Power storage device and method for manufacturing power storage device

Abstract

A power storage device 100 includes: an exterior body 10 that is open on one side and houses an electrode body 12 therein; a sealing body 30 that is disposed on the one side of the exterior body 10 and joined to the exterior body 10; and a sealing cover 20 that is disposed inside the exterior body 10 and overlaps the boundary between the exterior body 10 and the sealing body 30.

Description

Power storage device and method for manufacturing the same

[0001] The present disclosure relates to a power storage device, particularly to the joining of an outer package and a sealing body.

[0002] A power storage device such as a lithium-ion battery houses an electrode body and an electrolytic solution in an outer package open on one side, and seals the open end with a sealing body. Usually, the outer package is made of metal, one electrode of the electrode body is connected, a terminal body is arranged at the center of the sealing body, and the other electrode of the electrode body is connected thereto.

[0003] In such a power storage device, for example, with the sealing body arranged on the inner peripheral side of the upper end portion of the outer package, the peripheral edge portion of the sealing body is sandwiched and caulked by the outer package, thereby sealing the open end of the outer package with the sealing body.

[0004] Also, a structure in which the open end of the outer package is closed with a sealing plate and the two are laser welded is also known (see Patent Document 1).

[0005] Japanese Patent No. 6375172

[0006] In the future, further evolution of the power storage device is required in order to perform charge and discharge under even more severe conditions.

[0007] A power storage device according to an example of the present disclosure includes an outer package open on one side and housing an electrode body therein, a sealing body arranged on one side of the outer package and joined to the outer package, and a sealing cover arranged in the outer package and overlapping with the boundary between the outer package and the sealing body.

[0008] According to the power storage device and the method for manufacturing the same according to the present disclosure, the reliability of the power storage device can be improved.

[0009] This is a cross-sectional view showing the configuration of an energy storage device according to Configuration Example 1 of this disclosure. This is a diagram illustrating the process of attaching a sealing body to the outer can. This is a diagram showing another configuration example of the sealing cover. This is a diagram showing yet another configuration example of the sealing cover. This is a diagram showing yet another configuration example of the sealing cover. This is a diagram showing a configuration in which the top and bottom are reversed compared to the example in Figure 1 and the positive electrode is placed at the bottom of the outer can. This is a cross-sectional view showing the configuration of an energy storage device according to Configuration Example 2 of this disclosure. This is a diagram illustrating the process of attaching a sealing body to the outer can. This is a diagram showing another configuration example of the sealing cover. This is a diagram showing yet another configuration example of the sealing cover. This is a diagram showing a configuration in which the top and bottom are reversed compared to the example in Figure 7 and the positive electrode is placed at the bottom of the outer can. This is a cross-sectional view showing the configuration of an energy storage device according to Configuration Example 3 of this disclosure. This is a diagram illustrating the process of attaching a sealing body to the outer can. This is a diagram showing another configuration example of the sealing cover. This is a diagram showing the configuration of an energy storage device using a pipe-shaped sealing cover. This is a diagram showing a configuration in which the top and bottom are reversed compared to the example in Figure 13 and the positive electrode is placed at the bottom of the outer can.

[0010] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are not limiting to this disclosure, and configurations formed by selectively combining multiple examples are also included in this disclosure.

[0011] The energy storage device of this disclosure may be a secondary battery using an aqueous electrolyte or a secondary battery using a non-aqueous electrolyte. The energy storage device of this disclosure may be a cylindrical battery with a cylindrical (e.g., bottomed cylindrical) outer casing or a prismatic battery with a prismatic outer casing. In these batteries, the cylindrical outer casing or the prismatic outer casing constitutes the outer casing. Alternatively, the energy storage device of this disclosure may be a capacitor that undergoes repeated charging and discharging.

[0012] "Example of Energy Storage Device Configuration 1" Figure 1 is a cross-sectional view showing an example of the configuration 1 of the energy storage device 100 according to the present disclosure, where (A) shows the state before the sealing body 30 is attached to the outer container 10, and (B) shows the state after the sealing body 30 is attached to the outer container 10.

[0013] The outer container 10 is a bottomed cylindrical shape with an open top. Inside the outer container 10 are the electrode body 12 and the electrolyte 14. An insulating plate 16 is placed on top of the electrode body 12. The outer container 10 is preferably made of a metal such as aluminum or steel.

[0014] In this example, the electrode body 12 is cylindrical in shape, constructed by winding together film-like positive electrodes, separators, and negative electrodes. A bottomed cylindrical sealing cover 20 is positioned between the sides and bottom of the electrode body 12 and the inner surfaces of the side and bottom walls of the outer container 10. The sides of the sealing cover 20 are positioned along the inner circumferential surface of the outer container 10, and the bottom is positioned along the inner surface of the bottom wall of the outer container 10. Here, the sealing cover 20 can be made of an insulating material.

[0015] The sealing body 30 has an overall inverted U-shape in cross-section and includes a terminal body 32 located in the center and a lid body 36 that extends radially outward from the periphery of the terminal body 32 via a gasket 34. The terminal body 32 and lid body 36 are preferably made of the same metal as the outer can 10, and the gasket 34 is preferably made of resin.

