Method for manufacturing power storage element, and power storage element

Abstract

Provided is a method for manufacturing a power storage element that includes a container for storing an electrode body. The container includes a container body having an opening portion, and a lid body that closes the opening portion. The container body includes a bottom portion, and a cylindrical wall portion rising from the entire peripheral edge of the bottom portion and having the opening portion at a distal end portion. The distal end portion of the wall portion includes two first recesses formed by cutting out a part of the wall portion. The lid body has a shape corresponding to the shape of the opening portion of the wall portion. The manufacturing method includes continuously welding the entire peripheral edge of the lid body around the entire peripheral edge of the opening portion of the wall portion.

Description

Electricity storage element manufacturing method and electricity storage element

[0001] The present invention relates to a method for manufacturing an energy storage element and to an energy storage element.

[0002] Patent Document 1 discloses a sealed battery in which a sealing plate is fitted into the opening of an outer can that houses an electrode body, and the sealing plate is joined to the opening of the outer can by welding along the boundary between the opening of the outer can and the outer periphery of the sealing plate.

[0003] JP 2011-204396 A

[0004] In recent years, energy storage elements with more complex shapes have been developed, but as the container shapes become more complex, the welds also become more complex. When the welds become more complex, the possibility of welding defects increases.

[0005] Therefore, an object of the present invention is to provide a method for manufacturing an energy storage element that can suppress welding defects.

[0006] A manufacturing method for a storage element according to one embodiment of the present invention is a manufacturing method for a storage element including a container that houses an electrode body, wherein the container includes a container body having an opening and a lid body that closes the opening, the container body having a bottom and a cylindrical wall portion that rises from the entire periphery of the bottom and has the opening at its tip, the tip of the wall portion including two first recesses formed by cutting out a portion of the wall portion, the lid body having a shape that corresponds to the shape of the opening in the wall portion, and the manufacturing method includes continuously welding the entire periphery of the lid body to the entire periphery of the opening in the wall portion all around.

[0007] Another aspect of the present invention provides an energy storage element comprising an electrode body and a container for accommodating the electrode body, the container comprising a container body having an opening and a lid body closing the opening, the container body comprising a bottom and a cylindrical wall portion rising from the entire periphery of the bottom and having the opening at its tip, the tip of the wall portion including two first recesses formed by cutting out a portion of the wall portion, the lid body having a shape corresponding to the shape of the opening in the wall portion, the lid body and the opening in the wall portion forming a weld that is continuously welded around the entire circumference, and the weld portion having only one overlap portion.

[0008] According to the present invention, it is possible to provide a method for manufacturing an energy storage element that can minimize the welded portion and suppress welding defects even in an energy storage element having a container with a complex shape.

[0009] FIG. 1 is a perspective view showing the appearance of an energy storage element according to an embodiment. FIG. 2 is an exploded perspective view showing each component when the energy storage element according to the embodiment is disassembled. FIG. 3 is a perspective view showing the configuration of an electrode body according to an embodiment. FIG. 4 is a perspective view showing a metal sheet that becomes a container body according to an embodiment. FIG. 5 is a perspective view showing a container body before assembly according to an embodiment. FIG. 6 is a perspective view showing a state in which an opening and a lid according to an embodiment are aligned. FIG. 7 is a plan view showing a start point and an end point of a weld according to an embodiment. FIG. 8 is an enlarged cross-sectional view showing a boundary portion between an opening of a container body and a lid according to Modification 1. FIG. 9 is a perspective view showing the appearance of an energy storage element according to Modification 2. FIG. 10 is an exploded perspective view showing a container according to Modification 2. FIG. 11 is an explanatory diagram showing a laser welding method in which the container body and the lid according to Modification 3 are moved. FIG. 12 is an explanatory diagram showing a laser welding method in which the container body and the lid according to Modification 4 are moved. FIG. 13 is an explanatory diagram showing an energy storage device including an energy storage element according to an embodiment.

[0010] (Inventor's Knowledge) The welding process is essentially a technique for locally applying a large amount of heat energy to the interface of the objects to be welded, thereby melting and joining the objects. Therefore, in order to obtain a uniform weld interface, it is necessary to apply uniform heat energy to the weld.

[0011] Laser welding, a typical welding method for energy storage devices, requires (1) a constant-power laser (2) to be irradiated at a constant irradiation angle relative to the welding surface at the weld interface, and (3) to be irradiated at a constant scanning speed. Therefore, in energy storage devices with complex containers, such as those targeted by the present invention, controlling (2) and (3) is particularly difficult, making welding the entire device difficult. For this reason, dividing the complex container into sections and welding them intermittently has been considered, but this increases the overlap between adjacent welds. Because the overlap is subjected to thermal history from multiple welding processes, the weld is prone to hardening and cracking. Therefore, increasing the overlap increases the likelihood of welding defects due to the overlap. Furthermore, when the welds on containers with complex shapes are large, the probability of defects increases, so it has been necessary to minimize the welds as much as possible. The present disclosure aims to provide a manufacturing method for an energy storage device that can suppress welding defects due to overlaps and further reduce welding defects by minimizing the welded area.

[0012] (1) A manufacturing method for a storage element according to one aspect of the present invention is a manufacturing method for a storage element including a container that houses an electrode body, the container including a container body having an opening and a lid body that closes the opening, the container body including a bottom and a cylindrical wall portion that rises from the entire periphery of the bottom and has the opening at its tip, the tip of the wall portion including two first recesses formed by cutting out a portion of the wall portion, the lid body having a shape that corresponds to the shape of the opening in the wall portion, and the manufacturing method including continuously welding the entire periphery of the lid body to the entire periphery of the opening in the wall portion all around.

