Electrode group, storage battery, battery pack, electric vehicle, and method of manufacturing electrode group

Abstract

To provide an electrode group, an accumulator battery, a battery pack, a motor car, and a method of manufacturing the electrode group capable of suppressing generation of short circuit.SOLUTION: An electrode group 3 comprises a positive electrode 10, a separator 13, and a negative electrode 12 sequentially laminated in a first direction X. The separator 13 has: a first surface 41A that covers one surface in the first direction X of the negative electrode 12; and a second surface 41B that covers the other surface. The negative electrode 12 is sandwiched between the first surface 41A and the second surface 41B. When seen from the first direction X, an upper region of the first surface 41A opposed to the positive electrode 10 is located above an upper end 41Ba of the second surface 41B at least in a region corresponding to a positive electrode ear part 14c of the positive electrode 10.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an electrode group, a storage battery, a battery pack, an electric vehicle, and a method for manufacturing an electrode group. [Background technology]

[0002] Storage batteries including an electrode group are widely used as secondary batteries for industrial or consumer use, and there is particularly high demand for them as storage batteries for electric vehicles (so-called batteries) or as backup storage batteries for UPS (Uninterruptible Power Supply), disaster prevention (emergency) radios, telephones, etc.

[0003] The storage battery includes an electrode group including a positive electrode, a negative electrode, and a separator, and a battery case that houses the electrode group. The positive electrode includes a cylindrical body, a rod-shaped core metal inserted into the cylindrical body, and an electrode material containing an active material that is filled inside the cylindrical body (see, for example, Patent Document 1). The separator is disposed between the positive electrode and the negative electrode to prevent short-circuiting between the positive electrode and the negative electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 61-232572 Summary of the Invention [Problem to be solved by the invention]

[0005] In batteries used in electric vehicles, stratification of the electrolyte (sulfuric acid) can occur due to differences in season, usage environment, or the charging frequency of the end user. Stratification occurs when sulfate ions (SO4 2- Stratification occurs due to the tendency of sulfuric acid to settle to the bottom. When stratification occurs, the concentration of dilute sulfuric acid at the bottom of the electrode increases, causing deterioration of the negative electrode active material in particular. If the battery continues to be used in this state, the battery capacity will decrease and the battery's characteristics (lifespan) will be reduced.

[0006] Stirring the electrolyte is particularly effective in suppressing stratification. In the case of liquid storage batteries such as those used in electric vehicles, it is particularly effective to charge the battery beyond the consumed discharge capacity to cause electrolysis of water, which is a component of the electrolyte (gassing). This gassing removes sulfate ions (SO4 2- ) rises to the top, creating an electrolyte solution of uniform concentration and preventing stratification. However, when the electrolyte solution is stirred in a storage battery, the positive electrode active material that falls off the positive electrode and floats in the electrolyte solution rises up inside the case (battery container). In this case, the positive electrode active material that has risen and accumulated may cause a short circuit between the negative electrode and the positive electrode.

[0007] An object of one aspect of the present invention is to provide an electrode group, a storage battery, a battery pack, an electric vehicle, and a method for manufacturing an electrode group that can suppress the occurrence of short circuits. [Means for solving the problem]

[0008] An electrode group according to one aspect of the present invention comprises a positive electrode, a separator, and a negative electrode stacked in order in a first direction, the positive electrode having a positive electrode ear connected to a positive electrode connecting member that connects multiple positive electrodes, and the negative electrode having a negative electrode ear connected to a negative electrode connecting member that connects multiple negative electrodes, the positive electrode ear and the negative electrode ear being arranged at a predetermined interval in a second direction perpendicular to the first direction as viewed from the first direction, the separator having a first surface that covers one surface of the negative electrode in the first direction and a second surface that covers the other surface, the separator sandwiching the negative electrode between the first surface and the second surface, and as viewed from the first direction, at least in a region corresponding to the positive electrode ear of the positive electrode, the upper region of the first surface facing the positive electrode is located above the upper end of the second surface.

[0009] In an electrode group according to one aspect of the present invention, when viewed from a first direction, at least in a region corresponding to the positive electrode lug of the positive electrode, the upper region of the first surface facing the positive electrode is located higher than the upper end of the second surface. That is, the upper end of the first surface facing the positive electrode is located higher than the upper end of the second surface. In this way, in the electrode group, the first surface is located between the positive electrode lug and the negative electrode, so that the path from the negative electrode to the positive electrode lug (the path from the positive electrode lug to the negative electrode) beyond the upper end of the first surface is longer. Therefore, in the electrode group, the positive electrode active material can be prevented from accumulating between the positive electrode lug and the negative electrode, causing a short circuit between the positive electrode and the negative electrode via the separator. Therefore, the electrode group can prevent the occurrence of a short circuit.

[0010] In one embodiment, the negative electrode is disposed at each of both ends in the first direction, and in the separators covering the negative electrodes disposed at each of the both ends in the first direction, an upper region of the first surface facing the positive electrode may be located above the upper end of the second surface. In a configuration in which the negative electrode is disposed in the outermost layer, the second surface of the separator covering the negative electrode is not disposed opposite the positive electrode. Therefore, by employing the above configuration for the separator covering the negative electrode disposed in the outermost layer, short-circuiting between the positive electrode and the negative electrode can be effectively suppressed.

[0011] In one embodiment, in the separator covering the negative electrode arranged at other than both ends in the first direction, the upper end of the first surface and the upper end of the second surface may be at the same height position.

[0012] In one embodiment, the upper ends of the first and second surfaces are linear in the second direction, and the upper end of the second surface may be inclined relative to the upper end of the first surface such that a first distance between the upper end of the first surface and the upper end of the second surface on the positive electrode lug side is greater than a second distance between the upper end of the first surface and the upper end of the second surface on the negative electrode lug side. In this configuration, the upper region of the first surface facing the positive electrode can be positioned higher than the upper end of the second surface. Furthermore, since the second distance between the upper end of the first surface and the upper end of the second surface on the negative electrode lug side is reduced, the negative electrode (negative electrode lug) can be covered by the second surface. Therefore, short circuits between the negative electrode and the positive electrode can be suppressed.

