Power storage device

Abstract

This power storage device comprises: an electrode body that is obtained by stacking metal foils in a stacking direction, the electrode body including active material layer formation parts in which active material layers are formed on the metal foils, and active material layer non-formation parts in which no active material layers are formed on the metal foils; current collectors joined to the active material layer non-formation parts; and clips clasping the active material layer non-formation parts in the lamination direction. The electrode body includes the active material layer non-formation parts at both end parts thereof. The current collectors and the clips are provided to at least a portion of the active material layer non-formation parts. The clips are disposed at positions separated from joint parts between the active material layer non-formation parts and the current collectors.

Description

Energy storage element

[0001] The present invention relates to an energy storage element.

[0002] Conventionally, a battery configuration has been known for a prismatic secondary battery in which a positive electrode external terminal is electrically connected to a positive electrode of a wound electrode group via a positive electrode current collector, and a negative electrode external terminal is electrically connected to a negative electrode of the wound electrode group via a negative electrode current collector (see, for example, Patent Document 1).

[0003] JP 2014-072190 A

[0004] In recent years, there has been a demand for an energy storage element that can further reduce the electrical resistance from the wound electrode group to each external terminal.

[0005] Therefore, an object of the present invention is to provide an energy storage element capable of further reducing electrical resistance.

[0006] An energy storage element according to one embodiment of the present invention comprises an electrode body in which metal foils are stacked in a stacking direction, the electrode body having an active material layer-forming portion in which an active material layer is formed on the metal foil and an active material layer-non-forming portion in which the active material layer is not formed on the metal foil, a current collector joined to the active material layer-non-forming portion, and a clip that clamps the active material layer-non-forming portion in the stacking direction, the electrode body having the active material layer-non-forming portion at both ends, the current collector and the clip being provided on at least a part of the active material layer-non-forming portion, and the clip being positioned away from the joint between the active material layer-non-forming portion and the current collector.

[0007] According to the present invention, it is possible to provide an energy storage element capable of reducing electrical resistance.

[0008] 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 plan view showing a pair of positive electrode side clips and their periphery according to an embodiment, as viewed from the Y axis direction. FIG. 5 is a side view of the positive electrode side clip according to an embodiment, as viewed from the X axis direction. FIG. 6 is a cross-sectional view of the positive electrode side clip according to an embodiment, as viewed from the Z axis direction. FIG. 7 is a side view of the positive electrode side clip according to Modification 1, as viewed from the X axis direction. FIG. 8 is a cross-sectional view of the positive electrode side clip according to Modification 2, as viewed from the Z axis direction. FIG. 9 is a plan view of the pair of positive electrode side clips and their periphery according to Modification 3, as viewed from the Y axis direction. FIG. 10 is a perspective view of the positive electrode side clip according to Modification 3. FIG. 11 is a plan view of the positive electrode side end of an electrode body according to Modification 4, as viewed from the Y axis direction. FIG. 12 is a plan view of the positive electrode side end of an electrode body according to Modification 5, as viewed from the Y axis direction. FIG. 13 is an explanatory diagram showing an energy storage device including an energy storage element according to an embodiment.

[0009] (1) An energy storage element according to one aspect of the present invention comprises an electrode body in which metal foils are stacked in a stacking direction, the electrode body comprising an active material layer-forming portion in which an active material layer is formed on the metal foil, and an active material layer-non-forming portion in which the active material layer is not formed on the metal foil, a current collector joined to the active material layer-non-forming portion, and a clip that clamps the active material layer-non-forming portion in the stacking direction, the electrode body having the active material layer-non-forming portion at both ends, the current collector and the clip being provided on at least a part of the active material layer-non-forming portion, and the clip being positioned away from the joint between the active material layer-non-forming portion and the current collector.

[0010] According to the energy storage element described in (1) above, at least a portion of the active material layer-free portions provided at both ends of the electrode body is clamped by clips, so that the active material layer-free portions of each layer can be electrically connected by the clips. This allows regions other than the joints in the active material layer-free portions to be electrically connected, thereby reducing electrical resistance. This makes it possible to provide an energy storage element that can reduce electrical resistance.

[0011] (2) In the energy storage element described in (1) above, the current collector may include a terminal joint portion to which a terminal is joined, and a leg portion extending from the terminal joint portion in a direction intersecting the stacking direction and joined to the active material layer non-forming portion.

[0012] According to the energy storage element described in (2) above, the clip is positioned away from the joint between the leg portion of the current collector and the portion without an active material layer, so the clip does not get in the way when joining the leg portion to the portion without an active material layer. This makes it possible to facilitate the joining work. Furthermore, as a secondary effect of the clip of the present invention, the leg portion of the current collector and the portion without an active material layer can be joined after the clip is positioned, which prevents metal contamination generated during a joining process such as welding from scattering onto the surface of the portion with an active material layer of the electrode body, thereby reducing the occurrence of problems with the energy storage element due to metal contamination.

