Battery

Abstract

To provide a battery that can effectively prevent foreign matter from entering an electrode body without reducing the capacity.SOLUTION: A battery according to the present invention includes an electrode body in which positive and negative electrode plates are stacked with a separator between them, an exterior body having an opening and housing the electrode body, a sealing plate that seals the opening, and an external terminal attached to the sealing plate. A tab portion provided on at least one of the positive and negative electrode plates is electrically connected to the external terminal via a current collector arranged between the electrode body and the sealing plate. The tab portion and the current collector are welded, and the portion where the tab portion and the current collector are welded is covered with a covering member.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a battery. [Background technology]

[0002] Batteries such as alkaline secondary batteries and non-aqueous electrolyte secondary batteries are used in stationary storage battery systems, such as power sources for driving electric vehicles (EVs) and hybrid electric vehicles (HEVs, PHEVs), for suppressing output fluctuations in solar power generation, wind power generation, etc., and for peak shifting of grid power by storing electricity at night for use during the day.

[0003] Foreign matter may be mixed into the battery during assembly, etc., and if the mixed foreign matter is metallic, an internal short circuit may occur. The mechanism of the internal short circuit is as follows.

[0004] First, when metallic foreign matter adheres to the positive electrode material, it dissolves as metal ions in the electrolyte due to the high potential of the positive electrode, and when these metal ions reach the negative electrode, they deposit as metal. The metal then deposits, growing toward the positive electrode, and if the metal breaks through the separator and comes into contact with the positive electrode, an internal short circuit occurs.

[0005] To prevent foreign matter such as metallic particles from getting into the battery, secondary batteries are usually assembled in a clean room. Any metallic particles that adhere to the electrode body during assembly are removed by air blowing, suction, magnetic attraction, wiping with abrasive tape, etc.

[0006] Patent Document 1 proposes a sealed battery formed by inserting an electrode body into a bag-shaped porous body, and then inserting the porous body with the electrode body inserted into a sealed container. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-87812 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method described in Patent Document 1 does not specifically explain the method or advantages of placing a porous body between the electrode assembly and the lid of the sealed container, and the specific method is unclear. In addition, because a bag-shaped porous body is used, the amount of active material is reduced accordingly, resulting in a lower battery capacity.

[0009] The present invention has been made in consideration of these points, and its purpose is to provide a battery that can effectively prevent foreign matter from entering the electrode body without reducing the battery capacity. [Means for solving the problem]

[0010] The battery of the present invention comprises an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, an exterior body having an opening and housing the electrode assembly, a sealing plate that seals the opening, and an external terminal attached to the sealing plate, wherein a tab portion provided on at least one of the positive electrode plate and the negative electrode plate is electrically connected to the external terminal via a current collector arranged between the electrode assembly and the sealing plate, the tab portion and the current collector are welded, and the portion where the tab portion and the current collector are welded is covered with a covering member, and the sealing plate is provided with a liquid injection hole for injecting electrolyte into the exterior body, and the opening of the liquid injection hole on the electrode assembly side faces the covering member at a distance.

[0011] Furthermore, the battery of the present invention may include an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, an exterior body having an opening and housing the electrode assembly, a sealing plate that seals the opening, and an external terminal attached to the sealing plate, wherein a tab portion provided on at least one of the positive electrode plate and the negative electrode plate is electrically connected to the external terminal via a current collector arranged between the electrode assembly and the sealing plate, the tab portion and the current collector are welded, and the portion where the tab portion and the current collector are welded is covered with a coating member.

[0012] The electrode body includes a first electrode body element including the positive electrode plate and the negative electrode plate, and a second electrode body element including the positive electrode plate and the negative electrode plate, the first electrode body element has a first tab group consisting of a plurality of the tab portions, the second electrode body element has a second tab group consisting of a plurality of the tab portions, the first tab group and the second tab group are each welded to the current collector, a first welded portion where the first tab group and the current collector are welded and a second welded portion where the second tab group and the current collector are welded are each covered by the covering member, and the covering member may also be disposed on an area between the first welded portion and the second welded portion.

[0013] The current collector may have a first current collector and a second current collector, the tab portion may be welded to the first current collector, and a portion of the second current collector may be covered by the covering member.