[0013] In one embodiment, the upper ends of the first and second surfaces may be linear in the second direction, and the distance between the upper ends of the first and second surfaces may be constant from one side of the separator to the other in the second direction. In this configuration, the upper region of the first surface facing the positive electrode may be positioned higher than the upper end of the second surface.

[0014] In one embodiment, the separator may have the first and second surfaces connected at the lower end. In this configuration, the lower end of the negative electrode is covered by the separator. Therefore, short-circuiting between the positive electrode and the negative electrode can be suppressed even at the lower end of the electrode assembly.

[0015] In one embodiment, the separator may be provided with a joint that joins the first surface and the second surface at least in a region corresponding to the positive electrode lug of the positive electrode. In this configuration, even if the deposited positive electrode active material passes through the side of the first surface and reaches the negative electrode from the positive electrode lug (or reaches the negative electrode from the positive electrode lug), the first surface and the second surface are joined by the joint, so that a short circuit between the positive electrode and the negative electrode can be suppressed.

[0016] In one embodiment, the positive electrode may include a cylindrical body extending in a third direction perpendicular to the first and second directions and housing a current collector and a positive electrode active material. In this configuration, the positive electrode active material is housed in the cylindrical body, which can prevent the positive electrode active material from falling off. This can prevent short circuits caused by the positive electrode active material.

[0017] In one embodiment, the distance between the upper end of the first surface and the positive electrode connecting member may be 3 mm or more and 30 mm or less. With this configuration, when the positive electrode lug and the positive electrode connecting member are joined by, for example, welding, damage to the separator due to heat generated during welding can be suppressed.

[0018] A storage battery according to one aspect of the present invention includes the electrode group described above and a case that houses the electrode group.

[0019] A storage battery according to one aspect of the present invention includes the electrode group described above, and therefore, the occurrence of short circuits in the electrode group can be suppressed.

[0020] In one embodiment, the case has a main body that houses the electrode group and a lid that covers the opening of the main body, and the lid is provided with a liquid refill tap that allows liquid to be refilled. In the electrode group housed in the main body, the upper end of the separator may be located below the lower end of the liquid refill tap. In a storage battery, the length (height) of the positive and negative electrodes within the case may be increased to ensure battery capacity. Increasing the length of the positive and negative electrodes may cause contact between the separator and the liquid refill tap. In this configuration, the upper end of the separator is located below the lower end of the liquid refill tap, so the separator and the liquid refill tap do not come into contact. This can prevent damage to the separator, etc.

[0021] A battery pack according to one aspect of the present invention includes a plurality of the above-described storage batteries.

[0022] An electric vehicle according to one aspect of the present invention includes the above-described storage battery.

[0023] A manufacturing method of an electrode group according to one aspect of the present invention is a manufacturing method of a storage battery having a positive electrode, a separator, and a negative electrode stacked in order in a first direction, and includes a step of sandwiching the negative electrode between a separator having a first surface covering one surface of the negative electrode in the first direction and a second surface covering the other surface, and in the step of sandwiching the negative electrode between the separators, when viewed from the first direction, the upper region of the first surface facing the positive electrode is positioned above the upper end of the second surface, at least in the region corresponding to the positive electrode ear portion of the positive electrode.

[0024] In a method for manufacturing an electrode assembly according to one aspect of the present invention, the separator sandwiches the negative electrode so that, as viewed from a first direction, at least in a region corresponding to the positive electrode lug of the positive electrode, the upper region of the first surface facing the positive electrode is located higher than the upper end of the second surface. As a result, the upper end of the first surface facing the positive electrode is located higher than the upper end of the second surface. In this way, in the electrode assembly, the first surface is located between the positive electrode lug and the negative electrode, so that the path from the negative electrode to the positive electrode lug (the path from the positive electrode lug to the negative electrode) beyond the upper end of the first surface is lengthened. Therefore, in the electrode assembly, the positive electrode active material can be prevented from accumulating between the positive electrode lug and the negative electrode, causing a short circuit between the positive electrode and the negative electrode. Therefore, the occurrence of a short circuit in the electrode assembly can be prevented. [Effects of the Invention]

[0025] According to one aspect of the present invention, the occurrence of a short circuit can be suppressed. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing a forklift equipped with a battery pack according to one embodiment. [Figure 2] FIG. 2 is a perspective view showing a part of a storage battery according to one embodiment in a cutaway state. [Figure 3] FIG. 3(a) is a diagram showing the positive electrode as viewed from a first direction, and FIG. 3(b) is an enlarged cross-sectional view taken along line IIIb-IIIb in FIG. 3(a). [Figure 4] FIG. 4 is a plan view showing the negative electrode according to the embodiment. [Figure 5] FIG. 5 is an enlarged plan view showing a part of the separator sheet. [Figure 6] FIG. 6 is a plan view showing the negative electrode according to the embodiment. [Figure 7] FIG. 7 is an enlarged plan view showing a part of the electrode group. [Figure 8] FIG. 8 is an enlarged plan view showing a part of an electrode group according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are designated by the same reference numerals, and redundant description will be omitted.

[0028] Fig. 1 is a diagram showing a forklift equipped with a battery pack. As shown in Fig. 1, a forklift (electric vehicle) 100 is equipped with a battery pack 200. The forklift 100 is driven by power supplied from the battery pack 200. The battery pack 200 is configured to include a plurality of storage batteries 1.

[0029] Fig. 2 is a partially cutaway perspective view of a storage battery according to this embodiment. As shown in Fig. 2, the storage battery 1 is, for example, a lead-acid battery. The storage battery 1 is not limited to use in the forklift 100, but can also be used, for example, as a battery for an automobile or as a backup power source used during a power outage. In this embodiment, the storage battery 1 is, for example, a clad-type storage battery equipped with clad-type electrodes.