[0013] (3) In the energy storage element described in (1) or (2) above, the electrode body may have a recess formed by cutting out a portion of the active material layer non-forming portion, and the clip may be positioned at a position corresponding to the recess.

[0014] According to the energy storage element described in (3) above, the clip is disposed at a position corresponding to the recess of the electrode body, and therefore, the provision of the clip prevents the generation of extra space between the electrode body and the inner surface of the energy storage element container, thereby reducing electrical resistance and suppressing an increase in the volume of the energy storage element due to the clip.

[0015] (4) In the energy storage element described in (3) above, the recess may have a first side portion and a second side portion extending in different directions when viewed from the stacking direction, and the clip may have a first portion that sandwiches the first side portion in the stacking direction and a second portion that sandwiches the second side portion in the stacking direction.

[0016] According to the energy storage element described in (4) above, the first part of the clip sandwiches the first side portion, and the second part sandwiches the second side portion, so that the area of ​​the active material layer-free portion that is electrically connected by the clip can be increased, thereby further reducing the electrical resistance.

[0017] (5) In the energy storage element described in (2) above, the electrode body may be rectangular when viewed from the stacking direction, and the clip may be spaced apart from the leg portion in the intersecting direction.

[0018] According to the energy storage element described in (5) above, the clips are positioned away from the legs in the direction in which the legs extend (the intersecting direction), so the clips are less likely to get in the way when joining the legs to the portions without an active material layer. This makes it possible to easily perform the joining process. This also applies to the procedure in which the legs are first joined to the portions without an active material layer and then the portions without an active material layer are clamped with the clips.

[0019] (6) In the energy storage device according to any one of (1) to (5) above, an edge of the active material layer-free portion may be in contact with the clip.

[0020] According to the energy storage element described in (6) above, the edge of the active material layer-free portion is in contact with the clip, so that the contact area of ​​the active material layer-free portion with the clip can be increased, thereby further reducing the electrical resistance.

[0021] (Embodiments) Hereinafter, with reference to the drawings, an energy storage element according to an embodiment of the present invention (including its modified examples) 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 each component (each component) in this embodiment are those used in this embodiment and may differ from the names of each component (each component) in the background art.

[0022] 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 Ωm or more, more preferably 1×10 １０ It is preferable that the insulating material has a resistance of Ωm or more. In the following description, the term "insulating" means "electrically insulating."

[0023] 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.

[0024] [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 a perspective view showing each component when the energy storage element 10 according to the embodiment is disassembled.

[0025] 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.

[0026] 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 be a primary battery instead of a secondary battery. Furthermore, the energy storage element 10 may be an all-solid-state lithium battery using a solid electrolyte, or a polymer lithium battery.

[0027] The energy storage element 10 has a rectangular parallelepiped shape (square, rectangular) in which the length in the X-axis direction is longer than the Y-axis direction and the length in the X-axis direction is longer than the Z-axis direction. In particular, in this embodiment, the energy storage element 10 has a rectangular parallelepiped shape in which the length in the Z-axis direction is longer than 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, two pairs of clips 650, and an electrode assembly 700 are housed inside the container 100. Specifically, the positive electrode components (terminals 300, external gasket 400, internal gasket 500, current collectors 600, and a pair of clips 650, etc.; the same applies below) are arranged 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 refers to the range from the end face of the container 100 in the positive X-axis direction where the positive electrode components are arranged. The first side surface portion 110 is a portion in the X-axis direction that is within a range of 1% to 15% of the length of the container 100 from the end face of the container 100 in the positive X-axis direction.

[0028] The components of the negative electrode are disposed on a second side surface portion 120 in the negative X-axis direction of the container 100. 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 15% of the length of the container 100 from the end surface of the container 100 in the negative X-axis direction.

[0029] 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.

[0030] The container 100 is a case having an external shape (approximately rectangular parallelepiped shape) based on a rectangular parallelepiped shape that is elongated 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 reference rectangular parallelepiped shape is illustrated by a two-dot chain line L1. Specifically, the container 100 has an external shape that is elongated and flat in the X-axis direction, with rectangular notches formed at the top and bottom of both ends in the X-axis direction. When viewed from the reference rectangular parallelepiped shape, each notch can be considered to form a recess. Of the multiple notches, a pair of notches located at the top of the container 100 each form a first recess 101, and a pair of notches located at the bottom of the container 100 each form a second recess 102. In other words, the first side surface portion 110 and the second side surface portion 120 of the container 100 each have a first recess 101 and a second recess 102 formed at different positions in the Z-axis direction so as to face each other in the Z-axis direction. A terminal 300 is disposed in the first recess 101, and a gas exhaust valve 800 is disposed in the second recess 102. The gas exhaust valve 800 is a safety valve that releases pressure inside the container 100 when the pressure rises excessively.

