the ridge line R1 of the folded portion 33. In this case, even if the protrusion 160a is located at a position overlapping the ridge line R1, a flow path for the electrolyte 40 is easily ensured.

[0061] In the battery separator 30, a plurality of 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.

[0062] In the battery separator 30, the multiple slits 37 have the same length. In this case, it is easy to control the flow rate of the electrolyte 40 through the slits 37 to be constant. Since it is sufficient to form the slits 37 with the same length, production efficiency can be improved.

[0063] In the battery separator 30, the slits 37 divide the ribs 36. In this case, since the ribs 36 are located at the end faces of the slits 37, the strength of the end faces of the slits 37 can be increased by the ribs 36. The end faces of the slits 37 become less susceptible to breakage.

[0064] 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 more resistant to breakage.

[0065] 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 unlikely to occur.

[0066] In the battery separator 30, the multiple ribs 36 include a third rib 363 and a fourth rib 364 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 cutting end position (the position where the cutter blade leaves), so defects such as the cutter blade getting caught on the rib 36 are unlikely to occur.

[0067] In battery separator 30, the width of slit 37 at the first position is different from the width of slit 37 at the second position. This makes it easier to ensure a flow path for electrolyte 40 when protrusion 160a having a certain width is located at a position overlapping slit 37.

[0068] In the battery separator 30, the slits 37 are formed at positions spaced apart from the legs 20d, 20e in the width direction. Since the protrusions 160a are located at positions facing the legs 20d, 20e, the slits 37 are formed at positions spaced apart from the legs 20d, 20e, so that the slits 37 are less likely to be blocked by the protrusions 160a. This makes it easier to prevent the legs 20d, 20e from shorting out through the slits 37 due to fallen active material.

[0069] In the battery separator 30, the slits 37 are formed on both sides of the leg portion 20e in the width direction. In this case, a flow path for the electrolyte 40 is easily secured, making it possible to suppress short circuits.

[0070] 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.

[0071] 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 part of the slit 37, the electrolyte 40 can flow through the other part of the slit 37.

[0072] 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 likely to be located at a position that does not overlap with the protrusions 160a, and a flow path for the electrolyte 40 through the slit 37 is likely to be secured.

[0073] Although the embodiments have been described above, one aspect of the present invention is not limited to the above-described embodiments.

[0074] In the above embodiment, the rib 36 extends linearly, but is not limited thereto. For example, the rib 36 may extend in a wavy line or a zigzag line. The rib 36 may be formed intermittently, may be dot-shaped, may be circular, may be elliptical, or may be polygonal. The rib 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 rib 36 may be semicircular or polygonal. The rib 36 may extend along the up-down direction, or alternatively or additionally may extend along the width direction.

[0075] In the above embodiment, the slit 37 divides a plurality of 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 these may be the same. The first position and the second position are not particularly limited as long as they are different positions of the slit 37. In the above embodiment, the ridge line R1 is also the center line of the folded-back portion 33, but the ridge line R1 does not have to be the center line.

[0076] 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.

[0077] Fig. 9 is a view of a battery separator 530 according to a modified example, viewed from below. As shown in Fig. 9, in place of or in addition to the slit 37 (see Fig. 8), the folded portion 33 may have a slit 337 extending in a direction inclined with respect to a center line and / or a ridge line R1 passing through the center in the thickness direction of the folded portion 33. In this case, even if the protruding portion 160a is located at a position overlapping with the center line and / or the ridge line R1, the slit 337 is unlikely to be completely blocked, and a flow path for the electrolyte 40 is likely to be secured.

[0078] In addition, when slits 337 are formed in addition to slits 37, they are formed at positions asymmetrical with respect to the center line of the folded-back portion 33. In this case, it is easier to determine the orientation of the battery separator 30 during manufacturing. The slits 37 may also extend in a direction inclined with respect to the center line and / or ridge line R1 passing through the center of the thickness direction of the folded-back portion 33.

[0079] In the above embodiment, the separator body 31 includes the folded portion 33, but is not limited thereto as long as it is configured to cover at least 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 portions of the pair of sheet portions 32 (the lower end portions 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 portion of the sheet portion 32. Note that, for convenience, the rib 36 is omitted in Fig. 10(a).

[0080] 11, the separator body 31 may be configured such that both ends of a pair of sheet parts 32 in the width direction are integrally connected via a folded 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 end or the other end of a pair of sheet parts 32 in the width direction are integrally connected via a folded portion 633. As shown in particular, in the stacked sheet parts 32, one end and the other end in the width direction that are continuous at the folded 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 portions 533 and 633. For convenience, the ribs 36 are omitted in FIG. 11 and FIG. 12.

[0081] In the above embodiment, the protrusion 160a is provided on the bottom surface of the battery case 120 as a separate body 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 has been described as an example of an electric vehicle (motorized vehicle), 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 on the forklift 1, but the forklift 1 may be equipped with a lead-acid battery 100.

[0082] The respective configurations in the above-mentioned embodiment and modified examples are not limited to the above-mentioned materials and shapes, and various materials and shapes can be applied. The respective configurations in the above-mentioned embodiment or modified examples can be arbitrarily applied to the respective configurations in other embodiments or modified examples. A part of each configuration in the above-mentioned embodiment or modified example can be appropriately omitted within the scope of the gist of one aspect of the present invention. [Explanation of symbols]

[0083] 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...convex portion, 200...battery assembly, 361...first rib, 362...second rib, 363...third rib, 364...fourth rib, R1...ridge line.

Claims

1. A battery comprising: a plate group in which a plurality of positive and negative 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.

2. The lead-acid battery for a forklift according to claim 1 , wherein the slit is formed in a plurality of the folded portion.

3. The lead-acid battery for a forklift according to claim 2 , wherein some or all of the plurality of slits have the same length.

4. The lead-acid battery for a forklift according to claim 2 , wherein some or all of the plurality of slits have different lengths.

5. 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.

6. 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 slit is formed at a position spaced apart from the foot portion in a direction perpendicular to the predetermined direction and the thickness direction.

7. 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.

8. A battery pack comprising a plurality of the forklift lead-acid batteries according to any one of claims 1 to 7.

9. A forklift comprising the battery pack according to claim 8.

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