[0013] According to the manufacturing method for an energy storage element described in (1) above, the welded portion can be minimized even in an energy storage element having a container with a complex shape. In particular, when welding the lid to the opening of the wall portion having two first recesses, the entire periphery of the lid is continuously welded around the entire periphery of the opening, so only the start and end points of the weld overlap. In other words, when welding the container body and the lid, there is only one overlap, so welding defects caused by the overlap can be suppressed. In this way, the manufacturing method for an energy storage element disclosed herein can suppress welding defects in an energy storage element.

[0014] (2) The manufacturing method of the energy storage element described in (1) above may include bending a flat plate to form the rectangular bottom and a pair of opposing first wall portions in the wall portion, and welding a pair of second wall portions to the bottom and the pair of first wall portions to form the container body.

[0015] According to the manufacturing method of the energy storage element described above in (2), the bottom and the pair of first walls are formed by bending a flat plate, and the pair of second walls are welded to the bottom and the pair of first walls to form the container body. In other words, the container body can be formed by a relatively simple method compared to forming the container body by extrusion processing.

[0016] (3) In the method for manufacturing an energy storage element according to (1) or (2) above, one of the lid and the opening may have a step formed thereon into which the periphery of the other fits.

[0017] According to the manufacturing method of the energy storage element described in (3) above, a step portion into which the periphery of one of the lid and the opening fits is formed, so that the lid and the container body can be positioned by fitting the step portion onto the periphery of the other before welding. When laser welding is performed with the periphery of the other fitted into the step portion, the step portion blocks the laser light, thereby preventing the laser light from affecting the electrode body inside the container.

[0018] (4) In the method for manufacturing an energy storage element described in any one of (1) to (3) above, the two first recesses may be provided only at the tip end of the wall portion.

[0019] According to the manufacturing method of the energy storage element described in (4) above, poor welding can be suppressed even when welding the container body having the two first recesses only at the tip end of the wall portion to the lid.

[0020] (5) In the method for manufacturing an energy storage element described in any one of (1) to (3) above, the end of the wall portion on the bottom side may include two second recesses formed by cutting out a portion of the wall portion.

[0021] According to the manufacturing method of the energy storage element described in (5) above, poor welding can be suppressed even when welding the container body having two first recesses and two second recesses to the lid body.

[0022] (6) An energy storage element according to one aspect of the present invention comprises an electrode body and a container for accommodating the electrode body, the container comprising a container body having an opening and a lid body closing the opening, the container body comprising a bottom and a cylindrical wall portion rising from the entire periphery of the bottom and having the opening at its tip, the tip of the wall portion including two first recesses formed by cutting out a portion of the wall portion, the lid body having a shape corresponding to the shape of the opening in the wall portion, the lid body and the opening in the wall portion forming a welded joint that is continuously welded around the entire circumference, and the welded joint having only one overlap portion.

[0023] According to the energy storage element described in (6) above, the weld between the opening of the wall portion having the two first recesses and the lid body has only one overlap portion, so that welding defects caused by the overlap portion can be suppressed. In this way, the energy storage element of the present disclosure can suppress welding defects.

[0024] (Embodiments) Hereinafter, with reference to the drawings, a manufacturing method of an energy storage element and an energy storage element according to embodiments of the present invention (including variations thereof) will be described. Note that the embodiments described below all show comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same reference numerals are used for identical or similar components. The names of the components (each component) in this embodiment are those used in this embodiment and may differ from the names of the components (each component) in the background art.

[0025] In the following description and drawings, the longitudinal direction of the energy storage element, or the direction along the winding axis of the electrode body provided in the energy storage element, is defined as the X-axis direction. The thickness direction of the container of the energy storage element is defined as the Y-axis direction. The direction in which the bottom surface of the container body and the top surface of the lid of the container are aligned, or the up-down direction, is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect with each other (orthogonal in this embodiment). Note that, depending on the mode of use, the Z-axis may not be the up-down direction, but for ease of explanation, the following description will be made assuming that the Z-axis is the up-down direction. In the following description, the term "insulation" means "electrical insulation". An insulating material has a volume resistivity of 1×10 6 Ωm or more, more preferably 1×10 7 It is preferable that the material be made of a material with a resistance of Ωm or more.

[0026] In the following description, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions. Furthermore, expressions indicating relative directions or attitudes, such as parallel and perpendicular, also include cases where the direction or attitude is not strictly that. "Two directions are perpendicular" does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, i.e., there is a difference of about a few percent.

[0027] [Energy Storage Element] First, a schematic configuration of an energy storage element 10 according to the present embodiment will be described. Fig. 1 is a perspective view showing the appearance of the energy storage element 10 according to the embodiment. Fig. 2 is an exploded perspective view showing each component of the energy storage element 10 according to the embodiment.

[0028] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, more specifically, a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a battery for driving or starting the engine of a moving object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, automatic guided vehicle (AGV), or electric railway vehicle. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The energy storage element 10 may also be used as a stationary battery for home or business use.

[0029] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may not be a secondary battery, but may be a primary battery that can use stored electricity without the user having to charge it. Furthermore, the energy storage element 10 may be an all-solid-state lithium battery using a solid electrolyte, or a polymer lithium battery.