[0016] The terminal body 32 has a shape in which the centers of two discs, positioned above and below, are connected by a cylinder, and functions as an electrode terminal for the energy storage device 100. The inner portion of the gasket 34 is positioned in the annular space sandwiched between the two discs of the terminal body 32. That is, the inner portion of the gasket 34 has a shape corresponding to the recess of the terminal body 32. The gasket 34 has an inwardly recessed annular recess in the middle of its outer circumference in the vertical direction. In this example, the recess of the gasket 34 is smaller in the vertical direction than the recess of the terminal body 32. The radial inner end of the gasket 34 extends to the outer circumference of the cylindrical portion of the terminal body 32.

[0017] The lid 36 includes a disc-shaped top wall 36a with a through hole in the center and a cylindrical peripheral wall portion 36b extending downward from the periphery of the top wall 36a. The inner end of the top wall 36a fits into a recess in the gasket 34 and is fixed in place. The annular lower end surface of the peripheral wall portion 36b corresponds to the annular upper end surface of the outer can 10.

[0018] The electrode body 12 is constructed, for example, by winding a positive electrode and a negative electrode with a separator in between. An upper lead 40, one end of which is connected to one electrode (the positive electrode in this example), extends through an opening in the insulating plate 16, and the other end is connected to the bottom surface of the terminal body 32. In this example, the upper lead 40 is the positive electrode lead.

[0019] After the electrolyte 14 is injected into the outer container 10, it is absorbed by the electrode body 12, causing the liquid level to drop below the initial level and be contained within the outer container 10.

[0020] The sealing cover 20 is a bottomed cylindrical shape that follows the inner surface of the outer can 10, and has a cylindrical side and a disc-shaped bottom, with a cylindrical electrode body 12 housed inside.

[0021] A lower lead 42, one end of which is connected to the other electrode of the electrode body 12, for example, the negative electrode, extends through the sealing cover 20, and the other end is connected to the surface of the bottom wall of the outer container 10. In this example, the lower lead 42 is the negative electrode lead.

[0022] As shown in (B), with the upper lead 40 connected to the terminal body 32 and the electrode body 12, the sealing body 30 is lowered so that the lower end of the lid 36 comes into contact with the upper end of the outer can 10, forming a joint. In this state, as indicated by the triangular mark in the figure, the joint between the lid 36 and the outer can 10 is irradiated with a laser, thereby laser welding the two together.

[0023] Here, the sealing cover 20 has a projection 20a that extends upward beyond the upper end of the outer can 10, and the projection 20a extends to the inside of the side wall of the lid 36. Therefore, the inside of the joint to be laser-welded is covered by the outer surface of the sealing cover 20. Thus, when the outer can 10 is sealed with the sealing body 30 after the electrolyte is injected, there is no electrolyte present in the joint to be laser-welded, and no problems arise when performing laser welding.

[0024] "Manufacturing Process" Figure 2 is a diagram illustrating the process of attaching the sealing body 30 to the outer can 10.

[0025] In (A), the electrode body 12 with the upper lead 40 and lower lead 42 attached is inserted into the sealing cover 20. The insulating plate 16 may be attached to the electrode body 12 beforehand, or it may be placed later.

[0026] In (B), the upper lead 40 and the lower lead 42 are bent to form a predetermined shape.

[0027] In (C), the upper lead is laser-welded to the terminal body 32 of the sealing body 30, and the lower lead 42 is laser-welded to the bottom surface of the outer can 10.

[0028] In (D), the electrolyte 14 is injected into the sealing cover 20. In this example, the lower lead 42 penetrates the sealing cover 20, but the electrolyte 14 is injected up to the protruding portion 20a of the sealing cover 20, preventing leakage of the liquid.

[0029] In (E), the injection of the electrolyte is completed, and the sealing body 30 is lowered toward the outer can 10. This step corresponds to (A) in Figure 1.

[0030] In (F), the sealing body 30 is lowered further, the lid is placed on the outer can 10, and the joint is irradiated with a laser to perform laser welding. This process corresponds to (B) in Figure 1.

[0031] Thus, according to this embodiment, laser welding can be performed without the presence of electrolyte 14 at the joint between the outer can 10 and the sealing body 30.

[0032] "Other Configuration Examples" Figure 3 shows another configuration example of the sealing cover 20, where (A) shows the electrode body 12 inserted into the outer container 10, and (B) shows the state after the electrode body 12 and electrolyte 14 have been inserted and the upper end of the outer container 10 has been closed with the sealing body 30. In this example, the sealing cover 20 is pipe-shaped with no bottom. Therefore, an insulating plate 44 is placed on the underside of the electrode body 12 so that the electrode body 12 does not come into direct contact with the bottom of the outer container 10. The lower lead 42 can be pulled out from the side of the insulating plate 44. Also, the electrolyte 14 is filled to the bottom of the outer container 10.

[0033] Figure 4 shows yet another configuration example of the sealing cover 20, where (A) shows the state after the electrode body 12 and electrolyte 14 have been inserted and the upper end of the outer container 10 has been closed with the sealing body 30, and (B) shows the shape of the sealing cover 20.