[0031] Specifically, the first side surface portion 110 has a first upper side surface 111, a first top surface 112, a first middle side surface 113, a first bottom surface 114, and a first lower side surface 115, and is elongated in the Z-axis direction when viewed in the X-axis direction. The first upper side surface 111 is located at the top of the first side surface portion 110 and is a rectangular plane parallel to the YZ plane and elongated in the Z-axis direction. The first top surface 112 is a plane extending from the lower end of the first upper side surface 111 in the positive X-axis direction, and is a rectangular plane parallel to the XY plane and elongated in the X-axis direction. The first middle side surface 113 is a plane extending downward from the end of the first upper surface 112 in the positive X-axis direction, and is a rectangular plane parallel to the YZ plane and elongated in the Z-axis direction. The first lower surface 114 is a plane extending from the lower end of the first middle side surface 113 in the negative X-axis direction, and is a rectangular plane parallel to the XY plane and elongated in the X-axis direction. The first lower side surface 115 is a plane that extends downward from the end of the first lower surface 114 in the negative X-axis direction, and is a rectangular plane that is parallel to the YZ plane and elongated in the Z-axis direction.

[0032] 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 this way, the inner wall surface of the first recess 101 of the first side surface portion 110 has the first upper side surface 111 (an example of a first surface) and the first top surface 112 (an example of a second surface) that extend in different directions when viewed from the Y-axis direction.

[0033] The second recess 102 of the first side surface portion 110 is formed by a first lower surface 114 and a first lower side surface 115, and is open at its end in the negative Z-axis direction and its end in the positive X-axis direction, penetrating in the Y-axis direction. In this way, the inner wall surface of the second recess 102 of the first side surface portion 110 includes the first lower side surface 115 (an example of a first surface) and the first lower surface 114 (an example of a second surface) that extend in different directions when viewed from the Y-axis direction.

[0034] In other words, the first recess 101 of the first side surface portion 110 is a recess in which a corner portion of the container 100 in the positive X-axis direction and the positive Z-axis direction is recessed (cut out) into a quadrangular (L-shaped) shape when viewed from the Y-axis direction. The second recess 102 of the first side surface portion 110 is a recess in which a corner portion of the container 100 in the positive X-axis direction and the negative Z-axis direction is recessed (cut out) into a quadrangular (L-shaped) shape when viewed from the Y-axis direction.

[0035] The second side surface portion 120 has a second upper side surface 121, a second top surface 122, a second middle side surface 123, a second bottom surface 124, and a second lower side surface 125, and is elongated in the Z-axis direction when viewed in the X-axis direction. The second upper side surface 121 is located at the top of the second side surface portion 120 and is a rectangular plane parallel to the YZ plane and elongated in the Z-axis direction. The second top surface 122 is a plane extending from the lower end of the second upper side surface 121 in the negative X-axis direction and is a rectangular plane parallel to the XY plane and elongated in the X-axis direction. The second middle side surface 123 is a plane extending downward from the end of the second upper surface 122 in the negative X-axis direction and is a rectangular plane parallel to the YZ plane and elongated in the Z-axis direction. The second lower surface 124 is a plane extending from the lower end of the second middle side surface 123 in the positive X-axis direction and is a rectangular plane parallel to the XY plane and elongated in the X-axis direction. The second lower side surface 125 is a plane that extends downward from the end of the second lower surface 124 in the positive X-axis direction, and is a rectangular plane that is parallel to the YZ plane and elongated in the Z-axis direction.

[0036] 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 the end portion facing the positive Z-axis direction and the end portion facing the negative X-axis direction are open and penetrate the Y-axis direction. In this way, the inner wall surface of the first recess 101 of the second side surface portion 120 has the second upper side surface 121 (an example of a first surface) and the second top surface 122 (an example of a second surface) that extend in different directions when viewed from the Y-axis direction.

[0037] The second recess 102 of the second side surface portion 120 is formed by a second lower surface 124 and a second lower side surface 125, and its end in the negative Z-axis direction and its end in the negative X-axis direction are open and penetrate the Y-axis direction. In this way, the inner wall surface of the second recess 102 of the second side surface portion 120 has the second lower side surface 125 (an example of a first surface) and the second lower surface 124 (an example of a second surface) that extend in different directions when viewed from the Y-axis direction.