[0030] The energy storage element 10 has a shape in which the length in the X-axis direction is longer than the Y-axis direction, specifically, a rectangular parallelepiped shape (rectangular, square) that is flattened in the Y-axis direction. The energy storage element 10 includes a container 100, a pair of terminals 300, and a pair of external gaskets 400. A pair of internal gaskets 500, a pair of current collectors 600, and an electrode assembly 700 are housed inside the container 100. Specifically, the positive electrode components (terminals 300, external gaskets 400, internal gaskets 500, current collectors 600, etc.; the same applies below) are disposed on a first side surface portion 110 of the container 100 in the positive X-axis direction. In other words, the first side surface portion 110 is the range from the end face of the container 100 in the positive X-axis direction where the positive electrode components are disposed. The first side surface portion 110 is a portion in the X-axis direction that is within 1% to 10% of the length of the container 100 from the end face of the container 100 in the positive X-axis direction.

[0031] The components of the negative electrode are disposed on the second side surface portion 120 of the container 100 in the negative X-axis direction. In other words, the second side surface portion 120 is the range from the end surface of the container 100 in the negative X-axis direction where the components of the negative electrode are disposed. The second side surface portion 120 is a portion in the X-axis direction that is within a range of 1% to 10% of the length of the container 100 from the end surface of the container 100 in the negative X-axis direction.

[0032] An electrolyte solution (non-aqueous electrolyte) is sealed inside the container 100, but is not shown in the figure. There are no particular restrictions on the type of electrolyte solution, and various types can be selected as long as they do not impair the performance of the energy storage element 10. In addition to the above components, spacers arranged on the sides, above, or below the electrode assembly 700, an insulating film that wraps around the electrode assembly 700, etc. may also be arranged.

[0033] The container 100 is a case having an outer shape (approximately rectangular parallelepiped shape) based on a rectangular parallelepiped shape that is long and flat in the X-axis direction. The length of the container 100 in the X-axis direction is at least three times longer than its length in the Z-axis direction. In FIG. 1 , the rectangular parallelepiped shape that serves as the reference is illustrated by a two-dot chain line L1. Specifically, the container 100 has an outer shape that is long and flat in the X-axis direction, with rectangular notches formed at the top of both ends in the X-axis direction. In other words, the container 100 has an outer shape that has two notches based on a prismatic container (rectangular parallelepiped container). When viewed from the rectangular parallelepiped shape that serves as the reference, each notch can be said to form a first recess 101. A terminal 300 is disposed in the first recess 101.

[0034] Specifically, the first side surface portion 110 has a first upper side surface 111, a first top surface 112, and a first side surface 113, and is elongated in the Z-axis direction when viewed from the X-axis direction. The first upper side surface 111 is disposed at the top of the first side surface portion 110, and is a rectangular flat surface parallel to the YZ plane and elongated in the Z-axis direction. The first top surface 112 is a flat surface extending in the positive X-axis direction from the lower end of the first upper side surface 111, and is a rectangular flat surface parallel to the XY plane and elongated in the X-axis direction. The first side surface 113 is a flat surface extending downward from the end of the first top surface 112 in the positive X-axis direction, and is a rectangular flat surface parallel to the YZ plane and elongated in the Z-axis direction.

[0035] The first recess 101 of the first side surface portion 110 is formed by a first upper side surface 111 and a first top surface 112, and is open at its end in the positive Z-axis direction and its end in the positive X-axis direction, penetrating in the Y-axis direction. In other words, the first recess 101 of the first side surface portion 110 is a recess in which the corners of the container 100 in the positive X-axis direction and the positive Z-axis direction are recessed (cut out) in a quadrangular (L-shaped) shape when viewed from the Y-axis direction.

[0036] The second side surface portion 120 has a second upper side surface 121, a second top surface 122, and a second side surface 123, and is elongated in the Z-axis direction when viewed from the X-axis direction. The second upper side surface 121 is disposed at the top of the second side surface portion 120, and is a rectangular flat surface parallel to the YZ plane and elongated in the Z-axis direction. The second top surface 122 is a flat surface extending in the negative X-axis direction from the lower end of the second upper side surface 121, and is a rectangular flat surface parallel to the XY plane and elongated in the X-axis direction. The second side surface 123 is a flat surface extending downward from the end of the second top surface 122 in the negative X-axis direction, and is a rectangular flat surface parallel to the YZ plane and elongated in the Z-axis direction.

[0037] The first recess 101 of the second side surface portion 120 is formed by a second upper side surface 121 and a second top surface 122, and is open at its end in the positive Z-axis direction and its end in the negative X-axis direction, penetrating in the Y-axis direction. In other words, the first recess 101 of the second side surface portion 120 is a recess in which the corners of the container 100 in the negative X-axis direction and the positive Z-axis direction are recessed (cut out) into a quadrangular shape when viewed from the Y-axis direction.

[0038] In this container 100, both end faces opposing each other in the Y-axis direction are long side faces 130. Each long side face 130 is a flat surface parallel to the XZ plane and elongated in the X-axis direction, and both end portions in the X-axis direction have shapes corresponding to the first side face portion 110 and the second side face portion 120.

[0039] Of the two end faces of the container 100 that face each other in the Z-axis direction, the end face in the positive Z-axis direction is the top face 140, and the end face in the negative Z-axis direction is the bottom face 150. The top face 140 is a rectangular flat surface that is parallel to the XY plane and elongated in the X-axis direction, connecting the upper end of the first upper side face 111 of the first side face portion 110 and the upper end of the second upper side face 121 of the second side face portion 120. The bottom face 150 is a rectangular flat surface that is parallel to the XY plane and elongated in the X-axis direction, connecting the lower end of the first side face 113 of the first side face portion 110 and the lower end of the second side face 123 of the second side face portion 120.