[0034] In this example, the sealing cover 20 is pipe-shaped, similar to that in Figure 3, but it is tapered, widening downwards. Therefore, when inserted into the outer container 10, the lower part of the sealing cover 20 is pressed against the inner wall of the outer container 10, but a space is created between the upper part and the inner wall of the outer container 10. This prevents the electrolyte 14 from rising between the sealing cover 20 and the inner wall of the outer container 10 due to capillary action or other factors.

[0035] Figure 5 shows yet another example of the configuration of the sealing cover 20. In this example, the sealing cover 20 is pipe-shaped, similar to Figure 3, but has an outwardly facing protrusion 20c at its lower end. In example 5(A), the protrusion 20c has a hemispherical cross-section, while in example 5(B), the protrusion 20c has a rectangular cross-section.

[0036] Figure 6 shows a configuration in which the top and bottom are reversed compared to the example in Figure 1, with the positive electrode placed at the bottom of the outer can. A hole is made in the center of the bottom wall of the outer can 10, and the terminal body 32 and gasket 34 are attached thereto. The other end of the lower lead 42, one end of which is connected to the positive electrode of the electrode body 12, passes through the sealing cover 20 and is connected to the terminal body 32. Also, the other end of the upper lead 40, one end of which is connected to the negative electrode of the electrode body 12, passes through the opening in the insulating plate 16 and is connected to the sealing body 50. The sealing body 50 is placed over the top of the outer can 10 from above, and its lower end is in contact with the top of the outer can 10, forming a joint. The protruding portion 20a of the sealing cover 20 is located inside this joint.

[0037] In this way, even when the top and bottom are reversed, the outer can 10 and the sealing body 30 can be laser-welded without the electrolyte adhering to the joint.

[0038] "Example 2 of the configuration of the energy storage device" Figure 7 is a cross-sectional view showing example 2 of the configuration of the energy storage device 100 according to the present disclosure, where (A) shows the state before the sealing body 30 is attached to the outer container 10, and (B) shows the state after the sealing body 30 is attached to the outer container 10.

[0039] The outer container 10 is cylindrical with a bottom, and one end in the first direction, the top, is open. Inside the outer container 10 are the electrode body 12 and the electrolyte 14. An insulating plate 16 is placed on top of the electrode body 12. The outer container 10 may be made of a metal such as aluminum or steel.

[0040] In this example, the electrode body 12 is cylindrical in shape, and is constructed by winding together film-like positive electrodes, separators, and negative electrodes. A bottomed cylindrical sealing cover 20 is positioned between the side and bottom surfaces of the electrode body 12 and the inner surfaces of the side and bottom walls of the outer container 10. The sides of the sealing cover 20 are positioned along the inner circumferential surface of the outer container 10, and the bottom is positioned along the inner surface of the bottom wall of the outer container 10.

[0041] The sealing body 30 has an overall inverted U-shape in cross-section and includes a terminal body 32 located in the center of a second direction perpendicular to the first direction, and a lid body 36 that extends radially outward from the periphery of the terminal body 32 via a gasket 34. The terminal body 32 and lid body 36 may be made of the same metal as the outer can 10, and the gasket 34 may be made of resin.

[0042] The terminal body 32 has a shape in which the centers of two discs, positioned above and below, are connected by a cylinder, and functions as an electrode terminal for the energy storage device 100. The inner portion of the gasket 34 is positioned in the annular space sandwiched between the two discs of the terminal body 32. That is, the inner portion of the gasket 34 has a shape corresponding to the recess of the terminal body 32. The gasket 34 has an inwardly recessed annular recess in the middle of its outer circumference in the vertical direction. In this example, the recess of the gasket 34 is smaller in the vertical direction than the recess of the terminal body 32. The radial inner end of the gasket 34 extends to the outer circumference of the cylindrical portion of the terminal body 32.

[0043] The lid 36 is a disc-shaped plate material with a through hole in the center. The inner end of the lid 36 fits into the recess of the gasket 34 and is fixed in place. The outer circumferential end of the lid 36 is fixed to the inner circumferential surface of the upper end of the outer can 10.

[0044] The electrode body 12 is formed, for example, by winding a positive electrode and a negative electrode with a separator interposed therebetween. An upper lead 40 having one end connected to one of the electrodes (the positive electrode in this example) extends through an opening of the insulating plate 16, and the other end is connected to the bottom surface of the terminal body 32. In this example, the upper lead 40 serves as a positive electrode lead.

[0045] After the electrolytic solution 14 is injected into the exterior can 10, it is absorbed by the electrode body 12, so that the liquid level drops below that at the initial injection and is contained within the exterior can 10.