[0038] In other words, the first recess 101 of the second side surface portion 120 is a recess in which a corner of the container 100 in the negative X-axis direction and the positive Z-axis direction is recessed (cut out) into a quadrangular shape when viewed from the Y-axis direction. The second recess 102 of the second side surface portion 120 is a recess in which a corner of the container 100 in the negative X-axis direction and the negative Z-axis direction is recessed (cut out) into a quadrangular shape when viewed from the Y-axis direction.

[0039] 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.

[0040] 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 lower side face 115 of the first side face portion 110 and the lower end of the second lower side face 125 of the second side face portion 120.

[0041] 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 has a pair of long sides 130 and a bottom surface 150. The lid 170 has a first upper side surface 111, a first top surface 112, a first middle side surface 113, a first bottom surface 114, a first lower side surface 115, a second upper side surface 121, a second top surface 122, a second middle side surface 123, a second bottom surface 124, a second lower side surface 125, and a top surface 140.

[0042] Specifically, the container body 160 is a generally U-shaped metal plate that is open at the top when viewed from the X-axis direction. The container body 160 has flat long side wall portions that form a pair of long sides 130 at both ends in the Y-axis direction, and a flat, rectangular bottom wall portion that forms the bottom surface 150 at the end in the negative Z-axis direction.

[0043] The lid 170 is a metal plate that is open downward when viewed in the Y-axis direction. The lid 170 has a curved plate portion forming a first upper side surface 111, a first top surface 112, a first middle side surface 113, a first bottom surface 114, and a first bottom side surface 115 at its end in the positive X-axis direction, a curved plate portion forming a second upper side surface 121, a second top surface 122, a second middle side surface 123, a second bottom surface 124, and a second bottom side surface 125 at its end in the negative X-axis direction, and a flat, rectangular top wall portion forming a top surface 140 at its end in the positive Z-axis direction. A gas exhaust valve 800 is provided in the lid 170 at portions corresponding to the first bottom side surface 115 and the second bottom side surface 125.

[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, an aluminum alloy, iron, or plated steel sheet.

[0045] Although not shown, a liquid injection portion is formed on the lid 170. The liquid injection portion is a portion for injecting an electrolyte into the container 100 when the energy storage element 10 is manufactured.

[0046] 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, and the terminals 300 (positive electrode terminal 310 and negative electrode terminal 320) are formed, for example, 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.

[0047] 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.

[0048] The current collectors 600 are arranged on both sides of the electrode body 700 in the X-axis direction, and are connected (joined) to the electrode body 700 and the terminal 300. These current collectors (positive electrode current collector 610 and negative electrode current collector 620) are conductive current collectors that electrically connect the electrode body 700 and the terminal 300. Specifically, the current collector 600 integrally includes a leg 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 terminal joint portion 640 that is connected (joined) to the terminal 300 by crimping, welding, or the like, as described above. The leg portion 630 and the terminal joint portion 640 are each flat plate-shaped portions formed by bending a single piece of sheet metal. The leg portion 630 extends from the terminal joint portion 640 in the negative Z-axis direction. The material of the current collector 600 is not particularly limited, but for example, 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.

[0049] 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 obtained by adding a filler to any of these resins.

[0050] [Electrode Body] The electrode body 700 is an electricity 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 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, for example, 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. For example, 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.

[0051] 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. For example, 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.

[0052] 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.

[0053] The positive electrode plate 740 is an electrode plate having a positive electrode active material layer-forming portion 742 in which a positive electrode active material layer is formed on both sides of a positive electrode current collector foil 741, which is a long strip of metal foil. A positive electrode active material layer-non-forming portion 744 in which a positive electrode active material layer is not formed on the positive electrode current collector foil 741 is provided at the end of the positive electrode plate 740 in the X-axis positive direction. The positive electrode active material layer-forming portion 742 is an example of an active material layer-forming portion, and the positive electrode active material layer-non-forming portion 744 is an example of an active material layer-non-forming portion. The positive electrode current collector foil 741 is made of aluminum, an aluminum alloy, or the like.

[0054] The negative electrode plate 750 is an electrode plate having a negative electrode active material layer-forming portion 752 in which a negative electrode active material layer is formed on both sides of a negative electrode current collector foil 751, which is a long strip of metal foil. An anode active material layer-non-forming portion 754 in which a negative electrode active material layer is not formed on the negative electrode current collector foil 751 is provided at the end of the negative electrode plate 750 in the negative X-axis direction. The negative electrode active material layer-forming portion 752 is an example of an active material layer-forming portion, and the negative electrode active material layer-non-forming portion 754 is an example of an active material layer-non-forming portion. Copper, a copper alloy, or the like is used for the negative electrode current collector foil 751.