[0014] The current collector may be provided with a liquid injection hole for injecting an electrolyte into the exterior body, and the opening of the liquid injection hole on the electrode body side may be covered and spaced apart by the covering member. The opening on the electrode body side being covered and spaced apart by the covering member means that the opening is covered by the covering member and is spaced apart from the current collector covering member.

[0015] An insulating tubular member protruding toward the electrode body may be disposed in the liquid inlet.

[0016] It is preferable that a gap through which the electrolyte passes is formed between the current collector and the periphery of the covering member covering the opening on the electrode body side of the liquid inlet hole. That is, there is an opening between the current collector and the periphery of the covering member covering the opening on the electrode body side of the liquid inlet hole, allowing the electrolyte to pass through.

[0017] The covering member covering the opening on the electrode body side of the liquid injection hole may have a hole formed in a part other than the part directly above the opening through which the electrolyte passes.

[0018] The battery of the present invention may include an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, an exterior body having an opening and housing the electrode assembly, a sealing plate that seals the opening, and a positive electrode external terminal and a negative electrode external terminal attached to the sealing plate, wherein a positive electrode tab provided on the positive electrode plate is electrically connected to the positive electrode external terminal via a positive electrode current collector arranged between the electrode assembly and the sealing plate, and a negative electrode tab provided on the negative electrode plate is electrically connected to the negative electrode external terminal via a negative electrode current collector arranged between the electrode assembly and the sealing plate, the positive electrode tab and the positive electrode current collector are welded, and the negative electrode tab and the negative electrode current collector are welded, and the welded portion of the positive electrode tab and the positive electrode current collector is covered with a first covering member, and the welded portion of the negative electrode tab and the negative electrode current collector is covered with a second covering member.

[0019] The electrode body includes a first electrode body element including the positive electrode plate and the negative electrode plate, and a second electrode body element including the positive electrode plate and the negative electrode plate, the first electrode body element has a first positive electrode tab group consisting of a plurality of the positive electrode tabs and a first negative electrode tab group consisting of a plurality of the negative electrode tabs, the second electrode body element has a second positive electrode tab group consisting of a plurality of the positive electrode tabs and a second negative electrode tab group consisting of a plurality of the negative electrode tabs, the first positive electrode tab group and the second positive electrode tab group are each welded to the positive electrode current collector, the first negative electrode tab group and the second negative electrode tab group are each welded to the negative electrode current collector, a first welded portion at which the first negative electrode tab group and the negative electrode current collector are welded, and a second welded portion at which the second positive electrode tab group and the positive electrode current collector are welded, are each covered by the first covering member, and the first covering member is also disposed on a region between the first welded portion and the second welded portion; a third welded portion at which the first negative electrode tab group and the negative electrode current collector are welded, and a fourth welded portion at which the second negative electrode tab group and the negative electrode current collector are welded, are each covered by the second covering member, and the second covering member is also disposed on a region between the third welded portion and the fourth welded portion.

[0020] The positive electrode current collector may have a first positive electrode current collector and a second positive electrode current collector, the first positive electrode tab group and the second positive electrode tab group are welded to the first positive electrode current collector, and a portion of the second positive electrode current collector is covered with a first current collector covering member, and the negative electrode current collector may have a first negative electrode current collector and a second negative electrode current collector, the first negative electrode tab group and the second negative electrode tab group are welded to the first negative electrode current collector, and a portion of the second negative electrode current collector is covered with the second covering member.

[0021] At least one of the positive electrode current collector and the negative electrode current collector may be provided with an injection hole for injecting an electrolyte into the outer casing, and the opening of the injection hole on the electrode body side may be covered at a distance by at least one of the first covering member and the second covering member.

[0022] An insulating tubular member protruding toward the electrode body may be disposed in the liquid inlet.

[0023] It is preferable that a gap through which the electrolyte passes is formed between the peripheral edge of at least one of the first covering member and the second covering member, which covers the opening on the electrode body side of the liquid injection hole, and at least one of the positive electrode current collector and the negative electrode current collector.