[0040] The container 100 includes a container body 160 and a lid 170, and is formed into a substantially rectangular parallelepiped shape by assembling the container body 160 and the lid 170. The container body 160 includes a pair of long sides 130, a bottom surface 150, a first side surface 113, and a second side surface 123. The lid 170 includes a first upper side surface 111, a first top surface 112, a second upper side surface 121, a second top surface 122, and a top surface 140.

[0041] The container body 160 includes a flat, rectangular bottom portion 161 at the end in the negative Z-axis direction, and a cylindrical wall portion 162 rising from the entire periphery of the bottom portion 161. The bottom portion 161 includes a bottom surface 150. An opening 163 is provided at the tip (upper end) of the wall portion 162. The tip of the wall portion 162 includes two first recesses 101. The wall portion 162 includes a pair of first wall portions 164 facing each other in the Y-axis direction and a pair of second wall portions 165 facing each other in the X-axis direction. Each first wall portion 164 has a long side surface 130, and the second wall portion 165 facing the positive X-axis direction has a first side surface 113, and the second wall portion 165 facing the negative X-axis direction has a second side surface 123.

[0042] The lid 170 is a metal plate having a shape corresponding to the opening 163 of the wall 162. The lid 170 has a first bent plate portion 171 forming the first upper side surface 111 and the first top surface 112 at its end in the positive direction of the X axis, a second bent plate portion 172 forming the second upper side surface 121 and the second top surface 122 at its end in the negative direction of the X axis, and a top wall portion 173 connecting these portions in the middle in the X axis direction. The top wall portion 173 is flat and rectangular and has a top surface 140.

[0043] Although not shown, the container 100 is provided with a gas release valve and a liquid injection part. The gas release valve is a safety valve that releases pressure when the pressure inside the container 100 increases excessively. The liquid injection part is a part for injecting the electrolyte into the container 100 during the manufacture of the energy storage element 10.

[0044] With this configuration, the container 100 is configured such that the electrode assembly 700 and the like are housed inside the container body 160, and then the container body 160 and the lid 170 are joined by welding or the like, thereby sealing the interior. The material of the container 100 (container body 160 and lid 170) is not particularly limited, but is preferably a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet.

[0045] The terminals 300 are terminals (positive electrode terminal 310 and negative electrode terminal 320) electrically connected to the electrode assembly 700 via the current collector 600. In other words, the terminals 300 are metal members that draw out electricity stored in the electrode assembly 700 to the external space of the energy storage element 10 and introduce electricity into the internal space of the energy storage element 10 to store electricity in the electrode assembly 700. The material of the terminals 300 is not particularly limited, but the terminals 300 (positive electrode terminal 310 and negative electrode terminal 320) are formed from a conductive material such as aluminum, an aluminum alloy, copper, or a copper alloy. The terminals 300 are connected (joined) to the current collector 600 by crimping, welding, or the like, and are attached to the lid 170.

[0046] In the present embodiment, the terminal 300 has a terminal body 330 and a shaft 340 protruding from the terminal body 330. The terminal body 330 is a portion that protrudes outward from the terminal installation surface of the container 100. Here, the terminal installation surface is the first upper surface 112 or the second upper surface 122. On either terminal installation surface, the terminal body 330 protrudes outward from the container 100 along the Z-axis direction. Through holes 112a, 122a through which the shaft 340 penetrates are formed in the lid 170 at locations corresponding to each terminal installation surface. The shaft 340 is connected (joined) to the current collector 600 by being crimped while penetrating the terminal installation surface, the external gasket 400, the internal gasket 500, and the current collector 600.

[0047] The current collectors 600 are arranged one on each side of the electrode body 700 in the X-axis direction, connected (joined) to the electrode body 700 and the terminal 300, and are conductive current collecting members (positive electrode current collector 610 and negative electrode current collector 620) that electrically connect the electrode body 700 and the terminal 300. Specifically, the current collector 600 integrally includes a first joint portion 630 that is connected (joined) to a tab portion 720 of the electrode body 700 (described later) by welding, crimping, or the like, and a second joint portion 640 that is connected (joined) to the terminal 300 by crimping, welding, or the like, as described above. The first joint portion 630 and the second joint portion 640 are each flat plate-shaped portions formed by bending a single piece of sheet metal. The material of the current collector 600 is not particularly limited, but the positive electrode current collector 610 is formed of a conductive material such as aluminum or an aluminum alloy, similar to the positive electrode current collector foil 741 of the electrode body 700 described later, and the negative electrode current collector 620 is formed of a conductive material such as copper or a copper alloy, similar to the negative electrode current collector foil 751 of the electrode body 700 described later.

[0048] The outer gasket 400 is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 170 of the container 100 and the terminal 300, and provides insulation and a seal between the lid 170 and the terminal 300. The inner gasket 500 is a plate-shaped, rectangular insulating sealing member that is disposed between the lid 170 and the current collector 600, and provides insulation and a seal between the lid 170 and the current collector 600. The external gasket 400 and the internal gasket 500 are formed from an electrically insulating resin such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), ABS resin, or a composite material containing any of these with a filler added thereto.