[0055] As the positive electrode active material used in the positive electrode active material layer forming portion 742 and the negative electrode active material used in the negative electrode active material layer forming portion 752, any known material can be used as long as it is capable of absorbing and releasing charge transport ions.

[0056] Specifically, LiMPO is used as the positive electrode active material. ４ , LiMSiO４ , 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.

[0057] 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.

[0058] 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.

[0059] A plurality of protruding pieces 743 protruding outward are arranged at intervals on the edge of the positive X-axis direction of the positive electrode plate 740. Each protruding piece 743 is a portion where no positive electrode active material layer is disposed and the positive electrode current collector foil 741 is exposed. A strip-shaped portion 745 continuous with each protruding piece 743 is provided on the end of the positive X-axis direction of the positive electrode plate 740, and this strip-shaped portion 745 is also a portion where no positive electrode active material layer is disposed and the positive electrode current collector foil 741 is exposed. In other words, the positive electrode active material layer-free portion 744 includes each protruding piece 743 and the strip-shaped portion 745.

[0060] 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 protruding piece 753 is a portion where no negative electrode active material layer is disposed and the negative electrode current collector foil 751 is exposed. The end of the negative electrode plate 750 in the X-axis negative direction is provided with a strip-shaped portion 755 continuous with each protruding piece 753, and the strip-shaped portion 755 is also a portion where no negative electrode active material layer is disposed and the negative electrode current collector foil 751 is exposed. In other words, the negative electrode active material layer-free portion 754 includes each protruding piece 753 and the strip-shaped portion 755. In FIG. 3 , the positive electrode active material layer-free portion 744 and the negative electrode active material layer-free portion 754 are indicated by diagonal lines.

[0061] When the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 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 region where multiple pieces (protruding pieces 743) of the electrode plates (positive electrode plate 740 and negative electrode plate 750) of the same polarity are stacked. Here, the strip-shaped portion 745 of the positive electrode active material layer non-forming portion 744 does not overlap the negative electrode plate 750 or the separators 761 and 762, but protrudes from them in the positive direction of the X axis. When the positive electrode active material layer non-forming portion 744 is viewed from the Y-axis direction after winding, rectangularly cut-out recesses 746 and 747 are provided on both sides of the positive electrode tab portion 721 in the Z-axis direction. The recess 746 is disposed in the positive direction of the positive electrode tab portion 721 in the Z-axis direction, and the recess 747 is disposed in the negative direction of the positive electrode tab portion 721 in the Z-axis direction. The recesses 746 and 747 are portions that penetrate in the Y-axis direction and include first side portions 7461 and 7471 and second side portions 7462 and 7472 that extend in different directions when viewed from the Y-axis direction. Specifically, the first side portions 7461 and 7471 extend linearly in the X-axis direction, and the second side portions 7462 and 7472 extend linearly in the Z-axis direction.

[0062] Similarly, the portion of the negative electrode plate 750 where multiple protruding pieces 753 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is a region where multiple pieces (protruding pieces 753) provided on the electrode plate (negative electrode plate 750) of the same polarity among multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked. Here, the strip portion 755 of the negative electrode active material layer non-forming portion 754 does not overlap the positive electrode plate 740 or the separators 761, 762 and protrudes from them in the negative X-axis direction. When the negative electrode active material layer non-forming portion 754 is viewed from the Y-axis direction after winding, rectangular recesses 756, 757 are provided on both sides of the negative electrode tab portion 722 in the Z-axis direction. The recesses 756, 757 are portions that penetrate in the Y-axis direction and include first sides 7561, 7571 and second sides 7562, 7572 that extend in different directions when viewed from the Y-axis direction. Specifically, the first sides 7561, 7571 extend linearly in the X-axis direction, and the second sides 7562, 7572 extend linearly in the Z-axis direction.

[0063] As such, the electrode body 700 comprises a main body portion 710 that constitutes the main body of the electrode body 700, and a positive electrode active material layer non-forming portion 744 and a negative electrode active material layer non-forming portion 754 that protrude from each end face of the main body portion 710 in the X-axis direction.

[0064] The main body 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 forming portion 742 is arranged (formed, coated), a portion of the negative electrode plate 750 where the negative electrode active material layer forming portion 752 is arranged (formed, coated), and separators 761, 762. The outer surface of the main body 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.

[0065] 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 from 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. In the wound electrode body 700, the flat portion 712 is a main portion, so the stacking direction of the electrode plates is the Y-axis direction.

[0066] 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.).