[0024] It is preferable that at least one of the first covering member and the second covering member that cover the opening on the electrode body side of the liquid injection hole has a hole through which the electrolyte passes formed in a part other than the part directly above the opening. [Effects of the Invention]

[0025] In the battery of the present invention, the portion where the tab portion and the current collector are welded is covered with a covering member, which more effectively prevents dust generated during welding from entering the inside of the electrode body. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a perspective view of a secondary battery according to an embodiment; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 2 is a plan view of a first positive electrode current collector (positive electrode current collector). [Figure 7] FIG. 2 is a plan view of a first negative electrode current collector (negative electrode current collector). [Figure 8] FIG. 10 is a diagram showing a state in which a positive electrode tab group is connected to a first positive electrode current collector and a negative electrode tab group is connected to a first negative electrode current collector. [Figure 9] FIG. 10 is a view showing the surface of the sealing plate facing the electrode body after the second positive electrode current collector and the second negative electrode current collector have been attached. [Figure 10]FIG. 10 is a view showing the surface of the sealing plate facing the electrode body after the first positive electrode current collector is attached to the second positive electrode current collector and the first negative electrode current collector is attached to the second negative electrode current collector. [Figure 11] FIG. 11 is a diagram showing a state in which a covering member is attached to the state shown in FIG. 10. [Figure 12] 12 is a diagram showing the state in which a cover member is attached to the state shown in FIG. 11. FIG. [Figure 13] FIG. 2 is a schematic enlarged perspective view of a portion where a first covering member is provided. [Figure 14] 14 is a schematic diagram showing a state in which a first covering member is removed from FIG. 13. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses. In the following drawings, for the sake of simplicity, components having substantially the same functions are designated by the same reference numerals.

[0028] (Embodiment 1) The following describes the configuration of a prismatic secondary battery 20 as a secondary battery according to embodiment 1. Note that the present invention is not limited to the following embodiment.

[0029] As shown in FIGS. 1 and 2 , a prismatic secondary battery 20 includes a battery case 100 made of a prismatic outer casing 1 in the shape of a bottomed rectangular cylinder having an opening, and a sealing plate 2 that seals the opening of the prismatic outer casing 1. The prismatic outer casing 1 and the sealing plate 2 are each preferably made of metal, preferably aluminum or an aluminum alloy. The prismatic outer casing 1 houses an electrode assembly 3, which is made of a positive electrode plate and a negative electrode plate stacked with a separator interposed between them, together with an electrolyte. As will be described later, in this embodiment, the electrode assembly 3 is made of a first electrode assembly element and a second electrode assembly element, and these two electrode assembly elements have the same structure.

[0030] As shown in FIG. 5, a positive electrode tab group 40A consisting of multiple positive electrode tabs (tab portions) 40 and a negative electrode tab group 50A consisting of multiple negative electrode tabs (tab portions) 50 are provided on the end of the electrode assembly 3 facing the sealing plate 2. The positive electrode tab group 40A is electrically connected to a positive electrode terminal 7 via a first positive electrode current collector (positive electrode current collector) 6a and a second positive electrode current collector 6b. The negative electrode tab group 50A is electrically connected to a negative electrode terminal 9 via a first negative electrode current collector (negative electrode current collector) 8a and a second negative electrode current collector 8b. The first and second positive electrode current collectors 6a, 6b and the first and second negative electrode current collectors 8a, 8b are attached to the sealing plate 2 on the inner side of the battery, and are connected to the positive electrode tab group 40A and the negative electrode tab group 50A on the inner side of the battery.

[0031] The second positive electrode current collector 6b, the first positive electrode current collector 6a, and the positive electrode terminal 7 are preferably made of metal, more preferably aluminum or an aluminum alloy. An outer resin insulating member 10 is disposed between the positive electrode terminal 7 and the sealing plate 2. An inner resin insulating member 11 is disposed between the second positive electrode current collector 6b, the first positive electrode current collector 6a, and the sealing plate 2.

[0032] The second negative electrode current collector 8b, the first negative electrode current collector 8a, and the negative electrode terminal 9 are preferably made of metal, more preferably copper or a copper alloy. The negative electrode terminal 9 preferably has a portion made of aluminum or an aluminum alloy and a portion made of copper or a copper alloy. In this case, it is preferable that the portion made of copper or a copper alloy is connected to the second negative electrode current collector 8b, and that the portion made of aluminum or an aluminum alloy protrudes outward beyond the sealing plate 2. A resin outer insulating member 12 is disposed between the negative electrode terminal 9 and the sealing plate 2. A resin inner insulating member 13 is disposed between the second negative electrode current collector 8b, the first negative electrode current collector 8a, and the sealing plate 2.