[0030] The storage battery 1 includes an electrode group 3, a positive electrode terminal 5A, a negative electrode terminal 5B, a water refill tap (fluid refill tap) 6, and a case 7. The case 7 has a main body 8 and a lid 9. The main body 8 is a box-shaped battery container. The main body 8 is made of a material such as polypropylene. The main body 8 contains the electrode group 3 and an electrolyte. The main body 8 is composed of four side surfaces and a bottom (described in detail below). The lid 9 covers the opening of the main body 8. The lid 9 is provided with a positive electrode terminal 5A, a negative electrode terminal 5B, and a water refill tap (fluid refill tap) 6 that can refill the electrolyte (liquid). The water refill tap 6 is provided between the positive electrode terminal 5A and the negative electrode terminal 5B.

[0031] The electrode group 3 includes a plurality of positive electrodes 10, a plurality of negative electrodes 12, and a plurality of separators 13. In the electrode group 3, the positive electrodes 10 and the negative electrodes 12 are alternately arranged. A separator 13 is located between adjacent positive electrodes 10 and negative electrodes 12. Therefore, the positive electrodes 10, the separators 13, and the negative electrodes 12 are stacked in order in a predetermined direction. In this embodiment, in the electrode group 3, the negative electrodes 12 are arranged at the ends of the arrangement direction of the positive electrodes 10, the negative electrodes 12, and the separators 13 (hereinafter, sometimes simply referred to as the "arrangement direction" or the "stacking direction"). In addition, the assembly of the positive electrodes 10, the negative electrodes 12, and the separators 13 is also referred to as a battery electrode group (electrode plate group). When the electrode group 3 and the electrolyte are housed in the main body 8, the electrolyte is present in the gap between the positive electrodes 10 and the separators 13, inside the separators 13, etc.

[0032] Hereinafter, the direction in which the multiple positive electrodes 10, the multiple negative electrodes 12, and the multiple separators 13 overlap each other (stacking direction) is referred to as the first direction X. The direction perpendicular to the first direction X is referred to as the second direction Y, and the direction perpendicular to the first direction X and the second direction Y is referred to as the third direction Z. In this embodiment, the third direction Z corresponds to the direction in which the electrode group 3 is housed in the case 7. The second direction Y and the third direction Z are perpendicular to each other, but are not limited to this. The second direction Y and the third direction Z may intersect each other as long as they intersect.

[0033] FIG. 3(a) is a view showing a positive electrode as viewed from a first direction, and FIG. 3(b) is an enlarged cross-sectional view taken along line IIIb-IIIb in FIG. 3(a). As shown in FIG. 2 and FIGS. 3(a) and 3(b), the positive electrode 10 is, for example, a clad positive electrode plate (second electrode plate). In the storage battery 1, each positive electrode 10 is electrically connected to a positive electrode terminal 5A. Each positive electrode 10 and the positive electrode terminal 5A are electrically connected by a positive electrode strap (positive electrode connecting member) 17. The positive electrode 10 includes a current collector 14, a plurality of cylindrical bodies 15 (tubes) that house portions of the current collector 14, a positive electrode material 16 housed in the cylindrical bodies 15, and upper and lower connecting seats 21 and 22 that are attached to the current collector 14.

[0034] The current collector 14 has a plurality of cores 14a, a connecting portion (not shown) connecting the plurality of cores 14a, and a positive electrode lug portion 14c protruding from the connecting portion. The current collector 14 is formed, for example, by casting. The constituent material of the current collector 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 lead alloy may contain selenium, silver, bismuth, etc.

[0035] The multiple cores 14a are rod-shaped portions extending along the third direction Z and are arranged in a row along the second direction Y. One end of each core 14a in the third direction Z is connected to a connecting portion covered by the upper link seat 21. The other end of each core 14a in the third direction Z is fixed to the lower link seat 22. The length of each core 14a is, for example, 170 to 650 mm. The length of each core 14a may be 600 mm or less, or may be 450 mm or less. The connecting portion is a portion that supports the core 14a and the positive electrode lug 14c and extends along the second direction Y. When the positive electrode 10 is accommodated in the case 7, the connecting portion is located on the positive electrode terminal 5A side in the third direction Z. The positive electrode lug 14c is a terminal portion that protrudes from the connecting portion in the third direction Z and is connected to the positive electrode strap 17. The protruding direction of the positive electrode lug 14c is opposite to the protruding direction of the metal core 14a in the third direction Z. When the positive electrode 10 is housed in the case 7, the positive electrode lug 14c is located on the lid 9 side in the third direction Z.

[0036] The multiple cylindrical bodies 15 are insulating members that constitute a group of tubes (clad tubes) for holding active material. The group of tubes for holding active material is an assembly of cylindrical porous tubes also known as "gauntlets." For this reason, multiple holes are provided in each cylindrical body 15. In this embodiment, the cylindrical bodies 15 have a uniform thickness, but this is not limited to this. Each cylindrical body 15 extends along the third direction Z and houses a corresponding core metal 14a. Each cylindrical body 15 is, for example, a resin molded product.

[0037] The cathode material 16 is filled inside the cylindrical body 15 together with the metal core 14a. Therefore, the metal core 14a and the cathode material 16 are housed in the cylindrical body 15. As shown in FIG. 3(b), the cathode material 16 surrounds the metal core 14a inside the cylindrical body 15. The cathode material 16 includes an active material. The active material includes both the active material after chemical conversion and the raw material of the active material before chemical conversion. The cathode material 16 contains the active material after chemical conversion. The cathode material 16 after chemical conversion includes, for example, the raw material of the cathode active material. In this embodiment, the cathode material 16 may include a cathode active material and an additive. Examples of the cathode active material include lead powder, red lead, etc. Examples of the additive include a carbon material, short reinforcing fibers, etc. The cathode active material after chemical conversion is, for example, lead dioxide, etc.