[0067] 2 , the pair of clips 650 on the positive electrode side are disposed in the positive electrode active material layer non-forming portion 744, and the pair of clips 650 on the negative electrode side are disposed in the negative electrode active material layer non-forming portion 754. The pair of clips 650 on the positive electrode side are formed of a conductive material such as aluminum or an aluminum alloy, similar to the positive electrode current collector foil 741. The pair of clips 650 on the negative electrode side are formed of a conductive material such as copper or a copper alloy, similar to the negative electrode current collector foil 751.

[0068] Here, the pair of clips 650 on the positive electrode side and the pair of clips 650 on the negative electrode side are made of different materials but have basically the same configuration. Therefore, the pair of clips 650 on the positive electrode side will be described in detail, and a description of the pair of clips 650 on the negative electrode side will be omitted.

[0069] Fig. 4 is a plan view of a pair of clips 650 on the positive electrode side according to an embodiment and their periphery as viewed from the Y-axis direction. Fig. 5 is a side view of the clip 650 on the positive electrode side according to an embodiment as viewed from the X-axis direction. Fig. 6 is a cross-sectional view of the clip 650 on the positive electrode side according to an embodiment as viewed from the Z-axis direction. Fig. 6 is a cross-sectional view of a cut surface including line VI-VI shown in Fig. 4.

[0070] As shown in Figures 4 to 6, each clip 650 is a member formed by bending a flat plate material into a generally U-shape. Each clip 650 is disposed in a recess 746, 747 of a positive electrode active material layer non-forming portion 744 in the electrode assembly 700. Therefore, each clip 650 is disposed at a position spaced apart from the leg portion 630 of the current collector 600. In Figure 4, the joint 690 between the leg portion 630 and the positive electrode tab portion 721 of the electrode assembly 700 is indicated by a dashed line. In this way, each clip 650 can be said to be disposed at a position spaced apart from the joint 690.

[0071] Specifically, the clip 650 corresponding to the recess 746 in the positive direction of the Z axis is disposed on the second side 7462 of the recess 746, sandwiching the second side 7462 in the Y axis direction. The clip 650 corresponding to the recess 747 in the negative direction of the Z axis is disposed on the second side 7472 of the recess 747, sandwiching the second side 7472 in the Y axis direction. As shown in FIGS. 5 and 6 , each clip 650 sandwiches and compresses the entire layer consisting of the strip-shaped portion 745 of the positive electrode active material layer non-forming portion 744. This brings adjacent layers into close contact with each other.

[0072] Each clip 650 is fixed to the positive electrode active material layer non-forming portion 744 by clamping the positive electrode active material layer non-forming portion 744. In other words, each clip 650 does not necessarily have to be welded to the positive electrode active material layer non-forming portion 744. This can prevent contamination caused by welding.

[0073] 6, the edges in the positive X-axis direction of all layers made up of the strip-shaped portion 745 are in contact with the clip 650. It is sufficient that the edges in the positive X-axis direction of at least one layer are in contact with the clip 650, and it is not necessary that the edges in the positive X-axis direction of all layers are in contact with the clip 650.

[0074] Because the active material layer-free portions of the electrode body 700 (the positive electrode active material layer-free portion 744 and the negative electrode active material layer-free portion 754) are clamped by the clips 650, the active material layer-free portions, which have weak mechanical strength, can be reinforced by the clips 650. This makes it possible to improve the vibration and impact resistance of the electrode body 700. In particular, in the case of a wound-type electrode body 700, higher vibration and impact resistance can be achieved by combining the curved portion 711 of the electrode body 700 with the clips 650. From the viewpoint of mechanical strength, it is preferable to weld the clips 650 to the active material layer-free portions.

[0075] [Explanation of Effects] As described above, according to the embodiment, at least one of the active material layer-free portions (positive electrode active material layer-free portion 744, negative electrode active material layer-free portion 754) provided at both ends of the electrode body 700 is clamped by the clip 650. This allows the active material layer-free portions to be tightly attached by the clip 650 and to be electrically conductive. As a result, regions other than the joint portion 690 in the active material layer-free portion are also electrically conductive, thereby reducing electrical resistance.

[0076] Since the clip 650 is positioned away from the joint 690 between the leg portion 630 of the current collector 600 and the portion without an active material layer, the clip 650 is unlikely to get in the way when joining the leg portion 630 to the portion without an active material layer.

[0077] Since the clips 650 are disposed at positions corresponding to the recesses 746, 747, 756, and 757 of the electrode assembly 700, electrical resistance can be reduced while the clips 650 are housed within the recesses 746, 747, 756, and 757. This makes it possible to suppress an increase in space consumption due to the clips 650.