[0033] An electrode assembly holder 14 made of a resin sheet is disposed between the electrode assembly 3 and the rectangular outer casing 1. The electrode assembly holder 14 is preferably formed by folding an insulating resin sheet into a bag or box shape. This electrode assembly holder 14 reliably maintains electrical insulation between the electrode assembly 3 and the rectangular outer casing 1.

[0034] The sealing plate 2 is provided with an electrolyte injection hole 15, which is sealed with a sealing member (not shown) after the electrolyte is injected. The sealing plate 2 is provided with a gas release valve 17 that breaks when the pressure inside the battery case 100 reaches or exceeds a predetermined value, thereby releasing gas inside the battery case 100 to the outside.

[0035] Next, a method for manufacturing the prismatic secondary battery 20 and the details of each component will be described.

[0036] [Positive electrode] First, a method for manufacturing the positive electrode plate will be described.

[0037] [Preparation of Positive Electrode Active Material Mixture Layer Slurry] The positive electrode active material mixture layer slurry is prepared by kneading, for example, a positive electrode active material, a conductive agent, and a binder. Examples of the positive electrode active material include lithium composite oxides such as lithium nickel cobalt manganese composite oxide. Examples of the binder include fluororesins such as polyvinylidene fluoride (PVdF). Examples of the conductive agent include carbon materials such as carbon black.

[0038] [Preparation of positive electrode protective layer slurry] Alumina powder, graphite as a conductive agent, polyvinylidene fluoride (PVdF) as a binder, N-methyl-2-pyrrolidone (NMP) as a dispersion medium, and the like are mixed together to prepare a positive electrode protective layer slurry.

[0039] [Formation of Positive Electrode Active Material Mixture Layer and Positive Electrode Protective Layer] The positive electrode active material mixture layer slurry and the positive electrode protective layer slurry prepared by the above-described method are applied to both sides of a 15 μm thick aluminum foil serving as a positive electrode core using a die coater, and the positive electrode protective layer slurry is applied to at least one end in the width direction of the region where the positive electrode active material mixture layer slurry is applied.

[0040] The positive electrode core coated with the positive electrode active material mixture layer slurry and the positive electrode protective layer slurry is dried to remove the NMP from the slurry. This forms the positive electrode active material mixture layer and the protective layer. The positive electrode active material mixture layer is then compressed by passing it through a pair of press rollers to form a positive electrode base plate. This positive electrode base plate is cut to a predetermined size to produce the positive electrode plate 4 shown in FIG. 3. The positive electrode plate 4 is rectangular, with a positive electrode tab 40 protruding from the top edge of the rectangle. A narrow positive electrode protective layer 4c is formed along the top edge of the positive electrode plate 4, and a positive electrode active material mixture layer 4b is formed from below the positive electrode protective layer 4c to the bottom edge of the positive electrode plate 4. As described above, the positive electrode tab 40 may be formed from the positive electrode core, or a separate member may be connected to the positive electrode plate to form the positive electrode tab.

[0041] [Negative electrode] Next, a method for manufacturing the negative electrode plate will be described.

[0042] [Preparation of negative electrode active material mixture layer slurry] The negative electrode active material mixture layer slurry is prepared by kneading, for example, a negative electrode active material, a conductive agent, a binder, and a thickener. Examples of the negative electrode active material include carbon materials such as graphite. Examples of the binder include styrene butadiene rubber (SBR). Examples of the thickener include carboxymethyl cellulose (CMC).

[0043] [Formation of negative electrode active material mixture layer] The negative electrode active material mixture layer slurry prepared by the method described above is applied to both sides of a copper foil having a thickness of 8 μm as a negative electrode substrate using a die coater.

