Energy storage element

Abstract

A power storage element provided with an electrode assembly comprising a winding of a plurality of electrode plates (positive electrode plates and negative electrode plates), and a container containing the electrode assembly. The electrode assembly is provided with: a body portion having a flat portion and a pair of curved portions sandwiching the flat portion; and a plurality of tab portions formed by laminating a plurality of sections (protruding sections) of the electrode plates of the same polarity among the plurality of electrode plates, a pair of the tab portions protruding from each of the end surfaces of the body portion in a winding axis direction. Of the plurality of tab portions, at least one tab portion (positive electrode tab portion) includes a bend portion continuous with the curved portion, and a pair of extending portions extending from the bend portion and continuous with the flat portion.

Description

Technical Field

[0001] The present invention relates to a power storage element including an electrode body.

Background Art

[0002] Conventionally, in a power storage element, a power storage element in which an electrode body formed by winding electrode plates is housed in a container is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, when a power storage element is subjected to an impact or the like, the electrode body in the container may vibrate and be damaged.

[0005] An object of the present invention is to provide a power storage element capable of suppressing damage to an electrode body.

Means for Solving the Problems

[0006] A power storage element according to an aspect of the present invention is a power storage element including an electrode body in which a plurality of electrode plates are wound and a container that houses the electrode body, the electrode body including a main body portion having a flat portion and a pair of curved portions sandwiching the flat portion, and a plurality of tab portions formed by laminating a plurality of pieces of electrode plates having the same polarity and projecting from both end faces of the main body portion in the winding axis direction, and at least one of the plurality of tab portions having a bent portion continuous with the curved portion and a pair of extending portions extending from the bent portion and continuous with the flat portion.

Effects of the Invention

[0007] According to the present invention, it is possible to provide an energy storage element that can suppress damage to the electrode body. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view showing the external appearance of an energy storage element according to an embodiment. [Figure 2] Figure 2 is an exploded perspective view showing the individual components of the energy storage element according to the embodiment. [Figure 3] Figure 3 is a perspective view showing the configuration of the electrode body according to the embodiment. [Figure 4] Figure 4 is a schematic diagram showing the general configuration of the positive electrode tab portion according to the embodiment. [Figure 5] Figure 5 is a schematic diagram showing the state in which the positive electrode tab portion according to the embodiment is joined to the current collector. [Figure 6] Figure 6 is a perspective view showing a current collector according to a modified example 1 of the embodiment. [Figure 7] Figure 7 is a front view showing a current collector according to a modified example 1 of the embodiment. [Figure 8] Figure 8 is a front view showing the current collector and positive electrode tab portion according to a modified example 2 of the embodiment. [Figure 9] Figure 9 is a front view showing the current collector and positive electrode tab portion according to a modified example 3 of the embodiment. [Modes for carrying out the invention]

[0009] An energy storage element according to one aspect of the present invention comprises an electrode body in which a plurality of electrode plates are wound, and a container for housing the electrode body, wherein the electrode body comprises a main body having a flat portion and a pair of curved portions sandwiching the flat portion, and a plurality of tab portions formed by stacking multiple pieces of electrode plates of the same polarity from among the plurality of electrode plates, and a pair of tab portions protruding from each of the end faces in the winding axis direction of the main body, wherein at least one of the plurality of tab portions has a bent portion continuous with the curved portion and a pair of extended portions extending from the bent portion and continuous with the flat portion.

[0010] According to this, since at least one tab portion has a bent portion continuous with the curved portion and a pair of extended portions extending from the bent portion, the strength of the entire tab portion is increased by the bent portion. Thereby, even if the electrode body vibrates in the container due to an impact or the like, the tab portion having the bent portion can receive the movement of the electrode body. Therefore, damage to the electrode body can be suppressed.

[0011] The energy storage element may have a plurality of current collectors respectively joined to the plurality of tab portions, and at least one of the pair of extended portions may be joined to the current collector.

[0012] According to this, since at least one of the pair of extended portions is joined to the current collector, the tab portion and the current collector can be stably joined as compared with the case of joining the bent portion and the current collector. Thereby, the tab portion and the current collector can be firmly joined, and the movement of the electrode body can be restricted by the current collector. Therefore, damage to the electrode body can be further suppressed.

[0013] The pair of extended portions may be joined to the current collector in a state where a plurality of pieces of the electrode plate forming the extended portion are bundled.

[0014] According to this, since the plurality of pieces forming the pair of extended portions are joined to the current collector in a bundled state, the tab portion as a whole can be in an annularly closed state. Thereby, the strength of the entire tab portion is further increased, and the movement of the electrode body can be more reliably received. Therefore, damage to the electrode body can be further suppressed.

[0015] In a state before being joined to the current collector, the plurality of pieces forming the pair of extended portions of the tab portion may be such that both ends thereof are gradually arranged forward as going from the innermost piece to the outer periphery.

[0016] According to this, since a plurality of pieces forming a pair of extended portions of the tab portion are arranged such that both ends thereof are gradually disposed forward from the innermost piece toward the outer periphery, when collecting and bundling the pair of extended portions at the center, they can be easily collected. Thereby, the workability when bundling the pair of extended portions can be enhanced, and the stability at the time of joining can also be improved. If the stability at the time of joining is improved, the overall strength of the tab portion after joining can also be enhanced, so that the movement of the electrode body can be more reliably received. Therefore, damage to the electrode body can be more effectively suppressed.