[0046] The sealing cover 20 has a bottomed cylindrical shape along the inner surface of the exterior can 10, has a cylindrical side portion and a disc-shaped bottom portion, and houses the cylindrical electrode body 12 therein. As the material of the sealing cover 20, any material may be used as long as it has permeability resistance and chemical resistance to the electrolytic solution and heat resistance to the heat generated by laser welding, such as an insulating material or a conductive material such as metal. For example, it may be composed of inexpensive polyolefin-based resins such as PP (polypropylene) and PE (polyethylene). Also, from the viewpoint of heat resistance, PFA (perfluoroalkoxy alkane), PPS (polyphenyl sulfide), PI (polyimide), PEI (polyether imide), PEEK (polyether ether ketone), and PBT (polybutylene terephthalate) may be used. Furthermore, from the viewpoint of heat insulation, glass fiber, aramid fiber, carbon fiber, talc, mica, etc., or a mixed material of these materials and other resin materials may be used. Furthermore, the sealing cover may be composed of a laminate in which a plurality of layers of these materials are laminated. For example, a laminate using a material with higher heat resistance or heat insulation in the outer layer than in the inner layer, a laminate using a material with higher chemical resistance in the inner layer than in the outer layer, a laminate in which a metal layer is formed on a resin layer, or a laminate in which both sides of a heat insulating material are laminated with a resin film may be used. Furthermore, a laminate in which a metal foil is pressure-bonded to a resin layer may be used, and among the electrode bodies, the electrode connected to the exterior body may be connected, and the metal foil and the exterior body may be connected. Note that the meaning of a cylindrical shape such as a cylinder includes a shape formed by winding a sheet-like material with some overlap or a hollow portion.

[0047] The lower lead 42, one end of which is connected to the other electrode of the electrode body 12, for example, the negative electrode, extends through the bottom of the sealing cover 20, and the other end is connected to the surface of the bottom wall of the outer can 10. In this example, the lower lead 42 serves as the negative electrode lead.

[0048] As shown in (B), with the upper lead 40 connected to the terminal body 32 and the electrode body 12, the sealing body 30 is lowered, so that the lower end of the peripheral edge of the lid body 36 contacts the upper end of the outer can 10, and this becomes the joint portion. In this state, as shown by the triangular mark in the figure, by irradiating the joint portion of the lid body 36 and the outer can 10 with a laser, the two can be laser-welded.

[0049] Here, as shown in (A), the sealing cover 20 has a protruding portion 20a that extends upward beyond the upper end of the outer can 10. The sealing cover 20 is in the form of a thin resin film such as polypropylene and is flexible. Therefore, as in (A), when the tip of the sealing cover 20 is pushed by the lower surface of the lid body 36 of the sealing body 30, it inclines inward of the protruding portion 20a. Then, as shown in (B), when the lower end of the sealing body 30 has descended to the position of the upper end of the outer can 10, the protruding portion 20a of the sealing cover 20 bends inward, and in this example, the tip of the sealing cover 20 reaches below the lid body 36.

[0050] The bending method of the protruding portion 20a of the sealing cover 20 is not necessarily uniquely determined, but it is sufficient that the inside of the joint portion is covered by the sealing cover 20. The bending method of the protruding portion 20a of the sealing cover 20 can also be controlled by, for example, making a crease in advance at a predetermined position of the lid body 36, such as the final position.

[0051] In this way, the protruding portion 20a of the sealing cover extends to the inside of the peripheral wall portion 36b of the lid body 36. Therefore, the inside of the joint portion to be laser-welded is covered by the outer peripheral surface of the sealing cover 20. Therefore, when the outer can 10 is sealed by the sealing body 30 after injecting the electrolytic solution, there is no electrolytic solution in the joint portion to be laser-welded, and no problem occurs in performing the laser welding.

[0052] "Manufacturing Process" Figure 8 is a diagram illustrating the process of attaching the sealing body 30 to the outer can 10.

[0053] In (A), the electrode body 12 with the upper lead 40 and lower lead 42 attached is inserted into the sealing cover 20. The insulating plate 16 may be attached to the electrode body 12 beforehand, or it may be placed later.

[0054] In (B), the upper lead 40 and the lower lead 42 are bent to form a predetermined shape.

[0055] In (C), the upper lead 40 is laser-welded to the terminal body 32 of the sealing body 30, and the lower lead 42 is laser-welded to the bottom surface of the outer can 10.

[0056] In (D), the electrolyte 14 is injected into the sealing cover 20. In this example, the lower lead 42 penetrates the sealing cover 20, but the electrolyte 14 is injected up to the protruding portion 20a of the sealing cover 20, preventing leakage of the liquid.

[0057] In (E), the injection of the electrolyte is completed, and the sealing body 30 is lowered toward the outer can 10. This step corresponds to (A) in Figure 7.

[0058] In Figure 8(F), the sealing body 30 is lowered further, the lid is placed on the outer can 10, and the joint is irradiated with a laser to perform laser welding. This process corresponds to Figure 7(B).

[0059] Thus, according to this embodiment, laser welding can be performed without the presence of electrolyte 14 at the joint between the outer can 10 and the sealing body 30.

[0060] "Other Configuration Examples" Figure 9 shows other configuration examples of the sealing cover 20. As shown in (A), in this example, the sealing cover 20 on film is wrapped around the electrode body 12. This allows the outer surface of the electrode body 12 to be covered with the sealing cover 20.

[0061] (B) shows a vertical cross-sectional view of the electrode body 12 after the sealing cover 20 has been wrapped around it. As shown, the vertical length of the sealing cover 20 is greater than the vertical length of the electrode body 12, and the sealing cover 20 protrudes from both the top and bottom sides of the electrode body 12. The A-A cross-section in (B) is shown in the lower diagram of (A).