[0049] The electrode body 700 is a storage element (power generating element) formed by winding electrode plates and capable of storing electricity. The electrode body 700 has an elongated shape extending in the X-axis direction and has an oval shape when viewed from the X-axis direction. The electrode body 700 has a shape in which the length in the X-axis direction is 300 mm or more, specifically, approximately 500 mm to 1500 mm. Therefore, the length in the X-axis direction of the electrode body 700 is longer than the length in the Z-axis direction. The length in the X-axis direction of the electrode body 700 is three or more times the length in the Z-axis direction. The electrode body 700 has a main body portion 710 and multiple tab portions 720 protruding from the main body portion 710. As described above, the tab portions 720 are connected (joined) to the current collector 600. The tab portions 720 are an example of a connection portion connected to the current collector 600.

[0050] Specifically, the multiple tab portions 720 protrude one from each of both end faces in the X-axis direction of the main body portion 710. A positive electrode tab portion 721 is provided on one end face of the main body portion 710 in the positive X-axis direction, and a negative electrode tab portion 722 is provided on the other end face of the main body portion 710 in the negative X-axis direction.

[0051] [Electrode Assembly] Fig. 3 is a perspective view showing the configuration of an electrode assembly 700 according to an embodiment. Specifically, Fig. 3 shows the configuration in a partially developed state in which the wound state of the electrode plates in the electrode assembly 700 is shown. As shown in Fig. 3, the electrode assembly 700 has a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0052] The positive electrode plate 740 is an electrode plate in which a positive electrode active material layer 742 is disposed on both sides of a positive electrode current collector foil 741, which is a long strip of metal foil. Aluminum, an aluminum alloy, or the like is used for the positive electrode current collector foil 741. The negative electrode plate 750 is an electrode plate in which a negative electrode active material layer 752 is disposed on both sides of a negative electrode current collector foil 751, which is a long strip of metal foil. Copper, a copper alloy, or the like is used for the negative electrode current collector foil 751. As the positive electrode active material used in the positive electrode active material layer 742 and the negative electrode active material used in the negative electrode active material layer 752, any known material can be used as long as it is capable of absorbing and releasing charge transport ions.

[0053] As a positive electrode active material, LiMPO４ , LiMSiO ４ , LiMBO ３ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), polyanion compounds such as lithium titanate, LiMn ２ O ４ and LiMn １．５ Ni ０．５ O ４ Spinel-type lithium manganese oxides such as α-NaFeO ２ LiMO having a type crystal structure ２ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) can be used. Examples of the negative electrode active material include lithium metal, alloys capable of absorbing and releasing lithium, carbon materials (graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), and silicon oxides.

[0054] Separators 761 and 762 are microporous sheets made of resin. Any known material can be used as the material for separators 761 and 762 as long as it does not impair the performance of energy storage element 10. Separators 761 and 762 may be made of a woven fabric or nonwoven fabric that is insoluble in organic solvents, a synthetic resin microporous film made of a polyolefin resin such as polyethylene, or the like.

[0055] The electrode assembly 700 is formed by winding a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. The electrode assembly 700 is formed by stacking and winding the negative electrode plate 750, the separator 761, the positive electrode plate 740, and the separator 762 in this order. In this embodiment, the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762 are wound around a winding axis L extending in the X-axis direction, thereby forming the wound electrode assembly 700. The winding axis L is an imaginary axis that serves as the central axis when winding the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762. In this embodiment, the winding axis is a straight line that passes through the center of the electrode assembly 700 and is parallel to the X-axis direction.

[0056] A plurality of protruding pieces 743 protruding outward are arranged at intervals on the edge of the positive electrode plate 740 in the X-axis positive direction. Similarly, a plurality of protruding pieces 753 protruding outward are arranged at intervals on the edge of the negative electrode plate 750 in the X-axis negative direction. Each of the plurality of protruding pieces 743 is a portion where no positive electrode active material layer is disposed and the positive electrode current collector foil 741 is exposed (a portion where no positive electrode active material layer is formed). Each of the plurality of protruding pieces 753 is a portion where no negative electrode active material layer is disposed and the negative electrode current collector foil 751 is exposed (a portion where no negative electrode active material layer is formed). In FIG. 3 , the portions where no active material layer is formed (portions where no positive electrode active material layer is formed, portions where no negative electrode active material layer is formed) are indicated by diagonal lines.

[0057] When the positive electrode plate 740, the negative electrode plate 750, and the separators 761, 762 are wound, the multiple protruding pieces 743 of the positive electrode plate 740 substantially overlap at the end face (one end face) of the main body 710 in the positive direction of the X axis, and the multiple protruding pieces 753 of the negative electrode plate 750 substantially overlap at the end face (the other end face) in the negative direction of the X axis. The portion of the positive electrode plate 740 where the multiple protruding pieces 743 overlap is the positive electrode tab portion 721. In other words, the positive electrode tab portion 721 is a portion where the multiple pieces (protruding pieces 743) of the electrode plates of the same polarity (positive electrode plate 740) among the multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked.

[0058] Similarly, the portion of the negative electrode plate 750 where the multiple protruding pieces 753 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is a portion where the multiple pieces (protruding pieces 753) provided on the electrode plate of the same polarity (negative electrode plate 750) among the multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked.

[0059] As described above, the electrode body 700 includes a main body portion 710 that constitutes the main body of the electrode body 700, and tab portions 720 (positive electrode tab portion 721 and negative electrode tab portion 722) that protrude from each end face in the X-axis direction of the main body portion 710. In other words, the electrode body 700 includes a pair of tab portions that are composed of the positive electrode tab portion 721 and the negative electrode tab portion 722.