[0044] The negative electrode core coated with the negative electrode active material mixture layer slurry is dried to remove water from the slurry. This forms a negative electrode active material mixture layer. The negative electrode core is then passed through a pair of press rollers to compress the negative electrode active material mixture layer into a negative electrode base plate. This negative electrode base plate is cut to a predetermined size to create the negative electrode plate 5 shown in FIG. 4. The negative electrode plate 4 is rectangular, with a negative electrode tab 50 protruding from the top edge of the rectangle. A negative electrode active material mixture layer 5b is formed on the entire surface of the negative electrode core excluding the negative electrode tab 50. As described above, the negative electrode tab 50 may be formed from the negative electrode core, or a separate member may be connected to the negative electrode plate to form the negative electrode tab.

[0045] [Preparation of electrode body] A plurality of positive electrode plates 4 and negative electrode plates 5 produced by the above-described method are stacked with separators interposed between them to produce a stacked electrode assembly 3. The number of positive electrode plates 4 and negative electrode plates 5 included in the electrode assembly 3 is not particularly limited, but several tens or more are preferable. As shown in FIG. 5 , a positive electrode tab group 40A consisting of a plurality of positive electrode tabs 40 and a negative electrode tab group 50A consisting of a plurality of negative electrode tabs 50 are provided at one end of the electrode assembly 3.

[0046] [Connection between current collector and tab] The positive electrode tab group 40A described above is connected by welding to the first positive electrode current collector 6a shown in Fig. 6. A current collector through-hole 6e is formed in the first positive electrode current collector 6a at a position facing the electrolyte injection hole 15 of the sealing plate 2. The negative electrode tab group 50A described above is connected by welding to the first negative electrode current collector 8a shown in Fig. 7. Fig. 8 shows a state in which the positive electrode tab group 40A and the first positive electrode current collector 6a are connected, and the negative electrode tab group 50A and the first negative electrode current collector 8a are connected.

[0047] In this embodiment, the electrode body 3 is composed of a first electrode body element 3a and a second electrode body element 3b, as shown in Fig. 8. The first electrode body element 3a and the second electrode body element 3b are fabricated by the same method as the fabrication method of the electrode body 3 described above.

[0048] The first positive electrode tab group 40A1 of the first electrode body element 3a and the second positive electrode tab group 40A2 of the second electrode body element 3b are connected to the first positive electrode current collector (positive electrode current collector) 6a, and the first negative electrode tab group 50A1 of the first electrode body element 3a and the second negative electrode tab group 50A2 of the second electrode body element 3b are connected to the first negative electrode current collector (negative electrode current collector) 8a. The first and second positive electrode tab groups 40A1 and 40A2 are welded to the first positive electrode current collector 6a to form welded connections 60a and 60b. The two welded connections 60a and 60b on the positive electrode side are formed spaced apart from each other in a direction perpendicular to the top edge of the electrode body 3, i.e., a direction perpendicular to the longitudinal direction of the sealing body 2. The current collector through-hole 6e is located between the two welded connections 60a and 60b of the positive electrode.

[0049] The negative electrode tab groups 50A1 and 50A2 are welded to the first negative electrode current collector 8a to form welded connections 61a and 61b. The two welded connections 61a and 61b on the negative electrode side are also formed spaced apart from each other in a direction perpendicular to the upper side of the electrode body 3, i.e., in a direction perpendicular to the longitudinal direction of the sealing body 2.

[0050] The first positive electrode current collector 6a has a thin portion 6c formed thereon, where the first positive electrode current collector 6a is connected to the second positive electrode current collector 6b.

[0051] A recess 8d is formed in the first negative electrode current collector 8a, and a thin portion 8c is formed in the recess 8d. The first negative electrode current collector 8a is connected to the second negative electrode current collector 8b at this thin portion 8c.

[0052] The welding connection between the positive electrode tab group 40A and the first positive electrode current collector 6a and the welding connection between the negative electrode tab group 50A and the first negative electrode current collector 8a can be performed by ultrasonic welding, resistance welding, laser welding, etc. In this embodiment, the welding connection is performed by ultrasonic welding.

[0053] The first positive electrode current collector 6a and the second positive electrode current collector 6b, and the first negative electrode current collector 8a and the second negative electrode current collector 8b can be connected by ultrasonic welding, resistance welding, laser welding, etc. In this embodiment, the connections are made by laser welding.

[0054] [Installing each part on the sealing plate] 9 is a diagram showing the surface of the sealing plate 2 on the inner side of the battery, to which the various components have been attached. The attachment of the various components to the sealing plate 2 will be described with reference to FIGS.