[0017] It may be that a positive electrode tab portion and a negative electrode tab portion are provided as a pair of tab portions on each of both end faces of the main body portion.

[0018] According to this, even in an electrode body in which a positive electrode tab portion and a negative electrode tab portion are provided on each of both end faces of the main body portion, since the strength of each tab portion is enhanced, it is possible to suppress damage to the electrode body.

[0019] It may be that the positive electrode tab portion and the negative electrode tab portion provided on one end face and the positive electrode tab portion and the negative electrode tab portion provided on the other end face among both end faces of the main body portion are arranged in an inverted manner.

[0020] According to this, in the main body portion of the electrode body, since the positive electrode tab portion and the negative electrode tab portion provided on one end face and the positive electrode tab portion and the negative electrode tab portion provided on the other end face are arranged in an inverted manner, the resistance of the electrode body during charge and discharge can be reduced. This is suitable for an electrode body that is long in the winding axis direction and is likely to have a high resistance.

[0021] Hereinafter, with reference to the drawings, a power storage element according to an embodiment (including a modified example thereof) of the present invention will be described. Note that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, manufacturing processes, order of manufacturing processes, etc. shown in the following embodiments are examples and are not intended to limit the present invention. In each figure, dimensions and the like are not strictly illustrated. In each figure, the same or similar components are denoted by the same reference numerals.

[0022] In the following description and drawings, the direction along the winding axis of the electrode body, the extension direction of the electrode body, or the opposing direction of the short side of the container is defined as the X-axis direction. The direction of the opposing direction of the long side of the container, or the thickness direction of the container, 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 are aligned, or the vertical direction, is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Note that depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation, the Z-axis direction will be described as the vertical direction below.

[0023] In the following explanation, the X-axis positive direction refers to the direction of the X-axis arrow, and the X-axis negative direction refers to the opposite direction. The same applies to the Y-axis and Z-axis directions. Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. For example, two directions being orthogonal does not only mean that the two directions are perfectly orthogonal, but also that they are substantially orthogonal, that is, they may include a difference of, for example, a few percent.

[0024] (Embodiment) [1. General explanation of energy storage elements] First, a general description of the energy storage element 10 in this embodiment will be given using Figures 1 and 2. Figure 1 is a perspective view showing the external appearance of the energy storage element 10 according to this embodiment. Figure 2 is an exploded perspective view showing the individual components of the energy storage element 10 according to this embodiment.

[0025] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, and specifically, is a non-aqueous 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 mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and gasoline automobiles. Examples of railway vehicles for electric railways include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage element 10 can also be used as a stationary battery for household or commercial use.

[0026] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or it may be a capacitor. The energy storage element 10 may not be a secondary battery, but a primary battery that allows the user to use the stored electricity without charging. The energy storage element 10 may be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is shown in a flat rectangular parallelepiped shape (square), but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, but may be a polygonal prism shape, an oblong cylinder shape, an elliptical cylinder shape, or a cylinder shape, etc.

[0027] As shown in Figures 1 and 2, the energy storage element 10 comprises a container 100, two pairs of electrode terminals 300, and two pairs of external gaskets 400. Inside the container 100 are two pairs of internal gaskets 500, two pairs of current collectors 600, and electrode bodies 700. Specifically, one pair of components (positive and negative) are arranged on one end face of the container 100 in the positive X-axis direction, and the remaining pair of components (positive and negative) are arranged on the other end face of the container 100 in the negative X-axis direction. More specifically, on one end face of the container 100 in the positive X-axis direction, the components on the positive side are arranged in the positive Z-axis direction, and the components on the negative Z-axis direction. On the other end face of the container 100 in the negative X-axis direction, the components on the negative side are arranged in the positive Z-axis direction, and the components on the positive side are arranged in the negative Z-axis direction. In other words, on one end face and the other end face of the container 100, the components on the positive electrode side and the components on the negative electrode side are arranged in a reversed (upside down) manner when viewed from the direction along the winding axis (viewed in the X-axis direction).

[0028] The container 100 contains an electrolyte (non-aqueous electrolyte), but its illustration is omitted. There are no particular restrictions on the type of electrolyte, as long as it does not impair the performance of the energy storage element 10, and various types can be selected. In addition to the above components, spacers placed to the side, above, or below the electrode body 700, an insulating film enclosing the electrode body 700, etc., may also be placed inside.

[0029] The container 100 is a rectangular parallelepiped (square or box-shaped) case that is elongated in the X-axis direction. In this container 100, the two opposing end faces in the X-axis direction are short sides 101, and the two opposing end faces in the Y-axis direction are long sides 102. The pair of short sides 101 are the one end face and the other end face in the X-axis direction on which the positive electrode side members and the negative electrode side members described above are provided. In the container 100, of the two opposing end faces in the Z-axis direction, the end face in the Z-axis positive direction is the top surface 103, and the end face in the Z-axis negative direction is the bottom surface 104.