[0078] Since the edge of the portion without an active material layer is in contact with the clip 650, it is possible to increase the contact area of ​​the portion without an active material layer with the clip 650. This makes it possible to further reduce the electrical resistance.

[0079] [Explanation of Modifications] Modifications of the above-described embodiment will be described below. In the following description, the same parts as those in the above-described embodiment or other modifications will be given the same reference numerals and their description may be omitted. In the following description, the positive electrode side will be exemplified, but the same applies to the negative electrode side.

[0080] (Variation 1) In the above embodiment, the case where the entire layer made up of the positive electrode active material layer non-forming portion 744 is clamped by one clip 650 has been exemplified. However, the entire layer made up of the positive electrode active material layer non-forming portion 744 may be divided into a plurality of parts and clamped by a plurality of clips. An example of this will be described in Variation 1.

[0081] 7 is a side view of the positive electrode clip 650a according to Modification 1, as viewed from the X-axis direction. As shown in FIG. 7, the entire layer made up of the positive electrode active material layer non-forming portion 744 is divided into two. Specifically, in the wound electrode body 700, the multiple layers made up of the positive electrode active material layer non-forming portion 744 are divided into two with respect to the middle portion in the Y-axis direction. One of the divided portions is clamped by one clip 650a, and the other is clamped by another clip 650a.

[0082] (Variation 2) In the above embodiment, clip 650 formed by bending a flat plate material into a substantially U-shape was exemplified. However, the shape of the clip may be any shape as long as it can clamp multiple layers made of active material layer-free portions. In Variation 2, an example of another shape of the clip will be described.

[0083] 8 is a cross-sectional view of a positive electrode side clip 650b according to Modification 2, as viewed from the Z-axis direction. As shown in FIG. 8, clip 650b is a member formed by bending a flat plate material into a substantially V-shape. In this case, too, the edges of all layers of strip portion 745 in the positive direction of the X-axis are in contact with clip 650b.

[0084] (Variation 3) In Variation 3, an example of another shape of the clip will be described. FIG. 9 is a plan view of a pair of positive electrode side clips 650c and their periphery according to Variation 3, as viewed from the Y-axis direction. FIG. 10 is a perspective view of the positive electrode side clip 650c according to Variation 3. As shown in FIGS. 9 and 10 , the clip 650c according to Variation 3 integrally includes a first portion 660c and a second portion 670c. Specifically, the first portion 660c is formed in a U-shape and extends in the Z-axis direction. The second portion 670c is formed in a U-shape and extends in the X-axis direction. The base end of the first portion 660c and the base end of the second portion 670c are connected.

[0085] 9 , the clip 650c corresponding to the recess 746 in the positive Z-axis direction has the first portion 660c sandwiching the first side portion 7461 of the recess 746 in the Y-axis direction and the second portion 670c sandwiching the second side portion 7462 in the Y-axis direction. The clip 650c corresponding to the recess 747 in the negative Z-axis direction has the first portion 660c sandwiching the first side portion 7471 of the recess 747 in the Y-axis direction and the second portion 670c sandwiching the second side portion 7472 in the Y-axis direction.

[0086] In this way, first portion 660c of clip 650c sandwiches first side portions 7461, 7471, and second portion 670c sandwiches second side portions 7462, 7472, so that the area of ​​the active material layer-free portion that is electrically connected by clip 650c can be increased, thereby further reducing electrical resistance.

[0087] (Variation 4) In the above embodiment, the electrode body 700 has been exemplified in which the portion 744 without a positive electrode active material layer formed includes the positive electrode tab portion 721 and the strip portion 745, and the portion 754 without a negative electrode active material layer formed includes the negative electrode tab portion 722 and the strip portion 755. In Variation 4, a case will be described in which the portion without a positive electrode active material layer formed includes only the positive electrode tab portion, and the portion without a negative electrode active material layer formed includes only the negative electrode tab portion.

[0088] 11 is a plan view of the positive electrode side end of an electrode body 700d according to Modification 4, as viewed from the Y-axis direction. As shown in Fig. 11, in the electrode body 700d, a positive electrode active material layer forming portion 742d is arranged in a region in the negative X-axis direction from a positive electrode tab portion 721d. The positive electrode tab portion 721d is formed from a positive electrode active material layer non-forming portion 744d.

[0089] Clip 650d corresponding to recess 746d is disposed on a first side 7461d of recess 746d, sandwiching first side 7461d in the Y-axis direction. Clip 650d corresponding to recess 747d is disposed on a first side 7471d of recess 747d, sandwiching first side 7471d in the Y-axis direction. In this case, the area of ​​the active material layer formation portion can be increased, and the electrical capacitance can be increased.