[0038] The upper connecting seat 21 is an insulating structure attached to the connecting portion of the current collector 14 and covers the connecting portion when viewed from the third direction Z. The upper connecting seat 21 seals one end of each cylindrical body 15 in the third direction Z. For example, the upper connecting seat 21 is welded to each cylindrical body 15, but this is not limited to this. The upper connecting seat 21 and each cylindrical body 15 may be fixed to each other, for example, via an adhesive or the like. The upper connecting seat 21 is provided, for example, by welding an insulating resin member to the current collector 14. The lower connecting seat 22 is an insulating structure attached to the multiple cores 14a of the current collector 14. The lower connecting seat 22 is attached to the current collector 14, for example, by inserting and fitting the cores 14a of the current collector 14 into an insulating resin member. The lower connecting seat 22 seals the other end of each cylindrical body 15 in the third direction Z. As a result, the position of each cylindrical body 15 in the positive electrode 10 is fixed by the upper linking seat 21 and the lower linking seat 22. For example, the lower linking seat 22 is welded to each cylindrical body 15, but this is not limited to this. The lower linking seat 22 and each cylindrical body 15 may be fixed to each other by, for example, an adhesive or the like.

[0039] FIG. 4 is a plan view showing a negative electrode according to an embodiment. As shown in FIG. 4, the negative electrode 12 is a negative electrode plate (first electrode plate) in the storage battery 1 and is electrically connected to the negative electrode terminal 5B. Each negative electrode 12 and the negative electrode terminal 5B are electrically connected by a negative electrode strap (negative electrode connecting member) 18. The negative electrode 12 includes a current collector 12a and a negative electrode material 12b. The current collector 12a is formed by casting, for example, and includes a negative electrode grid 12c and a negative electrode lug 12d. The negative electrode grid 12c is the main body of the negative electrode 12 and holds the negative electrode material 12b. In this embodiment, the thickness of the portion of the negative electrode 12 where the negative electrode material 12b is held is greater than the thickness of the negative electrode grid 12c, but is not limited to this.

[0040] The negative electrode material 12b may contain a negative electrode active material and an additive. The negative electrode active material may be, for example, spongy lead. Examples of the additive include barium sulfate, a carbon material, lignin, or short reinforcing fibers. The negative electrode lug 12d is a terminal portion protruding from the negative electrode grid 12c in the third direction Z and connected to the negative electrode strap 18. The negative electrode lug 12d and the negative electrode grid 12c do not overlap with each other in the first direction X. In this embodiment, the negative electrode grid 12c is covered by the separator 13. The negative electrode grid 12c has protrusions 12e and 12f. The protrusions 12e and 12f are arranged at a predetermined interval and are legs protruding outward from the negative electrode grid 12c. The protrusions 12e and 12f protrude in a direction opposite to the protruding direction of the negative electrode lug 12d. In this embodiment, the protruding direction of the negative electrode lug 12d and the protruding directions of the protrusions 12e and 12f are perpendicular to the arrangement direction, and the negative electrode lug 12d and the negative electrode grid 12c do not overlap with each other in the arrangement direction.

[0041] Returning to FIG. 2 , the separator 13 is a battery component (battery separator) for preventing a short circuit between the positive electrode 10 and the negative electrode 12. The separator 13 is not particularly limited as long as it provides electrical insulation between the positive electrode 10 and the negative electrode 12 while allowing ions to pass therethrough and is resistant to oxidation on the positive electrode 10 side and reduction on the negative electrode 12 side. Examples of materials for the separator 13 include glass fiber, resin, and inorganic substances. In this embodiment, the separator 13 covers the negative electrode grid 12c and the protruding portions 12e and 12f of the negative electrode 12, and the negative electrode lug portion 12d of the negative electrode 12 is exposed from the separator 13.

[0042] The structure of a separator sheet, which is a pre-processed product of separator 13, will now be described with reference to Fig. 5. Fig. 5 is an enlarged plan view showing a portion of the separator sheet. As shown in Fig. 5, separator sheet 30 has a main body portion 31.

[0043] The main body portion 31 is a sheet-like portion that forms the main part of the separator sheet 30 and is flexible. The main body portion 31 is provided with a plurality of protrusions 32. The plurality of protrusions 32 are provided, for example, to improve the durability of the separator sheet 30 and the fluidity of the electrolyte solution in the case 7. The plurality of protrusions 32 are arranged on the main body portion 31 along the second direction Y and protrude from the main surface along the thickness direction of the separator sheet 30. Each of the plurality of protrusions 32 is provided from one end to the other end of the separator sheet 30 in the third direction Z.

[0044] In this embodiment, each of the multiple protrusions 32 is composed of a group of multiple ribs 33 that are spaced apart from one another. Therefore, each protrusion 32 includes a portion that protrudes from the main surface (i.e., the rib 33) and a portion that does not protrude from the main surface (i.e., the gaps between the ribs 33). From the viewpoint of achieving both the ionic conductivity and durability of the separator 13, the proportion of the multiple ribs 33 in the protrusions 32 in a plan view is, for example, 5% or more and 50% or less. This proportion may be 10% or more, 15% or more, 45% or less, or 40% or less.

[0045] The multiple ribs 33 are protrusions that protrude from the second main surface 31b along the first direction X and are periodically arranged in a staggered pattern on the second main surface 31b as viewed in the first direction X. The proportion of the second main surface 31b occupied by the multiple ribs 33 as viewed in the first direction X is, for example, 10% to 50%. This proportion may be 15% or more, 20% or more, 45% or less, or 40% or less. In two adjacent protrusions 32 in the second direction Y, the ribs 33 included in one protrusion 32 and the ribs 33 included in the other protrusion 32 do not overlap with each other in the second direction Y. In each protrusion 32, the multiple ribs 33 are periodically arranged on the main body 31 along the third direction Z and are spaced apart from each other. As viewed in the first direction X, each rib 33 has a substantially rectangular shape, but this is not limited thereto. When viewed from the first direction X, each rib 33 may be in the shape of a dot, a circle, an ellipse, or a polygon.