[0030] The container 100 has a container body 110 and a lid 120, and when the container body 110 and the lid 120 are assembled, it forms a rectangular parallelepiped shape. The container body 110 has a pair of long sides 102 and a bottom surface 104. The lid 120 has a pair of short sides 101 and a top surface 103.

[0031] Specifically, the container body 110 is a roughly U-shaped sheet metal with an open top when viewed in the X-axis direction. The container body 110 has flat, rectangular long side walls forming a pair of long sides 102 at both ends in the Y-axis direction, and a flat, rectangular bottom wall forming a bottom surface 104 at the end in the negative Z-axis direction.

[0032] The cover 120 is a roughly U-shaped sheet metal with an open bottom when viewed in the Y-axis direction. The cover 120 has flat, rectangular short side walls forming a pair of short sides 101 at both ends in the X-axis direction, and a flat, rectangular top wall forming a top surface 103 at the end in the Z-axis positive direction.

[0033] With this configuration, the container 100 is structured so that after the electrode body 700 and the like are housed inside the container body 110, the container body 110 and the lid 120 are joined by welding or the like to seal the inside. The material of the container 100 (container body 110 and lid 120) is not particularly limited, but it is preferable that it be a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet.

[0034] Although not shown in the diagram here, the lid 120 has a liquid injection section and a gas discharge valve. The gas discharge valve is a safety valve that releases pressure if the pressure inside the container 100 rises excessively. The liquid injection section is the part used to inject electrolyte into the container 100 during the manufacturing of the energy storage element 10.

[0035] The electrode terminals 300 are terminal members (positive terminal 310 and negative terminal 320) that are electrically connected to the electrode body 700 via the current collector 600. In other words, the electrode terminals 300 are metallic members that lead the electricity stored in the electrode body 700 to the external space of the energy storage element 10, and also introduce electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode body 700. The material of the electrode terminals 300 is not particularly limited, but the electrode terminals 300 (positive terminal 310 and negative terminal 320) are made of conductive material such as aluminum, aluminum alloy, copper, or copper alloy. The electrode terminals 300 are connected (joined) to the current collector 600 by crimping, welding, etc., and are attached to the cover body 120. In this embodiment, the electrode terminal 300 is provided with a shaft portion 330, and this shaft portion 330 is crimped through the external gasket 400, the internal gasket 500, and the current collector 600, thereby connecting (joining) it to the current collector 600.

[0036] The current collector 600 is a conductive current collector (positive electrode current collector 610 and negative electrode current collector 620) that is arranged in pairs on both sides of the electrode body 700 in the X-axis direction and connected (joined) to the electrode body 700 and the electrode terminal 300 to electrically connect the electrode body 700 and the electrode terminal 300. Specifically, the current collector 600 integrally has a first connection part 630 that is connected (joined) to the tab part 720 of the electrode body 700 (described later) by welding, crimping, etc., and a second connection part 640 that is connected (joined) to the electrode terminal 300 by crimping, welding, etc., as described above, and fixed to the cover body 120. The first connection part 630 and the second connection part 640 are each flat plate-shaped parts and are formed by bending a single sheet of metal. The material of the current collector 600 is not particularly limited, but the positive electrode current collector 610 is made of a conductive material such as aluminum or an aluminum alloy, similar to the positive electrode base material 741 of the electrode body 700 described later, and the negative electrode current collector 620 is made of a conductive material such as copper or a copper alloy, similar to the negative electrode base material 751 of the electrode body 700 described later.

[0037] The external gasket 400 is a plate-shaped, rectangular insulating sealing member that is placed between the lid 120 of the container 100 and the electrode terminal 300, and insulates and seals the space between the lid 120 and the electrode terminal 300. The internal gasket 500 is a plate-shaped, rectangular insulating sealing member that is placed between the lid 120 and the current collector 600, and insulates and seals the space between the lid 120 and the current collector 600. The outer gasket 400 and the inner gasket 500 are formed from electrically insulating resins 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 composite materials thereof.

[0038] The electrode body 700 is an electrical storage element (power generation element) formed by winding electrode plates, capable of storing electricity. The electrode body 700 has a long 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 extends, for example, 300 mm or more, specifically to about 500 mm to 1500 mm. Therefore, the length of the electrode body 700 in the X-axis direction is longer than the length in the Z-axis direction. The electrode body 700 has a main body portion 710 and a plurality of tab portions 720 protruding from the main body portion 710, and as described above, the tab portions 720 are connected (joined) to the current collector 600. The plurality of tab portions 720 protrude in pairs from each of the two end faces in the X-axis direction of the main body portion 710. For example, on one end face of the main body 710 in the X-axis positive direction, a positive electrode tab portion 721 is provided at the end in the Z-axis positive direction, and a negative electrode tab portion 722 is provided at the end in the Z-axis negative direction. On the other hand, on the other end face of the main body 710 in the X-axis negative direction, a negative electrode tab portion 722 is provided at the end in the Z-axis positive direction, and a positive electrode tab portion 721 is provided at the end in the Z-axis negative direction. In other words, on one end face and the other end face of the main body 710, the positive electrode tab portion 721 and the negative electrode tab portion 722 are arranged in a reversed (upper and lower) configuration when viewed from the direction along the winding axis (viewed in the X-axis direction). The configuration of such an electrode body 700 will be described in detail below.