[0062] In this state, the upper and lower end faces of the electrode body 12 are exposed, and the upper lead 40 is connected to one electrode of the electrode body 12, for example, the positive electrode, through the opening in the insulating plate 16. The lower lead 42 is connected to the other electrode of the electrode body 12, for example, the negative electrode, from the side of the insulating plate 44.

[0063] (C) The portion of the sealing cover 20 that protrudes from the electrode body 12 below the sealing cover 20 is folded to form the bottom. At this time, the lower lead 42 is folded together with the sealing cover 20 with the lower lead 42 protruding from the lower end of the sealing cover 20. This allows the lower lead 42 to emerge from the bottom of the sealing cover 20 and be positioned along the lower surface of the bottom of the sealing cover 20.

[0064] (D) shows the electrode body 12 made in (C) with a sealing cover 20 wrapped around it, and upper leads 40 and lower leads 42 positioned at the upper and lower ends, respectively, and is inserted into the outer container 10. This (D) corresponds to the state in (B). As in (D), the bottom of the sealing cover may be made up of overlapping tongue-shaped sheets extending in a second direction from the side wall. In this case, the lower leads may be connected to the outer container by passing between the overlapping tongue-shaped sheets. The bottom of the sealing cover may also be the bottom of a single annular sheet. In this case, a through hole may be formed in the bottom, and the lower leads may be passed through this through hole.

[0065] In addition, although an insulating plate 44 is provided in (B)-(D), it can be omitted because of the bottom of the sealing cover 20.

[0066] Figure 10 shows yet another configuration example of the sealing cover 20. The electrode body 12 is constructed by overlapping a positive electrode and a negative electrode with a separator in between, and winding them together. If the separator is made longer than the positive electrode and the negative electrode is extended even further, the positive and negative electrodes can be separated by the separator, while the extended portion of the negative electrode can be positioned on the outer circumference of the electrode body 12. In this way, the extended portion of the negative electrode is exposed on the outer circumference side of the electrode body 12. Therefore, the exposed extended portion of the negative electrode can be brought into contact with the inner surface of the outer can 10. If the outer can 10 is used as the negative electrode, the electrical resistance from the negative electrode of the electrode body 12 to the outer can 10 can be reduced.

[0067] (A) This is an unfolded view of the electrode body 12. As shown, the positive electrode 62, separator 64, and negative electrode 60 are stacked in this order. The negative electrode 60 is placed in the longitudinal direction and made the longest, followed by the separator 64, and then the positive electrode 62, which are made shorter. Then, the wires are wound so that the negative electrode 60 and the positive electrode 62 do not come into contact. After the separator 64 is finished, only the negative electrode 60 is wound.

[0068] In this example, the sealing cover 20 is overlapped by a predetermined length in the intermediate portion of the area containing only the negative electrode 60 after the winding of the positive electrode 62 and separator 64 is complete. The vertical length of the sealing cover 20 is made greater than that of the negative electrode 60.

[0069] As a result, as shown in (B), the negative electrode 60 and the sealing cover are wound around the outer circumference of the electrode body 12, and thereafter only the negative electrode 60 is wound around it.

[0070] Figure 11 shows the state in which the electrode body 12 and the wound sealing cover 20 are housed in the outer container 10, as in the example of Figure 10. As shown in Figure 10(A), the sealing cover 20 protrudes from the electrode body 12 in the vertical direction. The sealing cover 20 and the negative electrode 60 are located on the outer circumference side of the electrode body 12. In this figure, only one turn of the sealing cover 20 and the negative electrode 60 is shown, but they may be wound multiple times.

[0071] In this state, the negative electrode 60 is located at the outermost circumference of the electrode body 12 and the winding of the sealing cover 20. Then, as shown in Figure 11(B), the lower part of the sealing cover 20 is folded and inserted into the outer container 10.

[0072] As shown in the figure, the upper end of the negative electrode 60 is lower than the upper end of the outer can 10, and therefore the sealing cover 20 is located inside the joint with the sealing body 30. The negative electrode 60 of the electrode body 12 is extended and directly contacts the inner surface of the outer can 10.

[0073] In the energy storage device of this disclosure, the sealing cover is positioned between the electrode body and the outer casing. In this case, "between the electrode body and the outer casing" means that even if the sealing cover is connected to the electrode body, a portion of the sealing cover is positioned outside the positive electrode, negative electrode, and separator in the second direction.

[0074] Figure 12 shows a configuration in which the top and bottom are reversed compared to the example in Figure 7, with the positive electrode placed at the bottom of the outer can. A hole is made in the center of the bottom wall of the outer can 10, and the terminal body 32 and gasket 34 are attached thereto. The other end of the lower lead 42, one end of which is connected to the positive electrode of the electrode body 12, passes through the sealing cover 20 and is connected to the terminal body 32. Also, the other end of the upper lead 40, one end of which is connected to the negative electrode of the electrode body 12, passes through the opening in the insulating plate 16 and is connected to the sealing body 50. The sealing body 50 is placed over the top of the outer can 10 from above, and its lower end is in contact with the top of the outer can 10, forming a joint. The protruding portion 20a of the sealing cover 20 is located inside this joint.

[0075] In this way, even when the top and bottom are reversed, the outer can 10 and the sealing body 30 can be laser-welded without the electrolyte adhering to the joint.