[0055] An external insulating member 10 is placed around the positive terminal insertion hole in the sealing plate 2. An internal insulating member 11 and a cup-shaped conductive member 65 are placed on the inner surface of the battery around the positive terminal insertion hole in the sealing plate 2. Then, a positive terminal 7 is inserted from the outside of the battery through the through hole in the external insulating member 10, the positive terminal insertion hole in the sealing plate 2, the through hole in the internal insulating member 11, and the terminal connection hole in the conductive member 65, and the tip of the positive terminal 7 is crimped onto the conductive member 65. In this way, the positive terminal 7 and the conductive member 65 are fixed to the sealing plate 2. Note that it is preferable to connect the crimped portion of the positive terminal 7 and the conductive member 65 by welding.

[0056] The conductive member 65 has an opening on the inner side of the battery. A disk-shaped deformable plate 66 is placed over the opening of the conductive member 65 so as to close the opening, and the periphery of the deformable plate 66 is welded and connected to the conductive member 65. This seals the opening. The conductive member 65 and the deformable plate 66 are preferably made of metal, and more preferably made of aluminum or an aluminum alloy. Then, the second positive electrode current collector 6b is placed on the inner side of the battery of the deformable plate 66, and the two are welded and connected.

[0057] Next, an external insulating member 12 is placed on the outer surface of the battery around the negative terminal insertion hole in the sealing plate 2. An internal insulating member 13 and a second negative electrode current collector 8b are placed on the inner surface of the battery around the negative terminal insertion hole in the sealing plate 2. Then, a negative electrode terminal 9 is inserted from the outside of the battery through the through hole in the external insulating member 12, the negative electrode terminal insertion hole in the sealing plate 2, the through hole in the internal insulating member 13, and the terminal connection hole in the second negative electrode current collector 8b, and the tip of the negative electrode terminal 9 is crimped onto the second negative electrode current collector 8b. This fixes the negative electrode terminal 9 and the second negative electrode current collector 8b to the sealing plate 2. Note that the crimped portion of the negative electrode terminal 9 is preferably connected to the second negative electrode current collector 8b by welding.

[0058] The positive electrode-side internal insulating member 11 has a liquid injection opening 11a at a portion facing the electrolyte injection hole 15 provided in the sealing plate 2. A cylindrical portion 11b that protrudes cylindrically into the battery interior is provided at the edge of the liquid injection opening 11a. Furthermore, opening cover portions 11c are provided that protrude from two points on the edge of the cylindrical portion 11b into the battery interior and connect the two points in a bridge-like manner. The cylindrical portion 11b and opening cover portions 11c are inserted into a current collector through-hole 6e provided in the first positive electrode current collector 6a.

[0059] [Connection between the first and second current collectors] FIG. 10 is a diagram showing the surface of the sealing plate 2 facing the inside of the battery after the first positive electrode current collector 6a has been attached to the second positive electrode current collector 6b and the first negative electrode current collector 8a has been attached to the second negative electrode current collector 8b.

[0060] The first positive electrode current collector 6a, to which the first and second positive electrode tab groups 40A1, 40A2 are connected, is placed on the inner insulating member 11 so that a portion of the first positive electrode current collector 6a overlaps the second positive electrode current collector 6b. Then, the thin-walled portion 6c is irradiated with a laser, thereby welding the first positive electrode current collector 6a and the second positive electrode current collector 6b together, forming a positive electrode current collector welded connection. Furthermore, the first negative electrode current collector 8a, to which the first and second negative electrode tab groups 50A1, 50A2 are connected, is placed on the inner insulating member 13 so that a portion of the first negative electrode current collector 8a overlaps the second negative electrode current collector 8b. Then, the thin-walled portion 8c is irradiated with a laser, thereby welding the first negative electrode current collector 8a and the second negative electrode current collector 8b together, forming a negative electrode current collector welded connection.