[0039] [2. Description of the configuration of electrode body 700] Figure 3 is a perspective view showing the configuration of the electrode body 700 according to this embodiment. Specifically, Figure 3 shows the configuration of the electrode body 700 with the winding state of the electrode plate partially unfolded.

[0040] [2.1 General Description of Electrode Body] As shown in Figure 3, the electrode body 700 includes a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0041] The positive electrode plate 740 is an electrode plate in which a positive electrode active material layer 742 is formed on the surface of a positive electrode substrate 741, which is a long, strip-shaped metal foil made of aluminum or an aluminum alloy. The negative electrode plate 750 is an electrode plate in which a negative electrode active material layer 752 is formed on the surface of a negative electrode substrate 751, which is a long, strip-shaped metal foil made of copper or a copper alloy. As the positive electrode substrate 741 and the negative electrode substrate 751, any known material that is stable against oxidation-reduction reactions during charging and discharging can be used, such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, and Al-Cd alloy. 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 that is capable of intercalating and deintercalating lithium ions can be used.

[0042] As positive electrode active materials, polyanionic compounds such as LiMPO4, LiMSiO4, LiMBO3 (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), lithium titanate, LiMn2O4, and LiMn 1.5 Ni 0.5 Spinel-type lithium manganese oxides such as O4, lithium transition metal oxides such as LiMO2 (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) can be used. As negative electrode active materials, lithium metals, lithium alloys (lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as Wood's alloys), alloys capable of intercalating and deintercalating lithium, carbon materials (e.g., graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), silicon oxides, metal oxides, lithium metal oxides (Li4Ti5O 12 Examples include polyphosphate compounds, or compounds of transition metals and group 14 to 16 elements, such as Co3O4 and Fe2P, which are generally called conversion negative electrodes.

[0043] Separators 761 and 762 are microporous sheets made of resin. Any known material can be used for separators 761 and 762, as long as it does not impair the performance of the energy storage element 10. For example, separators 761 and 762 can be woven fabrics, nonwoven fabrics, or synthetic resin microporous membranes made of polyolefin resins such as polyethylene, which are insoluble in organic solvents.

[0044] The electrode body 700 is formed by alternately stacking and winding a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. In other words, the electrode body 700 is formed by stacking and winding the negative electrode plate 750, separator 761, positive electrode plate 740, and separator 762 in this order. In this embodiment, the electrode body 700 is a wound type (so-called vertical winding type) electrode body formed by winding the positive electrode plate 740, negative electrode plate 750, etc., around a winding axis L extending in the X-axis direction. The winding axis L is a virtual axis that serves as the central axis when winding the positive electrode plate 740, negative electrode plate 750, etc., and in this embodiment, it is a straight line parallel to the X-axis direction that passes through the center of the electrode body 700.

[0045] On the positive electrode plate 740, multiple protruding pieces 743 projecting outward are arranged in a staggered pattern in a plan view of the positive electrode plate 740 at both ends in the winding axis direction. Similarly, on the negative electrode plate 750, multiple protruding pieces 753 projecting outward are arranged in a staggered pattern in a plan view of the negative electrode plate 750 at both ends in the winding axis direction. In the laminated state, each protruding piece 743 of the positive electrode plate 740 and each protruding piece 753 of the negative electrode plate 750 are arranged alternately and repeatedly in the longitudinal direction of the positive electrode plate 740 and the negative electrode plate 750, respectively. Each protruding piece 743 and 753 is a portion where the active material layer containing the active material is not formed and the base material layer is exposed (non-active material layer formed portion).

[0046] When the positive electrode plate 740 and the negative electrode plate 750 are wound with the separators 761 and 762, the protruding pieces 743 of the positive electrode plate 740 and the protruding pieces 753 of the negative electrode plate 750 overlap at one end face and the other end face of the main body portion 710. The portion where the protruding pieces 743 of the positive electrode plate 740 overlap is the positive electrode tab portion 721. In other words, the positive electrode tab portion 721 is a portion formed by stacking multiple pieces (protruding pieces 743) of electrodes (positive electrode plate 740) with the same polarity among multiple electrodes (positive electrode plate 740 and negative electrode plate 750).

[0047] Similarly, the portion where the protruding pieces 753 of the negative electrode plate 750 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is a portion formed by stacking multiple pieces (protruding pieces 753) of electrodes (negative electrode plate 750) of the same polarity among multiple electrodes (positive electrode plate 740 and negative electrode plate 750).

[0048] In other words, the electrode body 700 has a main body portion 710 that constitutes the body of the electrode body 700, and a plurality of tab portions 720 (positive electrode tab portion 721 and negative electrode tab portion 722) that protrude in pairs from each of the two end faces in the X-axis direction from the main body portion 710.