[0060] The main body portion 710 is an elongated cylindrical portion formed by winding together a portion of the positive electrode plate 740 where the positive electrode active material layer 742 is disposed (formed, coated), a portion of the negative electrode plate 750 where the negative electrode active material layer 752 is disposed (formed, coated), and separators 761, 762. The region of the main body portion 710 where at least one of the positive electrode active material layer 742 and the negative electrode active material layer 752 is laminated is referred to as the active material layer formation portion. The outer surface of the main body portion 710 has curved portions 711 at both ends in the Z-axis direction and flat portions 712 at both ends in the Y-axis direction.

[0061] The curved portion 711 is a portion that extends in the X-axis direction and protrudes in a curved shape in the Z-axis direction. When viewed in the X-axis direction, the curved portion 711 is curved in a semicircular arc shape. The flat portion 712 is a flat portion that extends in the X-axis direction and is parallel to the XZ plane, connecting the ends of the pair of curved portions 711. In the flat portion 712, multiple wound electrode plates and separators (positive electrode plate 740, negative electrode plate 750, separators 761, 762) are stacked in the Y-axis direction.

[0062] The shape of the electrode body is not limited to a wound type, but may be a stack type in which flat electrode plates are stacked, or a shape in which the electrode plates and / or separators are folded in an accordion-like manner (a form in which the separator is folded in an accordion-like manner to sandwich a rectangular electrode plate, a form in which the electrode plate and separator are stacked and then folded in an accordion-like manner, etc.).

[0063] [Manufacturing Method of Energy Storage Element] Next, a manufacturing method of the energy storage element 10 will be described. In this manufacturing method, metal sheets are laser-welded to each other, but welding methods other than laser welding can also be used as long as they can weld metal sheets to each other. Other welding methods include electron beam welding and plasma arc welding.

[0064] The container body 160 and the lid 170 are formed in separate processes. First, the process of forming the container body 160 will be described. FIG. 4 is a perspective view showing a metal sheet 190 that becomes the container body 160 according to the embodiment. As shown in FIG. 4, the metal sheet 190 is a flat metal sheet based on a rectangular plate shape. Each of the four corners of the metal sheet 190 is cut out in a rectangular shape. The dashed line L2 shown in FIG. 4 is a line that separates the bottom 161 and the pair of first wall portions 164, and by bending along this dashed line L2, each first wall portion 164 becomes shaped to stand up relative to the bottom 161.

[0065] FIG. 5 is a perspective view showing the container body 160 before assembly according to the embodiment. As shown in FIG. 5, a rectangular metal plate 191 that will become the second wall portion 165 in the positive direction of the X-axis and a rectangular metal plate 192 that will become the second wall portion 165 in the negative direction of the X-axis are welded to the bent metal plate 190. Specifically, the metal plate 191 is assembled to the end of the metal plate 190 in the positive direction of the X-axis, and the boundary between the metal plates 190 and 191 is laser-welded to join the metal plates 190 and 191 together. Similarly, the metal plate 192 is assembled to the end of the metal plate 190 in the negative direction of the X-axis, and the boundary between the metal plates 190 and 192 is laser-welded to join the metal plates 190 and 192 together. In this manner, the container body 160 is formed (see FIG. 2).

[0066] The process of forming the lid body 170 will be described. A rectangular flat metal plate that is elongated in the X-axis direction is prepared, and the metal plate is press-formed to form the lid body 170. The terminals 300, the external gaskets 400, the internal gaskets 500, the current collectors 600, and the electrode assembly 700 are attached to the lid body 170. Thereafter, the lid body 170 is aligned with the opening 163 of the container body 160 so that the internal gaskets 500, the current collectors 600, and the electrode assembly 700 are housed within the container body 160.

[0067] FIG. 6 is a perspective view showing the state in which the opening 163 and the lid 170 according to the embodiment are aligned. In this state, the entire peripheral edge of the lid 170 overlaps the entire peripheral edge of the opening 163. In this state, final welding is performed. In the final welding, the entire peripheral edge of the lid 170 is continuously welded around the entire peripheral edge of the opening 163. Specifically, a movable head unit 900 that irradiates laser light is positioned above the assembly of the container body 160 and the lid 170. Then, the head unit 900 irradiates laser light toward the boundary between the lid 170 and the opening 163. While continuing to irradiate the laser light, the head unit 900 is moved circumferentially to change its position, thereby continuously laser-welding the entire peripheral edge of the lid 170 around the entire peripheral edge of the opening 163 (see the arrow in FIG. 6 ). At this time, the head unit 900 continues to move and irradiate light without stopping until it has completed one revolution, and stops moving and irradiating light when it reaches the start point 178 of the welding portion 177 (see FIG. 7).

[0068] FIG. 7 is a plan view showing the start and end points of a weld 177 according to an embodiment. In FIG. 7 , the boundary between the container body 160 and the lid 170 is indicated by a two-dot chain line. As shown in FIG. 7 , the start point 178 of the weld 177 overlaps the end point 179 of the weld 177. This overlapping portion is an overlapping portion. As described above, the entire periphery of the lid 170 is continuously welded around the entire periphery of the opening 163, so the weld 177 overlaps only in one location. In the overlapping portion, there is a risk that the hardened start point 178 may not be sufficiently melted when the end point 179 is formed. Therefore, when forming the end point 179, the head unit 900 is stopped from moving and the laser beam irradiation is maintained for a predetermined time, thereby ensuring that the start point 178 is melted.