[0046] Next, with reference to FIG. 6 , the structure of the negative electrode 12 and separator 13 included in the electrode group 3 will be described in detail. FIG. 6 is a plan view showing a negative electrode wrapped in a separator. As shown in FIG. 6 , the separator 13 corresponds to a pouch-shaped product of a separator sheet and wraps the negative electrode 12. As described above, the negative electrode ear 12d of the negative electrode 12 is exposed from the separator 13, and the protrusions 12e and 12f of the negative electrode 12 are covered by the separator 13. The separator 13 is formed, for example, by folding a single separator sheet 30 in half along the second direction Y and then sealing desired locations. At this time, the separator sheet 30 is folded back on the side of the protrusions 12e and 12f of the negative electrode 12 in the second direction Y so that the negative electrode 12 is sandwiched between the separator sheets 30. Both ends of the main body 31 in the third direction Z are located outside the negative electrode 12. From the viewpoint of improving workability, the separator sheet 30 may be folded in half as the negative electrode 12 is moved. The separator 13 has a main portion 41, a pair of joint portions 42 and 43, a bent portion 44, and a seal portion (joint portion) 45.

[0047] The main portion 41 is a portion that houses the negative electrode grid 12c of the negative electrode 12. The main portion 41 is composed of the main body portion 31 (see FIG. 5) of the separator sheet 30. Therefore, in this specification, the main portion 41 can be referred to as the main body portion 31. The main portion 41 is formed by folding the separator sheet 30 in half so that the main surface on which the protrusions 32 are provided faces inward. The main portion 41 has a first surface 41A and a second surface 41B. The first surface 41A covers one surface of the negative electrode 12 that is formed by the negative electrode material 12b. The second surface 41B covers the other surface of the negative electrode 12 that is formed by the negative electrode material 12b.

[0048] The pair of joints 42, 43 are portions for maintaining the separator sheet 30 folded in half. The joint 42 is provided at one end of the main portion 41 in the third direction Z, and the joint 43 is provided at the other end of the main portion 41 in the third direction Z. Each of the joints 42, 43 is located outside the negative electrode 12 in the third direction Z. Each of the joints 42, 43 extends in the second direction Y. This allows the joints 42, 43 to suppress movement of the negative electrode 12 along the third direction Z. The joints 42, 43 do not need to be completely sealed. From the perspective of the fluidity of the electrolyte in the separator 13, at least one of the joints 42, 43 may have a region through which the electrolyte can pass. The joints 42, 43 are, for example, ultrasonic welded portions, heat sealed portions, cold sealed portions, gear sealed portions, etc. The gear sealed portion is a portion that is mechanically bonded by pressure using a gear. In this embodiment, each of the joints 42, 43 is a gear seal portion that extends from one end of the separator 13 in the second direction Y to the other end.

[0049] The bent portion 44 is a portion where the separator sheet 30 is folded back. The bent portion 44 can be said to connect the lower ends of the first surface 41A and the second surface 41B. At least a portion of the bent portion 44 can abut against the negative electrode grid 12c. An opening 44a is provided in a portion of the bent portion 44. The opening 44a is provided, for example, to improve the fluidity of the electrolyte in the separator 13. The opening 44a is provided at a position that does not overlap either of the protrusions 12e and 12f in the second direction Y. The opening 44a is provided, for example, in the center of the separator 13 in the third direction Z, but is not limited to this. For example, the opening 44a is formed by cutting a portion of the bent portion 44.

[0050] The sealing portion 45, like the joining portions 42 and 43, is a portion for maintaining the state of the separator sheet 30 folded in half. The sealing portion 45 joins a portion of the first surface 41A and a portion of the second surface 41B of the main portion 41. The portion of the first surface 41A and the portion of the second surface 41B include at least a region A (see FIG. 7) corresponding to the positive electrode lug 14c of the positive electrode 10, do not overlap the negative electrode 12 in the first direction X, and are located on the opposite side of the bent portion 44 in the second direction Y. Therefore, the sealing portion 45 is located on one end side of the separator 13 in the second direction Y and on the outer side of the negative electrode 12 as viewed from the first direction X. The sealing portion 45 faces the negative electrode grid 12c of the negative electrode 12 in the second direction Y and faces the negative electrode lug 12d in the third direction Z. In the storage battery 1, at least the sealing portion 45 is located closer to the lid 9 than the negative electrode 12 in the second direction Y. The seal portion 45 extends along the third direction Z. Specifically, the seal portion 45 extends from one end to the other end of the separator 13 in the third direction Z, and is provided in the main portion 41 and the joint portion 42. That is, a portion of the seal portion 45 overlaps the joint portion 42.

[0051] Next, the details of the configuration of the separator 13 covering the negative electrode 12 arranged in the outermost layer of the positive electrode 10, negative electrode 12, and separator 13 included in the electrode group 3 will be described with reference to FIG. 7. FIG. 7 is an enlarged plan view showing a portion of the electrode group. FIG. 7 shows the negative electrode 12 and separator 13 arranged in the outermost layer as viewed from the negative electrode 12 side in the first direction X. As shown in FIG. 7, when viewed from the first direction X, the positive electrode ear 14c of the positive electrode 10 and the negative electrode ear 12d of the negative electrode 12 are arranged at a predetermined interval in the second direction Y.

[0052] As shown in FIG. 7 , the first surface 41A of the separator 13 faces the positive electrode 10. When viewed from the first direction X, in at least a region A corresponding to the positive electrode ear 14c of the positive electrode 10, the upper region of the first surface 41A facing the positive electrode 10 is located higher than the upper end 41Ba of the second surface 41B. The region A corresponding to the positive electrode ear 14c may include a region facing the positive electrode ear 14c and a region defined by imaginary lines extending both ends of the positive electrode ear 14c in the second direction Y in the third direction Z. The upper region includes at least a region of the first surface 41A closer to the negative electrode ear 12d than the center of the first surface 41A in the third direction Z, and is a region defined by at least the upper end 41Aa. In this embodiment, the upper end 41Aa of the first surface 41A is linear in the second direction Y, and the upper end 41Ba of the second surface 41B is linear in the second direction Y. The term "straight line" as used herein is not limited to a "straight line" that has mathematical precision, but also includes a state that can be regarded as substantially straight line. "Straight line" means something that can be recognized as roughly straight line.