[0049] The main body portion 710 is an elongated cylindrical portion (active material layer forming portion) formed by winding the positive electrode plate 740 and the negative electrode plate 750, where the positive electrode active material layer 742 and the negative electrode active material layer 752 are formed (coated), with the separators 761 and 762. As a result, the main body portion 710 has a pair of curved portions 711 on both sides in the Z-axis direction, and a flat portion 712 that is flat overall between this pair of curved portions 711. It can also be said that the pair of curved portions 711 are positioned to sandwich the flat portion 712 in the Z-axis direction.

[0050] The curved portion 711 is a curved part that extends in the X-axis direction, curved in the shape of a semicircular arc so as to project in the Z-axis direction when viewed from the X-axis direction, and is positioned opposite the bottom wall of the container body 110 and the top wall of the lid 120. In other words, the pair of curved portions 711 are parts that curve so as to project from the flat portion 712 toward both sides in the Z-axis direction toward the bottom wall of the container body 110 and the top wall of the lid 120 when viewed from the X-axis direction. The flat portion 712 is a rectangular and flat part that connects the ends of the pair of curved portions 711, extending parallel to the XZ plane oriented in the Y-axis direction, and is positioned opposite the long side walls on both sides in the Y-axis direction of the container body 110. Note that the curved shape of the curved portion 711 is not limited to a semicircular arc shape, but may be part of an ellipse, or any other shape. The flat portion 712 is not limited to having a flat outer surface facing the Y-axis direction; the outer surface may be slightly concave or slightly convex.

[0051] [2.2 Explanation of the Tab Section] Next, we will describe the details of the tab portion 720. Since each tab portion 720 has a similar basic structure, we will focus on describing the positive electrode tab portion 721 provided on one end face of the main body portion 710 in the X-axis positive direction, and will omit descriptions of the other tab portions 720.

[0052] Figure 4 is a schematic diagram showing the general configuration of the positive electrode tab portion 721 according to the embodiment. In Figure 4, the positive electrode tab portion 721 is shown in a view along the X-axis before being joined to the current collector 600. Also, in Figure 4, the number of protruding pieces 743 constituting the positive electrode tab portion 721 is simplified in the illustration.

[0053] As shown in Figures 3 and 4, the positive electrode tab portion 721 has a curved portion 723 and a pair of extension portions 724. The curved portion 723 is a portion that is continuous with the curved portion 711 of the main body portion 710. For this reason, the curved portion 723 has a curved shape corresponding to the curved portion 711. The pair of extension portions 724 extend from both ends of the curved portion 723 and are portions that are continuous with the flat portion 712 of the main body portion 710. For this reason, the pair of extension portions 724 are generally flat before being joined to the current collector 600. Compared to each of the flat extension portions 724, the curved curved portion 723 has higher structural strength.

[0054] Here, as shown in Figure 4, in the state before joining to the current collector 600, the multiple protruding pieces 743 forming a pair of extensions 724 are positioned such that both ends gradually protrude forward (in the negative Z-axis direction in Figure 4) as you move from the innermost protruding piece 743 toward the outer circumference. Here, the forward end of the multiple protruding pieces 743 is the direction away from the curved portion 723, and is also the direction from one of the pair of curved portions 711 toward the other. In other words, of the multiple protruding pieces 743 forming a pair of extensions 724, both ends of the innermost protruding piece 743 are in the most recessed position. As you move from this protruding piece 743 toward the outermost protruding pieces 743, both ends of each protruding piece 743 gradually protrude forward, and both ends of the outermost protruding piece 743 are in the most forward-protruding position.

[0055] Next, the state after the positive electrode tab portion 721 is joined to the current collector 600 will be described. Figure 5 is a schematic diagram showing the state in which the positive electrode tab portion 721 according to the embodiment is joined to the current collector 600. Specifically, Figure 5 corresponds to Figure 4.

[0056] As shown in Figure 5, before being joined to the current collector 600, the multiple protruding pieces 743 forming a pair of extensions 724 are gathered and bundled together in the center (the center in the direction in which the multiple protruding pieces 743 are aligned). As previously mentioned, since the ends of the multiple protruding pieces 743 forming a pair of extensions 724 are gradually positioned forward from the innermost protruding piece 743 toward the outer circumference, the multiple protruding pieces 743 can be easily gathered and bundled together in the center. This bundling causes the entire positive electrode tab portion 721 to be closed in an annular shape with the bent portion 723 and the pair of extensions 724. In other words, the entire positive electrode tab portion 721 is reinforced by the bent portion 723, and damage to the positive electrode tab portion 721 is suppressed. Figure 5 shows the case where the innermost protruding piece 743 of the pair of protruding pieces 743 forming an extension portion 724 is not bundled with the other protruding pieces 743. Even in this state, the overall strength of the positive electrode tab portion 721 can be increased, but if a higher level of strength improvement is desired, all the protruding pieces 743 can be bundled together. After bundling, the first connection portion 630 of the current collector 600 is joined (welded) to the pair of extension portions 724.

[0057] Even after joining the pair of extensions 724 to the current collector 600, it is possible to determine the state of each protruding piece 743 before joining by observing each protruding piece 743 on the pair of extensions 724. For example, as shown in Figure 5, after joining, the multiple protruding pieces 743 forming the pair of extensions 724 are positioned so that their ends are gradually moved forward from the innermost protruding piece 743 towards the outer circumference, so it can be determined that they were in a similar state before joining.