[0069] [Explanation of Effects] As described above, according to the embodiment, when welding the lid 170 to the opening 163 of the wall 162 having the two first recesses 101, the entire periphery of the lid 170 is continuously welded all the way around the entire periphery of the opening 163, so that only the start point 178 and the end point 179 of the weld 177 overlap. In other words, when welding the container body 160 and the lid 170, the overlap portion can be limited to one location, and therefore poor welding caused by the overlap portion can be suppressed.

[0070] In this embodiment, the container body 160 is formed first, and then the container body 160 and the lid 170 are welded together in the final welding. Alternatively, the lid 170 and the metal sheets 191 and 192 can be integrated together first, and then the integrated piece can be welded to the metal sheet 190 in the final welding. In this case, the welding path during final welding becomes larger than the welding path during final welding in this embodiment. That is, in this embodiment, the wall 162 having the two first recesses 101 is cylindrical, which prevents the welding path during final welding from becoming larger. In this case, the electrode body 700 can be efficiently inserted into the wall 162.

[0071] The container body 160 is formed by bending a flat metal sheet 190 to form the bottom 161 and the pair of first wall portions 164, and by laser welding the pair of second wall portions 165 to the bottom 161 and the pair of first wall portions 164. In other words, the container body 160 can be formed by a relatively simple method compared to forming the container body 160 by extrusion processing.

[0072] Even when welding the container body 160 having the two first recesses 101 only at the tip end of the wall portion 162 to the lid 170, welding defects can be suppressed.

[0073] The following describes various modifications of the above embodiment. In the following description, the same parts as those in the above embodiment or other modifications are designated by the same reference numerals, and the description thereof may be omitted.

[0074] (Variation 1) In Variation 1, a case will be described in which a step portion is formed on one of the opening of the container body and the lid body, into which the periphery of the other fits. Here, a case in which a step portion is formed on the lid body, into which the periphery of the opening of the container body fits, is illustrated, but a step portion into which the periphery of the lid body fits may also be formed on the opening of the container body.

[0075] FIG. 8 is an enlarged cross-sectional view showing the boundary between the opening 163 of the container body 160 and the lid 170a according to Modification 1. A stepped portion 174a into which the opening 163 fits is formed along the entire periphery of the lid 170a. The stepped portion 174a is a groove cut out into a rectangular shape in cross section and is continuously formed around the entire circumference of the lid 170a. When the lid 170a is aligned with the opening 163 of the container body 160, the opening 163 fits into the stepped portion 174a. This enhances stability during alignment. In this state, the end face of the lid 170a in the positive Y-axis direction and the outer surface of the container body 160a in the positive Y-axis direction are flush with each other. During welding, a laser beam is irradiated toward the boundary between the opening 163 and the stepped portion 174a (see arrow L10). At this time, the step portion 174 a blocks the laser light, so that the laser light can be prevented from affecting the electrode body 700 inside the container 100 .

[0076] (Modification 2) In Modification 2, a container will be described in which two second recesses are formed by cutting out parts of the wall at the end (base end) on the bottom side of the wall.

[0077] Fig. 9 is a perspective view showing the appearance of an energy storage device 10b according to Modification 2. As shown in Fig. 9, in a container body 160b of a container 100b provided in the energy storage device 10b, a base end portion of a wall portion 162b includes two second recesses 102b. The two second recesses 102b are disposed at both ends of the container body 160b in the X-axis direction and penetrate the container body 160b in the Y-axis direction. Each second recess 102b is a recess that is recessed (cut out) into a rectangular shape (L-shape) when viewed in the Y-axis direction.

[0078] FIG. 10 is an exploded perspective view showing a container 100b according to Modification 2. Components other than the container 100b are not shown in FIG. 10 . As shown in FIG. 10 , a metal plate 190b is formed by bending a flat metal plate. Notches that become a first recess 101b and a second recess 102b are formed at both ends of the bent metal plate 190b in the X-axis direction. Metal plates 191b and 192b that are bent to correspond to the shapes of the ends are welded to both ends of the bent metal plate 190b in the X-axis direction, thereby forming a container body 160b having a cylindrical wall portion 162b.

[0079] Thereafter, the lid 170, to which the terminals 300, the external gaskets 400, the internal gaskets 500, the current collectors 600, and the electrode assembly 700 are attached, is aligned with the opening 163b of the container body 160b. After alignment, the entire periphery of the lid 170 overlaps with the entire periphery of the opening 163b. In this state, final welding is performed. In the final welding, the entire periphery of the lid 170 is continuously welded to the entire periphery of the opening 163b all the way around. This forms the container 100b. In this way, even when welding the lid 170 to the container body 160b, which has two first recesses 101b and two second recesses 102b, there is only one overlap, which prevents welding defects.

[0080] (Other Modifications) Although the energy storage element according to the embodiment of the present invention (including its modifications, the same applies hereinafter) has been described above, the present invention is not limited to the above-described embodiment. The embodiment disclosed herein is illustrative in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0081] In the above embodiment, the head unit 900 moves relative to the container body 160 and the lid 170. However, any configuration is possible as long as the entire peripheral edge of the lid 170 can be continuously welded around the entire peripheral edge of the opening 163. A movable optical system that reflects the laser light irradiated from the fixed head unit may be provided, and by moving the optical system, the laser light may be continuously irradiated around the entire peripheral edge of the lid 170 and the entire peripheral edge of the opening 163. In this case, the optical system includes at least one mirror, and the irradiation position of the laser light can be controlled by moving the at least one mirror or changing the attitude of the at least one mirror.