[0053] The upper end 41Ba of the second surface 41B is inclined relative to the upper end 41Aa of the first surface 41A. Specifically, the upper end 41Ba of the second surface 41B is inclined relative to the upper end 41Aa of the first surface 41A so that a first distance D1 between the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B at one end of the main portion 41 on the positive electrode lug 14c side in the second direction Y is larger than a second distance D2 between the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B at the other end of the first surface 41A on the negative electrode lug 12d side in the second direction Y (D1>D2). The upper end 41Ba of the second surface 41B is inclined upward from the positive electrode lug 14c side of the positive electrode 10 toward the negative electrode lug 12d side of the negative electrode 12 when viewed from the first direction X. In other words, the upper end 41Ba of the second surface 41B is inclined downward from the negative electrode lug 12d of the negative electrode 12 toward the positive electrode lug 14c of the positive electrode 10 as viewed from the first direction X. In the third direction Z, the upper end 41Aa of the first surface 41A is located higher than the upper end 41Ba of the second surface 41B. With this configuration, the upper region of the first surface 41A facing the positive electrode 10 is located higher than the upper end 41Ba of the second surface 41B. As viewed from the first direction X, the surface (inner surface) of the first surface 41A facing the negative electrode 12 is exposed. In other words, the upper region can also be said to be the region where the surface facing the negative electrode 12 is exposed as viewed from the first direction X.

[0054] The distance D3 between the upper end 41Aa of the first surface 41A of the separator 13 and the lower surface of the positive electrode strap 17 is, for example, 3 mm or more and 30 mm or less, and preferably 10 mm or more and 20 mm or less. In this embodiment, the distance D3 is 13 mm. The upper end 41Aa of the first surface 41A of the separator 13 is located below the lowest position (lower end) of the water refill tap 6. In other words, the upper end 41Aa of the first surface 41A of the separator 13 does not overlap with the lowest position of the water refill tap 6 when viewed from the first direction X.

[0055] In the positive electrode 10, negative electrode 12 and separator 13 included in the electrode group 3, in the separator 13 covering the negative electrode 12 arranged in a position other than the outermost layer, the upper end 41Ba of the second surface 41B and the upper end 41Aa of the first surface 41A are located at approximately the same height.

[0056] Next, an example of a manufacturing method of the storage battery 1 according to this embodiment will be briefly described. First, the separator sheet 30 and the negative electrode 12 are prepared. Next, the separator sheet 30 is folded in half to form a bent portion 44, and the first surface 41A and the second surface 41B are opposed to each other in the first direction X. At this time, the first surface 41A and the second surface 41B are opposed to each other in the first direction X so that, at least in a region A corresponding to the positive electrode ear portion 14c of the positive electrode 10, the upper region of the first surface 41A facing the positive electrode 10 is positioned above the upper end 41Ba of the second surface 41B. By folding the separator sheet 30 in half, the negative electrode 12 is sandwiched between the separator sheets 30 (a process of sandwiching the negative electrode 12). That is, the negative electrode 12 is disposed between the first surface 41A and the second surface 41B in the first direction X. As a result, the negative electrode grid 12c of the negative electrode 12 is completely covered with the separator sheet 30, and a part of the negative electrode lug 12d of the negative electrode 12 is exposed from the separator sheet 30.

[0057] Next, a joint 42 is formed on the separator sheet 30. Here, the first surface 41A and the second surface 41B are processed using a gear seal device to form the joint 42 extending in the third direction Z. Furthermore, a joint 43 is formed on the separator sheet 30 using a method similar to that for forming the joint 42. At this time, a first rib mark and a second rib mark are formed on each of the joints 42, 43. Next, a seal portion 45 is formed. The seal portion 45 is formed, for example, by ultrasonic welding using an ultrasonic welding device including a horn. Next, an opening 44a is formed in the bent portion 44, thereby forming the separator 13 that wraps the negative electrode 12.

[0058] Next, multiple positive electrodes 10 and multiple negative electrodes 12 wrapped in separators 13 are prepared. The positive electrodes 10 and the negative electrodes 12 wrapped in separators 13 are alternately stacked. The positive electrodes 10, separators 13, and negative electrodes 12 are stacked in the first direction X so that the protrusions 32 and the cylindrical bodies 15 overlap in the thickness direction of the separator 13. The positive electrode strap 17 is then electrically connected to the ear 10a of the positive electrode 10, and the negative electrode strap 18 is electrically connected to the negative electrode ear 12d of the negative electrode 12. This forms an electrode group 3 including multiple positive electrodes 10, multiple negative electrodes 12, and multiple separators 13. The electrode group 3 is then housed in the main body 8. The main body 8 is then sealed with the lid 9. Each positive electrode 10 is electrically connected to the positive electrode terminal 5A, and each negative electrode 12 is electrically connected to the negative electrode terminal 5B. Next, the electrolyte is supplied into the case 7 via the water supply valve 6. In this way, the storage battery 1 is manufactured.

[0059] As described above, in the storage battery 1 according to this embodiment, when viewed from the first direction X, at least in a region corresponding to the positive electrode lug 14c of the positive electrode 10, the upper region of the first surface 41A facing the positive electrode 10 is located higher than the upper end of the second surface 41B. That is, the upper end 41Aa of the first surface 41A facing the positive electrode 10 is located higher than the upper end 41Ba of the second surface 41B. In this manner, in the storage battery 1, the first surface 41A is located between the positive electrode lug 14c and the negative electrode 12, thereby lengthening the path through which the positive electrode active material passes over the upper end 41Aa of the first surface 41A and reaches the negative electrode 12 from the positive electrode lug 14c (the path from the positive electrode lug 14c to the negative electrode 12). Therefore, in the storage battery 1, accumulation of the positive electrode active material between the positive electrode lug 14c and the negative electrode 12, which would otherwise cause a short circuit between the positive electrode 10 and the negative electrode 12 via the separator 13, can be suppressed. Therefore, in the storage battery 1, the occurrence of a short circuit can be suppressed.