[0058] [3. Explanation of the effect] As described above, the energy storage element 10 according to an embodiment of the present invention comprises an electrode body 700 around which a plurality of electrode plates (positive electrode plate 740 and negative electrode plate 750) are wound, and a container 100 for housing the electrode body 700. The electrode body 700 comprises a main body portion 710 having a flat portion 712 and a pair of curved portions 711 sandwiching the flat portion 712, and a plurality of tab portions 720 formed by stacking multiple pieces (protruding pieces 743 and 753) of electrode plates of the same polarity from the plurality of electrode plates, and a pair of tab portions 720 protruding from each of the end faces in the winding axis direction of the main body portion 710. Of the plurality of tab portions 720, at least one tab portion (positive electrode tab portion 721) has a bent portion 723 continuous with the curved portion 711 and a pair of extended portions 724 extending from the bent portion 723 and continuous with the flat portion 712.

[0059] According to this, the positive electrode tab portion 721 has a bent portion 723 that is continuous with the curved portion 711 and a pair of extended portions 724 that extend from the bent portion 723, so the strength of the entire positive electrode tab portion 721 is increased by the bent portion 723. As a result, even if the electrode body 700 vibrates inside the container 100 due to impact or the like, the movement of the electrode body 700 can be absorbed by the positive electrode tab portion 721 having the bent portion 723. Therefore, damage to the electrode body 700 can be suppressed.

[0060] The energy storage element 10 has a plurality of current collectors 600, each joined to a plurality of tab portions 720. At least one of a pair of extension portions 724 is joined to a current collector 600.

[0061] According to this, since at least one of the pair of extensions 724 is joined to the current collector 600, the tab portion 720 and the current collector 600 can be joined more stably than when the bent portion 723 and the current collector 600 are joined. As a result, the tab portion 720 and the current collector 600 can be firmly joined, and the movement of the electrode body 700 can be restricted by the current collector 600. Therefore, damage to the electrode body 700 can be further suppressed.

[0062] The pair of extensions 724 are joined to the current collector 600 with multiple pieces (protruding pieces 743) of the electrode plates forming the extension 724 bundled together.

[0063] According to this, since the multiple protruding pieces 743 forming a pair of extensions 724 are joined to the current collector 600 in a bundled state, the entire positive electrode tab portion 721 can be closed in an annular shape. As a result, the overall strength of the positive electrode tab portion 721 is increased, and the movement of the electrode body 700 can be more reliably supported. Therefore, damage to the electrode body 700 can be further suppressed.

[0064] In the state before being joined to the current collector 600, the multiple pieces (projecting pieces 743) that make up a pair of extensions 724 of the tab portion (positive electrode tab portion 721) are arranged so that their ends are gradually positioned forward as you move from the innermost piece toward the outer circumference.

[0065] According to this, the multiple protruding pieces 743 that make up the pair of extensions 724 of the positive electrode tab portion 721 are arranged so that their ends are gradually positioned forward from the innermost protruding piece 743 toward the outer circumference, making it easy to gather the pair of extensions 724 together when bundling them in the center. This improves the workability when bundling the pair of extensions 724 and also improves the stability during joining. Improved stability during joining increases the overall strength of the positive electrode tab portion 721 after joining, allowing it to more reliably withstand the movement of the electrode body 700. Therefore, damage to the electrode body 700 can be further suppressed.

[0066] Here, as a comparative example, let's consider an electrode body in which a pair of tabs are provided only on one end face of the main body. In this case, the other end face of the main body is flat as a whole. When the electrode body moves, the tabs on the one end face of the main body receive the movement of the electrode body, while the large flat surface on the other end face of the main body receives the movement of the electrode body. As a result, the stress during reception is distributed on the other end face of the main body, and the load acting on the electrode body is suppressed.

[0067] On the other hand, in the electrode body 700, as in this embodiment, where a positive electrode tab portion 721 and a negative electrode tab portion 722 are provided on each end face of the main body portion 710, the positive electrode tab portion 721 and the negative electrode tab portion 722 on each end face of the main body portion 710 receive the movement of the electrode body 700. In other words, because the movement of the electrode body 700 is also received by the positive electrode tab portion 721 and the negative electrode tab portion 722 on the other end face of the main body portion 710, a larger stress acts on the positive electrode tab portion 721 and the negative electrode tab portion 722 compared to the comparative example, making them more susceptible to damage. In this embodiment, since the strength of each tab portion 720 is increased, it is possible to suppress damage to the electrode body 700 even in the electrode body 700, where a positive electrode tab portion 721 and a negative electrode tab portion 722 are provided on each end face of the main body portion 710.

[0068] Furthermore, of the two end faces of the main body 710, the positive electrode tab portion 721 and negative electrode tab portion 722 on one end face are arranged in reverse, while the positive electrode tab portion 721 and negative electrode tab portion 722 on the other end face are arranged in reverse.