[0076] "Example 3 of the configuration of the energy storage device" Figure 13 is a cross-sectional view showing example 3 of the configuration of the energy storage device 100 according to the present disclosure, where (A) shows the state before the sealing body 30 is attached to the outer container 10, and (B) shows the state after the sealing body 30 is attached to the outer container 10.

[0077] The outer container 10 is a bottomed cylindrical shape, open at the top, and has a hollow cylindrical portion 10a and a bottom portion 10b that closes the bottom of the cylindrical portion 10a. Inside the outer container 10 are the electrode body 12 and the electrolyte 14. An insulating plate 16 is placed on top of the electrode body 12. The outer container 10 is preferably made of a metal such as aluminum or steel.

[0078] In this example, the electrode body 12 is constructed by winding together a film-like positive electrode, a separator, and a negative electrode, and is cylindrical in shape.

[0079] A hat-shaped sealing cover 20 is provided to cover the upper side and the peripheral side of the top surface of the electrode body 12. The sealing cover 20 includes a side wall portion 20dd arranged along the upper inner circumferential surface of the outer container 10, and an annular top wall portion 20b that extends inward from the side wall portion 20dd. The inside of the top wall portion 20b is open.

[0080] Therefore, the sealing cover 20 is located inside the upper end of the inner space of the outer can 10.

[0081] The sealing body 30 has a disc-shaped cross-section and includes a terminal body 32 located in the center and a lid body 36 that extends radially outward from the periphery of the terminal body 32 via a gasket 34. The terminal body 32 and lid body 36 are preferably made of the same metal as the outer can 10, and the gasket 34 is preferably made of resin.

[0082] The terminal body 32 has a shape in which the centers of two discs, positioned above and below, are connected by a cylinder, and functions as an electrode terminal for the energy storage device 100. The inner portion of the gasket 34 is positioned in the annular space sandwiched between the two discs of the terminal body 32. That is, the inner portion of the gasket 34 has a shape corresponding to the recess of the terminal body 32. The gasket 34 has an inwardly recessed annular recess in the middle of its outer circumference in the vertical direction. In this example, the recess of the gasket 34 is smaller in the vertical direction than the recess of the terminal body 32. The radial inner end of the gasket 34 extends to the outer circumference of the cylindrical portion of the terminal body 32.

[0083] The lid 36 is a disc-shaped plate material with a through hole in the center. The inner end of the lid 36 fits into the recess of the gasket 34 and is fixed in place. The outer peripheral edge of the lid 36 is fixed to the inner circumferential surface of the upper end of the outer can 10.

[0084] The electrode body 12 is constructed, for example, by winding a positive electrode and a negative electrode with a separator in between. An upper lead 40, one end of which is connected to one electrode (the positive electrode in this example), extends through an opening in the insulating plate 16, and the other end is connected to the bottom surface of the terminal body 32. In this example, the upper lead 40 is the positive electrode lead.

[0085] After the electrolyte 14 is injected into the outer container 10, it is absorbed by the electrode body 12, causing the liquid level to drop below the initial level and be contained within the outer container 10.

[0086] The sealing cover 20 is a bottomed cylindrical shape that follows the inner surface of the outer can 10, and has a cylindrical side wall portion 20d and a disc-shaped top wall portion 20b, housing a cylindrical electrode body 12 inside. The material of the sealing cover 20 can be an insulating material or a conductive material such as metal, as long as it has resistance to permeation and chemicals to the electrolyte and heat resistance to the heat generated by laser welding. For example, it may be made of inexpensive polyolefin resins such as PP (polypropylene) or PE (polyethylene). Also, from the viewpoint of heat resistance, PFA (perfluoroalkoxyalkane), PPS (polyphenyl sulfide), PI (polyimide), PEI (polyetherimide), PEEK (polyetheretherketone), or PBT (polybutylene terephthalate) may be used. Furthermore, from the viewpoint of heat insulation, it may be glass fiber, aramid fiber, carbon fiber, talc, mica, or a mixture of these materials and other resin materials. Furthermore, the sealing cover may be made of a laminate formed by stacking multiple layers of these materials. For example, the laminate may be made of a material with higher heat resistance and heat insulation properties in the outer layer than the inner layer, or a material with higher chemical resistance properties in the inner layer than the outer layer, or a laminate in which a metal layer is formed on a resin layer, or a laminate in which both sides of the heat insulating material are laminated with a resin film. Furthermore, a laminate in which a metal foil is pressed onto a resin layer may be used, and the electrode body may be connected to an electrode electrically connected to the outer casing, thereby connecting the metal foil to the outer casing.

[0087] A lower lead 42, one end of which is connected to the other electrode of the electrode body 12, for example, the negative electrode, has its other end, the sealing cover, connected to the surface of the bottom wall of the outer container 10. In this example, the lower lead 42 is the negative electrode lead.

[0088] As shown in Figure 13(B), with the upper lead 40 connected to the terminal body 32 and the electrode body 12, the sealing body 30 is lowered so that the peripheral edge of the lid 36 comes into contact with the inner surface of the upper end of the outer can 10, forming a joint. In this state, as indicated by the triangular mark in the figure, the joint between the lid 36 and the outer can 10 can be laser welded by irradiating it with a laser.