[0082] Furthermore, a variation mechanism may be provided that varies the posture and position of the container body 160 and the lid body 170 in the aligned state. In this case, the posture and position of the container body 160 and the lid body 170 may be varied by this variation mechanism, and the laser light from the head unit may be continuously irradiated around the entire periphery of the lid body 170 and the entire periphery of the opening 163.

[0083] Fig. 11 is an explanatory diagram showing a laser welding method in which the container body 160 and the lid body 170 according to Modification 3 are moved. In Fig. 11, the head unit 900c is fixed and irradiates laser light in the negative Y-axis direction. In this state, the moving mechanism moves the aligned container body 160 and the lid body 170 in the positive X-axis direction. This results in continuous laser welding of the boundary between the container body 160 and the lid body 170.

[0084] FIG. 12 is an explanatory diagram showing a laser welding method in which the container body 160 and the lid body 170 are moved according to Modification 4. In Modification 4, the lid body 170 is housed within the opening 163 of the container body 160. Therefore, the upper end of the container body 160 and the upper surface of the lid body 170 are flush with each other, and the boundary between them faces upward (in the positive Z-axis direction). The head unit 900d is fixed and irradiates laser light in the negative Z-axis direction. In this state, the moving mechanism moves the aligned container body 160 and the lid body 170 in the negative X-axis direction. This results in continuous laser welding of the boundary between the container body 160 and the lid body 170. In both cases of Figures 11 and 12, at the change of direction point, the fluctuation mechanism changes the posture of the container body 160 and the lid body 170, and then moves the container body 160 and the lid body 170 in a predetermined direction, thereby continuously welding the entire peripheral edge of the lid body 170 to the entire peripheral edge of the opening 163 all around.

[0085] By using at least two of a movable optical system, a movable head unit, and a moving mechanism, the laser light may be continuously irradiated around the entire periphery of the lid body 170 and the entire periphery of the opening 163.

[0086] In the above embodiment, the bottom 161 and the pair of first walls 164 are formed by bending the flat metal sheet 190, and the pair of second walls 165 are laser-welded to the bottom 161 and the pair of first walls 164 to form the container body 160. However, the method for forming the container body is not limited to this. The container body may also be formed by extrusion.

[0087] In the above embodiment, the first recess 101 has a rectangular shape when viewed in the Y-axis direction, but the first recess may have any shape as long as it penetrates in the Y-axis direction. Another example of the shape of the first recess is a staircase shape having at least one step. The same applies to the second recess.

[0088] The energy storage elements of the above-described embodiments and the like may be used in an energy storage device. In this case, the technology of the present invention may be applied to at least one energy storage element included in the energy storage device. FIG. 13 is an explanatory diagram showing an energy storage device 800 including energy storage elements 10 according to the embodiments. As shown in FIG. 13, a plurality of energy storage elements 10 are arranged inside the energy storage device 800. The energy storage device 800 may include bus bars (not shown) that electrically connect the energy storage elements 10. The energy storage device 800 may also include a status monitoring device (not shown) that monitors the status of one or more energy storage elements 10.

[0089] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0090] The present invention can be applied to an energy storage device such as a lithium ion secondary battery.

[0091] 10, 10b Energy storage element 100, 100b Container 101, 101b First recess 102b Second recess 160, 160a, 160b Container body 161 Bottom 162 Wall 163, 163a Opening 164 First wall 165 Second wall 170, 170a Lid 174a Step 177 Welded portion 178 Starting point 179 Ending point 190, 190b, 191, 191b, 192, 192b Sheet metal 300 Terminal 330 Terminal body 340 Shaft 600 Current collector 700 Electrode body 710 Body 711 Curved portion 712 Flat portion 720 Tab 800 Energy storage device 900 head part

Claims

1. A method for manufacturing an energy storage element comprising a container that houses an electrode body, the container comprising: a container body having an opening; and a lid body that closes the opening; the container body comprising: a bottom; and a cylindrical wall portion that rises from the entire periphery of the bottom and has the opening at its tip; the tip portion of the wall portion includes two first recesses formed by cutting out a portion of the wall portion; the lid body has a shape that corresponds to the shape of the opening in the wall portion; and the manufacturing method comprises continuously welding the entire periphery of the lid body to the entire periphery of the opening in the wall portion all the way around.

2. A method for manufacturing an energy storage element as described in claim 1, comprising: bending a flat plate to form the rectangular bottom portion and a pair of opposing first wall portions of the wall portion; and welding a pair of second wall portions to the bottom portion and the pair of first wall portions to form the container body.

3. The method for manufacturing an energy storage element according to claim 1 or 2, wherein one of the lid and the opening has a stepped portion formed therein into which the periphery of the other fits.

4. The method for manufacturing an energy storage element according to claim 1 or 2, wherein the two first recesses are provided only at the tip end of the wall portion.

5. The method for manufacturing an energy storage element according to claim 1 or 2, wherein the end of the wall portion on the bottom side includes two second recesses formed by cutting out parts of the wall portion.

6. An energy storage element comprising: an electrode body; and a container that houses the electrode body, wherein the container comprises: a container body having an opening; and a lid that closes the opening, wherein the container body comprises: a bottom; and a cylindrical wall that rises from the entire periphery of the bottom and has the opening at its tip, wherein the tip of the wall includes two first recesses formed by cutting out a portion of the wall, wherein the lid has a shape that corresponds to the shape of the opening in the wall, and wherein the lid and the opening in the wall form a weld that is continuously welded around the entire circumference, and the weld has only one overlapping portion.

Images