[0069] The inventors of the present invention have found that when the positive electrode tab portion 721 and the negative electrode tab portion 722 are reversed on one end face and the other end face of the main body portion 710 of the electrode body 700, the resistance of the electrode body 700 during charging and discharging is reduced compared to when they are not reversed. In other words, when the positive electrode tab portion 721 and the negative electrode tab portion 722 on one end face of the main body portion 710 of the electrode body 700 are reversed on the other end face, the resistance of the electrode body 700 during charging and discharging can be reduced. This is particularly suitable for electrode bodies 700 that are long in the winding axis direction, which tend to have high resistance.

[0070] [4. Explanation of variations] The following describes various modifications of the above embodiments. In the following description, parts identical to those in the above embodiments or other modifications may be denoted by the same reference numerals and their descriptions may be omitted.

[0071] (Variation 1) Next, a modified example 1 of the above embodiment will be described. Figure 6 is a perspective view showing the current collector 600a according to modified example 1 of the embodiment. Figure 7 is a front view showing the current collector 600a according to modified example 1 of the embodiment.

[0072] As shown in Figures 6 and 7, in this modified example, the current collector 600a is provided with a crimping shaft portion 631a. Specifically, the current collector 600a comprises a current collector body 630a, a shaft portion 631a, and a pair of connecting portions 632a.

[0073] The current collector body 630a is a flat, rectangular portion that is parallel to the YZ plane and elongated in the Z-axis direction. The shaft portion 631a protrudes from the main surface of the current collector body 630a in the positive X-axis direction. The main surface of the current collector body 630a in the negative X-axis direction is formed as a flat surface. The shaft portion 631a is a cylindrical portion that extends in the X-axis direction. This shaft portion 631a is connected (joined) to the electrode terminal by being crimped through the internal gasket, external gasket, and electrode terminal.

[0074] The pair of connecting portions 632a are plate-shaped portions that protrude in the negative X-axis direction from a pair of end portions of the current collector body 630a in the negative Z-axis direction. Specifically, each connecting portion 632a is a flat, rectangular portion that is parallel to the XZ plane and elongated in the Z-axis direction. Each connecting portion 632a is joined (welded) to each extension portion 724 of the positive electrode tab portion 721. In this modified example, the pair of extension portions 724 are not bundled together, and each extension portion 724 is joined to each connecting portion 632a. However, if the pair of extension portions 724 are bundled together, the bundled pair of extension portions 724 may be joined to only one of the pair of connecting portions 632a. In this case, the other connecting portion 632a does not need to be provided on the current collector 600a.

[0075] When each connecting portion 632a and each extension portion 724 are joined, the current collector body 630a is in contact with the end face of the curved portion 723. Here, the end face of the curved portion 723 is the tip surface of the curved portion 723 in the protruding direction (X-axis direction) from which the positive electrode tab portion 721 protrudes from the main body portion 710. As mentioned above, the curved portion 723 is a part with higher structural strength compared to the extension portion 724. Since the current collector body 630a is in contact with the end face of this relatively strong curved portion 723, the movement of the electrode body 700 joined to the current collector body 600a can be restricted more effectively. Therefore, damage to the electrode body 700 can be further suppressed.

[0076] (Modification 2) Next, a modified example 2 of the above embodiment will be described. Figure 8 is a front view showing the current collector 600b and the positive electrode tab portion 721b according to the modified example 2 of the embodiment. Figure 8 corresponds to Figure 7.

[0077] The current collector 600b is basically configured the same as the current collector 600a of Modified Example 1, but the difference is that the length of the current collector body 630b in the Z-axis direction is shorter than that of the current collector body 630a. For this reason, even when each connection part 632b of the current collector body 630b is joined to each extension part 724b, Curved section 723 It does not reach the end face. In other words, the current collector body 630b is in view in the X-axis direction. Curved section 723 They are positioned so as not to overlap the end faces.

[0078] On the other hand, in the positive electrode tab portion 721b, a recess 728b is formed in each extension portion 724b to accommodate at least a part of the current collector body 630b. The recess 728b is a notch formed at the end of each extension portion 724b in the positive X-axis direction before joining. Since at least a part of the current collector body 630b is accommodated in this recess 728b, the amount of protrusion of the current collector 600b from the positive electrode tab portion 721b can be reduced. This makes it possible to improve space efficiency within the container 100. Furthermore, if the depth of the recess 728b is made deeper than the wall thickness of the current collector body 630b, the entire thickness of the current collector body 630b can be accommodated in the recess 728b. Therefore, the amount of protrusion of the current collector 600b from the positive electrode tab portion 721b can be further reduced, which is preferable.

[0079] (Variation 3) Next, a third modification of the above embodiment will be described. Figure 9 is a front view showing the current collector 600b and the positive electrode tab portion 721c according to the third modification of the embodiment. Figure 9 corresponds to Figure 8.

[0080] In Modification 2, the case where the recess 728b is a notch formed in each extension 724b before joining is illustrated. In Modification 3, the case in which the recess 728c is formed in each extension 724c by the joining process is described. In Figure 9, the end faces of each extension 724c before joining are shown by dashed lines. Before joining, the end faces of each extension 724c are flush with the end faces of the curved portion 723.

[0081] During the joining process, the current collector body 630b of the current collector 600b is pressed against the end faces of each extension portion 724c, causing the end faces of each extension portion 724c to deform into a concave shape, forming a recess 728c. At least a portion of the current collector body 630b is housed within the recess 728c, thus reducing the amount of protrusion from the positive electrode tab portion 721c of the current collector 600b. This makes it possible to improve space efficiency within the container 100.