[0060] In the storage battery 1 according to this embodiment, the electrode group 3 has a positive electrode 10 and a negative electrode 12, and the negative electrode 12 is disposed at each of both ends in the first direction X. In the separators 13 covering the negative electrodes 12 disposed at each of both ends in the first direction X, the upper region of the first surface 41A facing the positive electrode 10 is positioned higher than the upper end 41Ba of the second surface 41B. In a configuration in which the negative electrode 12 is disposed in the outermost layer, the second surface 41B of the separator 13 covering the negative electrode 12 is not disposed opposite the positive electrode 10. Therefore, by employing the above configuration for the separator 13 covering the negative electrode 12 disposed in the outermost layer, short-circuiting between the positive electrode 10 and the negative electrode 12 can be effectively suppressed.

[0061] In the storage battery 1 according to this embodiment, the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B of the separator 13 are linear in the second direction Y. In the storage battery 1, the upper end 41Ba of the second surface 41B is inclined relative to the upper end 41Aa of the first surface 41A such that a first distance D1 between the upper end 41Aa of the first surface 41A on the positive electrode ear portion 14c side and the upper end 41Ba of the second surface 41B is greater than a second distance D2 between the upper end 41Aa of the first surface 41A on the negative electrode ear portion 12d side and the upper end 41Ba of the second surface 41B. In this configuration, the upper region of the first surface 41A facing the positive electrode 10 can be positioned higher than the upper end 41Ba of the second surface 41B. Furthermore, since the second distance D2 between the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B on the negative electrode ear portion 12d side is small, the negative electrode 12 (negative electrode ear portion 12d) can be covered by the second surface 41B. Therefore, a short circuit between the negative electrode 12 and the positive electrode 10 can be suppressed.

[0062] In the storage battery 1 according to this embodiment, the first surface 41A and the second surface 41B of the separator 13 are connected at the lower end portion. In this configuration, the lower end portion of the negative electrode 12 is covered by the separator 13. Therefore, a short circuit between the positive electrode 10 and the negative electrode 12 can be suppressed even at the lower end portion of the electrode group 3.

[0063] In the storage battery 1 according to this embodiment, the separator 13 is provided with a seal portion 45 that joins the first surface 41A and the second surface 41B together in at least a region corresponding to the positive electrode ear portion 14c of the positive electrode 10. In this configuration, even if the deposited positive electrode active material reaches the negative electrode 12 via the side portion of the first surface 41A and reaches the positive electrode ear portion 14c (or reaches the negative electrode 12 from the positive electrode ear portion 14c), the first surface 41A and the second surface 41B are joined together by the seal portion 45, so that a short circuit between the positive electrode 10 and the negative electrode 12 can be prevented.

[0064] In the storage battery 1 according to this embodiment, the positive electrode 10 extends in the third direction Z and includes a current collector 14 and a cylindrical body 15 that houses the positive electrode active material. In this configuration, the positive electrode active material is housed in the cylindrical body 15, which can prevent the positive electrode active material from falling off. This can prevent the occurrence of a short circuit due to the positive electrode active material.

[0065] In the storage battery 1 according to this embodiment, the distance between the upper end 41Aa of the first surface 41A of the separator 13 and the positive electrode strap 17 is 13 mm. With this configuration, when the positive electrode lug 14c and the positive electrode strap 17 are joined by, for example, welding, it is possible to prevent the separator 13 from being damaged by heat generated during welding.

[0066] In the storage battery 1 according to this embodiment, the upper end of the separator 13 in the electrode group 3 housed in the main body 8 of the case 7 is located below the lower end of the refill tap 6. In the storage battery 1, the length (height) of the positive electrode 10 and the negative electrode 12 within the case 7 can be increased to ensure battery capacity. Increasing the length of the positive electrode 10 and the negative electrode 12 can cause the separator 13 to come into contact with the refill tap 6. In this configuration, the upper end of the separator 13 is located below the lower end of the refill tap 6, so the separator 13 does not come into contact with the refill tap 6. This prevents damage to the separator 13, etc.

[0067] Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0068] In the above embodiment, an example was described in which the upper end 41Ba of the second surface 41B of the separator 13 is inclined relative to the upper end 41Aa of the first surface 41A. However, as shown in FIG. 8 , the distance D4 between the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B may be constant from one side to the other side of the separator 13 in the second direction Y. That is, the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B may be substantially parallel to each other. Even in this configuration, the first surface 41A is located between the positive electrode lug 14c and the negative electrode 12, so that the path along which the positive electrode active material travels from the negative electrode 12 to the positive electrode lug 14c (the path from the positive electrode lug 14c to the negative electrode 12) is lengthened. Therefore, in the storage battery 1, it is possible to prevent the positive electrode active material from accumulating between the positive electrode lug portion 14c and the negative electrode 12, causing a short circuit between the positive electrode 10 and the negative electrode 12. Therefore, in the storage battery 1, it is possible to prevent the occurrence of a short circuit.

[0069] In the above embodiment and the above modified example, a configuration in which a plurality of protrusions 32 are provided on the main body portion 31 of the separator sheet 30 has been described as an example. However, the main body portion 31 does not necessarily have to be provided with the protrusions 32.

[0070] In the above embodiment and each of the above modifications, an example has been described in which the separator 13 is provided with the seal portion 45. However, the seal portion 45 does not necessarily have to be provided.

[0071] In the above embodiment and each of the above modified examples, the positive electrode 10 has been described as having the current collector 14 and the cylindrical body 15. However, the positive electrode may have a configuration in which the positive electrode active material is held in a positive electrode grid.

[0072] In the above embodiment and each of the above modified examples, a configuration in which the negative electrodes 12 are arranged at both ends (outermost layers) of the electrode group 3 in the first direction X has been described as an example. However, the electrode group 3 may have positive electrodes 10 arranged at both ends in the first direction X. In this configuration, it is preferable that the separator 13 is provided with a seal portion 45. Furthermore, the electrode group 3 may have negative electrodes 12 arranged at at least one end in the first direction X.