[0061] [Coating of connection parts] 11 , the welded connection 60a between the first positive electrode current collector 6a and the first positive electrode tab group 40A1 and the welded connection 60b between the first positive electrode current collector 6a and the second positive electrode tab group 40A2 are covered with a first covering member 81. In this manner, the first covering member 81 captures foreign matter present at the welded connections 60a, 60b, particularly metal powder generated during the welding process, and prevents the foreign matter from entering the inside of the electrode assembly 3. This significantly reduces the occurrence of internal short circuits due to foreign matter. The first covering member 81 is attached to the welded connections 60a, 60b, and in the region between the two welded connections 60a, 60b, the first covering member 81 is spaced from and covers the region.

[0062] Next, the welded connection 61a between the first negative electrode current collector 8a and the first negative electrode tab group 50A1 and the welded connection 61b between the first negative electrode current collector 8a and the second negative electrode tab group 50A2 are covered with a second covering member 82. The second covering member 82 also covers the surface of the first negative electrode current collector 8a sandwiched between the two welded connections 61a, 61b. In this manner, the second covering member 82 captures foreign matter present at the welded connections 61a, 61b, particularly metal powder generated during the welding process, and prevents the foreign matter from entering the inside of the electrode assembly 3. This significantly reduces the occurrence of internal short circuits due to foreign matter. The second covering member 82 is attached to the covered portions.

[0063] Furthermore, the second covering member 82 also covers the connection portion (negative electrode current collector welded connection portion) between the first negative electrode current collector 8a and the second negative electrode current collector 8b. That is, a portion of the second negative electrode current collector 8b is covered with the second covering member 82. Therefore, the second covering member 82 captures foreign matter (metal powder) generated by welding the first negative electrode current collector 8a and the second negative electrode current collector 8b, and can prevent this foreign matter from entering the inside of the electrode body 3.

[0064] Then, a third covering member 83 is placed and attached so as to cover the connection portion (positive current collector welded connection portion) between the first positive current collector 6a and the second positive current collector 6b. By doing so, the third covering member 83 can capture foreign matter present at the positive current collector welded connection portion, particularly metal powder generated during the welding process between the first positive current collector 6a and the second positive current collector 6b, so as to prevent it from entering the inside of the electrode body 3. Then, as shown in FIG. 12, the second positive current collector 6b and the third covering member 83 are covered with a cover member 88.

[0065] In this embodiment, the first to third covering members 81, 82, and 83 are adhesive sheets made of plastic films coated with an adhesive. The plastic films are not particularly limited, but polypropylene films are preferred. Note that the first to third covering members 81, 82, and 83 are not limited to adhesive sheets.

[0066] [Secondary battery production] Next, the two positive electrode tab groups 40A1, 40A2 and the two negative electrode tab groups 50A1, 50A2 are bent so that the upper surface of the first electrode body element 3a and the upper surface of the second electrode body element 3b in Fig. 12 are in contact with each other directly or via another member. This combines the two electrode body elements 3a, 3b into a single electrode body 3. The combined electrode body 3 is then placed in an electrode body holder 14 made of an insulating sheet formed into a box or bag shape.

[0067] The electrode body 3 wrapped in the electrode body holder 14 is inserted into the prismatic outer casing 1. Then, the sealing plate 2 and the prismatic outer casing 1 are welded together, and the opening of the prismatic outer casing 1 is sealed with the sealing plate 2. Then, electrolyte is poured into the prismatic outer casing 1 through an electrolyte pouring hole 15 provided in the sealing plate 2. After that, the electrolyte pouring hole 15 is sealed with a sealing member such as a blind rivet. This completes the prismatic secondary battery 20.

[0068] [Aspects of the first covering member and the liquid injection portion] FIG. 13 is an enlarged perspective view of a portion where the first covering member 81 is provided. The first covering member 81 includes bonded portions 81a and 81b bonded to the welded connections 60a and 60b, and a separated portion 81c that is separated and raised from the first positive current collector 6a. As shown in FIG. 14, which illustrates a state in which only the first covering member 81 has been removed from FIG. 13, the separated portion 81c is separated from the first positive current collector 6a so as not to block the opening of the current collector through-hole 6e provided in the first positive current collector 6a or the opening of the cylindrical portion 11b. A gap 87 is formed between a peripheral edge 85 of the separated portion 81c of the first covering member 81 and the first positive current collector 6a.