[0090] (Modification 5) In the above embodiment, an example was given of the electrode body 700 that includes the recesses 746, 747, 756, and 757. In Modification 5, a case will be described in which the electrode body has a rectangular shape when viewed in the Y-axis direction.

[0091] Fig. 12 is a plan view of the positive electrode side end of an electrode assembly 700e according to Modification 5, as viewed from the Y-axis direction. In Fig. 12, the outline of the container 100e is indicated by a two-dot chain line. The container 100e has a rectangular shape when viewed from the Y-axis direction.

[0092] The positive electrode active material layer non-forming portion 744e of the electrode body 700e is formed in a band shape and wound up. A clip 650e is attached to the positive electrode active material layer non-forming portion 744e at a position separated from the leg portion 630 of the current collector 600 in the negative Z-axis direction.

[0093] In this way, the clips 650e are positioned apart from the legs 630 in the direction in which the legs 630 extend (the Z-axis direction), so the clips 650e are less likely to get in the way when joining the legs 630 to the positive-electrode active material layer-free portions 744e. This makes it possible to easily perform the joining work. This also applies to the procedure in which the legs 630 are first joined to the positive-electrode active material layer-free portions 744e and then the positive-electrode active material layer-free portions 744e are clamped with the clips 650e.

[0094] (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.

[0095] In the above embodiment, the current collector 600 is illustrated as having the terminal joint portion 640 and the leg portion 630. However, the electrode body may have any shape as long as it is joined to the terminal and the electrode body 700.

[0096] 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 900 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 900. The energy storage device 900 may include bus bars (not shown) that electrically connect the energy storage elements 10. The energy storage device 900 may also include a status monitoring device (not shown) that monitors the status of one or more energy storage elements 10.

[0097] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0098] The present invention can be applied to an energy storage device such as a lithium ion secondary battery.

[0099] REFERENCE SIGNS LIST 10 Energy storage element 100, 100e Container 160 Container body 170 Lid 300 Terminal 600 Current collector 630 Leg portion 640 Terminal joint portion 650, 650a, 650b, 650c, 650d, 650e Clip 660c First portion 670c Second portion 690 Joint portion 700, 700d, 700e Electrode body 720 Tab portion 721, 721d Positive electrode tab portion 722 Negative electrode tab portion 740 Positive electrode plate 741 Positive electrode current collector foil (metal foil) 742, 742d Positive electrode active material layer forming portion (active material layer forming portion) 743, 753 Protruding piece 744, 744d, 744e Positive electrode active material layer non-forming portion (active material layer non-forming portion) 745, 755 Strip-shaped portion 746, 746d, 747, 747d, 756, 757 Recessed portion 750 Negative electrode plate 751 Negative electrode current collector foil (metal foil) 752 Negative electrode active material layer formed portion (active material layer formed portion) 754 Negative electrode active material layer non-forming portion (active material layer non-forming portion) 761, 762 Separator 800 Gas release valve 900 Electricity storage device 7461, 7461d, 7471, 7471d, 7561, 7571 First side portion 7462, 7472, 7562, 7572 Second side portion

Claims

1. An energy storage element comprising: an electrode body in which metal foils are stacked in a stacking direction, the electrode body comprising an active material layer-formed portion where an active material layer is formed on the metal foil, and an active material layer-non-formed portion where the active material layer is not formed on the metal foil; a current collector joined to the active material layer-non-formed portion; and a clip that clamps the active material layer-non-formed portion in the stacking direction, wherein the electrode body has the active material layer-non-formed portion at both ends, the current collector and the clip are provided on at least a part of the active material layer-non-formed portion, and the clip is located at a position away from the joint between the active material layer-non-formed portion and the current collector.

2. The energy storage element according to claim 1, wherein the current collector comprises: a terminal joint portion to which a terminal is joined; and a leg portion extending from the terminal joint portion in a direction intersecting the stacking direction and joined to the portion where an active material layer is not formed.

3. The energy storage element according to claim 1 or 2, wherein the electrode body has a recess formed by cutting out a part of the active material layer non-forming portion, and the clip is disposed at a position corresponding to the recess.

4. The energy storage element according to claim 3, wherein the recess has a first side portion and a second side portion extending in different directions when viewed from the stacking direction, and the clip has a first portion that sandwiches the first side portion in the stacking direction and a second portion that sandwiches the second side portion in the stacking direction.

5. The energy storage element according to claim 2, wherein the electrode body has a rectangular shape when viewed from the stacking direction, and the clip is disposed spaced apart from the leg portion in the intersecting direction.

6. The energy storage element according to claim 1 or 2, wherein an edge of the portion without an active material layer is in contact with the clip.

Images