[0089] Here, the joint where the sealing body 30 and the outer can 10 are laser-welded is located outside the position of the radially inner end of the upper end of the sealing cover 20. Therefore, the inside of the joint is covered by the outer surface of the sealing cover 20. Thus, when the outer can 10 is sealed with the sealing body 30 after the electrolyte is injected, the presence of electrolyte at the joint to be laser-welded is suppressed, and problems during laser welding are less likely to occur.

[0090] "Manufacturing Process" Figure 14 is a diagram illustrating the process of attaching the sealing body 30 to the outer can 10.

[0091] In (A), the electrode body 12, to which the upper lead 40, lower lead 42, and insulating plate 16 are attached, is inserted into the outer can 10, and the sealing cover 20 is inserted from above the electrode body 12.

[0092] In (B), the upper lead 40 and lower lead 42 are bent to a predetermined shape, the upper lead is laser-welded to the terminal body 32 of the sealing body 30, and the lower lead 42 is laser-welded to the bottom surface of the outer can 10. The sealing cover 20 is then inserted so that the outer circumferential surface of its side wall portion 20d is in contact with the inner circumferential wall of the upper end of the outer can 10, thereby positioning the sealing cover 20 in a predetermined position. The lower outer circumferential surface of the side wall portion 20d of the sealing cover 20 is made larger in diameter than the upper part, and the outer diameter of this portion is made slightly larger than the inner diameter of the outer can 10. As a result, when the sealing cover 20 is inserted into the outer can 10, the side wall portion 20d of the sealing cover 20 is pressed against the outer can 10. At this stage, the top wall portion 20b of the sealing cover 20 is located above the upper end of the outer can 10.

[0093] (C) In this step, the electrolyte 14 is injected into the outer container 10. The electrolyte 14 is injected up to the inside of the top wall portion 20b of the sealing cover 20.

[0094] In (D), the injection of the electrolyte is completed, and the sealing body 30 is lowered toward the outer can 10. This step corresponds to (A) in Figure 13.

[0095] In (F), the sealing body 30 is lowered further, and the sealing cover 20 is moved downward by the sealing body 30, thereby covering the outer can 10. Then, a laser is irradiated onto the joint to perform laser welding. This process corresponds to (B) in Figure 13.

[0096] As described above, according to this embodiment, when the electrolyte 14 is injected, the outer surface of the side wall portion 20d of the sealing cover 20 is pressed against the inner circumferential wall of the upper end of the outer can 10. Therefore, it is possible to suppress the adhesion of the electrolyte 14 to the inner circumferential wall of the upper end of the outer can 10. Furthermore, when closing the outer can 10 with the sealing body 30, the side wall portion 20d of the sealing cover 20 descends while rubbing against the inner circumferential wall of the outer can 10. Therefore, even after injection, it is possible to suppress the adhesion of the electrolyte 14 to the inner circumferential wall of the upper end of the outer can 10. As a result, the presence of electrolyte 14 at the joint between the outer can 10 and the sealing body 30 is suppressed, and laser welding can be performed.

[0097] "Example of Ceiling Cover Configuration" Figure 15 shows an example of the configuration of a ceiling cover 20.

[0098] In (A), the sealing cover 20 has a cylindrical side wall portion 20d that is straight in the vertical direction and an annular top wall portion 20b that widens inward from its upper end.

[0099] In (B), the side wall portion 20d is tapered, widening towards the bottom, and the annular top wall portion 20b is the same as in example (A).

[0100] In (C), the upper part of the side wall portion 20d is tapered, widening towards the bottom, and the lower part is a straight cylinder, while the annular top wall portion 20b is the same as in example (A).

[0101] In (D), the side wall portion 20d is a straight cylindrical shape in the vertical direction, but the thickness at the bottom is increased, and the bottom bulges outward, resulting in a larger diameter. The annular top wall portion 20b is the same as in example (A).

[0102] (E)–(F) are examples in which the top wall portion 20b of the sealing cover 20 has been removed. The configuration of the side wall portion 20d is such that (E)–(H) corresponds to (A)–(D), respectively.

[0103] Figure 16 shows the configuration of the energy storage device 100 using the sealing cover 20 shown in Figure 15(E). The sealing cover 20 is pressed down by the sealing body 30, and the sealing cover 20 is positioned inside the joint.

[0104] Figure 17 shows a configuration in which the top and bottom are reversed compared to the example in Figure 12, with the positive electrode placed at the bottom of the outer can. A hole is made in the center of the bottom wall of the outer can 10, and the terminal body 32 and gasket 34 are attached thereto. The other end of the lower lead 42, one end of which is connected to the positive electrode of the electrode body 12, passes through the sealing cover 20 and is connected to the terminal body 32. Also, the other end of the upper lead 40, one end of which is connected to the negative electrode of the electrode body 12, passes through the opening in the insulating plate 16 and is connected to the sealing body 50. The sealing body 50 is placed over the top of the outer can 10 from above, and its lower end is in contact with the top of the outer can 10, forming a joint. The sealing cover 20 is located inside this joint.

[0105] In this way, even when the top and bottom are reversed, the adhesion of electrolyte to the joint is suppressed, and the outer can 10 and the sealing body 30 can be laser welded.