[0082] (Other variations) Although embodiments of the present invention (including modifications thereof; the same applies hereinafter) of energy storage elements have been described above, the present invention is not limited to the above embodiments. The embodiments disclosed herein are illustrative in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims.

[0083] For example, in the above embodiment, the case is illustrated in which all tab portions 720 on the electrode body 700 have a bent portion and a pair of extended portions. However, it is sufficient if at least one tab portion on the electrode body has a bent portion and a pair of extended portions. For example, even if only one tab portion has a bent portion and a pair of extended portions, that tab portion can withstand the movement of the electrode body to some extent.

[0084] In the above embodiment, an example was given in which the multiple protruding pieces 743 forming a pair of extensions 724 of the positive electrode tab portion 721 are arranged such that their ends are gradually positioned further forward from the innermost protruding piece 743 toward the outer circumference. The positions of the ends of each of the multiple protruding pieces forming each extension portion can be any. For example, the ends of each of the multiple protruding pieces forming each extension portion may be flush with the surface.

[0085] In the above embodiment, the positive electrode tab portion 721 and the negative electrode tab portion 722 are arranged inverted (upside down) in the X-axis direction on one end face and the other end face of the main body portion 710 of the electrode body 700, but they do not have to be inverted.

[0086] In the above embodiment, an example was given in which a positive electrode tab portion 721 and a negative electrode tab portion 722 are provided on both end faces of the main body portion 710 of the electrode body 700, respectively. However, the positive electrode tab portion and the negative electrode tab portion may be provided on only one of the end faces of the main body portion of the electrode body. In this case, the electrode terminals 300, the current collector 600, the external gasket 400, and the internal gasket 500 will also be provided only on one short side 101 of the container 100 corresponding to the positive electrode tab portion and the negative electrode tab portion.

[0087] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples. [Industrial applicability]

[0088] This invention can be applied to energy storage elements such as lithium-ion secondary batteries. [Explanation of symbols]

[0089] 10 Energy storage elements 100 containers 101 Short side 102 Long side 103 Top surface 104 Bottom 110 Container body 120 Lid 300 electrode terminal 310 Positive terminal 320 Negative terminal 330, 631a shaft part 400 External gasket 500 Internal Gasket 600, 600a, 600b current collectors 610 Positive electrode current collector 620 Negative electrode current collector 630 First connection section 630a, 6430b Current collector body 632a, 632b connection 640 Second connection section 700 Electrode body 710 Main Unit 711 Curved section 712 Flat area 720 Tab section 721, 721b, 721c Positive electrode tab section 722 Negative electrode tab section 723 Curve 724, 724b, 724c extension part 728b, 728c recess 740 Positive Plate 741 Positive electrode substrate 742 Cathode active material layer 743, 753 Projecting piece 750 Negative plate 751 Negative electrode substrate 752 Negative electrode active material layer 761, 762 Separators

Claims

1. A power storage element comprising an electrode body in which multiple electrode plates are wound, and a container for housing the electrode body, The electrode body is A main body having a flat portion and a pair of curved portions sandwiching the flat portion, The above-mentioned plurality of electrode plates are formed by stacking multiple pieces of electrode plates of the same polarity, and comprises a plurality of tab portions that protrude in pairs from each of the end faces in the winding axis direction of the main body, Of the plurality of tab portions, at least one tab portion has a bent portion continuous with the curved portion and a pair of extended portions extending from the bent portion and continuous with the flat portion. The system has multiple current collectors, each of which is joined to the aforementioned multiple tab portions, At least one of the pair of extensions is joined to the current collector, In the state before being joined to the current collector, the plurality of pieces forming the pair of extensions of the tab portion are arranged such that both ends are gradually positioned forward from the innermost piece toward the outer circumference. Energy storage element.

2. The pair of extensions are joined to the current collector in a state where multiple pieces of the electrode plates forming the extensions are bundled together. The energy storage element according to claim 1.

3. Each of the two end faces of the main body is provided with a pair of tabs, consisting of a positive electrode tab and a negative electrode tab. The energy storage element according to claim 1 or 2.

4. Of the two end faces of the main body, the positive electrode tab portion and the negative electrode tab portion on one end face, and the positive electrode tab portion and the negative electrode tab portion on the other end face are arranged in reverse. The energy storage element according to claim 3.

5. A power storage element comprising an electrode body in which multiple electrode plates are wound, and a container for housing the electrode body, The electrode body is A main body having a flat portion and a pair of curved portions sandwiching the flat portion, The above-mentioned plurality of electrode plates are formed by stacking multiple pieces of electrode plates of the same polarity, and comprises a plurality of tab portions that protrude in pairs from each of the end faces in the winding axis direction of the main body, Of the plurality of tab portions, at least one tab portion has a bent portion continuous with the curved portion and a pair of extended portions extending from the bent portion and continuous with the flat portion. Each of the two end faces of the main body is provided with a pair of tabs, consisting of a positive electrode tab and a negative electrode tab. Energy storage element.

Images