[0073] In the above embodiment and each of the above modified examples, an example has been described in which the upper end 41Aa of the first surface 41A is linear in the second direction Y, and the upper end 41Ba of the second surface 41B is linear in the second direction Y. However, the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B may be uneven or curved. Regardless of the shape of the upper end 41Aa of the first surface 41A and the upper end 41Ba of the second surface 41B, it is sufficient that the upper region of the first surface 41A facing the positive electrode 10 is located higher than the upper end of the second surface 41B, at least in a region corresponding to the positive electrode ear portion 14c of the positive electrode 10, as viewed from the first direction X.

[0074] In the above embodiment and each of the above modifications, the ribs are arranged in a staggered pattern, but this is not limiting. For example, the ribs may form a fishbone structure.

[0075] In the above embodiment and each of the above modified examples, the separator sheet is folded in half along the third direction, but this is not limited thereto. For example, depending on the dimensions of the electrode group, the separator sheet may be folded in half along the second direction. In this case, an opening does not need to be provided at the bent portion of the separator.

[0076] In the above embodiment and each of the above modified examples, the separator is a bag-shaped workpiece, but is not limited thereto. For example, the separator may be a cylindrical workpiece. In this case, the seal portion may be provided on both sides in the third direction, or on only one side in the third direction.

[0077] In the above embodiment and each of the above modified examples, the separator is formed from a single separator sheet, but this is not limited thereto. For example, the separator may be formed from multiple separator sheets. In this case, seals may be formed on both ends of the separator in the third direction, or on only one side in the third direction. Furthermore, joints may be formed on both sides of the separator in the second direction, or on only one side in the second direction. Therefore, when the separator is formed from multiple separator sheets, the separator may be a bag-shaped product, a tubular product, or a product different from a bag-shaped product or a tubular product. In a tubular product, the folded portion of the separator sheet may extend along the third direction, and the joints formed along the third direction may be provided not only at the ends in the second direction but also at other positions (e.g., the center in the second direction).

[0078] In the above embodiment and each of the above modified examples, the forklift 100 has been described as an example of an electric vehicle. However, the electric vehicle may be, for example, a golf cart. Furthermore, although the forklift 100 is described as having the battery pack 200 mounted thereon, the forklift 100 may also be equipped with the storage battery 1. [Explanation of symbols]

[0079] 1...storage battery, 3...electrode group, 6...water refill tap (liquid refill tap), 7...case, 9...lid, 10...positive electrode, 12...negative electrode, 12d...negative electrode lug, 13...separator, 14c...positive electrode lug, 17...positive electrode strap (positive electrode connecting member), 18...negative electrode strap (negative electrode connecting member), 41A...first surface, 41Aa, 41Ba...upper end, 41B...second surface, 45...seal portion (joint), 100...forklift (electric vehicle), 200...battery pack, A...area, D1...first distance, D2...second distance, X...first direction, Y...second direction, Z...third direction.

Claims

1. a positive electrode, a separator, and a negative electrode stacked in this order in a first direction; the positive electrode has a positive electrode lug connected to a positive electrode connecting member that connects the plurality of positive electrodes; the negative electrode has a negative electrode lug connected to a negative electrode connecting member that connects the plurality of negative electrodes; The positive electrode lug and the negative electrode lug are arranged at a predetermined interval in a second direction perpendicular to the first direction when viewed from the first direction, the separator has a first surface covering one surface of the negative electrode in the first direction and a second surface covering the other surface, and the negative electrode is sandwiched between the first surface and the second surface, The negative electrode of the positive electrode and the negative electrode is disposed at each of both end portions in the first direction, an upper region of the first surface of the separator that faces the positive electrode is located above an upper end of the second surface of the separator that covers the negative electrode located at each of the two end portions in the first direction.

2. 2 . The electrode group according to claim 1 , wherein in the separator covering the negative electrode disposed at portions other than the both end portions in the first direction, an upper end of the first surface and an upper end of the second surface are at the same height position.

3. an upper end of each of the first surface and the second surface is linear in the second direction; 3. The electrode group according to claim 1, wherein the upper end of the second surface is inclined relative to the upper end of the first surface so that a first distance between the upper end of the first surface on the positive electrode ear side and the upper end of the second surface is greater than a second distance between the upper end of the first surface on the negative electrode ear side and the upper end of the second surface.

4. an upper end of each of the first surface and the second surface is linear in the second direction; 3. The electrode group according to claim 1, wherein the distance between the upper end of the first surface and the upper end of the second surface is constant from one side of the separator to the other side in the second direction.

5. The electrode group according to claim 1 , wherein the first surface and the second surface of the separator are connected at a lower end portion thereof.

6. The electrode group according to any one of claims 1 to 5, wherein the separator is provided with a joining portion that joins the first surface and the second surface at least in a region corresponding to the positive electrode ear portion of the positive electrode.

7. The electrode group according to any one of claims 1 to 6, wherein the positive electrode extends in a third direction perpendicular to the first direction and the second direction, and has a cylindrical body that accommodates a current collector and a positive electrode active material.

8. The electrode group according to any one of claims 1 to 7, wherein the distance between the upper end of the first surface and the positive electrode connecting member is 3 mm or more and 30 mm or less.

9. The electrode group according to any one of claims 1 to 8, a case that houses the electrode group.

10. the case has a main body that houses the electrode group and a lid that covers an opening of the main body, The lid is provided with a liquid refill valve that allows liquid to be refilled, 10. The lead-acid battery according to claim 9, wherein in the electrode group housed in the main body, an upper end of the separator is located lower than a lower end of the fluid refill tap.

11. A battery pack comprising a plurality of lead-acid batteries according to claim 9 or 10.

12. An electric vehicle comprising the lead-acid battery according to claim 9 or 10.

13. A method for manufacturing a lead-acid battery comprising: a positive electrode, a separator, and a negative electrode stacked in order in a first direction; and the negative electrode being one of the positive electrode and the negative electrode and disposed at each of both end portions in the first direction; sandwiching the negative electrode between the separators having a first surface covering one surface of the negative electrode in the first direction and a second surface covering the other surface of the negative electrode; In the step of sandwiching the negative electrode between the separators, an upper region of the first surface of the separator that faces the positive electrode is positioned higher than an upper end of the second surface of the separator that covers the negative electrode located at each of the both end portions in the first direction.

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