[0069] As described above, after assembling the secondary battery 20, electrolyte is poured through the electrolyte pouring hole 15. At this time, the electrolyte passes through the cylindrical portion 11b and strikes the opening cover 11c. Then, it strikes the separation portion 81c of the first covering member 81, flows along the inner surface of the separation portion 81c, and flows into the electrode assembly 3 through the gap 87. If the opening cover 11c and the first covering member 81 were not present and the electrolyte flowed directly into the electrode assembly 3 from the cylindrical portion 11b, the electrolyte would strike the electrode assembly 3 with the same momentum and inflow velocity as when it was poured. In this case, the electrolyte would strike the upper end of the separator protruding from the top edge of the electrode assembly 3, causing the separator to curl up, potentially resulting in an internal short circuit. However, in the battery of this embodiment, the inflow velocity of the electrolyte is reduced, so the separator does not curl up. In this embodiment, the inflow speed of the electrolyte is reduced by both the opening covering portion 11c and the first covering member 81, so that the separator can be effectively prevented from curling up.

[0070] (Other embodiments) The above-described embodiments are merely examples of the present invention, and the present invention is not limited to these examples. These examples may be combined with well-known, commonly used, or publicly known technologies, or may be partially replaced. Modified inventions that would be easily conceived by a person skilled in the art are also included in the present invention.

[0071] The electrode assembly may have a structure in which a positive electrode plate, a negative electrode plate, and a separator are stacked and then wound. The electrode assembly element may also have a wound structure.

[0072] In the above-described embodiment, an example in which two electrode elements are arranged inside the exterior body is shown, but the number of electrode elements may be one, or three or more.

[0073] In the above-described embodiment, an example was shown in which the positive electrode current collector and the negative electrode current collector each consisted of two parts, but the positive electrode current collector and the negative electrode current collector each may consist of a single part.

[0074] Known materials can be used for the positive electrode plate, negative electrode plate, separator, electrolyte, and the like.

[0075] The covering member may be any material capable of capturing foreign matter, and is not limited to an adhesive sheet using a plastic film. For example, a coating material such as a sealing resin that hardens when exposed to heat or light may be used as the covering member, or an adhesive sheet using a metal foil or nonwoven fabric may be used.

[0076] The first covering member does not need to have a gap around the periphery of the separation portion. In that case, it is sufficient to provide a hole through which the electrolyte can flow out in the first covering member. This hole is provided at a position horizontally separated from the opening of the cylindrical portion. In other words, the hole is provided in a location other than directly above the opening of the cylindrical portion. This allows the electrolyte to first collide with the first covering member, slowing down its inflow, before flowing through the hole toward the electrode body. [Explanation of symbols]

[0077] 1. Rectangular exterior body (exterior body) 2...Sealing plate 3...electrode body 3a...First electrode body element 3b...Second electrode body element 4. Positive electrode plate 5. Negative electrode plate 6a...First positive electrode current collector 6b...Second positive electrode current collector 6e...Collector through hole (liquid inlet hole) 7 Positive terminal (positive external terminal) 8a...First negative electrode current collector 8b...Second negative electrode current collector 9 Negative terminal (negative external terminal) 11b Cylindrical part 11c Opening cover 15...Electrolyte injection hole 20··· Prismatic secondary battery (battery) 40 Positive electrode tab (tab part) 40A···Positive electrode tab group 40A1: First positive electrode tab group 40A2: Second positive electrode tab group 50 Negative electrode tab (tab part) 50A···Negative electrode tab group 50A1: First negative electrode tab group 50A2: Second negative electrode tab group 60a, 60b... Welded connection portion (first welded portion) 61a, 61b... Welded connection (second welded portion) 81... First covering member 82... Second covering member

Claims

[Claim 1] an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween; an exterior body having an opening and accommodating the electrode body; a sealing plate that seals the opening; an external terminal attached to the sealing plate; Equipped with a tab portion provided on at least one of the positive electrode plate and the negative electrode plate is electrically connected to the external terminal via a current collector disposed between the electrode body and the sealing plate, The tab portion and the current collector are welded together, a portion where the tab portion and the current collector are welded is covered with a covering member, an injection hole for injecting an electrolyte into the exterior body is provided in the sealing plate, and an opening of the injection hole on the electrode body side faces the covering member while being spaced apart from the covering member; a portion of the electrode body facing the opening is covered by the covering member.

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