[0106] 10 Outer container, 12 Electrode body, 14 Electrolyte, 16 Insulating plate, 20 Sealing cover, 20a Protruding part, 30 Sealing body, 32 Terminal body, 34 Gasket, 36 Lid, 40 Upper lead, 42 Lower lead, 100 Energy storage device

Claims

1. An energy storage device comprising: an outer casing that is open on one side and houses an electrode body inside; a sealing body disposed on one side of the outer casing and joined to the outer casing; and a sealing cover disposed inside the outer casing and overlapping the boundary between the outer casing and the sealing body.

2. The sealing cover comprises a sealing cover, a side portion arranged along the inner circumferential surface of the side wall of the exterior body, and a projection portion extending from the side portion beyond the side wall of the exterior body to one side; the sealing body comprises a circumferential wall portion covering the outer circumferential surface of the sealing cover and having the other end in contact with the one end of the exterior body, and a lid extending inward from the one end of the circumferential wall portion and covering one side of the exterior body, wherein the other end of the circumferential wall portion of the sealing body is joined to the one end of the exterior body, the energy storage device according to claim 1.

3. The energy storage device according to claim 2, wherein the outer diameter of the sealing cover on the other side is larger than the outer diameter of the one side.

4. The energy storage device according to claim 2, wherein the sealing cover is in the shape of a bottomed cylinder.

5. A method for manufacturing an energy storage device according to claim 1, comprising: preparing an exterior body in which a sealing cover is disposed at one end of the side wall of the exterior body, extending from the inner circumferential surface of the side wall beyond the end of the side wall; injecting liquid into the exterior body; closing one side of the exterior body with a sealing body having a circumferential wall portion that covers the outer circumferential surface of the sealing cover and whose other end is in contact with one end of the side wall of the exterior body; and welding the other end of the sealing body to one end of the side wall of the exterior body.

6. The energy storage device according to claim 1, wherein the exterior body is open at one end in a first direction, the sealing cover has a cylindrical side portion arranged along the inside of the side wall of the exterior body, and a top wall portion that is bent inward in a second direction perpendicular to the first direction from one end of the side portion and extends toward the center in the second direction perpendicular to the first direction, and the sealing body covers one side of the top wall portion of the sealing cover and has a peripheral edge that contacts one end of the exterior body, and the peripheral edge of the sealing body is joined to one end of the exterior body in a first direction.

7. The energy storage device according to claim 6, wherein the sealing cover is a resin film.

8. The energy storage device according to claim 6, wherein the sealing cover is wound around the outer circumference of the electrode body.

9. The energy storage device according to claim 6, wherein the electrode body is an electrode body in which a pair of electrodes are wound around a separator, one of the electrodes extends outward from the electrode body, and the extended portion is wound around the outer circumference of the sealing cover.

10. A method for manufacturing an energy storage device according to claim 1, comprising: preparing an outer casing having a sealing cover disposed at one end of the outer casing, the sealing cover having a side portion arranged along a side wall and a protruding portion projecting in a first direction from one end of the side portion; injecting liquid into the outer casing; pressing down on the protruding portion of the sealing cover with the sealing body and bending it inward to form a top wall portion extending toward the center in a second direction perpendicular to the first direction; covering one end of the top wall portion and closing one side of the outer casing so that its peripheral edge contacts one end of the outer casing; and welding the peripheral edge of the sealing body to one end of the outer casing.

11. The method for manufacturing an energy storage device according to claim 10, wherein the sealing cover is hollow and cylindrical, and a bottom is formed at the other end by folding a tongue-shaped sheet inward in a second direction.

12. The energy storage device according to claim 10, wherein the sealing cover is wound around the outer circumference of the electrode body.

13. The energy storage device according to claim 1, wherein the outer casing is open at one end in the first direction, the sealing cover covers the inner circumferential surface near the one end in the first direction of the cylindrical portion of the outer casing and is pressed against the inner circumferential surface, the sealing body has its peripheral edge in contact with the end in the first direction of the outer casing outside the inner end in the second direction perpendicular to the first direction of one end of the sealing cover, and the outer peripheral edge of the sealing body is joined to the one end in the first direction of the outer casing.

14. The energy storage device according to claim 13, wherein the sealing cover includes a top wall portion that extends inward in the second direction from the upper end of a side wall portion that is pressed from the inside to the cylindrical portion of the outer casing.

15. The energy storage device according to claim 13, wherein the sealing cover has a larger outer diameter at the other end than at the one end in the first direction.

16. A method for manufacturing an energy storage device according to claim 1, comprising: preparing an outer casing in which the inner circumferential surface of one end of the side wall of the outer casing is covered by a sealing cover, and one end of the sealing cover protrudes from the upper end of the outer casing; injecting liquid into the outer casing; pressing a sealing body against one end of the sealing cover in the first direction and moving it to the other end in the first direction, thereby bringing the outer peripheral edge of the sealing body into contact with one end of the outer casing, thereby closing one end of the outer casing; and welding the outer peripheral edge of the sealing body to one end of the outer casing.

17. The method for manufacturing an energy storage device according to claim 16, wherein the welding of the peripheral edge of the sealing body and the end of the outer casing in the first direction is performed by laser welding.

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